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HEREDITY AND EUGENICS 
 
HEREDITY AND 
 EUGENICS 
 
 BY 
 
 R. RUGGLES GATES, Ph.D., F.L.S. 
 
 PROFESSOR OF EOTAKY IN 1 HE UNIVERSITY OK LONDO.N A.ND HEAD OF THE 
 
 DEPARTMENT OF BOTANY AT KING'S COLLEGE: 
 
 SOMETI.ME ASSOCIATE PROFESSOR OF ZOOLOGY, UNIVERSITY OF CALIFoKNIA; 
 
 AUTHOR OF "the MUTATION FACTOR IN EVOLUTION," ETC. 
 
 CONSTABLE AND CO. LTD, 
 
 LONDON BOMBAY SYDNEY 
 
 1923 
 
 fltO^ERTT mRARY 
 
 N. C. SiMte C^Uegf 
 
PRINTED IN GREAT BRITAIN BY 
 BILLING AND SONS, LTD., GUILDFORD AND ESHER 
 
TO 
 
 MY MOTHER 
 
 THIS BOOK IS AFFECTIONATELY DEDICATED 
 
 QlH-i 
 
 „■ .r.,; 
 
PREFACE 
 
 This book has been written partly by the accident of 
 circumstances and partly by request. It is based 
 upon a couple of articles which appeared in the 
 Eugenics Review for January and April, 1920, and 
 part of it was written during a holiday in America in 
 1 92 1. Although m}' present interests are occupied 
 with the field of modern botany, I was impelled to 
 write this book by my interest in Eugenics, which is 
 in turn founded upon a knowledge of genetics. The 
 actual writing of it was, however, only made possible 
 by the many friends in various parts of the world who 
 have sent me their publications. 
 
 It is clear to scientific men, although rarely to 
 statesmen and law-makers, that any intelligent 
 attempt to improve the conditions and qualities of the 
 human race must be founded upon some knowledge 
 of the manner in which these qualities arise and are 
 inherited and maintained or lost. In this book I have 
 confined myself as strictly as possible to an examina- 
 tion of the facts of human inheritance, in so far as 
 they are at present known, and I have laid particular 
 emphasis — possibly too much — upon the many cases 
 now known of Mendelian inheritance in man. This 
 is not on account of any partiality for this particular 
 form of inheritance; but because the Mendehan 
 differences are clear cut and more easily recognised, 
 and the manner of their inheritance is more easil}^ 
 traced and analysed and investigated than that of 
 differences which can only be recognised as quantita- 
 
 vii 
 
viii PREFACE 
 
 tive, and whose precise manner of inheritance must 
 still be regarded as under discussion. 
 
 The literature of the last two decades has recorded 
 many cases of Mendelian inheritance in man, as the 
 present book will, I think, testify. But it will also 
 be seen that even the pre-Mendelian literature 
 contained many scattered records of great interest 
 which are now seen to fall into the Mendelian categories 
 of explanation. I have made no attempt to search 
 the literature exhaustively, as the work is really only 
 a by-product of my own evolutionary interests, 
 but I hope that no records of first-rate importance 
 have been omitted, and I believe that several valuable 
 early papers are here for the first time brought into 
 orientation with the twentieth-century literature. 
 The book might easily have grown to considerably 
 greater proportions, but I have endeavoured to include 
 only the more essential subjects and discussions which 
 a book of this kind, written from the biological point of 
 view, ought to contain. Whenever experiments with 
 animals or plants bear directly on the topic in hand, 
 I have not hesitated to use them, and I trust this 
 will add to the value of the w^ork, both to the general 
 public interested in Eugenics, and the medical 
 profession, who should always be on the alert to 
 detect the inheritance element which so frequently 
 is present in the functional derangements with which 
 they have to deal. 
 
 Many matters which are primarily of genetic 
 interest, but without at present any special bearing 
 on human heredity, have been omitted altogether. 
 If this work aids in the diffusion of an intelligent 
 interest and understanding of heredity in its bearing 
 on the welfare of future generations, its object will 
 have been achieved. The conceptions of heredity 
 are no longer vague and ill-defined, as in the writings 
 of a generation ago. They are clear and sharply 
 
PREFACE ix 
 
 defined, and are based on much accurate knowledge 
 of organic structure and development. The germ 
 plasm of the race is a uniquely precious material, 
 and its conservation and improvement in each genera- 
 tion should be the first aim of the State. The first 
 essential for such a conservation is the recognition of 
 the inherent (inherited) differences in the capacities 
 of individuals. Everything goes to show that once 
 a particular strain of germ plasm is lost, it is gone for 
 ever. In State recognition of the value of human 
 germinal qualities, perhaps no country has equalled 
 Sweden, where family records and genealogies have 
 been kept for centuries in an exceptionally complete 
 form, and where race biology is already recognised as 
 a subject of the greatest national importance. 
 
 While it is necessary to recognise the fundamental 
 importance of inherited physical and mental differ- 
 ences, as the foundation of Eugenics, one must 
 also remember that environment counts in the sense 
 that a favourable or suitable environment is required 
 to bring out the potential qualities of any develop- 
 ing organism. Nevertheless, it is these potential 
 (germinal) differences on which the Eugenist must 
 rely in any effort to improve the race or direct the 
 selection of germinal qualities which is going on in 
 every generation. 
 
 In conclusion, I wish to thank those who, in various 
 ways, have contributed to the production of this 
 book. I am indebted to Professor R. C. Punnett, 
 F.R.S., for permission to publish Figs. 4, ii, and 12, 
 from the Journal of Genetics ; to Sir Arthur Keith, 
 F.R.S., for the loan of the blocks from the Journal of 
 Anatomy and Physiology, January, 191 6, which 
 illustrate Figs. 13 and 14; to the Royal Society of 
 Medicine for permission to reproduce Fig. 15 (from 
 Proc. Roy. Soc. Med. {Path.), vol. x., p. 60); and to 
 the editorial board of the Journal of Heredity, for 
 
X PREFACE 
 
 permission to republish the photographs of twins 
 in Figs. 29 to 34. Professor J. A. Piatt has kindly 
 supplied the original reference to Caesar's horse, and 
 I am indebted to Professor F. J. C. Hearnshaw for 
 certain historical references. I am very much in- 
 debted to Professor E. W. MacBride, F.R.S., for 
 kindly reading the proof-sheets and offering many 
 valuable suggestions and criticisms; also to Professor 
 A. Dendy, F.R.S., for certain suggestions. I alone, 
 however, am responsible for the views expressed. 
 
 R. RUGGLES GATES. 
 
 King's College, 
 
 University of London, 
 
 December 27, 1922. 
 
CONTENTS 
 
 CHAPTER PAGE 
 
 I. INTRODUCTION - - - - - - I 
 
 DEFINITION OF HEREDITY. 
 
 II. THE GENERAL ASPECTS OF HEREDITY - - - 8 
 
 INHERITANCE OF DIFFERENCES — MENDELISM — INHERIT- 
 ANCE OF RESEMBLANCES DEVELOPMENT. 
 
 III. INHERITANCE OF PHYSICAL CHARACTERS IN MAN - 27 
 
 y STATURE EYE COLOLfR SKIN COLOUR AND HAIR 
 
 CHARACTERS ALBINISM LEFT-HANDEDNESS 
 
 DIGITAL ABNORMALITIES VARIOUS ABNORMALI- 
 TIES. 
 
 IV. INHERITANCE OF MENTAL CHARACTERS IN MAN - - I45 
 
 FEEBLE-MINDEDNESS INSANITY CACOGENIC FAMI- 
 
 LIES MUSICAL ABILITY HANDWRITING. 
 
 V. THE LIMITS OF HEREDITY - - - - 1 75 
 
 TWINS FINGER PRINTS INHERITANCE OF TWINNING 
 
 LETHAL FACTORS. 
 
 VI. SOCIAL AND WORLD ASPECTS OF EUGENICS - - 204 
 THE BASIS OF RACIAL AND TEMPERAMENTAL DIFFER- 
 ENCES THE RESULTS OF CROSSING BETWEEN 
 
 RACES THE PROBLEMS OF POPULATION POPULA- 
 TION AND QUALITY. 
 
 LIST OF GENERAL WORKS BEARING ON EUGENICS - - 252 
 
 BIBLIOGRAPHY OF PAPERS CITED IN THE TEXT - -254 
 
 INDEX - - - - - - - 273 
 
LIST OF ILLUSTRATIONS 
 
 FIC" I'AGE 
 
 1. DIAGRAM OF NORMAL X BRA CHYDACTYL - - - lO 
 
 2. DIAGRAM OF BRACHYDACTYL X BRACK YDACTYL - - II 
 
 3. DIAGRAM OF HETEROZYGOTE X HOMOZYGOTE - - 12 
 
 4. ANTHER SHOWING SEGREGATION - - - I5 
 
 5. DIAGRAM OF DOMINANT X RECESSIVE, F^ - - 18 
 
 6. DIAGRAM SHOWING THE Fo IN THE ABOVE CROSS - 18 
 
 7. DIAGRAM OF SEX CHROMOSOMES - - - I9 
 
 8. DIAGRAM OF INHERITANCE OF SEX-LINKED CHARACTERS- 23 
 
 9. PEDIGREE OF TORTOISESHELL-COLOURED EYES - - 49 
 
 10. PEDIGREE OF BOLLENBACH FAMILY - - " 5^ 
 
 11. PEDIGREE OF WHITE FORELOCK - - - 62 
 
 12. PEDIGREE OF ALBINIS:\I - - - - 67 
 
 13. BRACHYDACTYLOUS AND NORMAL HANDS - - 79 
 
 14. RADIOGRAM OF A BRACHYDACTYLOUS HAND - - 80 
 
 15. ABNORMAL SEGMENTATION OF FINGERS - - - 84 
 
 16. RADIOGRAPH OF HANDS OF A GIRL IN THE SAME FAMILY 85 
 
 17. SKIAGRAM OF HANDS OF A.T. - - - - 87 
 
 18. PEDIGREE OF HEXADACTYLY - - - - IO4 
 
 19. PEDIGREE OF HEXADACTYLOUS FAMILY - - IO5 
 
 20. PEDIGREE OF COLOUR-BLINDNESS - - - 112 
 
 21. PEDIGREE OF FEMALE SEX-LINKED BLINDNESS - - II 7 
 
 22. PEDIGREE OF MALE SEX-LINKED BLINDNESS - - II7 
 
 23. PEDIGREE OF MALE SEX-LINKED ICHTHYOSIS - - I18 
 
 24. PEDIGREE OF FEMALE SEX-LINKED COLOUR-BLINDNESS- I18 
 
 25. PEDIGREE OF CLEFT IRIS - - - - I20 
 
 26. PEDIGREE OF EARLY DECAY OF TEETH - - 1 24 
 
 27. PEDIGREE OF RIGHT BILOBED Ex\R _ - - 13^ 
 
 28. PEDIGREE OF SMALL PIT IN LEFT EAR- - - I36 
 
 29. PEDIGREE OF IMBECILITY IN FEMALE LINE - - 1 54 
 
 30. IRISH SAILOR TWINS - - - - - 1 82 
 
 31. THEIR FINGER PRINTS - - - - - 1 83 
 
 32. TWINS FROM YORK, PENN. - - - - 1 84 
 
 33. TWINS, MEN -__--_ 185 
 
 34. TWINS, WOMEN, MICHIGAN - _ - - 186 
 
 35. TWIN SISTERS, SWITZERLAND - - - - 1 86 
 
 XUl 
 
HEREDITY AND EUGENICS 
 
 CHAPTER I 
 
 INTRODUCTION 
 
 The central problem of evolution is still the nature 
 
 and causes of variation, while the practical problems 
 
 of eugenics centre about heredity. Variation in past 
 
 ages has already endowed the human race with an 
 
 almost infinite variety of types and characters, 
 
 many of the latter alternative in their inheritance. 
 
 We have only to compare those we know best with 
 
 their relatives and ancestors to realise how minute 
 
 are the resemblances and differences which ma}^ be 
 
 handed on to descendants and collateral lines. These 
 
 are, no doubt, chiefly a matter of biological inheritance, 
 
 though similarity of environment may play a part 
 
 in certain cases. Probably in no other species of 
 
 animal or plant does the number of differences between 
 
 individuals approach the number to be observed in 
 
 man. This is to be expected, because of the mental 
 
 and physical complexity of the human organism; but 
 
 it does not imply greater intrinsic variability than in 
 
 other animals or plants. 
 
 Given this enormous complexity of types in the 
 
 human species, and the inheritance of the innumerable 
 
 differences involved, it follows that the matings of 
 
 the present generation determine the characteristics 
 
 which will be handed on to future generations. A 
 
 knowledge of inheritance must, therefore, form the 
 
 basis of any enlightened attempt to influence the 
 
 I I 
 
2 HEREDITY AND EUGENICS 
 
 future development of the human race, which Sir 
 Francis Galton originally contemplated in the Eugenic 
 Movement. Popular writers frequently venture to 
 deny the importance of heredity to mankind. They 
 are willing to concede its cogency in animals, and, 
 in fact, practical breeders of horses and dogs and other 
 domestic animals rely upon heredity to perpetuate 
 even slight differences in their strains. But they are 
 often unwilling to accept for mankind the principles 
 of heredit}' which they themselves have practised 
 or seen in operation in other animals. Even those 
 w^ho recognise that the principles of heredity must be 
 the same for mankind as regards physical characters, 
 are sometimes inclined to deny that the same laws 
 hold for mental characteristics. 
 
 It is therefore hoped that this book ma}^ help to 
 bring the reader to a truer perspective regarding the 
 nature and meaning of heredity, and its fundamental 
 bearing on the future of the human race. False 
 conceptions regarding inheritance are widespread, 
 and this is not surprising in view of the complexity 
 of the subject and the general lack of education in 
 the biological sciences. Only in the last tw^o decades, 
 through experimental investigations with plants and 
 animals, has any clear road been found through a 
 mass of complicated data. It may now be claimed, 
 however, that the general mechanism of heredity 
 is well understood in many cases, and although, as 
 in every science, complications continually arise with 
 further knowledge, the principles already understood 
 will form a sound basis for future advance. 
 
 It is impossi-ble in this book to consider the whole 
 field of heredity in general terms. For that purpose, 
 reference ma}^ be made to various works on the subject 
 which have appeared in recent years, during which the 
 field of genetics has been an extremely active one. 
 In this w^ork an effort will be made to bring together 
 
INTRODUCTION 3 
 
 the more important data on human heredity which 
 have accumulated chiefly in the last twenty years ; 
 but the general principles will be briefly discussed, 
 and reference will be made to experiments, particu- 
 larly with regard to the higher animals, when the 
 results bear directly upon problems of human heredity. 
 It w^ill be seen that a large amount of information has 
 already been gained regarding the inheritance of a 
 multitude of traits, both physical and mental, in 
 mankind. And perhaps the most surprising feature 
 of these results is the minuteness and variety of the 
 differences which are now known to follow definite 
 laws of inheritance. But it is not necessary to rely 
 upon recent work to establish the minuteness and 
 peculiarity of some of the differences which are 
 inherited in man. Darwin, who was unsurpassed 
 as an observer, and, what is equally important, a 
 collator of the observations of others, has a chapter 
 on blushing in his book, The Expression of the Emo- 
 tions, in which (p. 312) he cites, not only a number 
 of cases of the inheritance of a tendency to blush, 
 but also one in which mother and daughter blushed 
 in the same peculiar manner. The tendency to blush 
 excessively is due to a psychological peculiarity, 
 while the distribution of the area over which a blush 
 spreads must have a physical basis. That gait, 
 gestures, voice, and general bearing are inherited, 
 was recognised in the scientific writings of over a 
 century ago, though imitation may also, of course, 
 play a part here, but this is excluded in some cases. 
 
 Further random examples of inheritance in man 
 will not be cited here, but the reader is invited to 
 consider the mass of evidence found in the body of 
 this book. It is believed that, in this way, any reader 
 who is inclined to doubt the universality and import- 
 ance of heredity in mankind will attain a truer per- 
 spective regarding the whole matter. But certain 
 
4 HEREDITY AND EUGENICS 
 
 misconceptions need to be pointed out first. The 
 question is often asked whether heredity or environ- 
 ment is more important in connection with develop- 
 ment. But the question cannot rightly be asked 
 in this way, because any organism is the result of 
 continuous complicated reactions and interactions, 
 not onl}^ between the developing germ and its environ- 
 ment, but also between the different parts of the 
 organism itself. Moreover, it is quite incorrect to 
 assume that the organic germ and the environment 
 mutually react with each other in any simple way. 
 A particular change in the environment ma}^ con- 
 spicuously affect one part of the developing organism 
 without visibly affecting other parts. Thus Stockard 
 (1909) showed that when magnesium chloride is 
 added to the sea water in which certain fish embryos 
 are developing, c3xlopean fishes are produced, with 
 one median eye instead of two lateral ones. This is 
 a surprising reaction of the organism, and more 
 particularly of the nervous system, to a definite 
 environmental stimulus.* Some differences in the 
 environment will therefore produce very marked 
 effects on the developing organism. 
 
 On the other hand, organisms developing in the 
 same environment may show marked differences, 
 because they have inherited different characters. 
 Tw^o hen's eggs in an incubator, under the same con- 
 ditions of temperature, moisture, etc., may develop 
 birds, one with a rose comb and the other with a 
 single comb, or one with white feathers and the other 
 with brow^n. Obvioush^ the environment is not a 
 differential, but the difference was in the original 
 eggs and is inherited from the previous generation. 
 
 * Stockard 's result has recently been shown to be due to 
 differential destruction of the nerve plate in the embryo, the 
 destruction beginning at the anterior end, as in Child's experi- 
 ments with potassium cyanide. 
 
INTRODUCTION 5 
 
 No one would suggest that even if the eggs were 
 incubated at different temperatures the single comb 
 would be altered to a rose comb. 
 
 Clearl}', then, some characters are produced by an 
 environmental stimulus and others are determined 
 by inheritance, although in both cases interaction 
 of organism and environment takes place in the 
 development of the character. A given character 
 may occur in either or both categories. Thus fascia- 
 tion or flattening of the stem in plants usually results 
 from over-nutrition and is then, as a rule at least, 
 not inherited at all. But in Celosia cristata, the 
 coxcomb of gardens, extreme fasciation is a specific 
 character, distinguishing this form from C. pluniosa. 
 Again, thickening of the epidermis or formation of 
 corns results from friction of the skin of the hands or 
 feet, and is not inherited. But keratosis is an inherited 
 condition in which there is abnormal thickening of 
 the skin without any excessive friction. 
 
 When a new character appears through a variation, 
 the first question one asks is whether it is inherited. 
 It is impossible to determine this with certainty 
 except by experiment — i.e., by breeding from the new 
 type. If it is inherited, one must conclude that a 
 germinal change has taken place, leading to the 
 production of a new character, or at least that a 
 germinal rearrangement has taken place, making 
 possible the appearance of the new^ character. If 
 it is not inherited, then the conclusion is that a 
 modification has been impressed on the organism 
 by some feature of the environment.* The question 
 to ask, then, is not whether heredity or environment 
 
 * The possibility of the inheritance of acquired characters has 
 not been considered here, because if it ever occurs in mankind 
 it is probably too slow in its action to affect the practical problems 
 of eugenics. The subject has been discussed from an evolu- 
 tionary point of view elsewhere (Gates, 192 1, chap, viii.-xii.). 
 
6 HEREDITY AND EUGENICS 
 
 is more important in the ontogeny of any character, 
 but whether a difference (variation) which appears 
 in an organism is due primarily to a difference in the 
 environment or a difference in heredity {cf. Sumner, 
 1922). 
 
 This leads us to emphasise a point w^hich is not 
 always recognised — namely, that the relation between 
 the organism and its environment is not the simple 
 and direct relation between two reacting chemical 
 substances — it is rather one of stimulus and re- 
 sponse. It is, moreover, clear that not all elements 
 of the environment are equally effective in modifying 
 the organism. For example, a change in the light 
 may have a striking effect on the development of 
 one organism and no appreciable effect on another. 
 The relations of an organism to its environment are 
 therefore extremely complex, and can only be under- 
 stood after elaborate analysis. But the higher 
 organisms, and particularly man, have many regula- 
 tory mechanisms which enable him to triumph over 
 extreme variations in the environment without being 
 vitally affected b}^ them. This, with his weapons 
 and his intelligence, has enabled mankind to people 
 the four corners of the earth in almost everv extreme 
 of climatic conditions w^here organisms can live at all. 
 From a eugenic point of view it is to be remembered 
 that while hereditary differences of all kinds are per- 
 petuated in all conditions, yet optimum conditions 
 are desirable for the full expression of the characters 
 inherited by the organism. From this it follows 
 that those who insist upon the importance of heredity 
 in perpetuating good stocks should, at the same time, 
 realise the desirability^ of creating an environment 
 in which the best ph3^sical, mental, and moral qualities 
 of the individuals can find free expression. 
 
 Before proceeding further it may be well to point 
 out that whereas heredity w^as formerly defined or 
 
INTRODUCTION 7 
 
 measured by the degree of resemblance between 
 parents and offspring, this treatment of the subject 
 will no longer suffice. Thus Brooks (1906) says, 
 C" So far as the word is used inductively in biology, 
 heredity is the resemblance of child to parent, of 
 offspring to ancestor, while the difference between 
 parent and child is called variation." The study 
 of alternative inheritance, which appears to be the 
 most usual form of heredity, has made it necessary 
 to revise such a definition of heredity, as well as our 
 outlook with regard to its incidence. It has now 
 become a commonplace of observation that the 
 differences between organisms, as well as their 
 resemblances, are often inherited, i If a tall is crossed 
 with a dwarf variety, we know that usually the second 
 generation will inherit tallness and dwarfness — 
 the parental differentiating characters — in a definite 
 proportion, and that certain of the tall individuals 
 will go on transmitting dwarfness. We may even 
 cross two white varieties of plants or two albino 
 animals, externally alike, and obtain coloured off- 
 spring. Yet we know that the colour in this case is 
 not the result of variation. One of the necessary 
 elements in its production has been inherited from 
 each parent, though neither possesses both. In 
 such instances invisible (probably nuclear) differences 
 have been inherited which, when combined, produce 
 a striking externalised difference. Hence it is neces- 
 sary, in speaking of inheritance, to recognise that 
 both similarities and differences may be inherited, 
 the one quite as truly as the other. Some of the 
 differences, particularly the quantitative ones, which 
 appear in offspring may, then, be the result of varia- 
 tion, germinal or otherwise; but many of them will 
 be the result of inheritance. 
 
CHAPTER II 
 
 THE GENERAL ASPECTS OF HEREDITY 
 
 Many vague conceptions of heredity were formerly 
 held, and much ink was unprofitably spilled in an effort 
 to explain or elucidate inheritance in the absence 
 of adequate experiment. Human inheritance par- 
 ticularly has been the subject of innumerable crude, 
 unscientific conceptions such as " failure " of 
 inheritance when a particular trait does not appear 
 in every generation, a belief in maternal impressions, 
 or scepticism regarding the inheritance of mental 
 traits. The scientific investigation of heredity may 
 almost be said to have begun with Mendel's studies 
 of single characters in garden peas, since the results 
 of the early hybridisers were so contradictory and 
 confused — owing partly to an unfortunate choice of 
 material for crossing and partly to an unsuitable 
 method of experiment — that they never led to a 
 consistent point of view on which future progress 
 could build. The rediscovery of Mendel's principle 
 of segregation in 1900 therefore marked the beginning 
 of an era in the study of heredity. It has become 
 progressively clearer that while mass statistics of 
 resemblances may furnish useful information where 
 no other is available, yet such data cannot furnish 
 a basis for an understanding of the hereditary 
 process. The experimental analytical method is 
 necessary here, as in other fields of biology. The 
 results of the experimental method, however, can 
 be and have been applied to genealogical pedigrees 
 
 of inheritance in man with illuminating results. 
 
 8 
 
 nOFERTY LIBRARY 
 
THE GENERAL ASPECTS OF HEREDITY 9 
 
 This method has, of course, certain definite limitations, 
 since evidence is available only from such marriages 
 as have taken place. But in many cases of simple 
 Mendelian inheritance this evidence is quite as clear 
 and unequivocal as though actual experimental 
 crosses had been made for the purpose of determining 
 the method of inheritance. 
 
 The number of characters in man which are now 
 known to follow a Mendelian t^'pe of inheritance 
 is surprisingly large. It is therefore desirable to 
 elucidate briefly the principles of Mendelian inherit- 
 ance for those who are not already familiar with the 
 matter. An elementary treatment of the subject 
 is to be found in Punnet t's Mendelism. While thus 
 emphasising the importance of Mendelian heredity", 
 particularly as regards the inheritance of abnormali- 
 ties in man, we wish also to stress the value of 
 biometric studies of inheritance, for there are many 
 characters in w^hich this is the only method of analysis 
 which can -be applied. The two methods are com- 
 plementary and are becoming more and more closely 
 interwoven in the study of heredity. On the one hand, 
 experimentalists are recognising the advantages of 
 a mathematical anal3^sis of their results, while on 
 the other, biometricians realise the advantages of 
 material under experimental control. The inter- 
 action of both methods produces the ideal result, but 
 this is, of course, not always possible. The view 
 taken here is that while Mendelian hereditv is verv 
 common in mankind, especially as regards the inheri- 
 tance of abnormalities, yet it is by no means universal. 
 Many quantitative characters, and perhaps racial 
 characters, will probably be found not to follow simple 
 laws of inheritance involving fixed germinal units. 
 
 As an example of Mendelian inheritance let us 
 consider brachydactyly or short fingers in man, the 
 digits having two joints instead of three. This condi- 
 
lo HEREDITY AND EUGENICS 
 
 tion is dominant to the normal, which is spoken 
 of as recessive. Brachydactylous individuals have 
 always married normals. Persons showing this trait 
 have therefore always been the children of one normal 
 and one abnormal parent. They are therefore hybrid 
 or heterozygous in nature as regards this character, 
 and, since they are brachydactylous in appearance, 
 this condition is said to be dominant to the normal. 
 Now the essential feature of Mendelian behaviour 
 is that the factors or determiners for such a pair of 
 characters as normal and brachydactylous fingers 
 separate in the formation of the germ cells, so that 
 half the germ cells of a brachydactylous person 
 who had one normal parent will carry the factor 
 
 Germ cells. Unions oF Germ cells oF 
 
 \ ■■' SO >i B ^.^^^ germ cells oFFspring. 
 
 parent 7 """--^ ^"""--^ __— 
 
 ' 50 Z n ^ B(n).(50%) — 
 
 Normal 
 
 n n (50 X) 
 
 parent. | --■^.,^ ^,^--^'^ ' ' 50 y. n 
 
 Fig. I. — Result of Cross between Heterozygous 
 Brack YDACTYL and a Normal Parent. 
 
 for brachydactyh' and half will carry the factor for 
 normal fingers. If such a person marries a normal 
 individual, all of whose germ cells are therefore 
 carrying the factor for normal fingers, then, on the 
 average, half the children will be brach3"dactylous 
 and half normal, for the chances for the germ cell 
 matings — (i) normal x normal and (2) normal X 
 brachy dactyl — are equal. The result will be clear 
 from the accompanying diagram (Fig. i). 
 
 Hence we see that as long as matings of brachy- 
 dactyls wdth normals continue, half the children will, 
 on the average, be heterozygous brachydactyls 
 (transmitting this character to half their offspring), 
 while the other half of the children will be pure normal. 
 
THE GENERAL ASPECTS OF HEREDITY ii 
 
 and transmit only the normal condition to all their 
 offspring. In other words, the heterozygous domi- 
 nants will continue to produce both types when 
 mated to normals, while the normals derived from such 
 a cross, being recessive, have entirely lost the brachy- 
 dactylous condition (or rather never had it), and will 
 therefore have only normal offspring even if two such 
 normals from a brachydactylous cross mate together. 
 For a full discussion of brachydactyly, see p. 78. 
 
 Many abnormalities in man are simple dominants 
 and will therefore be inherited in this manner. 
 
 In order to make clearer the nature of Mendelian 
 heredity, let us consider the other types of mating 
 which commonly occur in organisms showing a single 
 
 Heterozygous 
 brachydactyl 
 parent. 
 
 Heterozygous 
 brachydactyl 
 parent. 
 
 Germ cells 
 
 SO X B 
 
 Fi hybrids (zygotes) 
 25 y. B B 
 
 25 y. ..B \75X 'l^/Xcecty, 
 
 25 % B n 
 
 25 y. n. n 25 y^ normal 
 
 Fig. 2. — Results of Cross between Two Heterozygous 
 
 Brachydactyl Parents. 
 
 difference. If tw^o such individual organisms which 
 are pure or homozygous are crossed, the first hybrid 
 generation (written briefly Fj) will show only the 
 dominant character. But if two of these F^ hybrids 
 are intercrossed, their offspring will number on the 
 average three dominants to one recessive. Thus, 
 in a marriage between two heterozygous brachy- 
 dactyls, three-fourths of the children would be ex- 
 pected to be brachydactylous. The reason for this 
 will be understood from the following diagram (Fig. 2). 
 The four possible combinations of the two types 
 of germ cells will occur with equal frequenc}^ and 
 since the factor for brachydactyly is absent from only 
 
12 
 
 HEREDITY AND EUGENICS 
 
 one of the four combinations, it follows that only 
 25 per cent, of the offspring will be likely to have 
 normal lingers. Of the other 75 per cent, which are 
 brach3'dact3^1ous, two out of three will be heterozygous 
 {i.e., with half their germ cells of each type), while 
 one-third will be homoz^^gous, carrying the determiner 
 for brach^'dactyl}' in all their germ cells. 
 
 We may similarh' consider the case where a hetero- 
 zygous brach3'dactyl marries a homozygous brachy- 
 dact\d.* 
 
 From the diagram (Fig. 3) it will be seen that the 
 offspring from such a mating would be all brachy- 
 
 Heberozygous 
 brachydacbyl 
 parent. 
 
 Germ cells 
 50% B 
 
 ZvQotes 
 
 /homozygous 
 
 brachydacbyl 
 
 parent. 
 
 50% B 
 
 Fig. 3. — Theoretical Results of Cross between a 
 Heterozygous and a Homozygous Parent. 
 
 dact\dous, half of them heteroz3^gous and half homo- 
 Z3^gous. So long as the former continued mating 
 wdth homoz3^gous brach3^dact3ds the normal condition 
 would be completeh" suppressed, and the strain would 
 appear to be pure for brach3^dactyly. But if in 
 any generation two heterozygous individuals mated, 
 there would be one chance in four of the recessive 
 condition reappearing. The sudden appearance of 
 a reversion or throw back in a pedigree strain, for 
 example, of cattle, is no doubt often to be accounted 
 for in this wa3^ A recessive character ma3^ thus be 
 
 * There is some evidence that the homozygous brachy-phalan- 
 gous (related) condition is non-viable and therefore cannot exist 
 (see p. 90). 
 
THE GENERAL ASPECTS OF HEREDITY 13 
 
 carried in the germ plasm of a strain for many genera- 
 tions, only to crop out again when a chance mating 
 of two heterozygous individuals takes place. 
 
 It is not known how or when brachydactyly origi- 
 nated, but it probably occurred centuries ago, and pre- 
 sumably arose in the first instance as a mutation — i.e., 
 a sudden and probably spontaneous germinal change.* 
 
 Fortunately, the segregation which takes place in 
 germ-cell formation can now be referred to definite 
 elements in the cells — namely, the chromosomes. 
 These are the elements of the nucleus whose con- 
 stancy in number and shape for each species of animal 
 and plant is one of the remarkable features of organic 
 structure. In the complicated process of mitotic 
 nuclear division, w^hich happens whenever cells 
 divide in the growth and development of the organism, 
 the essential fact is that they are split lengthwise, 
 so that each daughter cell contains in its nucleus the 
 longitudinal halves of every chromosome. Although 
 these bodies seem to merge in the resting nucleus 
 into a mass in which the outlines of the separate 
 chromosomes are lost, yet there are cases in which 
 the outlines can still be traced, each chromosome 
 forming a separate compartment or vesicle of the 
 nucleus. There is also evidence that the parts of 
 the various chromosomes maintain their special re- 
 lationships throughout the period between one 
 division and another even when visible boundaries 
 are lost, or, at any rate, that the}^ reassemble with 
 the same arrangement as they disappeared. There 
 is something, not at present understood, which main- 
 tains the unity of the chromosome as a persisting 
 structure, and determines the constancy of its relative 
 size and shape during mitosis in the various parts of 
 the organism. 
 
 * For a discussion of the causes and nature of Mutation, see 
 Gates (1915, chap. ix.). 
 
14 HEREDITY AND EUGENICS 
 
 The organism begins its development from the 
 union of the nuclei of egg and sperm. But when 
 this union happens it is not a mere interminghng 
 of two fluid substances, for the chromosomes, which 
 are highly viscous in the condensed condition, 
 maintain their separate identity ; and in the subse- 
 quent nuclear divisions they frequently arrange them- 
 selves in pairs, each pair consisting of one chromo- 
 some of paternal origin (from the male germ cell) 
 and one of maternal origin (from the female germ 
 cell). In man}^ animals and plants the various pairs 
 are distinguishable from each other in size or shape. 
 The chromosomes may therefore be said to possess 
 individualit}' and to show genetic continuit}^ from 
 generation to generation. 
 
 When the germ cells of an organism undergo 
 maturation as the organism develops, the chromo- 
 some number in them is reduced to one-half. The 
 essential feature of this complicated process is the 
 separation of the pairs of chromosomes which are 
 characteristic of the somatic nuclei, so that the nuclei 
 of the eggs and sperms receive one member of each 
 pair and hence have half as many chromosomes as 
 the somatic cells.* Half the germ cells will thus 
 receive one member of each pair, and half the other. 
 This maturation process has been studied in great 
 detail in hundreds of plants and animals, as well as 
 in man (see p. 20). In the separation of pairs in the 
 reduction divisions there is free assortment of the 
 chromosomes. There are many reasons for believing 
 that the chromosomes are the basis of Mendelian 
 inheritance, and that the segregation of characters, 
 which IMendel's experiments indicated took place 
 in the formation of the germ cells, really depends 
 on the separation of the chromosome-pairs in the 
 reduction divisions. 
 
 * Further complications of this process need not concern us here. 
 
THE GENERAL ASPECTS OF HEREDITY 15 
 
 -^t^:' 
 
 That segregation of factors really takes place during 
 meiosis (the period during which chromosome reduc- 
 tion occurs) has been shown by the formation of two 
 types of pollen grain in certain hybrid rice plants. In 
 these Fi hybrids half the pollen grains contain starch 
 grains, like the pollen grains of one parent, while the 
 other half contain no starch. Fig. 4, from a section 
 of an anther treated 
 with iodine, shows 
 the two types of pol- 
 len grains scattered 
 in equal numbers 
 through the anther. 
 
 Thus in an organ- 
 ism which is hetero- 
 zygous for one pair 
 of characters, say 
 short hair (domin- 
 ant) or long " An- 
 gora " hair (reces- 
 sive) in guinea-pigs, 
 the Fj hybrid ani- 
 mals will have short 
 hair, and all their 
 cells w^ill contain a 
 pair of chromosomes 
 which differ in that 
 one chromosome 
 contains the deter- 
 miner for short coat, 
 
 while its mate contains the determiner for long 
 coat. When the germ cells of this guinea-pig are 
 formed, this pair of chromosomes, like the other 
 pairs, is separated, and half the eggs or sperms, 
 as the case may be, get the chromosome with 
 the determiner for short hair, while the other half 
 receive its mate containing the determiner for long 
 
 Fig. 4. — Photomicrograph showing 
 Segregation of Pollen Types in a 
 Rice Hybrid. (After F. R. Parnell.) 
 
i6 HEREDITY AND EUGENICS 
 
 hair. From this it follows, as shown in the diagram 
 in Fig. I (p. lo), that three-quarters of the individuals 
 in the next generation (Eg) will have short hair, the 
 remaining quarter having Angora hair. This is because 
 when the eggs and sperms unite in fertilisation, half 
 the eggs and half the sperms will contain the chromo- 
 some determining short hair, while the other half 
 carry its mate with the determiner for long hair. 
 The fertilised eggs will then be of three types : ( i ) con- 
 taining a pair of chromosomes, both of which carry 
 the determiner for short coat. When these eggs 
 develop into organisms which can be bred together, 
 they can obviously give only short-coated offspring. 
 They are homozygous dominants. (2) These ferti- 
 lised eggs will contain a pair of chromosomes with 
 determiners respect ivety for long and short coat, and, 
 according to the laws of chance combination, they will 
 be twice as numerous as the last. They are the 
 heteroz3^gous dominants, their bodies indistinguish- 
 able from the pure dominants (when dominance is 
 complete), but their germ plasm as well as all their body 
 cells containing an '' unequal " pair of chromosomes 
 which will separate as in the E^ to produce the next 
 generation. These two classes of F2 animals, together 
 making up three-quarters of the offspring, are visibly 
 short-coated. (3) In the third class of fertilised eggs 
 both chromosomes of this pair will contain the 
 determiner for long coat. They will develop into 
 long-coated animals, their body cells and germ cells 
 will all contain the descendants of this pair of chromo- 
 somes, and they wdll give long-coated offspring w^hen 
 bred together. They are the homozygous recessives, 
 and because they result from chromosome recom- 
 binations taking place according to chance, they 
 are as numerous as the first class, the homoz^^gous 
 dominants. 
 
 The history of the chromosomes in organisms was 
 
THE GENERAL ASPECTS OF HEREDITY 17 
 
 worked out quite independently of genetic experi- 
 ments, but they furnish precisely the mechanism 
 required to explain Mendelian behaviour, although 
 the main facts of their history were known before the 
 rediscovery of Mendel's laws in 1900. The number of 
 freely assorting groups of Mendelian characters in a 
 species should therefore be the same as the number 
 of pairs of chromosomes, and the experimental work, 
 particularly with the fruit fly Drosophila, clearly 
 indicates that this is the case. 
 
 Differences in the chromosomes in crossed races 
 appear to determine the different types and combina- 
 tions of characters which arise in the offspring. It 
 thus appears that Mendelian differences in general 
 have originated as mutations, probably through an 
 alteration in a portion or locus of a chromosome. That 
 the differences which arise in this way are inherited 
 as Mendelian factors results, then, from the manner 
 of distribution of the chromosomes in the reduction 
 divisions, when the nuclei of the germ cells are formed. 
 Mutations seem to arise in the germ plasm at relatively 
 infrequent intervals. They may then be handed 
 down to later generations for an indefinite period. 
 In some cases the same mutation appears indepen- 
 dently more than once. 
 
 Let us now consider the inheritance of a recessive 
 Mendelian character. Feeble-mindedness ma}'" be 
 taken as an example, for it appears to be generally 
 inherited as a simple Mendelian recessive. Con- 
 structing a diagram (Fig. 5), we see that all the 
 germ cells of a feeble-minded person will carry the 
 factor for feeble-mindedness, since the character 
 is recessive. 
 
 If mated with normal, the children will all be normal 
 for the same reason, and the defect will seem to have 
 disappeared. But these normals will all be hetero- 
 zygous, carrying the defect for feeble-mindedness in 
 
i8 
 
 HEREDITY AND EUGENICS 
 
 half their germ cells. If two such persons mate 
 together, it will be seen from the following diagram 
 (Fig, 6) that half the germ cells of each will be normal 
 and half carr}- the defect. 
 
 This will give four combinations of germ cells 
 occurring with equal frequency. Three of them, or 
 
 FeeblemindecA 
 parent 
 
 Germ cells 
 all F 
 
 Cro 
 
 Normal 
 parent. 
 
 all N 
 
 ss 
 
 N(F) 
 
 Fig. 5. — Result of Cross between a Dominant and a 
 Recessive Character in F^. 
 
 on the average three-fourths of the offspring, will 
 be normal, the other fourth will be feeble-minded. 
 Moreover, of the normals tw^o-thirds will be carrying 
 feeble-mindedness as a recessive character while the 
 other third will be untainted. Further, it is clear 
 
 Heterozygous 
 parents. 
 
 Germ cells. 
 
 ^ 50 % N 
 
 N(F) <; 
 
 ~-^ 50 % F 
 
 
 ^ 50 % N 
 
 Unions oF germ cells. 
 25 X N N 
 
 25 % N F 
 
 25 % N F 
 
 ^ (F) ^^ ^^^"'^_— — ^^ 25 % r F 
 
 50 % F 
 Fig. 6. — Results of above Cross in F., 
 
 that if the Mendelian behaviour is strictly adhered 
 to two feeble-minded parents can have only feeble- 
 minded offspring. The exceptions to this rule, if 
 they exist, are so few as to be negligible. For a further 
 account of feeble-mindedness see p. 149. 
 
 There is no doubt that the germ plasm of any human 
 
THE GENERAL ASPECTS OF HEREDITY 19 
 
 strain contains numbers of such recessive characters, 
 which may be transmitted for generations without 
 appearing, until union with an individual carrying 
 the same recessive character may ultimately bring 
 it out in some (25 per cent.) of the offspring. The 
 presence of similar, undesirable recessive characters 
 in the germ plasm is thus the chief danger from 
 inbreeding or intermarriage of cousins. The main 
 features of a recessive character are, then, that it 
 disappears in the first generation of a cross between 
 a pure dominant and a pure recessive, while it re- 
 appears in about one-quarter of the offspring of two 
 
 Germ cells X 
 
 XX XY 
 
 Fig. 7. — Diagram to show the History of the Sex 
 
 Chromosomes. 
 
 individuals heterozygous for the character. It will 
 appear in about half the offspring of matings between 
 a heterozygous normal and a (pure) recessive. 
 
 Another type of Mendelian character, which in its 
 inheritance follows exactly the distribution of the sex 
 chromosomes, is known as sex-linked inheritance. 
 Such characters evidently depend for their origin 
 upon mutations occurring in the sex chromosomes. 
 As an example of this in man we may consider colour- 
 blindness. The nature of this inheritance-mechanism 
 will be clear from the following diagram (Fig. 7), 
 showing the history of the sex chromosomes as they 
 appear to behave in man. 
 
20 HEREDITY AND EUGENICS 
 
 The history of the sex chromosomes has been clearly 
 shown in many animals, and in the fruit fly Drosophila 
 a large number of sex-linked mutations, determined 
 apparently by changes in loci of the X-chromosome, 
 have been studied. 
 
 A brief account is first necessary of the sex 
 chromosomes as they apparently exist in man. 
 Although many observations have been made on the 
 subject, the facts are not 3'et known with certainty; 
 but the details are gradually becoming clear. It 
 appeared at one time that the negro had 24 chromo- 
 somes and the white man 48, but this apparent 
 difference ma}^ have been due to clumping of the 
 chromosome pairs in the process of fixation, so that 
 they looked like single chromosomes. Also in the 
 earlier accounts one or two more chromosomes were 
 found in the female than in the male, but later investi- 
 gators are agreed that there is a pair (XY) of sex 
 chromosomes which are distinguishable b}^ their shape 
 and behaviour from the other chromosomes. It 
 appeared from the studies of Guyer (1910, 191 4) 
 and of Montgomery (191 2) on human spermato- 
 genesis that the male negro possesses 22 chromosomes, 
 including 2 sex or accessory chromosomes. Mont- 
 gomery found that the accessories were irregularly 
 distributed in the reduction divisions. It was inferred 
 that the female number was 24. Von Winiwarter 
 (191 2), however, studying members of the white race, 
 found 47 chromosomes in man and 48 in woman 
 (oogonial divisions). Farmer, Moore and Walker 
 (1906), in examining pathological tissue (somatic cells) 
 presumably of white people, found usually 32 chromo- 
 somes, while Wieman (191 3) counted 33 to 38 chro- 
 mosomes in a human embr3^o the parentage of which 
 is not stated. More recently Wieman (191 7) de- 
 scribes human spermatogenesis with 24 chromosomes 
 in both negro and white, including an XY pair of sex 
 
THE GENERAL ASPECTS OF HEREDITY 21 
 
 chromosomes which divide in the first reduction 
 division and segregate in the second, unUke the other 
 chromosomes which segregate in the first and divide 
 in the second. Still more recently, Painter (1921), 
 in a preliminary account of spermatogenesis in both 
 whites and negroes from Texas, finds approximately 
 48 chromosomes in both, including an XY pair of 
 sex chromosomes. This is a partial confirmation of 
 Von Winiwarter. It might appear that all these 
 investigators were right in their determinations of 
 numbers, and that human individuals exist with 
 24 (2X or diploid), about 36 (3X or triploid), and 48 
 (4X or tetraploid) chromosome numbers. The chro- 
 mosomes of all mammals are, however, notoriously 
 difficult to deal with, and it seems more likely that 
 clumping may have given rise to an appearance of 
 lower numbers. The existence of triploid and tetra- 
 ploid races of mankind would, however, be in accord 
 with their occurrence in man}^ species of plants and 
 animals (see Gates, 191 5, pp. 195 ff.). In an}^ case, 
 it seems clear that the higher number (48) of chromo- 
 somes is present at least in some men, and that an 
 XY pair of chromosomes exists in the male. 
 
 It may be pointed out that the number 48 is a rather 
 high one, and is approximately double the number 
 found in some mammals.* It has, therefore, probably 
 originated at some time by sudden doubling of the 
 chromosome number, as this was originally shown 
 to take place when CEnothera gigas appears as a 
 mutation from CE. Lamarckiana (see Gates, 191 5, 
 pp. 118, 209). Whether this doubling to produce 
 48 chromosomes occurred in some of the races of 
 mankind, or earlier in his ancestry, remains to be 
 determined. In the matter of relationships and 
 phylogeny, as has recently been shown, in the varieties 
 
 * Painter (1922) reports finding 54 chromosomes, including 
 an XY pair, in a ring-tail monkey. 
 
22 HEREDITY AND EUGENICS 
 
 of wheat, and in a number of other instances, the 
 determination of chromosome numbers and shapes is 
 of great value. 
 
 Returning to the question of human chromosomes, 
 there are many difficulties attending their study, so 
 that neither their total numbers nor the behaviour 
 of the sex chromosomes can be regarded as settled. 
 Von Winiwarter found an unpaired X chromosome 
 in the male, while later workers are agreed in finding 
 an XY pair. In either case, the mechanism of sex 
 determination and the inheritance of sex - linked 
 characters is essentially the same, so it will be assumed 
 that the later work is correct in describing an XY 
 pair. This type of sex -determining mechanism is 
 well known in some of the insects. It may be briefly 
 described as follows (see Fig. 8). Males have an 
 unequal XY pair of sex chromosomes, the X usually 
 being larger than the Y, while females have a pair 
 of X chromosomes (XX). In the spermatogenesis 
 of the male, the X passes undivided into half the 
 sperm, w^hile the other half receive the Y. Since the 
 females have a pair of X chromosomes, all the eggs 
 before fertilisation will contain one X. In fertilisa- 
 tion there is an equal chance that a sperm containing 
 an X will enter an egg, and produce a female, or, that 
 a sperm bearing a Y will function and so produce 
 a male. Through this general mechanism an approxi- 
 mation to equality of the sexes is maintained. But 
 it is now known that there are various conditions 
 which may come in to disturb this tendency to equality 
 in numbers of the sexes. 
 
 We are now in a position to understand the 
 mechanism of inheritance of sex-linked characters, 
 such as colour-blindness, in man. 
 
 The diagram shows only the sex chromosomes, 
 which are XX in the female and XY in the male. 
 
 The underlined X is carrying the factor for 
 
THE GENERAL ASPECTS OF HEREDITY 23 
 
 colour-blindness. The male, XY, would therefore be 
 colour-blind. Mated with a normal woman, their 
 male children would all be normal. The X chromo- 
 some of the father, however, goes to all his daughters, 
 
 Parents 
 
 XX 
 
 X Y 
 
 Germ cells 
 
 XX X Y 
 
 Zygotes 
 
 XX XYcf 
 
 OXX 
 
 Germ cells 
 
 XX XY 
 
 Zygotes OXX OXX XYCJ" XYd' 
 
 Germ cells 
 
 XX 
 
 XY 
 
 Zygotes 
 
 ^XX XX^ XYC? XYC/ 
 
 Fig. 8. — Diagram to illustrate the Inheritance of Sex- 
 Linked Characters through the X-Chromosome. 
 
 who are all, therefore, transmitters of the defect to 
 future generations. With a husband who is normal, 
 they will transmit the defect to half their children 
 of both sexes, as shown in the next two lines of the 
 
24 HEREDITY AND EUGENICS 
 
 diagram (Fig. 8), but onl}' the sons will be colour- 
 blind. 
 
 The last three lines show how a colour-blind father 
 and a heteroz3'gous mother will have a family in which 
 half the daughters show the defect and half the sons 
 will show it.* If the mother were homozygous for 
 colour-blindness and the father also carried it, then 
 all the children would be colour-blind. There is no 
 instance of a colour-blind father transmitting the 
 condition to the next generation, except in connec- 
 tion with a mother who transmits it. This criss- 
 cross type of inheritance is more complicated than 
 simple Mendelian behaviour in which both parents 
 take the same part in inheritance, but it is simply 
 explained by assuming the behaviour to be due to the 
 transmission of a defective X chromosome. 
 
 It appears, then, that in all these cases the fact 
 that the differences are inherited as Mendelian factors 
 results from the manner of distribution of the chro- 
 mosomes in the reduction divisions at the time the 
 germ cells of the organism are matured. It may be 
 that some of the fundamental resemblances betw^een 
 related organisms are inherited in a different wa}^ 
 Since in experimental breeding it is only possible 
 to study directl}^ the inheritance of differences, 
 evidence concerning the process of inheritance of 
 resemblances must necessarily be indirect and closel}' 
 wrapped up with development itself. 
 
 We ma}^ now consider some of the differences 
 appearing in man which so often follow one of these 
 types of Mendelian behaviour. While dominance 
 is very common, especiall}^ in connection with abnor- 
 malities, it is not by any means universal. There 
 is, for instance, no dominance in such a character 
 as skin colour, but the first generation is intermediate 
 
 * There appear to be some irregular cases in which colour- 
 bhndness shows in a heterozygous woman. 
 
 fnffparr librart 
 
 19, C. Statt Colkj^ 
 
THE GENERAL ASPECTS OF HEREDITY 25 
 
 and back-crosses will further dilute the colour. It is 
 probable that in organisms at large complete domi- 
 nance is the exception rather than the rule. Why 
 dominant mutations should be so numerous in man 
 is at present quite unexplained. In Drosophila, 
 only about a dozen dominant mutations have ap- 
 peared among some 300, all the rest being recessive, 
 and they are equally uncommon in other organisms. 
 
 The biological characters or differences observable 
 in the human race and for the most part inherited 
 include not merely the more striking racial divergen- 
 cies, but also the innumerable structural and mental 
 or temperamental differences that we see in the 
 individuals of any population, however " pure " the 
 race. Colour of hair and eyes, height and size of 
 various parts of the body (for there is some evidence 
 that these may be independently inherited for different 
 segments), conformation of the head and features, 
 size and shape of eyes, e-ars, nose, mouth, hands, and 
 feet — there is good reason to believe that the element 
 of inheritance enters largely into the perpetuation 
 of a host of such differences as well as others more 
 minute. Everyone can cite, from his own experi- 
 ence, cases of such essentially phj^siological traits as 
 longevity and early baldness* or greyness "running 
 in families." 
 
 * In an interesting study of the inheritance of baldness, by 
 Dorothy Osborn (1916), she tabulated the results for twenty-two 
 families and reached definite conclusions. Baldness is found to 
 be a sex-limited trait, being inherited as a dominant character 
 from father to son. In the woman it acts as a recessive, and 
 may be transmitted as such, only appearing as baldness when 
 present in the duplex (homozygous) condition. This may 
 explain the greater rarity of baldness in women. Baldness is 
 frequently associated with progressive decrease in the concentra- 
 tion of thyroid in the blood (see pp. 211 ^.). This view of early 
 baldness as a sex-limited trait is borne out by data of Sedgwick 
 
 (1863). 
 
 It is interesting to note in this connection that Duerden (191 8, 
 
26 HEREDITY AND EUGENICS 
 
 Differences in reactions to serums and to various 
 diseases, as well as other evidence, indicates the 
 existence of corresponding chemical and constitutional 
 differences between individuals. The inheritance of 
 such differences is now commonly recognised. Only 
 a few years ago, in the Law Courts, the disposal of a 
 large estate turned upon a peculiar conformation 
 of the ear occurring in the father and the supposed 
 son.* 
 
 A considerable bod}^ of detailed evidence concerning 
 heredity in man has accumulated in recent years. 
 It is not my purpose to attempt anything like a 
 complete citation of this work, but it may be of 
 interest to enumerate some of the studies which have 
 been made on this subject; for our knowledge of 
 the inheritance both of normal and abnormal traits 
 in man must always form the chief basis for eugenic 
 action. 
 
 1919) has shown that in crosses between the North African and 
 South African ostrich the bald spot of the former behaves as a 
 simple dominant character not sex-linked. In the chicks the 
 head is covered with a bristly down, but in the North African 
 birds this gradually falls out during the first few months and is 
 not replaced by feathers. 
 
 * On the other hand, a case is cited (Jenks, 1916), with some 
 evidence of authenticity, in which a girl of Swedish ancestry, 
 whose ancestors of both sexes had been accustomed for many 
 generations to wear earrings, was born with a hole in the proper 
 position in each ear-lobe. That such cases of inheritance of a 
 mutilation are admittedly rare does not necessarily prove that 
 they are non-existent. The fact that (Windle, 1891) a fissure 
 sometimes occurs in the sulcus intertragicus of the ear, as an 
 arrest of development, scarcely seems an adequate explanation 
 of the above case; but in an instance cited by Windle where the 
 mother tore the lobule of her left ear when eight years old, and 
 afterwards had eight children, one of whom, a boy, had cleft lobule 
 of the left ear, there is obviously no inheritance involved. 
 
CHAPTER III 
 
 INHERITANCE OF PHYSICAL CHARACTERS 
 
 IN MAN 
 
 Stature 
 
 Two of the earliest subjects studied in connection 
 with human heredity were naturally enough stature 
 and eye-colour. Galton dealt with these traits in his 
 Natural Inheritance. I have pointed out elsewhere 
 (191 4) that Galton was a believer both in continuity 
 and discontinuity in variation, and also in alterna- 
 tive as well as blended inheritance. His point of 
 view with regard to the inheritance of these two 
 characters may be well illustrated by a quotation 
 from Natural Inheritance (p. 138): "Stature and 
 eye-colour are not different as qualities, but they 
 are more contrasted in hereditary behaviour than 
 perhaps any other common qualities. Parents of 
 different statures usually transmit a blended heritage 
 to their children, but parents of different eye-colour 
 usually transmit an alternative heritage." He also 
 remarks (p. 139), " The blending in stature is due 
 to its being the aggregate of the quasi-independent 
 inheritance of many separate parts, while e3^e-colour 
 appears to be much less various in its origin." In- 
 stead of Galton's conception of particulate inheritance, 
 we now think in terms of such abstractions as multiple 
 allelomorphs or multiple factors. But this conclusion 
 of his concerning stature has been supported by 
 Davenport (191 7), who concludes from a considerable 
 aggregation of analysed data that the correlation 
 
 between " knee height " and " pubic arch minus knee 
 
 27 
 
28 HEREDITY AND EUGENICS 
 
 * 
 
 height " or length of thigh, is only 24 per cent.*^ 
 Knee height includes height of ankle, which is con- 
 sidered an independent variable. The correlation 
 between supra-pubic and sub-pubic portions of 
 stature is found to be 30 per cent., and striking differ- 
 ences in the relative lengths of these portions of the 
 bod}' occur in different races of man. Thus Eskimo, 
 Mongoloids, and some American Indian tribes have 
 a relativel}^ long trunk and short legs, while the 
 Australian aborigines and some negro groups have a 
 short trunk and long legs. Of the supra-pubic 
 region, the supra-sternal or head and neck, and sub- 
 sternal or trunk portion, are independent variables 
 as regards length, with a correlation between them 
 of onh' 9 per cent. A defect in these data is, however, 
 the use of " sitting height " as a measurement, and 
 the deduction of certain elements of the stature from 
 that. 
 
 Thus, while inherited general growth factors, such 
 as differences in the amount of secretion of various 
 glands, are concerned in determining the adult stature 
 as a whole, other factors are believed to control inde- 
 pendently the length of the various segments which 
 go to make up stature. Hence, according to this view, 
 an individual ma}" be tall because of the presence 
 of general growth factors, or because he happens to 
 have inherited length in each segment of his stature. 
 If this is true, then, of the four segments that combine 
 to form the total stature, any individual may be 
 long in some and short in others. It is commonly 
 stated that certain families have predominantly 
 long trunks and short legs, while others may have 
 short, stocky trunks combined with long or short 
 
 * The calculation of the length of different segments of the 
 body by this indirect method introduces sources of error, as Castle 
 points out, which, at any rate, weaken Davenport's conclusions 
 regarding the inheritance of stature. 
 
PHYSICAL CHARACTERS IN MAN 29 
 
 legs. A child may happen to inherit all the relatively 
 long or short segment-lengths of its two parents, and 
 may thus be considerably taller or shorter than either 
 parent. Thus uniformity is not to be expected in 
 marriages between tall and short people. I know 
 personally of two cases of marriages between a very 
 exceptionally tall man and an exceptionally short 
 woman. In one case the son is tall, though not so 
 tall as his father. In the other, the son is exception- 
 ally short, like his mother. 
 
 Castle (1922) has recently criticised these con- 
 clusions of Davenport. He made a study of size 
 inheritance in crosses between large and small varieties 
 of rabbits and found the F^ generations intermediate 
 between the parental races, but nearer the size of the 
 larger parent owing to heterosis or hybrid vigour. 
 The latter phenomenon is well known. It is largely 
 confined to the F^ of both plant and animal hybrids, 
 and probably occurs also in some first generation 
 crosses of man.* Castle found that in crosses between 
 two small varieties of rabbits, such as Polish and 
 Himalayan, the F^ was larger than either parent 
 owing to this " hybrid vigour," but the effect was lost 
 in the F2, which was strictly intermediate in average 
 size. In crosses of either of these races with the 
 much larger Flemish rabbit, the average size of the 
 F2 was strictly intermediate, but the range of varia- 
 tion was much greater than in F^. By the application 
 of statistical methods it was estimated that eight or 
 ten independent factors or linkage-systems affected 
 the size. 
 
 Extensive measurements were made of weight, 
 ear-length, and the dimensions of several bones. A 
 study of the correlation between these measure- 
 ments was made, in order to determine whether 
 
 * For a discussion of heterosis in hybrids see East and Jones 
 (1919)- 
 
30 HEREDITY AND EUGENICS 
 
 independent factors govern the size in different parts 
 of the bod}'. The correlation-coefficients obtained 
 were uniformly high, and Castle reaches the conclusion 
 that " the genetic agencies affecting size in rabbits 
 are general in their action, influencing in the same 
 general direction all parts of the body." 
 
 This important contribution of Castle to the subject 
 of size-inheritance seems to indicate that, in so far as 
 rabbits are concerned, there is no certain evidence of 
 factors independently influencing the size of particular 
 organs. Castle applies the same views to mammals 
 and man, but not to plants where " hormone action 
 is less in evidence." He regards the view of the 
 genetic independence in size of the various parts of 
 the body as a " sporadic relapse into preformation- 
 ism," and denies that any lack of co-ordination of 
 organs, such as Davenport has suggested, can arise 
 through the crossing of different races of man. He 
 points out also, that the measurements used by 
 Davenport were not sufficiently precise to give reliable 
 correlation-coefficients, and criticises the photographs 
 of a Dinka negro and a Chiriguan Indian as evidence 
 that length of legs and trunk is independently 
 inherited. Castle suggests that there is the same 
 difference in proportions between a boy and a man 
 as between the Chiriguan Indian and the Dinka 
 negro, and that the latter, therefore, merely repre- 
 sents a later stage of development. He believes 
 that Southern Italians are short of stature and short- 
 limbed because they cease to grow early, while Swedes 
 and Scotch are tall and long-limbed because they 
 mature later, in the same way that Flemish rabbits 
 are large and have long ears because of their late 
 maturity. Davenport also recognises general growth 
 factors, and it is evident that the last word has not 
 yet been said on this important subject. What is 
 required is a mass of more accurate measurements. 
 
PHYSICAL CHARACTERS IX MAN 31 
 
 Two earlier studies by Punnett and Bailey (191 4, 
 191 8) on the inheritance of weight in poultry and in 
 rabbits also bear directly on this question. They 
 crossed Gold-pencilled Hamburgs with Silver Sea- 
 bright Bantams. The F^ was not quite so large as 
 the larger parent, while in F, and F3 the range of 
 variation is beyond that of either parent — i.e., both 
 larger and smaller birds w^ere obtained. The results 
 were explained on the assumption that four factors 
 affecting weight were present, two of them being 
 assumed to give an increase of 38 per cent, in a 
 single dose or 61 per cent, when present in the homo- 
 zygous condition. The other two factors were 
 assumed to give 25 per cent, increase in weight in 
 the simplex condition, and 30 per cent, in the duplex 
 condition. The results are believed to give a clear 
 indication that weight in poultr}^ may depend on the 
 presence of definite segregating genetic factors, and 
 it is suggested that the increased size of some hybrids 
 is not due to hybrid vigour, but to the bringing to- 
 gether of independent growth factors. 
 
 In their later study of weight in rabbits, Punnett 
 and Bailey (191 8) made crosses between the large 
 Flemish rabbit and a mixed strain of Himalayan- 
 Dutch-Havana of nearly uniform size. They also 
 made certain crosses betw^een Flemish and Polish 
 rabbits. After making a careful study of the curves 
 of growth in these rabbits, they conclude that " though 
 animals belonging to large breeds may mature more 
 slow^ly than those belonging to small breeds, it does not 
 follow that age of maturity is closely correlated with 
 size." The very small Polish rabbit is believed to 
 mature a good deal more slowly than a larger form such 
 as the Dutch, and the conclusion is reached that size 
 and early maturit}' are to some extent transmitted 
 independently. These conclusions are contrary to 
 the view of Castle, who finds, from a stud}' of growth- 
 
32 HEREDITY AND EUGENICS 
 
 curves in pure and hybrid races, that in PoHsh rabbits 
 " the initial weight is less, the growth-rate lesS; 
 and the completion of growth comes earlier," all 
 these features combining to produce a smaller rabbit. 
 It is evident from these and other contradictory 
 results that further studies of size inheritance in 
 relation to rate of growth, etc., are necessar}- before 
 any final conclusion can be reached; but it is highly 
 probable that the same laws of size inheritance apply 
 to man as to mammals, whatever those laws may be.* 
 Castle's data provide strong evidence that in the 
 strains of rabbits he studied general growth factors 
 preponderated over any factors affecting only the size 
 of certain parts. Nevertheless, the effects of a genetic 
 factor are frequently confined almost entirely to one 
 organ, and we see no reason why this should not apply 
 to size factors as well as others. Wright (191 8) in 
 a statistical analysis of earlier measurements by 
 Castle, of a stock of rabbits w^hich gave strikingly 
 high correlations between skull and leg measure- 
 ments, brings out correlations which '' suggest the 
 existence of growth factors w^hich affect the size of 
 the skull independently of the body, others which 
 affect similarly the length of homologous long bones 
 apart from all else, and others which affect similarly 
 bones of the same limb." The five measurements 
 considered were length and breadth of skull, length 
 of humerus, femur, and tibia. Analysis of the rela- 
 tions shows that in a population of rabbits most 
 of the differences between individuals are those 
 which involve the size of the body as a whole. But 
 there is a certain amount of variation of each bone 
 length independently of all others measured. There 
 are also groups of bones, which vary together inde- 
 
 * There is much evidence in man (see p. 212) that the activities 
 of various ductless glands, such as the thyroid and pituitary, 
 control the size and development. 
 
PHYSICAL CHARACTERS IN MAN 33 
 
 pendently of the rest of the skeleton . Two such groups 
 are skull length and breadth and the three leg bones. 
 Again, femur and tibia form a group subject to 
 common influences which do not affect the humerus 
 (foreleg). How far these variations were controlled 
 by genetic factors is of course unknown. 
 
 Castle specifically confines to animals his view that 
 all size factors are general, excluding it from plants 
 on the ground of a greater hormone control in animals. 
 But the apparent difference may simply be due to 
 the present state of our knowledge. In plants it 
 has been shown (Gates, 191 7) that when a large- 
 flowered species is crossed with a small-flowered one, 
 an intermediate F^ ma}" be followed by later genera- 
 tions in which widely different sizes of flower occur 
 simultaneously on the same plant, and even different 
 lengths of petal in the same flower. This striking 
 result, which has been studied on a large scale in 
 CEnothera crosses, shows that in plants, at any rate, 
 organs of widely different size ma}" occur on the same 
 individual as the result of inherited differences. 
 
 Another important fact which bears on the whole 
 theory of multiple factors in the interpretation of 
 size inheritance has been brought out by Sumner 
 and Huestis (1921). From extensive measurements 
 of the right and left mandibles, femurs, and pelvic 
 bones of the Californian deer mouse, Peromysciis 
 maniculatiis , they have constructed curves for the 
 sinistro-dextral ratio for each bone — i.e., the relative 
 lengths of the corresponding right and left bones. 
 The range of variation on either side of equality in 
 this ratio is, of course, small in every case, but they 
 are able to show statistically that the difference — 
 i.e., excess of length or weight on the right or left 
 side — is, as might be expected, not inherited from one 
 generation to the next. Nevertheless, if pure races 
 are compared with hybrids, the Y^ generation shows 
 
 3 
 
34 HEREDITY AND EUGENICS 
 
 a considerable increase in the variability of these 
 ratios. The authors rightly insist that this increased 
 variability of the Eg in characters which are demon- 
 strably non-hereditar}^ weakens very much the force 
 of the evidence usually offered in favour of the 
 hypothesis of multiple factors in size inheritance. 
 An increased range of variation in Eg hybrids cannot 
 therefore in itself be accepted as evidence of the 
 inheritance of multiple size factors. In the light ol 
 these results, the whole subject of size inheritance 
 takes on new aspects and will require more critical 
 re-examination . 
 
 As regards human dwarfs, they ma}^ be achondro- 
 plasic* — having short legs and long trunk — or ate- 
 liotic,t with normal proportions and reduced size 
 (miniatures). The former condition frequently skips 
 a generation, and its heredity is uncertain, but it 
 appears to be connected with derangements of the 
 internal secretions. A number of pedigrees of both 
 types of dwarfs are described in the Treasury of 
 Natural Inheritance (Pearson). 
 
 Rischbieth and Barrington (191 2) have accumu- 
 lated an enormous amount of information regarding 
 dwarfism in the human race, with a number of pedi- 
 grees of its inheritance. Regarding achondroplasia, 
 the condition ma}' appear '' accidentally " or it may 
 be hereditar}'. Cases are known in which normal 
 and achondroplasic babies occur in the same twin 
 birth. The condition appears more commonl}' in 
 girls than in bo3'S, Kassowitz finding twenty-five 
 girls and four bo3's in a total of twenty-nine cases. 
 An achondroplasic mother may have children like 
 herself or normal, and delivery must be b}" Csesar- 
 otomy. 
 
 * Achondroplasia is a defect in the iormation of cartilage at 
 the epiphyses on the ends of the long bones, producing dwarfs, 
 t Ateliosis is arrest of development before it is complete. 
 
PHYSICAL CHARACTERS IX MAN 35 
 
 Ateliosis or true dwarfism is considered to be rather 
 rare. It is probably due to a defect of the pituitary. 
 
 There is a fair number of cases recorded in which 
 offspring have been born to parents one or both of 
 whom were ateliotic. These, however, with the 
 exception of the cases quoted, have grown to a normal 
 size, if the}^ survived to adult years." Usualh' the 
 condition is found in only one generation. In an 
 exceptional case, an achondroplasic mother produced 
 an ateliotic son by an ateliotic father. In another 
 case, ateliosis occurred in father and son, and probably 
 in the grandfather. 
 
 A condition in plants, which appears to correspond 
 with achondroplas}^, has been described in cotton, 
 under the name brachysm (Cook, 191 5). It consists 
 in a great shortening of the internodes without any 
 corresponding reduction in the diameter or in the 
 size or number of other organs. This condition exists 
 in the " bush " varieties of various vegetables and 
 cereals such as beans and peas, tomatoes, oats and 
 w^heat. Kempton (1921) has studied it in maize, 
 and finds that it is inherited as a simple recessive in 
 crosses with the normal tall. 
 
 Ateliosis* in man appears to correspond to many 
 of the ordinary dwarf varieties of plants and animals, 
 though Davenport thinks it is due to dominant in- 
 hibiting factors. In some plants at least smaller cell 
 size is involved. A w^ell-known pedigree of the ate- 
 liotic type of dwarfism occurs in two families in the 
 Tyrol which have intermarried, and Pearson suggests 
 that it may here be inherited as a recessive from an 
 ancestral stock. 
 
 Dwarfing of the t^'pe which produces general 
 reduction in size is often the result of unfavourable 
 
 * Among horses, most ponies, such as the Shetland variety, 
 appear to be atehotic miniatures, while the Chinese pony, with 
 short legs and stout body, is apparently an achondroplasic dwarf. 
 
36 HEREDITY AND EUGENICS 
 
 conditions or general inhibition to growth. The 
 Japanese method of producing dwarf trees b}- star- 
 vation is sometimes copied by nature. When a 
 tree seedhng germinates in a cleft of a rock where 
 little nourishment is obtainable it may struggle on 
 for decades, making an infinitesimal amount of 
 growth each ^xar. Various instances are known in 
 which domesticated animals in becoming feral under 
 a rigorous climate have decreased conspicuously in 
 size. This is probably the history of the Shetland 
 ponies and others. It is certainly the origin of the 
 somewhat larger ponies from Sable Island, Nova 
 Scotia. These are known to be descended (St. John, 
 1 921) from horses taken to this desolate little island 
 from Massachusetts. The historv of these horses 
 and other feral animals on Sable Island is of such 
 interest, in showing how a group of animals may 
 react when removed from the care and selection of 
 civilised man, that I refer to the subject at some 
 length. The facts are taken from St. John (1921) 
 and Gilpin (1864). 
 
 Sable Island is a long crescent of sand dunes, now 
 twxnt}' miles long and less than a mile wide, about 
 150 miles east of Halifax, Nova Scotia. When first 
 visited in the sixteenth centur}^, it was apparently 
 ten miles longer and two miles wide. Ever}^ few 
 years a great storm washes away some part of the 
 island. The higher dunes now reach nearly 100 feet, 
 but were formerly higher. It is surrounded by shoals, 
 and hundreds of wrecks have occurred on its shores, 
 giving it the lugubrious distinction of being the 
 " graveyard of the Atlantic." On this inhospitable 
 island the Portuguese landed cattle and pigs about 
 1520. In 1633 a writer reported, " about 800 cattle, 
 small and great, all red, and the largest he ever saw." 
 Large numbers of wild cattle were afterwards shipped 
 from the island, according to a letter written in 1686, 
 
PHYSICAL CHARACTERS IN MAN 37 
 
 and in i 738 there were no cattle left there. Evidently 
 the cattle never became so truly feral as the horses, 
 which were landed afterwards. Unlike the latter, 
 they sought shelter from human habitations in storms, 
 also they increased in size and remained uniform in 
 colour. The hogs also ran wild, and became quite 
 fierce. But they w^ere all destroyed in 1814 " because 
 of their ghoulish tastes when shipwrecks occurred." 
 English rabbits, as well as rats, cats, dogs, and foxes, 
 were introduced in turn, the native red and black 
 foxes having become extinct. These introductions 
 furnish an instructive instance of how one species 
 may prey upon and quickly exterminate another. 
 
 But the history of the horses is of greatest interest . 
 In 1753 there were twenty or thirty horses on the 
 island descended from animals landed some time 
 earlier. About 1760 Thomas Hancock, a Boston 
 (Mass.) merchant, landed horses, cows, sheep, goats, 
 and pigs. By the end of the American Revolution, 
 all had been killed except a number of horses. Many 
 of the horses, as well as other animals, had been eaten 
 as food by shipwrecked mariners. The horses de- 
 scended from this stock are well described by Gilpin 
 (1864), who visited the island about 1864, and found 
 some 400 wild ponies in about six herds, each headed 
 by an old male with masses of mane and tail. Each 
 herd had its own feeding ground, and they separated 
 again when driven together promiscuously. The 
 males often fought savagely, and they appeared to 
 sleep standing and never to lie down to rest, alwa^^s 
 fleeing from man and shelter. Thus in one hundred 
 and fifty years or less they had returned to the habits 
 of the wild tarpany horse, with which they agreed in 
 size, hairy heads, and thick coat, though differing in 
 form in some respects. They are said to reproduce 
 wonderfully the forms of horses known only from 
 the sculptures of Nineveh and the friezes of the Par- 
 
58 HEREDITY AND EUGENICS 
 
 thenon, having the same short cock-thrappled neck, 
 hairy jowl, and horizontal head. As regards colour, 
 bays and browns were most numerous, then chest- 
 nuts, a few blacks, no greys, one probable red roan, 
 one pure white, many piebald, and many '* bluish 
 mouse colour "* often wdth a black stripe along 
 the back, but none with black lines around the 
 legs. 
 
 The striking features in the history of these horses 
 appear to be ( i ) the complete reversion to an ancestral 
 condition, with change of form and decrease in size; 
 (2) the large number of colour varieties. Mere in- 
 breeding will not account for the former. The colour 
 varieties may, perhaps, all have been represented in 
 the germ plasm, the piebald and bluish colours being 
 extremelv old. Piebald horses have existed in all 
 ages. According to Gilpin, the}^ are depicted on the 
 most ancient coins of China and w^ere contemporary 
 with the siege of Tro\^, being still seen feral in Northern 
 Italy. They have also appeared in Patagonia and 
 among the horses of the North American Indians. 
 The structural changes involved in the reversion of 
 these Sable Island ponies must have resulted in some 
 w^ay from the rigorous conditions. How the environ- 
 ment acts in such cases is not clear. It ma}^ be parth' 
 by direct inhibition of development, and partly by 
 selection of smaller varieties requiring less food. It 
 may also involve the reappearance as fresh mutations 
 of conditions which had previously been selected out 
 of the germ plasm by the action of man. The small 
 human races in some inhospitable climates may, 
 perhaps, be accounted for in a similar wa}^ — i.e., by 
 the selection of variations, sometimes negative, which 
 made survival more likely, as well as by the direct 
 inhibiting effects of unfavourable conditions. But 
 
 * This " Phrygian cerulean blue of Homer " is scarcely known 
 among modern domestic breeds. 
 
PHYSICAL CHARACTERS IN MAN 39 
 
 this is obviousl}^ not the place to analyse such possi- 
 bilities from the evolutionary point of view. 
 
 That the diminution in size of a species may happen 
 very quickly is shown by garden vegetables which 
 are allowed to run wild, or bv the immediate and 
 rapid increase in size of wild species taken into a 
 garden. This appears to be due to the fact that con- 
 ditions of culture permit of the rapid accumulation 
 of reserve material. Such instances as the following 
 in animals show rapid decrease in size: Dr. John D. 
 Caton (1887) tells how a male and four female wild 
 turkeys were sent from his grounds in Ottawa to 
 Santa Cruz Island, twenty miles off the coast of 
 California. This island is thirt}^ miles long and five 
 to ten miles wide. Here the turke^^s had no enemies 
 except a small grey fox. In a few years they became 
 ver}^ abundant and very much smaller, the largest 
 weighing not over 6 pounds, or less than one-third 
 the size of the first and second generations bred there. 
 In this case the mild climatic conditions could not 
 have been responsible, the food supply was abundant, 
 the birds were vigorous and healthy, and there was 
 no evidence of any epidemic. The wild turkey was 
 formerly abundant in Arizona, and birds introduced 
 on the mainland of California north of San Francisco 
 were prolific and of normal size. The cause of the 
 decrease in size of the Santa Cruz birds, therefore^ 
 remains unexplained. 
 
 Davenport is inclined to conclude from his studies 
 of human stature that " in both ateliosis and achon- 
 droplasia in man there are multiple dominant (growth 
 inhibiting) factors, whose actions are often obscured 
 by opposing epigenetic growth factors, and which 
 are probably of a different sort in ateliosis than in 
 achondroplasia, for achondroplasia affects chiefly 
 or exclusively the appendages." Evidently much 
 has yet to be learned of the inheritance of these 
 
40 HEREDITY AND EUGENICS 
 
 conditions in man, as well as concerning the effec- 
 tive environmental factors which are involved in 
 producing racial differences in stature. 
 
 A condition which bears some resemblances to 
 achondroplasia, but was probably of a different 
 character, appeared in a flock of sheep in i 791 (Hum- 
 phreys, 1 813). The so-called Ancon sheep originated 
 from a single ram in the flock of a farmer in Massa- 
 chusetts, near Boston. This ram had short, bandy 
 legs and a short back. The character was evidently 
 a simple Mendelian recessive, and had probably been 
 carried in the stock for some time before it was brought 
 out b}' inbreeding. The breed seems to have attained 
 some popularity because they could not jump fences ; 
 but their crooked forelegs, loose joints, and flabby 
 subscapular muscles made them difficult to drive to 
 market, their carcasses were smaller, and they became 
 extinct some time after 181 3. This is an excellent 
 example of man's power over variations in domestic 
 animals, first to multiply them and afterwards to 
 bring about their extinction when the}^ were found 
 less serviceable. 
 
 A somewhat different account of the origin of this 
 breed was given b}^ Timothy Dwight (1822, vol. iii., 
 p. 134). Hesays that about i 798, in Mendon township 
 (Mass.), about eighteen miles south-east of Worcester, 
 *' an ewe belonging to one of the farmers had twins, 
 which he observed to differ in their structure from any 
 other sheep in this part of the countr}^." The twins 
 are said to have been of different sex, and to have been 
 bred together to produce the new race. Dwight stated 
 that their bodies were thicker and more clumsy, 
 they were more gentle, and have since multiplied to 
 many thousands; when crossed with other breeds, 
 they always resembled entirely either the sire or the 
 dam. 
 
 The dachshund among dogs appears to have re- 
 
PHYSICAL CHARACTERS IN MAN 41 
 
 suited from a similar mutation, although here the back 
 is long, as also in the turnspit. A variety like the 
 turnspit, having crooked legs and a long back, was 
 formerly known among the pariah dogs of India. 
 
 To quote some of the further conclusions of Daven- 
 port regarding heredity of stature in man, he finds 
 that the time of onset of puberty is probabh' an ele- 
 ment in determining the stature ultimately reached 
 by the individual, and that the factors for tallness 
 are mostly recessive — probabl}^ due to the absence 
 of inhibitions to prolonged growth. The least vari- 
 able offspring are, therefore, the children of two tall 
 parents, all being usuall}^ tall, while tall mated with 
 short will give the most variable result owing to the 
 recessive factors for greater stature carried b}^ the 
 short parent. 
 
 An interesting experimental result bearing on the 
 subject of gigantism has recentty been obtained 
 by Uhlenhuth (192 1). He fed young salamanders 
 {Ambly stoma) on a pure diet of the anterior lobe of 
 the M'pophysis (pituitary*) of cattle, control animals 
 being fed with earthworms. A greath' increased 
 rate of growth resulted, and when the normal adult 
 size was reached growth continued at a decreasing 
 rate, until animals of gigantic size w^ere produced. 
 The hormonef from the anterior lobe of the hypophysis 
 not onl}^ accelerates growth, but also maintains 
 growth after the normal adult size is reached. Carrel 
 finds that in tissue cultures the growth of the cells 
 of warm-blooded animals is not accelerated by hypo- 
 physis extract, and various investigators have shown 
 
 * The pituitary is a small reddish ellipsoid organ in a depression 
 (the sella turcica) at the base of the skull. It consists of anterior 
 and posterior lobes. 
 
 t A hormone is a chemical substance produced as an internal 
 secretion in a gland or organ and carried in the blood-stream in 
 minute quantities to control the activity of another organ. 
 
42 HEREDITY AND EUGENICS 
 
 that the division rate of protozoa is not affected 
 by the extract. The continued growth of the sala- 
 mander is evidently due to continued cell multipli- 
 cation rather than increase in the size of cells, the 
 hormone effect being probably not directly on the cells 
 of the body, but through the intermediary^ of some 
 other substance which stimulates cell growth and 
 division in all the tissues. 
 
 In plants it has been shown by Bottomley (191 7) 
 that auximones or growth-promoting substances, 
 bearing certain resemblances to the vitamins,* may 
 be obtained from the water extract of bacterised 
 peat. These substances are probably organic de- 
 composition products obtained in peat which has 
 partially decomposed under anaerobic conditions, 
 and is then acted upon by aerobic bacteria. When 
 368 parts per million of organic matter from the 
 water extract was added to a culture of Lemna minor, 
 grown in nutrient solution, the effect was remarkable. 
 In six weeks the increase compared with that of con- 
 trol plants was sixt^^-two times in weight and twenty 
 times in number of plants. The increase in size was 
 striking, not onty as regards the individual plants, 
 but also in the cells, nuclei, and chloroplasts. 
 
 That gigantism of body and of cells in plants is 
 also often associated with tetraploidy or doubling in 
 the chromosome number has been shown by Gates 
 (1909) and by Tupper and Bartlett (191 6), with de- 
 tailed measurements of cells and nuclei in various 
 tissues. This is another example of the same mor- 
 phological difference being produced by an external 
 stimulus, in which case it is not inherited, or by a 
 germinal change, when it is inherited. 
 
 * Vitamins are substances of vegetable origin whose presence 
 in minute quantities is necessary for the proper development of 
 the higher animals and man. In their absence such diseases as 
 scurvy, beri-beri, and rickets develop. 
 
PHYSICAL CHARACTERS IN MAX 43 
 
 The data of inheritance of gigantism in man include 
 some interesting cases in the tall Scotch population 
 of North Carolina and Kentucky. It is concluded 
 by Davenport that excessively tall stature is the 
 result of inherited excessive activity in the pituitary 
 gland, the factors for tallness being mostly recessive, 
 due to absence of inhibition to prolonged growth. 
 It is clear that gigantism and dwarfism are not merety 
 the extreme terms in a single series, but they are 
 conditioned in inheritance by entirely different 
 ph3^siological and developmental processes. 
 
 Windle (1891) quotes from Francesco Leporata 
 the case of a dwarf born of normal parents. At the 
 age of 83 years he was i -i 30 metres high. By a normal 
 wife he had six children whose heights are given. 
 They w^ere all dwarfs but one normal daughter, their 
 heights ranging around that of the father. One son, 
 Antonio, married twice, both wives being normal, 
 By the first he had a normal daughter, and b}' the 
 second three children who were below normal. 
 Another son, Pietro, married a normal woman and 
 had three small children, all of whom when measured 
 were below the normal height for their age. Dwarfing 
 in this family appears to be strongly dominant. 
 
 Stature is, of course, also a racial characteristic. 
 The tall races are found in North-Western Europe, 
 the Polynesians, North American Indians, and some 
 negro tribes of the Soudan and Central Africa. Their 
 height is 68 inches or over. The short races comprise 
 those of Indo-China, Japan, Malaya, the Hottentots, 
 and Eskimos. Many dwarfs are small because they 
 cease growth at an early age; others are ver}- small 
 at birth and grow slowly. According to Davenport 
 (191 7), the average stature of man ranges from 4 feet 
 6 inches' in the Negrillo Akkas to 5 feet 10 inches in 
 the Scots of Galloway. Frederick Wilhelm of Prussia 
 contemplated breeding a race of tall grenadiers for 
 
44 HEREDITY AND EUGENICS 
 
 his battalions, and Catherine de Medici is said to 
 have endeavoured to produce a race of dwarfs by 
 bringing about matings between them. 
 
 Eye Colour. 
 
 The Mendelian studies of eye colour up to 191 2 
 were summarised by Hurst (191 2). He defined three 
 patterns of distribution in the pigmented e^^e : self, 
 where the brown is distributed all the way to the 
 periphery of the iris; ringed, in w^hich the brown is 
 confined to a ring around the iris; and spotted, in 
 which irregular spots and patches occur on a blue 
 background. The blue or grey colour represents 
 absence of brown pigment, and is simply the apparent 
 colour of the muscle fibres in the iris as seen through 
 the cornea. 
 
 A recent paper (Boas, 1919) presents statistics 
 of e3'e colour which, it is claimed, do not support the 
 Mendelian contention that two blue-eyed individuals 
 have only blue-eyed offspring. But the wTiter admits 
 that in collecting these data, persons with a certain 
 amount of brown in their eyes may have been classed 
 as blue-e^^ed. Pearson and others have also studied 
 carefully some of the more detailed differences in eye 
 pigmentation which are important for a complete 
 anah^sis. It is clear that the conception of a single 
 Mendelian factor difference between brown and blue 
 e\^es is only a rough first approximation in the study 
 of this subject. 
 
 Usher (1920), from a careful histological examina- 
 tion of six albino eyeballs, found traces of pigment in 
 four. The fifth was unknown, and the sixth, that of an 
 infant, was devoid of pigment. Usher therefore con- 
 cludes that total absence of pigment cannot be used 
 as a definition of albinism in man . The fovea centralis* 
 
 * This is a pit in the middle of the macula lutea or point of 
 clearest vision at the centre of the retina. 
 
PHYSICAL CHARACTERS IN MAN 45 
 
 in albinotic eyes is shown to be absent or imperfect, 
 and this may be the chief cause of the imperfect vision 
 in such eyes. In the eyes of albinotic individuals 
 belonging to dark races the mesoblastic pigment 
 appears earlier and is found in much larger quantity 
 at time of birth than in European eyes. Chemical 
 examination indicates that there is more pigment in 
 the eyes of albinos of dark races than of white races. 
 This is in line with much evidence from mammals 
 of a close relation between density of coat colour and 
 of eye pigmentation. 
 
 Recent studies of brown and blue eyes indicate 
 that they are not alw^ays a simple pair of Mendelian 
 characters as formerly supposed, but sex-linkage 
 and other complications may come in. Br^^n (1920) 
 collected statistics in Norw^ay and states that in four 
 out of thirty marriages tw^o blue-eyed parents had 
 some brown-eyed children. From these four mar- 
 riages there were ten children with brow^n eyes and 
 seventeen with blue. One or both grandparents, in 
 all cases, had brown eyes. Winge (1921), in a much 
 more extended studv, criticises these results and 
 concludes that such cases are exceedingly rare if the 
 parents have normal vision. By means of a question- 
 naire, Winge collected data of eye colour in about 
 1 ,400 children of natural history association members 
 in Denmark and their parents. The data obtained 
 were carefully sifted, and the results are given in the 
 table on p. 46. 
 
 From the table it will be seen that, in addition to 
 the seven children with doubtfull}^ blue eyes from 
 blue-eyed parents, twelve children (belonging to eight 
 families) had brown pigment in their eyes. Further 
 information obtained from five of the families indi- 
 cates that the condition was due in two cases to 
 abnormalities in the eye. In another family of seven, 
 two of the daughters had some brown pigment in 
 
46 
 
 HEREDITY AND EUGENICS 
 
 their eyes, and one of the latter married a blue-eyed 
 man and had six children, all blue-e3^ed. This case 
 is thought to be explained b}" assuming that one of the 
 grandparents was genot3'picalh^* brown-eyed but had 
 a " pigment restrictive disposition " which made him 
 or her phenotypically (that is, visibty) blue-eyed. 
 The brown-eyed daughter having blue-eyed children 
 is explained by sex-linked inheritance. It is shown 
 from other evidence that pigment-inhibiting factors 
 ma}" be accompanied by abnormalities in vision, 
 but the interpretations in this part of the paper are 
 not always convincing. 
 
 TABLE I. 
 Inheritance of Eye Colour (Winge). 
 
 
 Number 
 
 of 
 
 Children. 
 
 
 Marriages. 
 
 Blue. 
 
 1 
 
 Browfi 
 
 I. 
 
 Greyish-Green 
 
 or 
 Bluish-Green. 
 
 Total. 
 
 Blue X blue 
 Blue X brown and 
 
 conversely 
 Brown x brown 
 
 625 
 
 '317 
 25 
 
 12 
 
 322 
 82 
 
 
 7 
 9 
 
 i 
 
 644 
 
 648 
 107 
 
 Total 
 
 967 i 
 
 416 
 
 1 
 
 16 
 
 1,399 
 
 Perhaps the most interesting results of Winge 
 concern the sex-linked inheritance of eye colour. 
 The statement that there are more brown-eyed 
 women than men was borne out by statistics of 
 300,000 school children, collected by S. Hansen. 
 Similar results have been obtained by others. Winge 
 shows the fact of sex-linkage by giving the results 
 of marriages in which the parents had different e^^e 
 colour. These are appended in the following tables : 
 
 * That is, in inherited germinal constitution. 
 
PHYSICAL CHARACTERS IX MAN 
 
 47 
 
 TABLE II. 
 Mother Blue x Father Browx. 
 
 Eye Colour of Children. 
 
 Sons. 
 
 Daughters. 
 
 Total. 
 
 Blue 
 
 Brown . . 
 
 Greyish-green or bluish-green 
 
 63 
 
 65 
 
 4 
 
 50 
 
 81 
 
 2 
 
 113 
 
 146 
 
 6 
 
 Total 
 
 132 
 
 133 
 
 265 
 
 TABLE III. 
 Mother Brown x Father 
 
 Blue. 
 
 
 Eye Colour of Children. 
 
 Sons. 
 
 Daughters. 
 
 Total. 
 
 Blue 
 
 Brown . . 
 
 Greyish-green or bluish-green 
 
 lOI 
 
 87 
 
 ■ 103 
 
 89 
 
 3 
 
 204 
 176 
 
 3 
 
 Total 
 
 188 
 
 195 
 
 383 
 
 Clearly from the tables, when the father has brown 
 eyes, half the sons have blue e3"es and half brown, 
 but many more daughters have brown than blue 
 eyes, although the total numbers of the sexes are 
 equal. On the other hand, when the mother has 
 brown eyes there is a marked excess of blue-eyed sons 
 and daughters. After an elaborate analysis these 
 results are explained by assuming that in addition 
 to the simple pair of factors originally recognised, 
 there is another dominant factor for brown eyes 
 which is sex-linked in inheritance. The writer is 
 further obliged to assume that female germ cells 
 (b W) containing the sex-linked factor (W) together 
 with the ordinary determiner for blue, cannot exist. 
 It should not be difficult to obtain extensive data of 
 eye colour to test these h3'potheses. All the assump- 
 tions made are reasonable enough in the light of 
 
48 HEREDITY AND EUGENICS 
 
 present genetic knowledge. It is well known that 
 in rabbits and guinea-pigs factors for coat colour also 
 often affect e^^e colour. 
 
 Having stated some of the facts as found, several 
 criticisms of the present Mendelian position as regards 
 e3^e colour are necessary. In the first place, many 
 grades of brown exist, both as regards shade of 
 colour of the iris and distribution of pigment. In an 
 accurate study of eye colour these shades and varying 
 distributions should be distinguished, and only lumped 
 together for certain statistical purposes. It may 
 turn out that all the shades of iris pigmentation do 
 segregate sharpty from pure blue, but much more 
 extensive and accurate data will be required than are 
 at present available before any certain conclusions 
 can be drawn. It appears that even a difference 
 in pigmentation of the two eyes ma}^ be inherited in 
 certain families, and when the effects of various 
 abnormalities of the eye in distorting or inhibiting 
 the pigmentation of the iris are considered, the neces- 
 sity for accurate and prolonged observation is obvious. 
 On the other hand, in the light of the complications 
 as regards eye pigmentation disclosed in Drosophila, 
 it is by no means improbable that w^hen sufficiently 
 anah'sed, the pigmentation of the iris in man will be 
 found also to follow^ Mendelian laws. But it is neces- 
 sary to emphasise the necessity of very accurate 
 and detailed first-hand observations of parents and 
 children. The existence of all intergrades of colour 
 and distribution of pigment in the iris is well known. 
 Whether the detailed facts will bear a complicated 
 Mendelian analysis remains to be seen, but there is 
 nothing at present to negative that possibilit}^. 
 
 The writer recently had the opportunit}'^ of ex- 
 amining the e3^e colour of people in Bergen, Norway. 
 Only about one in fifteen would be roughly classed 
 as brown-eyed, but the blues varied continuously 
 
PHYSICAL CHARACTERS IN MAN 49 
 
 from very light to very dark blue, and so through 
 greenish or yellowish shades (due to a small amount 
 of brown pigment) to pale brown, dark brown being 
 rare. Every grade of colour appeared to be repre- 
 sented, with a great predominance of the paler shades. 
 
 Sedgwick (1861) describes an interesting family in 
 County Wexford, Ireland, with tortoiseshell-coloured 
 eyes. The third generation, numbering sixteen sons 
 and five daughters, all had the peculiarity, which they 
 inherited from their mother. The mother had three 
 sisters and a brother with the same colour of eyes, 
 which was in turn inherited from their mother. Hence 
 the character was a simple Mendelian dominant. 
 
 Bond (191 2) has studied the inheritance of the con- 
 
 • ^ D 
 
 i 4 4 4 4xD 
 
 I I 
 
 /6 Sons 5 Dau. 
 
 Fig. 9. ^TORTOISESHELL-COLOURED EyES. 
 
 dition known as heterochromidia iridis, in which the 
 two eyes are of different colour. In addition to the 
 patterns recognised by Hurst, he distinguishes between 
 self colour and the ray pattern, in which only one or 
 more sections of the iris are pigmented. This con- 
 dition is a fairly frequent one, and shows inheritance, 
 though the position of the ra}^ or sector is variable 
 from one generation to another. Bond finds that the 
 two eyes are unlike in pigmentation in perhaps one or 
 two individuals per 1,000. In rabbits the condition is 
 much more common, sometimes four in 100. Horses 
 with a '' wall " eye are, of course, well known, and in 
 various breeds of dogs, such as Great Danes, English 
 collies, and Old English sheep dogs, the condition is 
 not uncommon. In both horses and dogs it is fre- 
 
 4 
 
50 HEREDITY AND EUGENICS 
 
 quently associated with a patchy or piebald coat. 
 Both conditions nia}^ arise when self colour is raated 
 with w^hite, and in some cases it may be looked upon 
 as a phenomenon of disintegration following on the 
 quantitative dilution of a factor for pigmentation. 
 It resembles in this respect the striping of flowers 
 (see p. 58). Because factors may be diluted and 
 disintegrated in this w^ay by crossing, it is not neces- 
 sar}' to assume, as Bond does, that there were originally 
 independent factors for each eye and subordinate 
 factors independently controlling different areas of 
 the iris. There is no evidence that factors have been 
 built up in this way. They appear rather to originate 
 as germinal changes or new conditions of equilibrium, 
 which may later become modified by crossing or 
 otherwise. 
 
 A number of observations on the e^^e colours of 
 birds and their inheritance are recorded b}^ the same 
 writer (Bond, 191 9). His studies were chiefly of 
 pigeons and fowls, although references are made to 
 many other species. The pigment granules producing 
 eye colour may be black, brown, ^^ellow, ruby, or 
 pearl. The '' bull " eye owes its black colour, as 
 in the white fantail pigeons, to the absence of pig- 
 ment from the anterior surface of the iris. The pos- 
 terior uveal pigment shines through the translucent 
 tissues of the iris and gives the eye its colour, as in 
 blue human eyes. Also, as with blue eyes in man, the 
 "bull" eye of the chick is retained in the adult. 
 The ruddy glow of this e3"e is due to the plexus 
 of bloodvessels. (A similar t3^pe of eye occurs in 
 guinea-pigs of the type which Castle calls red-eyed 
 silver agouti). But in most birds with dark or black 
 eyes, the colour is due to the presence of anterior 
 iris pigment. In the rock pigeon {Columba livia) the 
 iris colour is yellow or orange, while in other pigeons 
 it may be white or red, and in the stock dove (C. cenas) 
 
PHYSICAL CHARACTERS IN MAN 51 
 
 the e\^e is peculiar, its black colour being due to the 
 presence in the iris and in deeper tissues of branching 
 cells packed with dark granules. 
 
 In the pearl or white eye of pigeons and the " daw " 
 eye, as in the Malay fowl, there is no anterior pigment 
 in the iris, but its tissues are opaque, owing to the 
 presence of crow^ded colourless granules. This ap- 
 parently corresponds with the " wall " eye in horses, 
 dogs, and pigs. The muscle fibres of the avian e3^e, 
 however, are striated or voluntary, and not plain as 
 in the mammals. Pearl eye in pigeons is recessive 
 to yellow or " gravel " eye, as " daw " e^^e in fowls 
 is to amber or black eye when the latter is due to 
 anterior pigment. The yellow eye derives its colour 
 from a network of branching cells containing yellow 
 granules. If the latter are closely packed, the eye 
 may appear black. In fowls the ^^ellow e3^e ma}' be 
 due to (i) granules in the connective tissue cells; 
 (2) granules in the striated muscle cells, as in Dorkings 
 and Orpingtons. In owls the yellow eye is due to 
 bright 3"ellow granules in cells coating the iris. 
 
 Brown and black eyes in birds are produced b}' a 
 layer of branching cells on the iris containing dark 
 pigment granules. Ruby e3^es are produced in various 
 ways in different birds ; and some birds, such as certain 
 birds of paradise, have parti-coloured irides. Gene- 
 tically, black due to pigmented iris is dominant over 
 yellow and other grades of iris pigmentation. 
 
 Skin Colour and Hair Characters. 
 
 Hurst (191 2) has summarised the studies on hair 
 and skin colour in man, and added some observations 
 of his «wn. The main points with regard to hair 
 colour are: (i) That the brown shades of colour 
 appear to be continuous from white (albino) hair to 
 jet black; (2) the reds form a separate series due to a 
 
52 HEREDITY AND EUGENICS 
 
 lipochrome (a group of animal-fat pigments), while 
 the brown is a melanin (a dark pigment found in hair, 
 etc.); and (3) the generalisation of the Davenports 
 (1910) that (with rare exceptions) children never 
 have darker hair than their darker parent. This 
 '' non-transgressibility of the upper limit " applies 
 also to skin colour or complexion in the white races. 
 Davenport (191 3), from a study of mulatto families 
 in Bermuda, Jamaica, and the United States, con- 
 cluded that there are probably two segregating 
 Mendelian factors for black, and that other negroid 
 features, such as kink}^ hair and thick lips, segregate 
 independently. The same would appear to be true for 
 mental characters, since mulattoes sometimes display 
 high intellectual ability, but never pure negroes, as 
 far as is known. 
 
 The evidence in favour of a strictly Mendelian ex- 
 planation of colour inheritance in white-black crosses 
 is, however, by no means conclusive. Pearson (1909), 
 from data supplied b}^ a medical man in the West 
 Indies, gives quite a different picture. The first cross 
 gives a brown mulatto or a yellow mulatto, and the 
 basis or cause of this difference is not apparent. In 
 crosses between mulattoes " there are now and then 
 slight variations from the usual mulatto brown or 
 mulatto yellow," but never pure black or white. 
 Sports or throwbacks rarely occur, but the form 
 where the tint is barely evident is said to be not 
 uncommon. Mulatto x negro produces the sambo, 
 a deep mahogany brown, and it is said there is never 
 any other colour from this cross. Mulatto x white 
 produces the quadroon, which is never pure white, 
 but almost invariably lighter than the brown mulatto 
 and nearly always lighter than the yellow mulatto. 
 This gives the impression of intermediac}^ in the 
 various hybrid conditions, with a not very marked 
 tendency to segregation, which is never complete. 
 
PHYSICAL CHARACTERS IN MAN 53 
 
 Evidentl}^ what is required is an extensive collection 
 of accurate data based on careful measurements of 
 pigmentation with colour tops before this complex 
 subject can be fully understood. Probably something 
 more complicated than the two-factor hypothesis 
 of Davenport is required to explain all the facts of 
 colour inheritance in white-black crosses. In how 
 far real permanent blends occur remains to be seen. 
 Although individuals occur in later generations who 
 pass for whites, it is not certain that the pigment 
 is ever entirely lost, though it is probable that the 
 presence of other negroid features gives the impression 
 that more black pigment has been retained than in 
 the normal brunette skin. 
 
 Jordan (191 1), in a histological stud}' of melano- 
 genesis in mulatto and white skins, finds that the 
 only factor in skin pigmentation is the number of 
 (yellowish-brown) granules and the number of cells 
 containing such granules. Some mulattoes are iden- 
 tical with negroes and others with brunettes in amount 
 of pigment. The apparent continuit}' in the melano- 
 genetic process is believed to rest in mulatto families 
 upon discontinuities or discrete units controlling the 
 production of melanin granules. Such conditions 
 conform more or less closely to an alternative mode 
 of inheritance. 
 
 Sedgwick (1863) refers to silvery grey hair of very 
 coarse texture as being present in about one in ten or 
 twelve of the Mandan Indians, irrespective of age. 
 
 The various types of hair in the different races of 
 man — straight, wav}', kink}', and curly — are known 
 to differ in the shape of a cross-section, straight hair 
 being circular in cross-section, kinky hair elliptical, 
 with the other t3'pes intermediate. Little is actually 
 known regarding the inheritance of these differences. 
 Bean (1908) has studied the hair types among the 
 h3'brid Filipinos, in which the Chinese element fur- 
 
54 HEREDITY AND EUGENICS 
 
 nished the straight t3^pe of hair. Hair was classed 
 as straight when the relative diameters in cross- 
 section were 100:90 or over, wav}^ when 100:70-90, 
 and curly when 100:60-70. In 31 families in which 
 the cross was wavy X straight or curh' x straight, 
 there were i 57 children, of whom 84 had straight hair 
 to 73 curly or wavy. This approximates to a Men- 
 delian i : i ratio; but dominance, when it occurs, is 
 variable, and although segregation occurs to some ex- 
 tent, there is no close conformit}' to simple Mendelian 
 behaviour. Wav}^ is regarded as a heteroz^'gote of 
 curly and straight, curh^ being recessive, but there 
 is no sharp line between wavy and curl}'. W^avy x 
 wavy gives all three types in approximately^ equal 
 proportions. Straight X straight gives all three 
 types, but with a large preponderance of straight. 
 Curh' X straight gives mostly straight if the father's 
 hair is straight, but more curly if the father's hair 
 is curly. These results for Filipinos appear to be 
 general!}' the reverse of those obtained in America. 
 (See photographs in Journal of Heredity 7:412 [191 6].) 
 Bond (191 2) cites certain cases of negro-white crosses 
 in which wavy and kinky hair both appear in the 
 same individual, the hair being wavy on the vertex 
 and kinky on the sides of the head. Three such 
 cases are figured. 
 
 In a little-known work on the hair of mankind, 
 Friedenthal (1908) gives descriptions with numerous 
 coloured plates showing the distribution of hair on 
 the human body, and the extremes of plus and minus 
 variation in various races of man and in some apes. 
 Aino of Japan are figured, in some of which almost 
 the entire body has a hairy covering, and these are 
 compared with certain European variations in which 
 the whole face is covered with hair. Darwin* cites a 
 Siamese family which for three generations had the face 
 
 * Animals and Plants, i. 448. 
 
PHYSICAL CHARACTERS IN MAN 55 
 
 and body covered with long hair. This was accompa- 
 nied by deficient teeth. He also refers to a woman with 
 completely hairy face, exhibited in London in 1663. 
 
 E. Fischer (1910) has given the history of an 
 interesting family in Upper Alsace, near Colmar, 
 some of whose members were almost entirely devoid 
 of hair. Daniel BoUenbach, belonging to the second 
 generation of the pedigree (see Fig. 10), had no hair 
 of the ordinary type, but his whole head bore a very 
 scattered, soft down, about i centimetre long, com- 
 posed of soft, thin, colourless hairs. Under the 
 microscope they are seen to have no central medulla 
 or pigment granules, to be somewhat thinner than 
 ordinary hair, and twisted. Amongst these are a very 
 few longer (3 centimetres) and somewhat thicker, 
 pale reddish, delicate hairs. Under the microscope 
 these show a normal central medulla and a weak 
 reddish-brown pigmentation. Eyebrows and e3^e- 
 lashes are lacking. The arms and legs are hairless ; 
 also there is no breast hair or axillary hair. The 
 nails of the toes and fingers are deformed, becoming 
 thick and rough. The teeth deca\'ed early, leaving 
 many stumps. There is here the well-known corre- 
 lation between deficiencies in teeth, nails, and hair. 
 Some other members of the familv have a few hairs 
 on the body = 
 
 The inheritance of this hairless, condition shows 
 peculiarities (see chart. Fig. 10), which are difficult to 
 explain except perhaps on an hypothesis of variable 
 or reversed dominance of a single Alendelian factor. 
 The character itself seems to have appeared suddenty 
 through a germinal change, since the two generations 
 preceding its original appearance were all normal, 
 although they included cousin marriages which would 
 probably have brought out a recessive character it 
 it had been present. It will be seen (Fig. 10) that in 
 the Fi Mathias, who was normal, had only normal 
 
56 
 
 HEREDITY AND EUGENICS 
 
 to 
 
 .'0 
 
 5: 
 
 K> 
 
 
 
 
 
 
 
 < 
 
 
 0i 
 I— I 
 
 < 
 
 o 
 w 
 
 U 
 
 pq 
 
 -+-> TO 
 
 a ^ 
 
 O 
 
 ^O 
 
 u: 
 
 
 
 O 
 
 o 
 
 W 
 
 'O 
 
 ■+-> d 
 
 CD "^ 
 
 a ^ 
 IS 
 
 ^ o 
 
 ^ .1:3 
 o 
 crT 
 
 -H CD 
 
 U (X) 
 
 0) 
 
 u 
 
 biO 
 
 03 
 
 Ph o3 
 
 biD CT^^ 
 S CD n 
 
 nn H .S2 
 
 -2 8w 
 
 o3 
 
 <D 
 
 <D 
 
 ^ 3 
 
 13 fS OJ 
 
 k 
 
 ^ 
 
 K 
 
 «v 
 
 C 
 
 e 
 
PHYSICAL CHARACTERS IN MAN 57 
 
 descendants, but Katherine (abnormal) also had only 
 normal descendants through three generations. If 
 the character were recessive its absence here would 
 be explained, since her husband was probably homo- 
 zygous normal. Maria and Salome, if their husbands 
 (Bollenbach) were heterozygous, should have half 
 their children of each type. The actual numbers were 
 three normals to four hairless and seven normals to 
 seven hairless respectively. The numbers are, of 
 course, too small to make a certain interpretation, 
 but the most likely interpretation appears to be that 
 the character behaved as a recessive. In the case of 
 Katherine, it is very unlikely that it would fail to 
 appear in any of her four children if it were dominant. 
 The fact that the sex of so many of the children 
 is unrecorded indicates that the records are not, 
 perhaps, very accurate. 
 
 Inbreeding does not explain the origin of this 
 character, which was probably due to germinal change, 
 and if the Bollenbachs were homozve^ous it would 
 behave partly as a dominant. The abnormal section 
 of the family is fast dying out. Sexual selection is 
 apparently a factor, for abnormal members of the 
 family often remain single. Of the fourteen children 
 of Salome, all died but one (Daniel), who had two 
 children, only one of which reached maturity. Michel 
 remained childless. Only two abnormal members of 
 this famil}^ remain — both old men. At their death, 
 the abnormality will be lost after fifteen abnormal 
 individuals had appeared in three generations. This 
 is a marked case of an abnormality appearing sud- 
 denly and then disappearing in a few generations. 
 
 Albinism 
 The monograph on albinism in man, by Pearson, 
 Nettleship, and Usher (1911-1913) is a very elaborate 
 and detailed treatment, which will serve as a basis 
 
58 HEREDITY AND EUGENICS 
 
 for all future studies on this subject. It gives not 
 only an elaborately illustrated description of the ex- 
 ternal features and the histolog}^ of the skin and e^'^e 
 pigmentation in albinotic individuals, but also deals 
 with the histor}^ of the subject. Pure albinism is a 
 recessive character* : but the condition exists in vary- 
 ing degrees, and its inheritance, like that of so many 
 human qualities, frequently shows complications. 
 Complete albinism occurs in both white and coloured 
 races of man. Pearson divides albinotics into six 
 classes. Several cases of white spotting in negroes, 
 similar to the classical types seen in paintings of the 
 eighteenth century, have been described in modern 
 times. The evidence certainl}^, as Pearson (191 3) 
 contends, favours the hypothesis that spotting arises 
 de novo where a white-black cross or mixed race is 
 crossed back with a pure white or black. In other 
 words, spotting ma}^ be considered to arise in certain 
 cases as a somatic segregation, repulsion, or dilution 
 effect, and not to be clue to an inherited invisible 
 spotting factor. Striping in various flowers is 
 generall}^ believed to have originated in the same wa}^ 
 A similar case occurs in certain (Enothera hybrids 
 (Gates, 191 5). When (E. ruhricalyx having dark red 
 buds is crossed with CE. grandiflora having green buds, 
 the F;^ is paler red. If this F^ generation is crossed 
 back with Qi. grandiflora, the colour is further diluted, 
 becoming very pale; and in some families the pattern 
 breaks up into spots, a condition which is inherited. 
 
 Once this spotted condition has arisen, it appears 
 then to be fairly stable. Cases of human albinotic 
 spotting are on record which have been transmitted for 
 two to five generations (Stannus, 191 3). The con- 
 dition of spotting has, in some way, become stabilised 
 in the germ plasm, and should, therefore, probably 
 
 * A recent case in which two complete albino " white " 
 parents had an albino son is illustrated by Davenport (19 16). 
 
PHYSICAL CHARACTERS IN MAN 59 
 
 be looked upon as a mutation following crossing. 
 Moreover, the spotting in man often follows a charac- 
 teristic pattern, beginning as a blaze in the forehead, 
 with spotting of the arms, the back largely black, 
 as well as the extremities. Curiously enough, photo- 
 graphs of the Honduras piebald (Pearson, 191 3) seem 
 to show^ an extension of some of the coloured spots as 
 the child develops. The sporadic manner in which 
 spotting appears in all such cases remains to be ac- 
 counted for. The Honduras piebald had five siblings,* 
 all normal mulattoes. His mother combined Mexican 
 and negro blood, W'hile the father was a pure negro. 
 
 In an interesting case recorded by Dr. vSt annus 
 and cited in the monograph on albinism, piebaldism 
 was found to occur in five generations of a family of 
 natives at Florence Bay, Nyasaland, appearing in 
 nine individuals. Albinotic patches occurred in 
 the median line, on the anterior half of the scalp, 
 in the epigastric region, and broad " garters " about 
 the knees. The inheritance here extended to the 
 position of the patches. 
 
 In an English family the inheritance of a white 
 forelock has been traced through six generations by 
 Harman {Trans. OphUiaf. Soc, 1909). The white 
 forelock is accompanied by a patch of white skin 
 spreading like a flare down the middle of the forehead. 
 In some members of the famih^ there are also patches 
 of pure w^hite skin on the median line of the trunk 
 or the inner sides of the calves. The eyes were normal, 
 with no white eyelashes or parti-coloured irides. 
 The members of the family are long-lived and robust, 
 but have a tendency to early w^hitening ot the hair. 
 This piebald marking was found in twenty-four 
 individuals belonging to nine childships among a 
 total of 138 individuals in the six generations. The 
 children of normals were all normal. In the first 
 * This term means brothers and sisters taken collectively. 
 
6o HEREDITY AND EUGENICS 
 
 three generations all showing the mark were females, 
 but in the last three generations affected males and 
 females were equal in numbers, and inheritance was 
 thought to be through the males only. The data 
 indicate, however, that the peculiarit}^ is inherited 
 as a simple Mendelian dominant, chance accounting 
 for the absence of affected males in the early genera- 
 tions, and the small number of females who were 
 mothers in the later generations accounting for the 
 later lack of transmission through the mothers. 
 
 Pearson (1921) has recentl}^ described another 
 very similar case, with a white patch or flare on the 
 forehead and hair. In this famity there were seven 
 affected members hi four generations. This family 
 also goes gre}" ver}^ earty, and there is some tuber- 
 culosis but no consanguinity. This feature, of course, 
 resembles the white " star " marking often seen in 
 the forehead of horses and cattle, and frequentl}^ 
 accompanied by white patches on the extremities. 
 In this family the original great-grandmother in the 
 pedigree must have been heterozygous. In the 
 succeeding three generations the numbers of members 
 which were normal or flared were respectively 3:2, 
 4:1, and 6:3, making a total of 13:6. This is a rather 
 wide departure from the ratio which would be ex- 
 pected if the trait were a simple dominant, the odds 
 against its occurrence being 17-5 to i. But since un- 
 affected members never transmit the flare, it cannot 
 be a regular recessive. If the character is, as in other 
 cases, a simple dominant, the small numbers showing 
 the flare might, perhaps, be accounted for on the 
 assumption of the decreased viability of such hetero- 
 z3'gous individuals. 
 
 The occurrence and inheritance of a differently 
 coloured, usually white, patch of hair, is a fairl}- 
 common phenomenon. Darwin {Animals and Plants 
 under Domestication, chapter xii.) cites an English 
 
PHYSICAL CHARACTERS IN MAN 6i 
 
 family in which " for maii}^ generations some members 
 had a single lock differently coloured from the rest 
 of the hair," and an Irish family in which a small 
 white lock occurred in son, mother, and grandmother. 
 
 Cockayne (1914) states that piebalds are very un- 
 commion both in black and white races. He describes 
 a piebald English family of six generations with nine- 
 teen affected mem_bers, belonging to a farming stock 
 near Bury St. Edmunds, Suffolk. Some members 
 of the famil}^ are fair and some dark, but both inherit 
 the peculiarity, which consists of a blaze in the fore- 
 head. Three members of this family have hetero- 
 chromidia iridis, and some have additional white 
 patches of skin on the body. In the last four genera- 
 tions of affected families the total num.bers are seven- 
 teen having the flare to twelve* normal. This is near 
 enough to the equality which would be expected 
 if the flare were a heteroz^^gous dominant condition, 
 and is in general accord with Pearson's case, but the 
 excess is on the other side and is, perhaps, not signi- 
 ficant in either case. We ma}-, then, conclude that 
 the flare behaves as a simple dominant, at least in 
 these three independent families, and in the two de- 
 scribed in the following paragraphs. 
 
 A family with a white forelock occurring in four 
 generations has been described by Holmes and Scho- 
 field (191 7). This lock occurs in the centre of the 
 fore part of the scalp, the region affected being quite 
 small (size of a florin). Heterozygous females do not 
 show the mark. It would appear that the character 
 behaves as a dominant in males and as a recessive in 
 females (see Fig. 11), like the inheritance of horns 
 in crosses of a breed of sheep in which onh' the males 
 have horns with one in which both sexes are hornless. 
 In a white forelock family, described by Pearson, 
 Nettleship, and Usher in the monograph on albinism 
 
 * One of these is doubtful. 
 
62 HEREDITY AND EUGENICS 
 
 in man, the white lock occurred only in males, but 
 was transmitted through females, skipping a generation 
 in each case. 
 
 A much more interesting and extensive pedigree 
 of a white lock family is given by Miller (191 5). In 
 this familv the condition has been traced throucfh 
 six generations, including 203 individuals. Dr. W. B. 
 Little, whose mother is known to have had the lock, 
 emigrated from Carhsle, England, to New Brunswick, 
 Canada, about 1824, and his descendants through 
 four generations show the w^hite lock or flare. Some 
 members of the family also have one or more colour- 
 less spots on their bodies. The condition behaves as 
 a simple dominant, since in families with one normal 
 
 Fig. II. — Family showing a White Forelock. 
 
 and one marked parent the num.bers were fifty-one 
 normal and forty-five with the flare (where equality 
 would be expected) ; and where both parents are 
 norm.al all the children are the same. This family 
 traces its origin back through the Percys and Morti- 
 mers to Edward III. That the white lock is, at least, 
 as old as the family of Harrv (Hotspur) Percy is 
 know^n b}^ the tradition that the white lock originated 
 in connection with his death at the battle of Shrews- 
 bury in 1403. When the news of his death reached 
 his wife, she is said to have swooned and to have 
 given birth shortly afterwards to a son bearing a 
 white patch on his forehead. One member of the 
 famity has found from other records that the patch 
 
PHYSICAL CHARACTERS IN MAN 63 
 
 goes back at least to the Percys. It happens, also, 
 that Lad}^ Perc}^ was an albino. The white flare 
 may therefore, possibly, have originated with her, 
 for although no such case is on record, it is known 
 (see next paragraph) that spotted mulattoes arise 
 from an ancestr\^ in which different types of skin 
 pigmentation have been involved. 
 
 Another interesting case, first recorded by Simpson 
 and Castle (191 3), is of spotting arising in a coloured 
 race. It originated as a novelty — a spotted woman 
 born from ordinary mulatto parents in Louisiana in 
 1853. No case of spotting had previously been 
 known in that part of the country. She married 
 a normal black negro, and their children numbered 
 fifteen, eight spotted like the mother, and seven 
 normal, but var3dng in depth of colour as is usual with 
 mulattoes. Three of the normal children and three 
 spotted married normal negro mates. The normals 
 had in all seven children, all normal. The spotted 
 had in all nine spotted and two normal. This indi- 
 cates that all the spotted individuals, male and 
 female, behaved as heterozygotes, and that complete 
 segregation occurs between spotting and non-spotting. 
 The fact that spotting appears rarely and sporadically 
 among the innumerable mulatto crosses tells strongly 
 against it being the result of an inherited spotting 
 factor. The particularly clear evidence here indicates 
 that it arises as a mutation in the h\'brid stock, the 
 original spotted individual being heterozygous and 
 the piebald condition dominant to normal mulatto 
 pigmentation. 
 
 With regard to the ancestral colour of man, it seems 
 clear that the most primitive races were black (as 
 John Hunter concluded 150 3^ears ago), or at any 
 rate dark, as the}^ are now, and that the white race 
 arose from them wdth loss of pigmentation. It 
 appears unlikely that a simple mutation was involved. 
 
64 HEREDITY AND EUGENICS 
 
 Although albino mutations occur in black races, the 
 ' white " man is by no means devoid of pigmentation. 
 It appears probable that man}^ small germinal changes 
 affecting pigmentation were involved. The known 
 relations between skin pigmentation and the adrenal 
 capsules indicate that germinal changes which 
 affected the activity of these glands were really in- 
 volved. From recent studies of the endocrine gland 
 secretions, it appears that differences in the activities 
 of various endocrine glands are responsible not only 
 for the differences in pigmentation of the various 
 races of mankind, but also for their characteristic 
 physiognomies (see p. 211 ff.). 
 
 In the same way, it is highly probable that brown 
 w^as the primitive eye colour in man, and that blue 
 arose from it through one or more mutations, with 
 loss of pigment. (For a further discussion of this 
 subject see p. 44.) It may be that blue arose origin- 
 ally as a simple mutation from brown, and that 
 intermediate shades have come in later. This has 
 been shown to be the history of various cases of 
 melanism in Lepidoptera. But at present there is 
 no definite evidence to prove the point either way as 
 regards man. When blue e3'es were once established^ 
 they multiplied in the northern races, perhaps through 
 sexual selection, until blue eyes are characteristic of 
 the Scandinavian and other northern peoples. But 
 the native peoples in tropical countries appear always 
 to have retained brown e3^es, the pigment probably 
 being a protection for the e3^e against the strong rays 
 of the sun. The white race is thus in a sense an 
 albinotic variation, which has arisen through loss of 
 pigmentation. This loss has been carried still further 
 in the more northern races with fair complexion, 
 light hair, and blue e3^es. 
 
 In the Pearson monograph on albinism many early 
 records of albinotics are considered. It is concluded 
 
PHYSICAL CHARACTERS IN MAN 65 
 
 that there is no evidence that a tribe or clan of albi- 
 notics ever existed, but there are numerous records 
 indicating the existence of considerable numbers of 
 albino individuals. In connection with Dampier's 
 expedition to Darien in 1681, there is a long and 
 circumstantial account of the " white Indians," who 
 could see better by moonlight, etc. I'here is a 
 similar record for Brazil in 1775. Cortez, in connec- 
 tion with the Spanish conquest of Mexico, described 
 Montezuma's palace as containing an entourage of 
 albinos. In a similar w^ay, in the Middle Ages, fools 
 and dwarfs were considered a desirable accessor}- to 
 the retinue of kings and nobles. As late as 1841 
 Catlin described a " white Indian tribe " in Upper 
 Missouri containing many albinos. It appears that 
 albinism is now most frequent among the Indians of 
 Arizona and Mexico. Poole, in 1872, reported light- 
 haired and fair Indians from Queen Charlotte Islands 
 and British Columbia. Newspaper descriptions led 
 to a belief in a colony of albinos living in " the forest 
 country " back of Cape Cod, Massachusetts, but 
 Pearson could get no definite confirmation that such 
 a group ever existed, although it may have had some 
 basis in fact. 
 
 Albinism is known in most races and probably 
 occurs in all. Its frequency is unknown, but is esti- 
 mated at, perhaps, i in 5,000 or i in 30,000. In 
 Germany, out of nearly four million children dealt 
 with, about 400 had " w^hite hair." This would give 
 a frequency of i in 10,000. A similar proportion 
 was found in Norway. Of the 400 onl}' 32 had " red 
 eyes," and of these only 23 had also white hair: 
 hence only one complete albino in 200,000, but the true 
 prevalence may be greater. In Austria, from statis- 
 tics of insane albinotics, it was estimated that i in 
 400, or I in 2,000, of the population were albi- 
 notics. This very high estimate is probably due 
 
 5 
 
66 HEREDITY AND EUGENICS 
 
 to correlation between albinism and mental derange- 
 ment. 
 
 In Scotland loo to 150 living albinos were recorded 
 from about half the population. This indicates a 
 frequency of i in every 15,000 to 25,000 inhabitants. 
 Moreover, less satisfactory records are available from 
 many other countries and races. It appears that 
 albinism occurs as a mutation in the absence of cross- 
 ing of races, both in the dark and white races, but 
 it also frequently arises, as we have seen, a generation 
 or two after a mixture of races has taken place. The 
 piebald, apparently arising only from cross-breeds, 
 is far rarer than the complete albino. 
 
 Pearson also considers the pathological condition 
 known as leucoderma (white patches on the skin), 
 and finds there is no physiological differentiation from 
 albinism, the two being distinguishable only by the 
 inheritance of the latter. Pearson distinguishes 
 between spotlings and piebalds, the former including 
 those wdth white miarkings which do not extend to 
 extensive areas on the trunk. The extent of the 
 leucosis is probably hereditary, but there is no sharp 
 line between spotlings and piebalds. The spothng 
 of one generation may be the father of a piebald in 
 the next. Albinism, piebaldism, and leucoderma are 
 probably all to be accounted for by the same meta- 
 bolic defect. Leucoderma, however, is not necessarily 
 inherited. 
 
 A family in which albinism was carried as a reces- 
 sive for five generations is described by Sedgwick 
 (1861). The pedigree of this famil}' is given in 
 Fig. 12. One of the original great -grandparents 
 must have been carr3dng albinism as a recessive. 
 The wife of No. II. i must have been in the same 
 condition. Their daughter, Josephine (III. i), was 
 the only descendant of this son to show albinism. 
 The two grandsons, III. 2 and III. 3, married sisters. 
 
PHYSICAL CHARACTERS IN MAN 6- 
 
 both of whom evidently carried albinism recessive. 
 No. III. 3 had seven normal sons, five of whom 
 married, but only one of them had albino children. 
 This family numbered three normal sons, and nine 
 daughters, four of whom were albinos. The mother 
 again must have carried albinism as well as the 
 father, if the condition is, as usual, a strict recessive 
 (see p. 70). 
 
 In another record of Sedgwick, two grandsons in 
 a Swiss village had each two daughters, one normal 
 and one albino. The albino great-granddaughters 
 married. One had no children, the other had an 
 
 I 
 
 n 
 
 EL 
 
 m 
 
 D^O 
 
 xO 
 
 ^'xU 
 
 CF 
 
 X O 
 
 O X 
 
 V 
 
 Sisters 
 
 ^~^~^M, 
 
 thery 
 ch/ 
 
 4 ^5 A-.6 r^7 j^e J^9 J^IO ^ 
 
 xQ 
 
 4*«*66660 
 
 Fig. 12. — Pedigree of Albinism in a Family. 
 
 imperfect albino by a husband with black hair and 
 brown eyes. There was probably intermarriage in 
 both these lines of descent. 
 
 Little (1920) mentions that a piebald coat charac- 
 terises such breeds of dogs as foxhounds, beagles, 
 Boston terriers, St. Bernards, and collies. The 
 spotting reaches an extreme in bull terriers where 
 normally only the eyes are pigmented. The origin 
 of spotted individuals from t3'pical ancestors is 
 recorded in two pure breeds of pedigree dogs, and 
 it is considered that they may have arisen through 
 mutations. In the first a spotted female was born 
 from two solid-coloured pedigreed and registered 
 
68 HEREDITY AND EUGENICS 
 
 Scottish terriers, but since a certain dog occurs in 
 both the male and female ancestral lines the outcrop 
 of spotting would be accounted for if that animal 
 were carr34ng a recessive factor for spotting. In the 
 other case, four spotted puppies occurred in tw^o 
 litters of pedigree Airedale terriers. The pedigree 
 of the five previous generations shows that one male 
 occurred seven times and one female three times in 
 this pedigree, the former occurring on both sides of 
 each ancestral line. He was probably carr3"ing a 
 recessive factor for spotting, or possibly a mutation 
 giving rise to this factor took place in his gametes. 
 
 The wTiter (Gates, igoga) found in a cross between 
 a pure-bred Old Enghsh sheep dog and a Scotch 
 collie that F^ dogs were produced wdth several dif- 
 ferent lengths of tail, or no tail, like the mother, and 
 with many other differences in coat, build, and 
 temperament. It is probable that almost all our 
 pedigree breeds of domestic animals carr}^ some 
 recessive characters, w^hich have never been eliminated 
 since the original crosses, which in man}^ cases w'ere 
 the foundation of the breed. But these germinal 
 difi"erences must have arisen at some time through 
 germinal changes which gave rise to the parental t3^pes, 
 although similar germinal changes may equally well 
 occur afterwards and be carried as recessives in the 
 germ plasm until a cross or inbreeding brings them out. 
 
 The Pearson monograph includes also a study of 
 peculiarities of vision, such as night-blindness, as 
 well as the hair, of albinotics, and also albinism in 
 various animals. Complete albinos wdth pink eyes 
 are known to occur in " pure " races of man, just 
 as they occur in many mammals,* birds, and plants 
 
 * There are records, for example, of albino beavers, chipmunks 
 {Tamias), squirrels, woodchucks {Arctomys), robins {Turdus 
 migratorius\ and sparrows. Dean (1903) says: "True albinos 
 occur among hag-fishes, and partial albinos are not rare." 
 
PHYSICAL CHARACTERS IN MAN 69 
 
 (white petals). The monograph above mentioned 
 also includes a study of seasonal variation in animals 
 that are white in winter, such as Lepus variabilis in 
 Scotland. Crosses of white and black Pekinese does 
 are also believed to furnish evidence of the de novo 
 origin of spotting and blends. It is well knr^wn, 
 of course, that in certain breeds, as the Dalmatian, 
 particular types of spotting have become a fixed 
 characteristic of the breed. Numerous Mendelian 
 studies of spotting in mammals have been made in 
 recent years, especially in rabbits, rats, and mice, 
 and complicated theories of inheritance of spotting 
 have been formulated. The subject is complex and 
 far from settled, but it seems clear that in man}^ cases 
 degrees of spotting and their inheritance can be 
 explained on the basis of a series of factors for spotting. 
 The evidence clearly indicates, I think, the sporadic 
 de novo origin of spotting in man, but it does not 
 follow that the same is necessarily true for dogs. In 
 some breeds spotting, however attained, has the status 
 of a germinal factor, and the regularity with which 
 white-black crosses of Pekinese yield definite patterns 
 would seem to indicate another mode of heredity 
 behaviour — i.e., that a spotting or pattern factor is 
 present in these crosses. 
 
 Detlefson (1920) has described a herd of albino 
 cattle on a farm in Minnesota with several points of 
 interest. This herd originated from two albino 
 calves — a bull and a heifer — which resulted from 
 mating a " full-blooded " Holstein bull with " grade " 
 Holstein cows. The parents had the normal black- 
 and-white spotted coat colour, while the calves were 
 
 Standley (192 1) refers to an early American record of an albino 
 black bear with " four cubs, one white, with red eyes and red 
 nails, like herself," showing that albinism must have been 
 carried as a recessive in the strain. 
 
70 HEREDITY AND EUGENICS 
 
 pure white with pink eyes. The original bull produced 
 these two albinos out of matings with about twenty 
 grade Holstein cows, the remaining calves being nor- 
 mal. Unfortunately the original records of the herd 
 were destroyed by fire, for the later breeding behaviour 
 of these two albinos is peculiar. FYom its manner 
 of origin one would expect the albinism to be present 
 as a recessive character in the germ plasm of this 
 herd. But the young albino bull mated to grade 
 Holstein cows produced only albino offspring — about 
 twent}^ in number. The albinos mated inter se, 
 moreover, produced only albinos, and four albino cows 
 mated to a registered Holstein bull (the original bull 
 had been killed) produced three albinos and one 
 normal. It is not certain from these later matings 
 that the albinism behaved as a simple dominant, 
 for there is no record of coloured offspring from two 
 albino parents. But, at any rate, the later hereditary 
 behaviour is different from that at the time of its 
 original appearance as a mutation, and it is not clear 
 that this change in behaviour can be explained merely 
 as a reversal of dominance. 
 
 The albinos showed no pigment in the skin, eyes, 
 horns, or hoofs, except in one cow which had a small 
 black spot about one centimetre square in one ear. 
 There was no alteration in milk-production, but the 
 albinos were extremely sensitive to light, and grazed 
 listlessly during the day with partly closed eyes. 
 Such albinos are, of course, quite different from the 
 famous Chilhngham and Chartley herds and other 
 races of w^hite cattle. The evidence indicates that 
 in these the white is a dominant, and that they are 
 descended from original prehistoric wild white cattle 
 in Britain (see Storer, 1881, and MacDonald and Sin- 
 clair, 1882). The}^ are not pure white, but had typi- 
 cally black hoofs and muzzle, a circle round the eyes, 
 black tips to the horns, and in some cases a black tip 
 
PHYSICAL CHARACTERS IN MAN 71 
 
 to the tail. Wild white cattle from Thessah', etc., 
 were also known to the Greeks and Romans, and in 
 ItRly a white breed, in which the calves are yellowish, 
 continues down to the present time. 
 
 Three types of albino horses have recently been 
 described (Wriedt, 191 8) in two Norwegian breeds. 
 The heterozygous condition is intermediate in these 
 horses, and albinism appears to behave nearly the 
 same as in guinea-pigs. 
 
 Civilisation has often been credited with the pro- 
 duction of the numerous congenital deformities that 
 appear in man. But various studies, such as that of 
 Stannus (i 914) on the Bantus of Nyasaland, show that 
 the same abnormalities continue to appear, probably 
 with equal frequency, in native races, even though 
 the more marked of them are ruthlessly eliminated 
 by infanticide. It is evident that the conditions of 
 civilisation tend rather to preserve than to originate 
 abnormalities, and that natural selection in native 
 races, as in wild animals, combined with parental 
 selection, tends to eliminate individuals possessing 
 characters which place them at a disadvantage in 
 the struggle for existence. 
 
 A short account is published (Thadani, 1921) of a 
 Hindu Amil community in India, in which a toothless 
 type of man occurs. The men are not only toothless, 
 but bald-headed and extremely sensitive to heat. 
 The evidence, so far as it goes, indicates that the 
 character is sex-hnked. Anodont females are not at 
 present known, but if daughters of a toothless father 
 are married to a normal man, their male children are 
 toothless (Bhudas). 
 
 Left-handedness. 
 
 Another innocuous feature whose inheritance is 
 well known is left-handedness, which the results of 
 Jordan (191 1) and of Hurst {1912) indicate is inherited 
 
72 HEREDITY AND EUGENICS 
 
 as a simple Mendelian recessive character, at least in 
 some families. Ramale}^ (191 3) came to the same 
 conclusion, based on 1,740 cases. He estimated that 
 the condition is carried in about one-sixth of the 
 population. Left-handedness, as a character, may 
 bear some resemblance to reversed symmetry in 
 certain Gastropods. This reversal has been shown 
 by Conklin to begin in development with the cleavage 
 of the ^%%, the spiral cleavage being dextral in one 
 case and sinistral in the other, but its inheritance is 
 unknown. Ambidextrous individuals in man appear 
 to have inherited left - handedness and acquired 
 dexterity with the right hand. There are apparent 
 exceptions, how^ever (see Compton, 191 2, where a 
 number of references will be found), as in a family 
 quoted by D. J. Cunningham in the Journal of the 
 Anthropological Institute, xxxii., 1902, from Aime 
 Pere, where a left-handed mother and a right-handed 
 father had eight sons and six daughters, all left- 
 handed. If the father were heterozygous, this result 
 would be possible, though very improbable, even if 
 left-handedness were regarded as a recessive. It 
 would seem more probable that in such a case the 
 dominance has been reversed. There is also clear 
 evidence that in certain families the condition is 
 sex-linked. 
 
 A recent paper by Beeley (1920) considers left- 
 handedness from various points of view, and gives 
 a number of references to the literature of the subject. 
 Estimates of the frequency of left-handedness have 
 varied between 6 and 2 per cent., wdth 4 per cent, 
 as the medium frequency. This applies to American 
 Indians (Apaches and Pimas), as well as to white 
 races. That the condition is more frequent in man 
 than in woman has been affirmed and denied. Some 
 have found it more frequent among delinquents and 
 among negroes, but there seems to be no sufficient 
 
PHYSICAL CHARACTERS IX MAN 73 
 
 basis for these conclusions. Jordan, from an 
 examination of 700 university students, 1,394 
 coloured school children, and 668 others, concludes 
 that the condition is inherited, but is not very clear 
 that it follows Mendelian principles. Baldwin f(jund 
 that the tendency to use one hand more than the 
 other developed about the seventh month after birth, 
 when all influences to the greater use of one hand 
 were ehminated. The old idea that right-handedness 
 was developed because warriors held the shield with 
 their left hand to protect their heart and wielded the 
 spear with their right will not bear analysis with 
 modern conceptions. That right- or left-handedness 
 does not depend on a difference in the eyes is also 
 shown by the fact that there is the same proportion 
 of left-handed among the congenitally blind as among 
 those who use their eyes. 
 
 Beeley considers the results from 106,356 children 
 examined, and concludes that all degrees exist from 
 extreme left-handedness to extreme right-handedness. 
 Among this number of children were found fort}'- 
 two " mirror- writers." The results showed that 
 mirror- writing is not necessarily correlated with 
 mental deficiency, but rather it is characteristic of 
 extreme left-handedness. A method was devised 
 for measuring the degree of left-handedness by means 
 of a brass plate divided into squares, on which two 
 straight lines at right angles to each other were to be 
 traced. The squares were alternately insulated in 
 such a way that ever}^ error produced an electric 
 current which was recorded in a counter. The number 
 of errors in tracing the two lines, multiplied by the 
 time taken, was used as a measure of the degree of 
 left-handedness. Obviously general dexterity would 
 play an important part in a result of this kind, and 
 the age of the child would be an important element in 
 such a result. It is not, therefore, clear that the degree 
 
74 HEREDITY AND EUGENICS 
 
 of left-handedness forms such a continuous series as 
 these resuhs would indicate, although it is highly 
 probable, if not certain, that degrees of left-handed- 
 ness exist . Beeley suggests that a slightly left-handed 
 child should be taught to use its right, but that an 
 extreme left-hander should not. 
 
 That the right hemisphere of the brain controls 
 the left side of the body and vice versa is, of course, 
 well known ; also that the development of the speech- 
 centre may be interfered with by a too early attempt 
 to teach a left-handed child to use its right hand, 
 thus leading to stuttering. 
 
 The manner of clasping the hands, whether right- 
 handed or left-handed — i.e., with the right thumb 
 over the left or vice versa — although characteristic 
 enough for the individual, apparently bears no 
 relation to right or left-handedness. It does not 
 follow any known rule of inheritance, but appears, 
 nevertheless, to be partially inherited, for when both 
 parents show a right- or left - handed clasp the 
 majority of the children will be of the same t3^pe. 
 Statistics show that en masse the two methods usually 
 occur with equal frequenc}', but neither condition 
 breeds true. Compton (191 2) has studied the right 
 and left-handed seedlings (as regards the manner of 
 folding of the first leaf), which occur in various cereals, 
 but the condition is not inherited. Thus the seeds 
 from a left-handed (LH) plant produce the same 
 ratio of LHand RH plants as do the seeds of a right- 
 handed (RH) plant. In two-rowed barley this ratio 
 LH/RH was shown to be constant for three genera- 
 tions, and therefore inherited. In a total of 19,165 
 seedlings, the percentage of LH seedlings =58-362. 
 Seeds planted from the odd and even rows separately 
 also gave the same preponderance of left-handed 
 plants. Six-rowed barley gave a similar excess of 
 LH plants. In oats, however, there is regularly an 
 
PHYSICAL CHARACTERS IN MAX 75 
 
 excess of RH plants (LHr^44-88 per cent.)- This 
 difference may have some connection with the fact 
 that the leaf-blades of barley " are generally slightly 
 twisted into a right-handed screw, while in oats the 
 torsion is in the reverse direction." In maize, again, 
 there is no inheritance of left-handedness or right- 
 handedness as such, but the seeds in odd rows give 
 an excess of RH, those from even rows an equal excess 
 of LH seedlings. The ratios were 54-22 per cent, and 
 46-16 per cent. LH respectively. Thus, the total 
 numbers of LH and RH seedlings from a cob are 
 practically equal. Compton suggests that the 
 differences between row^s in this regard may perhaps 
 be accounted for by unequal pressure on the embryos. 
 In any case it is a relief to find something which is 
 definitely not inherited. The question of the limits 
 of human inheritance will be discussed in a later 
 chapter. 
 
 In 1908 a list of normal and abnormal features 
 in man, whose inheritance had been studied, was 
 published by Hurst, and Bateson (1909) devoted a 
 chapter to this subject. Davenport (191 2) also con- 
 sidered many cases, and Biomeirika contains masses 
 of statistical data on the inheritance of various 
 features. Abnormalities are frequently inherited as 
 dominants, and they probably originated as mutations. 
 Such are hexadactyly, brachydactyly, " lobster claw," 
 some forms of cataract, keratosis, congenital stationary 
 night-blindness (in certain famiUes), and many others. 
 Brittleness of bones or osteopsathyrosis (Conard and 
 Davenport, 191 5) is a remarkable congenital weakness 
 which appears to be inherited as a dominant character. 
 In one recorded case a boy suffered at least twelve 
 fractures of his limbs before reaching the age of three 
 years, being born with both thighs broken. Later 
 this extreme liability to fracture began to diminish, 
 but that it may still remain a serious defect in the 
 
76 HEREDITY AND EUGENICS 
 
 adult is shown by the fact that the mere tension of the 
 muscles or weight of the body, as in dancing, may be 
 sufficient to cause a fracture. Twins may be born 
 in families having the peculiarity, one showing the 
 defect and the other normal. Sedgwick (1863) cites 
 a family from Dr. Pauli with a less extreme form of 
 the condition, in which the brittleness was confined 
 to the bones of the upper extremities. It occurred in 
 three generations. 
 
 Digital Abnormalities. 
 
 We may now consider some of the digital peculiari- 
 ties whose inheritance has been studied in man. 
 A very good case is that of split hand and foot, or 
 " lobster claw." Lewis and Embleton (1908) consider 
 a collection of 180 cases of this deformity. They find 
 it by no means uncommon. Many varieties of the 
 condition occur. In the " G " family, to which many 
 of their data refer, the hands are variously misshapen, 
 and each foot consists of two toes separated by a 
 deep cleft. Rarely the toe on one side may be double, 
 and the toes are generally bent claw-wise at their 
 extremities. Both the hands and feet of these people 
 are said to have great functional capacity and 
 accuracy in use, including needlework and hand- 
 writing. The variations in the deformity are only 
 in degree. Rarely one or both hands ma}^ be normal 
 when the feet are split. The condition may also be 
 associated with syndactyly (fused fingers) or Poly- 
 dactyly (extra fingers or toes). Cross bones frequently 
 occur in the hands, but never in the feet. The in- 
 heritance is essentially that of a Mendelian domi- 
 nant, though the expected ratios are not always 
 adhered to. 
 
 In the " G " family this condition has been traced 
 through five generations. It never skips a generation. 
 
PHYSICAL CHARACTERS IN MAX -j-j 
 
 and derived normals x normals crive only normal 
 offspring. It is transmitted equally through either 
 sex. In the offspring of crosses between deformed 
 and normals, Lewis and Embleton find a total of 
 forty-four deformed to thirty-two normal. In some, 
 though not all, of the other data of inheritance of split 
 foot, they find a similar excess of deformed individuals, 
 w^hich appears to be significant. It does not neces- 
 sarily follow that the condition is not represented by 
 a single difference in the germ plasm. Indeed, they 
 agree that it has arisen as a " sport " or mutation 
 of germinal origin. They state " there are records of 
 over thirty instances of the origin of this same sport," 
 and account for this by the now widely accepted view 
 that mutations tend to occur and recur in definite 
 directions. Since the character is dominant it cannot 
 remain hidden in the germ plasm, but must appear 
 externally if the germ cell containing it develops into 
 an individual. 
 
 All writers agree that this character segregates 
 sharply, but they claim that it " does not follow the 
 laws of Mendel," because of the excess of abnormals 
 in the offspring of crosses with normals. This does 
 not necessarily follow, for it is now known that many 
 physiological and environmental conditions may cause 
 distortion of Mendelian ratios. Lewis and Embleton 
 beheve there is a " decided tendency for the de- 
 formity to die out " in later generations. They 
 appear to think that this results from the germinal 
 condition representing split-foot becoming unstable. 
 Perhaps the struggle for existence has something to 
 do with it, as well as sexual selection. 
 
 Pearson (1908) refers to the evidence for the 
 existence in Scotland of a family, " the Cleppie Bells," 
 with a deformed hand inheritance extending over 
 two centuries. He traces the deformity in another 
 family for four generations, and finds again an excess 
 
78 HEREDITY AND EUGENICS 
 
 of abnormals in the offspring of crosses with normals 
 (25 : 14). He concludes, " on the whole, w^hile these 
 cases give ver}- definite evidence of the segregation 
 factor, the}^ do not seem to me to favour the segrega- 
 tion in rigid Mendelian proportions." The stock of 
 this family is otherwise normal, and the}^ have no 
 difficulty in finding normal mates. The gait is un- 
 gainl}^, but the children at school hold their own in 
 writing, drawing, and needlework. Additional data 
 for this family are given by McMullen and Pearson 
 (191 3), the numbers of abnormals recorded having 
 increased from twenty-five to thirty-three. In the 
 third generation the result is in conformity with the 
 Mendelian expectation of equality of normals and 
 abnormals. In the fourth and fifth generations there 
 is a total of twenty-eight affected to thirteen normal. 
 Ever3'thing considered, it seems most reasonable to 
 regard the condition as due to a single Mendelian 
 dominant factor which arises from time to time as 
 a mutation, but which, through increased viability 
 or for some other reason, occurs in more than 50 per 
 cent, of the offspring from crosses with the normal. 
 Lewis (1909a) records certain other split-foot pedi- 
 grees. The only facts that need specially concern 
 us are : (i) a family of ten, in w^hich half are abnormal 
 and half normal; (2) a family of six, all abnormal. 
 In the latter the father may perhaps have been 
 homozygous. 
 
 Brachydact3dy is an abnormality which has been 
 even more studied in recent 3^ears, although it is 
 probabty much less frequent in its occurrence than 
 split-foot. The condition is illustrated in Fig. 13, 
 which shows normal and brachydactylous hands for 
 comparison, and Fig. 14, w^hich is a radiogram showing 
 the bones of a brachydact^dous hand. The earliest 
 stud}^ of the inheritance of brachydactyly was by 
 Farabee {1905) in an American family from 
 
PHYSICAL CHARACTERS IN MAN 79 
 
 Pennsylvania. He shows that the condition was 
 inherited as a simple Mendelian dominant, the off- 
 spring of the affected mated wdth normal giving 
 50 per cent, of each type (thirty-six affected, thirty- 
 three normal). Brachydactylous w^omen cannot play 
 the piano well owing to their inability to span the 
 octave. Brachydactylous men in this family include 
 farmers, mechanics, business men, and school teachers. 
 One was head of a commercial school and a fine pen- 
 
 FiG. 13. — Brachydactylous and Normal Hands for 
 Comparison. (After Drinkwater.) 
 
 man, another was a baseball catcher. The arms and 
 legs are short, but the sitting height is nearly normal, 
 and abnormals are stouter than their normal sibs.* 
 There is an unverified tradition in the family that the 
 first member with short fingers came from Normandy 
 in the army of William the Conqueror. Brachy- 
 dactylous individuals have never intermarried; but 
 the abnormals always marry first, and will soon 
 have gained a generation in this way. This was the 
 
 * That is, brothers and sisters. 
 
8o 
 
 HEREDITY AND EUGENICS 
 
 first case of Mendelian inheritance demonstrated 
 in man. 
 
 Drinkwater (1908) independently investigated a 
 British family, with the same results as regards 
 inheritance. He found that the strength of grip in 
 brachydactylous individuals was considerably below 
 
 Fig. 14. — Radiogram of a Brachydactylous Hand, showing 
 THE Two Phalanges in Each Finger. (After Drinkwater.) 
 
 the average. They complain that they cannot play 
 the piano or any other musical instrument requiring 
 normal length of fingers, their grasp of objects is 
 smaller than normal, and the women cannot do 
 netting. That they are handicapped is shown by the 
 fact that their social position is lower than that of 
 
PHYSICAL CHARACTERS IN MAN 8i 
 
 their normal relatives. They are engaged in un- 
 skilled labour, while their normal relatives include 
 farmers, grocers, etc. In a wild tribe where personal 
 defence with weapons is a necessity, brachydactylous 
 individuals would probably not survive. 
 
 In several papers Drinkwater has made a careful 
 anatomical investigation of brachydactylous hands 
 and feet, including radiographic studies. The con- 
 dition applies equall}^ to fingers and toes, and is 
 accompanied by short stature. In the digits he 
 showTd that the middle phalanx is very short, and 
 has become ankvlosed to the base of the terminal 
 phalanx. Hence the second phalanx is rudimentary, 
 and at a certain stage of development it unites with 
 the terminal phalanx. The most important feature 
 is the absence of the epiphysis (terminal cartilage, 
 which becomes ossified) at the base of the second 
 phalanx. The epiphysis may also, perhaps, be 
 missing in some cases from the third phalanx, the 
 second and third phalanges consisting at first of a 
 single piece of cartilage. The metacarpal (wrist) 
 bones are also more or less abnormal, but the meta- 
 tarsal (instep) bones are unaffected. This abnormal 
 f amity was ver}^ prolific, the number of children in 
 nine families averaging eleven each . A normal woman 
 had forty-five descendants, while a brachydactylous 
 woman in the same famity had ninety-nine descendants . 
 The numbers in successive generations show that the 
 condition is on the increase, and that there is no 
 chance of it becoming extinct so long as the brachy- 
 dact^dous members continue to marry. For some 
 unknown reason the}^ do marry more frequently than 
 their normal sisters. 
 
 The essential feature in brach3^dact3dy is, then, the 
 absence of the epiphysis at the base of the second 
 phalanx, with subsequent ankylosis of the second and 
 third phalanges. The fingers are about half the 
 
82 HEREDITY AND EUGENICS 
 
 normal length. Although brach3'dactylous individuals 
 are lacking in some forms of dexterity, and therefore 
 must accept a lower social status, yet they show a 
 decided increase in fecundity compared with normal 
 members of the same family. In this family twenty- 
 five now living in England and Wales are brach}^- 
 dactylous. Beginning with the fourth generation, the 
 total number of descendants from DR x RR* crosses 
 is seventy-five, of whom thirty-nine are abnormal. 
 
 No connection could be traced between Drink- 
 water's first brachydactylous family and the one 
 described by Farabee, there being no surname common 
 to the two families. Drinkwater (191 5) has since 
 described another family, how^ever, which he has 
 shown to be descended from a member of Farabee 's 
 familv, who removed from America and settled in this 
 country. In this family and its American ante- 
 cedents the abnormality can be traced for six genera- 
 tions. In both branches of this family the proportion 
 of females among the abnormals is exactly 61 per cent. 
 In the English branch fifty abnormals were recorded 
 to forty-eight normals, where 50 per cent, of each 
 type were expected, showing that heterozygous 
 brachydactyls produce the two types of germ cells in 
 equal numbers. Normals mated together invariably 
 have only normal offspring. The shortness of stature 
 of brach3^dactyls is shown to be due to the short legs, 
 both femur and tibia being shorter than in normal 
 members of the family. 
 
 Drinkw^ater has also described in two families the 
 condition which he calls minor brachydactyly (191 2, 
 1 91 4). In a Lancashire famil}^ this abnormality has 
 been traced through five generations, and sixteen 
 abnormals were living when the study was made. 
 The fingers are less shortened than in brachydactyly, 
 
 * D=dominant, R=recessive, hence DR is a heterozygous 
 dominant. 
 
PHYSICAL CHARACTERS IN MAN 83 
 
 but the middle phalanx of each finger is abnormally 
 short. This is partly due to the absence of the 
 epiphysis from the base of the second phalanx, 
 except in the thumb and middle finger, and also to 
 a slight shortening of the second phalanx, but is 
 chiefly due to the fact that the cartilage between the 
 shaft and the epiphysis becomes prematurely ossified, 
 thus causing cessation of growth in length of the 
 fingers at an early age. Ankylosis of the epiphysis 
 and the second phalanx frequently occurs earlier in 
 the first and fourth fingers than in the second and 
 third, thus leading to a greater shortening of the 
 former. The abnormality of the toes is practically 
 identical with that in ordinary brachydactyly. This 
 family is also shorter in stature. As in the brachy- 
 dactylous family, the women are 4I inches and the 
 men 8 inches shorter than their normal siblings. A 
 total of twenty-one abnormals to twenty-six normals 
 were recorded in families having one abnormal 
 parent. The abnormals in this family are said to 
 have better health than the normals. In the children 
 the abnormality is inconspicuous, and is sometimes 
 detected only by flexing the finger. 
 
 In the second family showing minor-brachydactyly 
 (Drinkwater, 191 4), the conditions closely resemble 
 those in the previous family, but so far as the records 
 go back there is no connection. It is found in five 
 generations, there being nine abnormals to ten 
 normals, eight of the former now living. They are 
 all descended from an illegitimate daughter of a short- 
 fingered man, the mother having been married to a 
 normal man by whom she had entirely normal descen- 
 dants . These forms of brachydactyly are, therefore, all 
 simple Mendelian dominants like split-foot, but they 
 show no appreciable excess of abnormals in inheritance, 
 and they show a clear tendency to increase rather 
 than die out, notwithstanding their social handicap. 
 
84 HEREDITY AND EUGENICS 
 
 or possibly on account of it. Bateson, who discussed 
 the earher records of brachydactyly (1909, p. 210), 
 refers to a four-generation pedigree, described by 
 Walker, of what appears to be a mild form of minor- 
 brachydactyly inherited in the same way. 
 
 Lewis (1909c), in a thesaurus of the results of the 
 study of brachydactyly, up to the time his paper 
 appeared, cites two other cases with interesting 
 
 Fig. 15. — Hand showing Abnormal Segmentation op' the 
 Index and Middle Fingers. (After Drinkwater.) 
 
 features. In Mercier's case a French family is 
 described in which eighteen members in three 
 generations are brachydactyl, having two phalanges 
 on all the fingers and toes. Hasselwander's case 
 (a German family) presents a feature of special 
 interest. There w^ere six abnormal members of the 
 family in three generations. The original brachy- 
 dactyl of this pedigree came from normal parents. 
 His advent must, then, mark an independent origin of 
 
PHYSICAL CHARACTERS IN MAN 
 
 8; 
 
 the condition through a mutation, unless possibly his 
 affected parent only had the condition in a slight 
 degree, and so was mistaken for a normal. The 
 actual origin of such a case is naturally difficult to 
 prove, and this can only be done where the conditions 
 in both parents and grandparents are accurately and 
 certainly knowai from observation to be normal. 
 
 Fig. i6. — Radiograph of the Two Hands of a Girl Aged 
 Nineteen, in the Same Family as Fig. 15. (After 
 Drinkwater.) 
 
 That various other modifications of typical brachy- 
 dactyly, in addition to those described above, are 
 inherited in the same way is shown b}^ such records 
 as those recently published by Dr. Drinkwater (191 6), 
 whose accurate work in recording these cases is of 
 great value. He traces through four generations a 
 case of abnormal segmentation of the index and middle 
 fingers, the third finger being much longer than any 
 
86 HEREDITY AND EUGENICS 
 
 of the others owing to the great length of its proximal 
 phalanx. The first and second fingers are also more 
 or less tilted away from the thumb (see Figs. 15 and 
 1 6) . There are thirty-six descendants of the abnormal 
 members of the family, fifteen of whom show the 
 abnormality. The feet in these individuals show 
 ordinary brachydactyly. From a careful study of 
 radiographs the following anatomical interpretation 
 emerges : The index finger has at its base an extra 
 triangular bone which sets the finger obliquely to the 
 hand. The proximal phalanx of the middle finger 
 appears to be divided equally or unequally into two 
 parts; the lower part, however, is probably an extra 
 bone corresponding to that in the index finger, and it 
 also is set somew^hat obliquety. In the adult hand 
 these extra bones become ossified with the proximal 
 phalanx of the corresponding finger. Another 
 peculiarity in this pedigree is the abnormal^ great 
 length of the proximal phalanx of the ring finger. 
 All these anatomical features behave as a unit in 
 inheritance, with remarkably little variation in their 
 development so far as observed. 
 
 Drinkwater (191 7) has described yet another digital 
 abnormality, which is remarkable for the number of 
 generations for w^hich it is known to have been 
 handed down in one family. The peculiarity is as 
 follow^s, as found in the hands of a gentleman, A. T., 
 of the present generation : In the middle finger the 
 joint between the middle and basal phalanges is only 
 very slightly movable, the articular surfaces of the 
 bones being enlarged, while in the ring and little 
 fingers there is no joint between the proximal and 
 middle phalanges, these two being completely fused 
 into one (see Fig. 17). All the fingers are movable 
 at the distal joint, and both hands are alike. All the 
 toes, except the hallux, are affected exactly like the 
 ring and little fingers. This man's father and his 
 
PHYSICAL CHARACTERS IN MAX 87 
 
 mother are known to have had precisely the same 
 abnormality. His father married twice, and one of 
 the half-brothers shows it. The most interesting 
 feature of this case is that A. T. is a direct descendant 
 in the male line from John Talbot, the first Earl of 
 Shrewsbury, who figures in Shakespeare's Henry VI., 
 
 Fig. 17. — Skiagram (Photograph by Rontgen Rays) of the 
 Hands of A. T., showing Continuity of the Proximal 
 AND Middle Phalanges in the Ring and Little Fingers. 
 (After Drinkwater.) 
 
 1 
 :> 
 
 and was killed in battle near Bordeaux in 145 
 Tradition has it that his thigh bone was broken 
 while on horseback, and that when he fell from his 
 horse he was killed by the blow of a battleaxe on the 
 head. His body was buried in a tomb inside the 
 church at Whitchurch, which was surmounted by a 
 
88 HEREDITY AND EUGENICS 
 
 stone effigy. In 1874 the tomb was opened and re- 
 paired by one of his descendants. The skeleton was 
 identified by the cleft skull and the fracture of the 
 right thigh bone. The finger bones, when examined, 
 showed the same ankylosis that exists in his modern 
 descendant. On the stone efhgy the fingers, w^hich 
 were somewhat damaged, also showed precisely the 
 same thickening of the middle joint as described in 
 his descendant. Clearly, then, this defect has been 
 handed down for more than 500 3^ears as a Mendelian 
 dominant, and the genealogy of the family shows that 
 it must have been inherited through fourteen genera- 
 tions. This, I believe, is the longest period on record 
 for the tracing of an anatomical abnormality in man, 
 though the Hapsburg jaw extends back equally far. 
 
 In America, Cushing (191 6) has described essentially 
 the same condition, but no connection with the 
 English family can be traced. The condition in this 
 family closely resembles, or is identical wdth, that 
 in Walker's Maryland family (see p. 84), though no 
 relationship between them has been traced (see also 
 p. 82). They are commonly spoken of as " straight- 
 fingered," because the fingers can only be partly 
 closed on the palm. There is complete absence of the 
 proximal joint in all except the index fingers, in 
 w^hich there is a trace of a joint. In this finger slight 
 movement is possible, but the middle phalanx is very 
 short. The greater effect on the middle phalanges is 
 true also of Drinkwater's minor-brachydactyly, and 
 is probabty due to the fact that the ossification 
 centres appear later in this phalangeal row, this being 
 the last row to ossify and the terminal row the first. 
 The toes are likewise affected, even occasionally, as 
 in '' lobster claw," when the hands appear normal. 
 It is quite probable, according to Cushing, that the 
 articulations betw^een the proximal and middle rows 
 of phalanges are the last to be laid down, and that 
 
PHYSICAL CHARACTERS IX jVIAN 89 
 
 " an inhibitory influence checks their development 
 at a stage a few days later than that which checks 
 the formation of the ossification centres and produces 
 brach3^dactyly." Hence both are conditions of 
 arrested development in different degree. 
 
 The original member of this " straight-fingered " 
 famil}^ Wilham B., migrated from Scotland to 
 Virginia in 1700. He married, and from him are 
 descended seven generations, most of whom still live 
 in the same region of Virginia. A member of the 
 fifth generation has communicated with a Scottish 
 relative w^ho shows the trait. The inheritance is that 
 of a Mendelian dominant, the family including 452 
 individuals in eight generations. Of the 150 children 
 of an affected parent in twent3'-eight completed 
 families, seventy-eight of them, or 52 per cent., 
 carried the trait. There is considerable variation in 
 the expression of the character, and the trait ma}' be 
 transmitted in extreme form b}' a parent who appears 
 to be but slightly affected. In one case a woman who 
 was doubtfull}' abnormal, but transmitted the trait, 
 was shown by radiogram to have the condition only 
 on the little finger of one hand. 
 
 Another family with the same peculiarity of fingers, 
 which cannot be flexed properly, is described by 
 Duncan (191 7). It is perhaps related to Cushing's 
 family, since its ancestors are said also to have come 
 from Scotland. The second joints of the fingers, 
 and frequently also of the toes, are perfectly inflexible. 
 The character is a Mendelian dominant and is traced 
 through four generations, the original affected parent 
 (male) being apparently heterozygous. 
 
 Another pedigree of a short-fingered family is given 
 by Mohr and Wriedt (191 9), who review the literature 
 of brachydact3dy. The case they describe, with 
 numerous photographs and radiographs, is of a 
 Norwegian family, some of whose members migrated 
 
90 HEREDITY AND EUGENICS 
 
 to North America. The malformation consists in 
 a shortening of the second phalanx of the second 
 fingers and toes only, and is called brachyphalangy. 
 There is no shortening of the stature. The condition 
 occurs in two degrees: (i) so slight as to be often 
 overlooked or even invisible; (2) more extreme, 
 probabh^ due to the presence of a modifying or 
 intensifying factor. The inheritance is that of a 
 simple Mendelian dominant. It has been traced 
 through five generations of descendants from a 
 brachyphalangous woman born in Norway in 1 764. 
 Detailed knowledge of the earlier generations is 
 obtained from a carefully kept " family book." In 
 two lines descended from an affected daughter and 
 an affected son of this woman, every individual is 
 recorded. In one case intermarriage within affected 
 lines apparently produced an individual homoz3^gous 
 for the character. She was a cripple without fingers 
 or toes, and died at the age of one year, being unable 
 to develop. This shows how serious even a slight 
 abnormality ma}^ become if present in the homoz3^gous 
 condition. It corresponds with many of the lethal 
 factors known in Drosophila. The writers refer to 
 Mackinder's (1857) record of a family, in which 
 brachyphalangy combined with h3^pophalangy (less 
 than five fingers) was transmitted for six generations 
 in the manner typical for a Mendelian dominant 
 character. This was in 1857, before even Mendel's 
 original work was done. 
 
 Cragg and Drinkwater (191 6) describe a much more 
 extreme case, w^hich Mohr and Wriedt refer to 
 as h\"pophalang3^ combined with brachyphalangy. 
 There is an entire absence of the distal phalanges 
 from all digits except the thumb and big toe, and an 
 extremely abortive condition of the middle phalanx 
 in the same digits. Nails are absent. The con- 
 dition was traced as a Mendelian dominant through 
 
PHYSICAL CHARACTERS IX .MAN 91 
 
 five generations, including twent^^-seven affected 
 individuals. In six of these there was also a bifurca- 
 tion of the thumbs, which may be due to the presence 
 of a dominant modifying factor. Wegelin ( 1 9 1 7) traces 
 through three generations an abnormalit}^ affecting 
 only the little fingers. The terminal phalanx is bent to 
 the radial side, the middle phalanx shortened, and its 
 distal end oblique. It is dominant, but there were four- 
 teen abnormal to two normal in the third generation. 
 
 The remarkable accuracy of the inheritance of 
 many digital malformations is shown incidentally by 
 a paternity case (Mohr, 1921), in which the alleged 
 father had a pronounced brachyphalangy affecting 
 the second row of phalanges on fingers and toes II, 
 III, and IV. The thumbs were normal, but the 
 basal phalanx of the great toe was shortened. The 
 hands and feet of the child showed exactly the same 
 malformation, and radiographs indicated absolute 
 correspondence in the bones. The man was there- 
 fore adjudged to be the father. 
 
 There is an early record* of a peculiar form of 
 brach3"dact\dy in which the mother and two children, 
 who were examined at Uxbridge, had normal thumbs, 
 but the fingers had only one phalanx each, except the 
 ring finger of the left hand, which had two phalanges. 
 There w^ere no nails on these fingers. All the rest 
 of the family were said to be the same, and the con- 
 dition was stated to have been inherited for nine 
 previous generations, but there are no records to 
 substantiate these statements. The character was 
 only transmitted by the w^omen, who sometimes had 
 a child wdth perfect fingers. 
 
 In another case (Rieder, 1899) the father had a 
 
 rudimentary (short) fourth metacarpal bone, the 
 
 ring finger being also short and small. The daughter 
 
 exhibited " lobster claw " in the right hand, while 
 
 * Edin. Med. and Surg. Journ., 1808, iv., 252. 
 
92 HEREDITY AND EUGENICS 
 
 the feet showed absence of certain toes, reduction of 
 certain phalanges, and syndactyly. Such combined 
 abnormalities in a line of descent are not infrequent. 
 Stieve (191 6) describes a case in which the thumbs 
 of both hands have an extra joint. He cites 39 cases 
 from the literature in which there is a supernumerary 
 phalanx on both thumbs, and 16 in which it is on 
 only one. In 33 cases of the former condition, 
 occurring in 10 different families, the condition is 
 known to be inherited, while there is no evidence of 
 its inheritance when it occurs on only one hand. 
 
 Danforth (igiga) describes a condition which he 
 calls brachydactyly in fowls. Such birds differ 
 from the normal in that digit IV, instead of having 
 five phalanges and being longer than digit II, 
 varies from as long as II (not longer) to a toe 
 having only two phalanges and no nail. He treated 
 with alcohol {igigb) fowls which w^ere heterozygous 
 for brachydactyly, Polydactyly (extra toes), and 
 white colour — both males and females, the alcohol 
 being inhaled for short periods. A larger percentage 
 of brachydactylous birds was consistently obtained 
 in the offspring of treated males, indicating that 
 germ cells carrying brachydactyly were more re- 
 sistant than normal germ cells, or possibly (though this 
 seems unlikely) that alcohol damaged the sperma- 
 tozoa so as to produce the defect. This experimental 
 method should be applicable to a variety of cases, 
 and furnish evidence of the relative viability of 
 different types of germinal differences. Ultimately 
 it might lead to a method of selectively eliminating 
 certain undesirable types of germ cells. The studies 
 of Pearl on the eifects of alcohol on pure races of 
 fowls, of Harrison with moths, and some other similar 
 results, indicate that in such cases there is a selective 
 weeding out of weaker germ cells, leaving the stronger 
 to take part in development. 
 
PHYSICAL CHARACTERS IX :\rA\ 93 
 
 Polydactyly and syndactyly (fingers or toes united 
 by a web of flesh) are also well known as inherited 
 conditions. Thus Reaumur's case of a Maltese couple 
 having a hexadactylous son, three of whose children 
 were again hexadactylous, is referred to by Huxley 
 {Darwiniana, p. 35). But usually such pedigrees are 
 incomplete, no account being taken of the normal 
 members of the family. Windle (1891) cites an 
 instance from Clement Lucas, where six fingers or 
 toes were inherited in a family through four genera- 
 tions. There appear to have been twenty-five 
 normals to seventeen hexadact^ds. In other records 
 the condition has been followed for six and five 
 generations respectively. There is some evidence that 
 Polydactyly is more common in negroes than in whites. 
 
 Lewis (1909^?) describes Lucas's case, in which 
 in several related families in two generations there 
 are twenty-four normals to fifteen polydactyls. 
 Other records cited show that the abnormality may 
 skip a generation. There is a large degree of variation 
 in the extent to which this dominant character is 
 developed. Polydactylism is found not only in man, 
 horses, fowls, and guinea-pigs, but also in monkeys, 
 dogs, cats, and other animals. Bonavia (1895) gives 
 several pedigrees of hexadact3dy in man, with a good 
 many cases of the inheritance of various abnormalities 
 and sudden monstrous variations in a number of 
 different animals. 
 
 Albert (191 5) describes a family with thirteen cases 
 of fused or webbed fingers or toes traced through finir 
 generations. The condition w^as obviously hereditary, 
 but was not inherited as a regular dominant or re- 
 cessive character. In three cases it appeared in 
 children neither of whose parents were affected, when 
 at least one of the parents had also a normal family 
 history. Probably such irregularities in the ex- 
 pression of a character result from inhibition of its 
 
94 HEREDITY AND EUGENICS 
 
 development by the presence of other determiners. 
 Many instances of the influence of hereditary de- 
 terminers upon each other are now known from 
 experimental breeding. 
 
 Schofield (1922) describes a case of webbed toes 
 which occurs in fourteen male members of a family 
 in four generations. The web appears only between 
 the two toes next the great toe, and is confined to the 
 skin and flesh. It is always more marked in the 
 right foot than the left, and is confined to the males, 
 being transmitted only from father to son. It thus 
 follows the course of the Y-chromosome. The only 
 case of this type of inheritance which has been 
 experimentally investigated (Schmidt, 1920) occurs 
 in the " millions " fish, Lebistes reticulatus, which is 
 a native of the West Indies. A dark spot on the 
 dorsal fin in certain males is transmitted in crosses 
 to all the male offspring, but is not transmitted 
 through the female line at all. Castle (1922) has also 
 recently pointed out the significance of this type of 
 inheritance in man. 
 
 Polydactyly and syndactyly in various forms are 
 not infrequently found together. A case of the kind 
 has been described in cats (Howe, 1902). A strain of 
 polydactylous cats in Cambridge, Massachusetts, was 
 descended from a polydactyl cat at the Harvard 
 Astronomical Observatory. One of these cats was 
 dissected, having six toes on each fore paw, and the 
 toes of the hind paws fused in pairs almost to the ends 
 of the claws. 
 
 Castle (1906) has described the origin of a poly- 
 dactylous race of guinea-pigs. He sa3^s that in man 
 " polydactylism usually makes its (recorded) ap- 
 pearance in some noteworthy form, is transmitted 
 more or less strongly through tw^o to five generations, 
 and then disappears, doubtless so weakened by re- 
 peated outcrosses that its manifestations, if any occur, 
 
PHYSICAL CHARACTERS IN MAN 95 
 
 are no longer observed." Normal guinea-pigs have 
 four toes on each front foot, but only three on each 
 hind foot. Castle's polydactylous race had four on 
 all feet. The missing digits in normals are the thumb 
 from the fore feet, and I and V from the hind feet. 
 The polydact\dous race was established from one rare 
 individual (mutation), and was afterwards found 
 twice in breeders' animals, but was not hitherto 
 known in any wild or domesticated Caviidce. By 
 selection through five generations a polydactylous 
 race was gradually established in which all the 
 offspring were polydactylous. The inheritance is 
 neither Mendelian nor blending, but probably inter- 
 mediate between the two. Without the aid of 
 selection, polydactylism would probabl}^ never become 
 a racial character. 
 
 In poultry, Bateson, Davenport, and others have 
 shown that the extra toe, which has for a long time 
 been an established character in some breeds, is not 
 strictly Mendelian in its inheritance, although it is 
 more strongly established than in the four-toed race 
 of guinea-pigs. 
 
 Radiograms of a hexadactylous Italian immigrant 
 with six fingers and toes are given in Joiirn. Heredity, 
 vii., 320 (1916). The condition appears to be due to 
 a split in the rudiment of the fifth finger. A five- 
 toed pigeon, due to a similar split in the rudiment of 
 one toe, is also shown. A case in which the thumb 
 is more or less completely missing from both hands 
 is photographed in Journ. Heredity, vii., 224 (191 6). 
 There were various digital malformations in the 
 relatives. 
 
 Bond (1920) crossed various five-toed and four- 
 toed breeds of fowls. The former were the silky 
 Dorking and Faverolle, and the latter Old English 
 Game, Wyandotte, and Orpington. The proportions 
 of four-toed to five-toed and heterodactylous birds 
 
96 HEREDITY AND EUGENICS 
 
 (with four toes on one foot and five on the other) 
 varied somewhat according to whether the male or 
 female belonged to the five-toed breed, and also in 
 Fj as compared with F^. In a total of 402 birds, 172 
 had four toes on both feet , and 3 8 were heterodact^dous . 
 Of the latter, 34 had the extra digit on the left side 
 and only 4 on the right. In 2 birds rudiments of 
 six toes appeared, suggesting that the character for 
 extra toe is not stable. Bateson and Punnett also 
 found that among 89 asymmetric birds from various 
 matings, the extra digit was on the left side in y2 
 cases, and on the right in 17. In 49 other birds the 
 extra toe was larger on one side than on the other, 
 being larger on the left side in 34 of these cases, and 
 smaller in 15. Barfurth, in similar matings between 
 normal and h^^perdact^dous fowls, obtained 556 
 four-toed and 475 hyperdact3dous. Of the latter, 
 6s were asymmetrical, 35 having the extra toe on 
 the left and 30 on the right. In another list 12 birds 
 were left-sided and 6 right-sided. Castle (1906) 
 in guinea-pigs also found a slight tendency for 
 the extra toe to appear on the left side. Out of 
 1,219 individuals, 630 had the extra digit on the 
 left and 582 on the right. The explanation is not 
 clear. 
 
 Bonnevie (191 9) describes a type of postaxial 
 Polydactyly in man, which is usualty stronger on the 
 right side of the body. The extra finger arises from 
 the base of the little finger, the metacarpal bones being 
 normal. There is much variation in this abnormality, 
 and families showing it are now distributed all over 
 Norway, but they are all probably descended from 
 the same ancestor about 300 3^ears ago. Boas (191 7) 
 assigns two causes for polydact3dy in horses : 
 (i) Atavism, " Hipparion-toes "; (2) doubling of 
 certain digital parts of the foot. The case of Caesar's 
 horse, which belonged to the former class, is well 
 
PHYSICAL CHARACTERS IN MAN 97 
 
 known.* This condition is rare. More or less complete 
 doubling of the extremities occurs in various mammals. 
 Cramer (1910) discusses cases of pol3^dactyly in man, 
 horses, a lamb, fowls, pigs, and a calf. Fackenheim 
 (1888) describes a family in which hereditary Poly- 
 dactyly is combined with tooth anomalies. The Heizler 
 family show^ed Polydactyly as a simple dominant in 
 four generations. A polydactylous man of the third 
 generation married a woman with tooth anomalies, 
 having two abnormally large, pointed teeth in place 
 of the incisors and only two cheek teeth. Of their 
 six children, three were normal and three showed 
 both abnormalities with some variations in the con- 
 dition of the teeth. 
 
 A recent case of polydactylism in cattle is described 
 (Roberts, 1921). Many instances have been recorded. 
 In this one, from a herd of dairy cattle in Illinois, a 
 normal bull mated with a polydactylous cow, having 
 three toes on each foot, produced a polydactN'lous 
 female. She was mated to a normal unrelated bull 
 and produced three male calves, all polydactylous, 
 but one with a duplication of the metatarsal bones 
 of the hind feet, which bore four and five toes re- 
 spectively. The character is evidently' dominant in 
 inheritance. The third or extra toe is on the inside, 
 and probably represents digit II. It is alwa3^s 
 larger on the hind feet than on the fore feet. 
 
 Bateson (1894, p. 376) describes a three-toed strain 
 of cattle from a three-tged cow bought in 1 861 . The 
 strain lasted until 1887, producing about ten genera- 
 
 * The reference is in Suetonius, Bk. I., chap. Ixi. : " Utebatur 
 autem equo insigni, pedibus prope humanis et in inoduin digi- 
 torum unguUs fissis." ("He rode a remarkable horse too, with 
 feet that were almost human, for its hoofs were cloven in such a 
 way as to look like toes.") The writer goes on to say that it was 
 born in Caesar's stables, that he tended it with great care and was 
 the first to mount it, and that a statue of it was afterwards dedi- 
 cated in front of the temple of Venus Genetrix. 
 
 7 
 
98 HEREDITY AND EUGENICS 
 
 tions. The condition appeared in both males and 
 females, but the bulls were not kept, so transmission 
 was only through the cows. About two calves in three 
 had the extra toe. The abnormality was confined 
 to the hind feet, except in one case. As the last 
 members of the strain were all males the breed was 
 lost. This instance of Polydactyly is very similar 
 to the last. The inheritance was evidently the same, 
 but the character itself show^s the interestinsr difference 
 that it is less extreme. It is confined to the hind feet, 
 except in one individual, whereas in Roberts's herd 
 it is present on all four feet, but is larger on the hind 
 feet. Such slight constant differences in abnormali- 
 ties are of fairly frequent occurrence, and they throw 
 an interesting sidelight on the structure of the germ 
 plasm and the almost infinite variety of the changes 
 which it can undergo. 
 
 A very good case of syndactyly in ungulates is 
 that of the mule-foot hog, a type with solid instead of 
 cloven hoofs, which has long been known in the 
 Western States of America, and is also found in 
 Germany and elsewhere. Detlefsen and Carmichael 
 (1921) find that in crosses between a pure-bred mule- 
 foot boar and pure-bred Duroc-Jersey sows the 
 offspring, numbering about 250, were all black and 
 mule-footed like the sire. Later generations showed 
 that syndactyly was a simple dominant to normal, 
 and black to red of various shades. 
 
 Bateson (p. 387) gives numerous data on the subject. 
 He states that solid hoofs in pigs is a relatively common 
 variation, that they are mentioned by Aristotle, 
 and are found in various parts of the world. Sir 
 N. Menzies at Rannock, Scotland, had a breed of such 
 hogs for forty years. They came from a pair, and 
 were black and of smaller size than the type, with 
 smaller ears. Their flesh was considered more sweet 
 and tender, and several hundred were bred at a time. 
 
PHYSICAL CHARACTERS IN MAN 99 
 
 In crosses they sliowed alternative inheritance, but 
 they tinally became extinct. Another pair of solid- 
 hoofed pigs was received by the Zoological vSociety 
 of London from Cuba in 1876. Auld (1889) reports 
 sohped (solid-hoofed) swine from Texas in 1878. They 
 bred true, and when crossed with the normal gave a 
 majority of solipeds. Another breed of solid-hoofed 
 hogs was reported from a farm at Sioux City, Iowa, 
 and a wild herd from near Baton Rouge, Louisiana. 
 In another instance a Poland-China boar with one 
 solid hoof had many offspring in the same condition. 
 Probably the solid-hoofed condition has arisen many 
 times through independent mutations. 
 
 A peculiar case is recorded by Colonel Hallam* of 
 a race of pigs observed in a town on the coast of the 
 Tanjore countr}' in 1795. Drawings of two in- 
 dividuals were submitted. The pigs had only two 
 legs, the hinder extremities being entirely wanting. 
 They bred true for at least three generations. Such 
 cases must arise through some mishap to an element 
 of the germ plasm. 
 
 Darwinf cites the following conditions in horses 
 as plainly hereditary: ring-bones, curbs, splints, 
 spavins, founder and weakness of the front legs, 
 roaring or broken and thick wind, melanosis, specific 
 ophthalmia, blindness, crib-biting, jibbing, and ill- 
 temper. He quotes Youatt : " There is scarcely a 
 malady to which the horse is subject which is not 
 hereditary." 
 
 Many records of syndactyly in man are extant, 
 but usually the inheritance has only been traced from 
 parent to offspring. It is recognised as a Mendelian 
 dominant condition. Hurlin (1921) describes a case 
 of limited syndactyl}^ in an old New England family 
 in which the web occurs only between the second and 
 
 * Proc. Zool. Soc, 1833, Part I., p. t6. 
 t Animals and Plants, chap, xii., p. -45^. 
 
loo HEREDITY AND EUGENICS 
 
 third toes, and is sometimes even there so slight as 
 to be scarcely noticeable. It is not found in the 
 hands at all. The condition is found in the grand- 
 father, in his onl}^ child (a son), and in three out of 
 six of the F2 generation in accordance with Mendelian 
 expectation. There is no doubt that innumerable 
 slight abnormalities of this kind occur in man and 
 are inherited in the Mendelian manner, as has been 
 shown to be the case with many similar mutations 
 in Drosophila. 
 
 Schultz (1922) adopts Weidenreich's term zygo- 
 dactyly for true webbing, confining the term syn- 
 dactyly to those cases where a union or fusion of 
 bones is involved. Zygodactyly is found in many 
 mammals. In a Sumatran ape Siamanga syndactyla 
 (see Wallace, Malay Archipelago, p. 134), the two first 
 digits of the feet are joined together nearly to the 
 end. In an early stage of development of the human 
 foot the toes are all webbed, and the webbing extends 
 slightly further between the second and third toes 
 than between any others. Webbing or zygodactyly 
 is, therefore, a case of arrested development. It is 
 also found that when certain toes are webbed the 
 corresponding tendons are joined for a greater dis- 
 tance. Schultz cites the observations of Schurmeier, 
 who examined 20,000 men in the American army 
 and found 8 cases of zygodactyly, always between 
 toes II and III. This condition was combined 
 in some cases with webbing of fingers III and IV, 
 or I and II and III and IV, or all fingers. In a 
 family described by Sommer, the webbing of toes 
 II and III was only on the right foot in all members, 
 the pedigree extending through five generations. 
 It was inherited by both sexes, probably as a simple 
 dominant. In Schofield's (1922) family the webbing 
 is always longer on the right foot and is transmitted 
 only from male to male, appearing in all the sons 
 
PHYSICAL CHARACTERS IN MAN loi 
 
 (13 cases) and none of the daughters (it cases) and 
 following the Y chromosome. In Hurlin's family, 
 mentioned above, the webbing was longer on the 
 left foot and was exhibited in both sexes. In three 
 other families, by Pfitzner, Wolff, and Wile, the 
 character also appears to be a simple dominant. 
 
 Sometimes syndactyly and polydactyl}^ appear in 
 the same family, as in the family described by 
 Manson (191 5). This family originated from one 
 William Joseph, born in Aberystwyth about the 
 beginning of the nineteenth centur3^ He had webbing 
 of the third and fourth fingers of his hands, and six 
 toes on each foot, and was probably homozygous for 
 this condition, since his nine children all had it. 
 They married normals, and had a total of eighteen 
 children affected, eighteen normal, four doubtful. 
 In only three descendants is the abnormality com- 
 plete in all four limbs. One, two, or three limbs may 
 escape. Skiagraphs show incomplete polydact^dism 
 in some cases. There is considerable variation in the 
 condition, but skiagraphs show clearly that the fourth 
 digit of the hands and feet is consistenth^ affected 
 by complete or partial reduplication. Another poly- 
 dactylous family is described by Atwood and Pond 
 
 (1917)- . _ 
 
 Many data concerning hyperdact}^}' are given in 
 
 a paper by Ballowitz (1904). Records of extra 
 
 fingers and toes are known not only in " Caucasians," 
 
 but also in Negroes, Arabs, Chinese, and Amerindians 
 
 (North American Indians). Most frequenth^ only an 
 
 extra terminal phalanx is present, but six-fingered 
 
 men have been known from the earliest times. In 
 
 the Bible (2 Sam. xxi. 20) a " giant " is mentioned 
 
 who had six fingers on each hand and six toes on 
 
 each foot. He was one of four men of exceptional 
 
 stature — sons of a giant. Pliny referred to hexa- 
 
 dactylous persons as Sedigiti. Anne Boleyn, the 
 
I02 HEREDITY AND EUGENICS 
 
 beautifulwifeof Henry VIII.,is said to have had super- 
 numerary breasts,* teeth anomalies, and an extra 
 terminal phalanx on hands and feet.f The " outside " 
 digits — i.e., thumb and little finger and great and 
 little toe — most commonly show doubling. Doubling 
 of other digits is much more uncommon, becoming 
 still more so as the number increases. Thus the 
 presence of ten digits on one hand or foot is extremely 
 uncommon in museums, while cases of seven are 
 relatively often described. This condition is often 
 combined with other abnormalities, but hexadactyly 
 and heptadactyly often occur in otherwise normal 
 individuals. The extra digits are frequently syn- 
 dactylous, not fully separated from their neighbours. 
 Hexadactyty is often symmetrical (two double 
 thumbs or two double little fingers), but there 
 are man}^ exceptions, and scarcely two cases agree 
 in detail. 
 
 Three main types of abnormality appear : 
 (i) Simplest and most common; the extra digit is a 
 small attachment not adherent to the skeleton, and 
 often without bones or cartilage, muscle or tendons. 
 (2) Often the extra digit is more or less like an 
 ordinary finger or toe, containing bones and con- 
 nected with the skeleton of the finger. (3) Ver}^ 
 seldom the extra digit is complete and also has its 
 
 * Other cases of supernumerary mammae in more than one 
 generation are cited, for example, by Darwin, Descent of Man, 
 p. 41. 
 
 t The only confirmation of this statement I have been able to 
 find is the following, from Wyat's Life of Anne Boleyn (Ed. Singer, 
 p. 423) : " There was found, indeed, upon the side of her nail 
 upon one of her fingers some little show of a nail, which yet was 
 so small, by the report of those that have seen her, as the work- 
 master seemed to leave it an occasion of greater grace to her hand, 
 which, with the tip of one of her other fingers, might be, and usually 
 was, by her hidden, without any least blemish to it." It is a fact, 
 however, that among the portraits of the wives of Henry VIII., 
 Anne Boleyn's is the only one in which the hands are not shown. 
 
PHYSICAL CHARACTERS IN MAN 103 
 
 own metacarpal or metatarsal bone. All possible 
 intergrades are said to occur between these forms. 
 
 Russian statistics are quoted of fourteen families 
 in w^hich the extra finger is inherited, also ten families 
 with six fingers and six toes, while Hennig in 1880 
 recorded Polydactyly in sevent3^-seven families. The 
 condition may extend through two to five or many 
 generations, and ten to forty h3^perdactylous in- 
 dividuals have been recorded in many families. 
 Polydactylous twins are twice recorded, and one 
 polydactylous twin sister had four normal sisters. 
 Reaumur's Maltese family is also quoted in detail 
 by Ballowitz. In two generations descended from 
 Gratio Kaleia, who had six fingers on each hand and 
 six toes on each foot, and his normal wife, there were 
 ten hexadactyls and six normals, but in the former 
 the abnormality did not always appear on all four 
 limbs. In the pedigree of Elizabeth Horstmann of 
 Rostock (Mecklenburg), who had six digits on all 
 four limbs, her daughter was like the mother, and 
 the next two generations from marriages with normals 
 gave seven hexadactyl to seven normal, in conformity 
 with expectation for a simple Mendelian dominant. 
 In another pedigree, Marie Schweizer of Fischbach, 
 three generations of descendants include eight hexa- 
 dactyl and ten normal. In yet another hexadactylous 
 pedigree (Alexander) there were in three generations 
 of descendants nine hexadactyls to ten normals. All 
 hexadactylous individuals in this pedigree showed 
 a striking symmetr}^ and in one male the condition 
 was combined with S3'ndactyly. In another pedigree, 
 quoted from Marchand, in which the condition ran 
 through five generations, a family of eight in the 
 fourth generation all had six fingers and six toes. 
 The father, who was hexadactylous, must have 
 been homozygous for the trait. The family of the 
 Sultan of Pontianak (Borneo) is hexadactylous, and 
 
I04 
 
 HEREDITY AND EUGENICS 
 
 this condition is recognised in each generation as a 
 mark of ro^^al distinction ! Ballowitz quotes from 
 the French hterature (1863) the case of an isolated 
 village in the Departement d'Isere, in which, through 
 inbreeding, nearly all the inhabitants had six fingers 
 and toes. Later, owing to increased communications, 
 marriages with normals took place, and the extra 
 fingers and toes in newborn children became smaller 
 and fewer, finally disappearing altogether. This is 
 a good example of the " weakening " and disappear- 
 ance of an abnormality through exogamy, but brachy- 
 dactyly does not appear to be affected in this way. 
 
 D X 
 
 6-6 
 ^6-6 
 
 ° □ X ^5 
 
 1 1 I I I I 
 
 6-6 
 
 10 Other children, all having 6 Fingers and toes. 
 
 m il«, X o 
 
 66 
 
 65 
 6-5 
 
 1 6-6 
 \6-6 
 
 i6-6 
 
 w 
 
 iff 6 i 
 
 6-6 
 6-6 
 
 i66 
 
 I 6-6 
 
 V — 
 
 Twins 
 
 ^6-6 
 
 mee 
 
 Zerah 
 
 ^^ 
 
 Fig. i8. — Pedigree of Hexadactyly. 
 
 If such weakening of a character like hexadactyly 
 can take place through exogamy, it is an important 
 hereditary principle which requires further elucida- 
 tion, especial^ in comparison with conditions like 
 brachydactyly where no weakening effect is observed 
 even after many generations of outcrossing. 
 
 An interesting hexadactylous family is described 
 by Carlisle (1814). Zerah Colburn, the son of Abiah 
 Colburn, born in \^ermont, was brought to London 
 on account of his " extraordinary powers in arith- 
 metical computations from memory." He had a 
 supernumerary little finger on each hand, and an 
 
PHYSICAL CHARACTERS IN MAN 105 
 
 extra little toe on each foot. The extra digits were 
 all perfectly formed, with nails and three phalanges. 
 The father also was hexadactylous, having five 
 metacarpal bones, but six metatarsals. The pedigree 
 of this family through four generations is given in 
 Fig. 18. Beside each is given (above) the number 
 of fingers and (below) the number of toes. The in- 
 heritance is strictly that of a Mendelian dominant, 
 with occasional failure of one hand or foot to exhibit 
 the abnormality. 
 
 In another hexadactylous famil}^ (Sedgwick, 1863, 
 p. 188) an extra finger with two phalanges and a nail 
 
 f 
 
 xO 
 
 o^ 
 
 'xn 
 
 ixo 
 
 i 
 
 i 
 
 6.6 
 
 6.6 
 
 I 
 
 6.5 
 
 W~^^ 
 
 66 66 
 
 Fig. 19. — Hexadactylous Family. 
 
 was attached to the base of the first phalanx of each 
 little finger. The condition was followed through 
 four generations. There was some variation in its 
 expression, and it skipped two generations both in 
 the male and the female line (see Fig. 19). 
 
 Schroeder (191 8) described a condition of hypo- 
 dactyly appearing in the hands and feet of a family 
 for five generations and accompanied by other 
 deformities. The strain originated with a woman, 
 who is said to have had normal parents. She j^ro- 
 duced three affected and two normal children, the 
 latter having only normal .descendants, while the 
 
io6 HEREDITY AND EUGENICS 
 
 former had twenty-eight normals to sixteen affected 
 offspring. The condition is transmitted by both 
 sexes, and shows a tendency to become less marked 
 in later generations. 
 
 Hawkes (191 4) has compared different t^^pes of 
 human foot as regards the relative lengths of the 
 first and second digits. From an examination of the 
 feet of 2,300 persons, chiefly children, he finds the 
 " L " type of foot, with the great toe longest and 
 the other toes sloping back in an oblique line, the 
 commonest. The '' S " type, in which the second 
 toe is longer than the great toe, is much less common. 
 Not very rarely one foot will be of the L type, and 
 one of the S type. This is in hetero zygotes, but 
 some persons with both feet L are heteroz3^gous. The 
 " E " type, in which digits I and II are of equal 
 length, is very unusual. The L t3^pe of foot shows 
 irregular dominance over the S t3^pe in inheritance, 
 but the S type occurs more commonty in females than 
 in males, and is commonest in the foetal stage. The 
 male heteroz}^gote tends to be L, and the female to 
 be S, in foot pattern. Occasionalh^ digit III is 
 longer than digit II, and this condition is also found 
 to be hereditar}^ 
 
 Various Abnormalities. 
 
 Lundborg (1920) concludes that hereditary deaf- 
 mutism is due to one Mendelian recessive factor, and 
 rejects Plate's h^^pothesis of two factors. Acquired 
 deaf-mutism ma\^ be either intra- or extra-uterine 
 in origin. Hence congenital deafness is not always 
 hereditar\^. Irish statistics of the ^xar 1891 register 
 congenital deaf-mutism as "jG per cent, of all cases. 
 In Norwa^^ (1897) the number was estimated at 50-9 
 per cent., in Sweden (1904) at 40-8 per cent., and in 
 the Malmohus district of Sweden (191 9) at only 
 28-2 per cent. (108 in 383). Meningitis and scarlatina 
 
PHYSICAL CHARACTERS IN MAN 107 
 
 are said to be the most common causes of acquired 
 deaf-mutism. In addition to the difhcuh}^ in dis- 
 tinguishing between genotypical (inherited) and 
 phenotypical (acquired) deaf-mutism a statistical error 
 is introduced by the fact that in small families the 
 children may all be normals, even when the parents 
 are heterozygous for the condition. Since these 
 children are not added to the offspring of matings of 
 heterozygotes, the result is more than 25 per cent, of 
 abnormals. This can be corrected by applying a 
 formula of Weinberg, and it then closely approxi- 
 mates to the expected 25 per cent. 
 
 From Fay's evidence of marriages of the deaf in 
 America (1898), twenty-two families had four to 
 nine children each, all deaf. The children numbered 
 112. Hence it appears that genotypical deaf-mutes 
 will have only deaf-mute children, and from this and 
 other evidence it appears that the character is prob- 
 ably a simple recessive. The difficulty in all statistics 
 on this subject is to distinguish between genotypic 
 and phenotypic deaf-mutism. Love (1920) also 
 reaches the conclusion that sporadic congenital 
 deafness is inherited as a Mendelian recessive, from 
 a stud}^ of an Ayrshire famil}^ which has branches in 
 America and Australia. This famil}' shows five 
 affected generations descended from a common 
 ancestor three generations further back. Yearsle}' 
 (1920) gives an account of a family with a history of 
 '' acquired " deafness, which produced offspring born 
 deaf. But as the acquired deafness is apparentl}' 
 hereditary otosclerosis, this is merely a case of the 
 earlier appearance of the abnormality. Home (1909), 
 in a study of deaf-mutism, says that the number of 
 deaf-mutes in Europe is estimated at about i in 1,350 
 of the population. In England the frequency (from 
 statistics) is i in 2,043, Scotland i in 1,860, Ireland 
 I in 1,398. Seven pedigrees are recorded, but 
 
io8 HEREDITY AND EUGENICS 
 
 there is no separation of hereditary and acquired 
 cases. 
 
 Myoclonus - epilepsy, marked by (degenerative) 
 spasms of various muscles, is also a disease transmitted 
 as a homogeneous recessive character. One of the most 
 complete of family studies is that of Lundborg (191 3) 
 on a farmer family in Southern Sweden having this 
 affliction. Among the 2,232 individuals examined 
 he groups (i) 11 families as DDxRR, with 166 
 children all normal; (2) 11 families DRxDR, with 
 93 children, of which jy reached an age of over 
 15 years. Of these, 24, or 31-2 per cent., were 
 abnormal. Applying the statistical correction of 
 Weinberg gives 21-8 per cent, abnormal where the 
 expectation is 25 per cent. (3) DRxRR, 5 families 
 with 46 children, of which 40 reached over 15 3^ears 
 of age. Twenty of these were normal, or 45-3 per 
 cent, with the statistical correction. This is the only 
 Swedish family known to have the peculiarity, and 
 the results are in very good agreement with Men- 
 delian expectation. 
 
 A condition which is said to be rare is hereditary 
 tremor. Bergman (1920) states that fifty families 
 showing this condition are mentioned in the literature. 
 It consists in rapid involuntary and rhythmic con- 
 tractions of certain groups of muscles. Usually the 
 arms and hands are affected, but sometimes also the 
 head or legs or the whole body. Hereditary tremor 
 most frequently appears in early youth, and often 
 increases in intensity later. It generally ceases during 
 sleep and perfect rest. Sometimes it appears only 
 in connection with exertions or emotions. The 
 tremor ma}^ be rapid (8 to 10 vibrations per second), 
 or slower (3 to 4 per second). People with hereditary 
 tremor are often nervous and emotionall}- unstable. 
 The handwTiting is affected, and may be almost 
 or quite illegible. Bergman traces this condition 
 
PHYSICAL CHARACTERS IN MAN 109 
 
 through three generations (four individuals) in a 
 Swedish peasant family. The condition is probably 
 similar to paralysis agitans, which is said to be due 
 to the degeneration of the parathyroid gland. 
 
 Ataxia in pigeons is apparently a very similar 
 condition. In 1914 Riddle (191 8) obtained in 
 breeding experiments a female pigeon with marked 
 lack of control over the voluntary movements of 
 head and body. It appeared, probably as a muta- 
 tion, under conditions of " reproductive overwork," 
 in which the bird is obliged to continue laying by 
 removing the eggs; and the condition has been in- 
 herited through five generations. About 175 young 
 have been reared, and of this number 1 19 were classi- 
 fied as normal and 46 as affected. From these and 
 other matings the evidence indicates that ataxia is 
 inherited as a simple recessive with some irregularities. 
 Affected birds show quivering movements, nodding 
 heads, unsteady gait, and irregular flight in various 
 degrees. Koch and Riddle (191 8) analysed the 
 brains of ataxic birds in comparison with the normal. 
 They found in the former higher values for water 
 content, protein, and extractive sulphur, with lower 
 values for lipoids, phosphatids, and cholesterol. 
 The results suggest a chemical immaturity or under- 
 development of the affected brain, more like those 
 of normals at a younger stage of development, but 
 further investigations of this subject are desirable. 
 
 In the mountains of Georgia a family is found 
 (vStuckey, 191 6) some of whose members for four 
 generations have had constricted eyelids. The sight 
 is normal, yet owing to this constriction it is necessary 
 for them to avert their heads in order to see. The 
 manner of inheritance indicates a segregating domi- 
 nant character. 
 
 Another peculiar case, of hereditary nose bleed, 
 is recorded (Lane, 191 6), members of a famil}' in 
 
no HEREDITY AND EUGENICS 
 
 Maine showing the trait through three generations. 
 It is not, hke haemophiha, sex-hnked. It manifests 
 itself by spontaneous bleeding at the nose almost 
 daily, beginning at the period of adolescence and 
 continuing until eighteen or twenty. Individuals 
 showing it are vigorous in health and grow rapidly, 
 often feeling discomfort if the bleeding does not 
 take place. 
 
 Diseases like haemophilia (abnormal tendency to 
 bleeding), Gower's disease (saltatory spasms), and 
 colour-blindness are well known to be sex-linked in 
 their inheritance, but with complications in the last 
 instance. Bulloch and Fildes (1910) bring together 
 a vast amount of information concerning haemophilia, 
 with many pedigrees. Nasse in 1820 asserted that 
 it is transmitted entirely by unaffected females to 
 their sons. Of the 171 recorded instances of trans- 
 mission, belonging to forty-four families, sixty conform 
 to the " law of Nasse." In the eleven other families, 
 in some of which inheritance from father to son was 
 supposed to have taken place, there is no good evidence 
 that this ever took place. Such apparent cases are 
 found to be explained by intermarriage of " bleeder " 
 families or in other ways. In the forty-four families 
 studied there were 644 males to 464 females — a great 
 excess of males . The marriage-rate of males in bleeder 
 families is ver}^ much lower than of females (9-6 per 
 cent. : 36-8 per cent.). The disease is rare. Lenz 
 (191 2) gives an extensive bibliography of haemophilia. 
 
 Among recessive conditions are alkaptonuria* and 
 albinism. The most extensive pedigrees of cataract 
 have been those collected by Nettleship {cf. Bateson, 
 1909). They show that various forms of cataract 
 are usually transmitted as dominants. Harman 
 (1910) classifies cataracts as lamellar, axial, stellate, 
 
 * A condition in which alkaptan (probably a derivative of 
 tyrosin) is present in the nrine. 
 
PHYSICAL CHARACTERS IN MAN iii 
 
 and polar. Details are given of a number of pedigrees 
 of inheritance, but no attempt is made to draw con- 
 clusions regarding the manner of inheritance. In 
 another paper, however, the same author (Harman, 
 1909) cites a pedigree of live generations showing 
 the condition to be a Mendelian dominant. Parents 
 who are normal have only normal children. Of 
 fifty-five persons, nineteen were known to be affected. 
 Others who w^ere not examined probably had the 
 defect slightly. Among forty-one persons personally 
 examined or certified, nineteen were cataractous. 
 This is very close to the expected 50 per cent. 
 
 The indications of the de novo origin of hereditar}' 
 congenital cataract are clearly substantiated by the 
 pedigree of a family whose history is described by 
 Danforth (191 4). That congenital cataract is a 
 dominant character has been disputed by Jones and 
 Mason {ig\6a), who, from a discussion of Harman's 
 data in the Treasury of Human Inheritance, conclude 
 that it is a simple Mendelian recessive. This con- 
 clusion was criticised by Danforth (191 6), who, how- 
 ever, did not hold that a single Mendelian factor was 
 involved. In their reply Jones and Mason (1916^^) 
 conclude that it is impossible to arrive at a satis- 
 factory view of cataract inheritance, but that the 
 hypothesis of a single Mendelian recessive is the one 
 that is best supported by the facts in hand. Detlefsen 
 and Yapp (1920) describe a case of congenital cataract 
 in cattle, which they conclude behaves as a simple 
 Mendelian recessive. A registered Holstein-Friesian 
 bull inbred with his own stock gave a number of 
 cataractous offspring. There is no record of cataract 
 in any of the ascendants. To unrelated cows this 
 bull produced only normal calves. But thirty-two 
 Fj daughters mated to an Fj son gave sixt^'-three 
 calves, fifty-five of which were normal and eight had 
 congenital cataract of the stellate t3'pe. 
 
I 12 
 
 HEREDITY AND EUGENICS 
 
 An early record of sex-linked colour-blindness 
 (*' Daltonism ") is of such interest that it is included 
 here. It was communicated to the Royal Society in 
 1 778 by the Rev. Michael Lort, and consists of a letter 
 from Mr. J. Scott to the Rev. Mr. Whisson of Trinity 
 College, Cambridge, describing his infirmity, and 
 stating which of his relatives also possessed it. This 
 has been thrown into the form of a pedigree chart 
 by Cole (191 9), from whom Fig. 20 is taken with 
 modifications. No. III. 3 is the deponent, and it 
 
 n 
 
 in 
 
 l^-^ 
 
 L_J 
 
 XYorXY 
 
 ffi 
 
 4 
 
 XX 
 
 k^ 
 
 /,— . 
 
 2,-s 
 
 XYorXY 
 
 XXorXX 
 
 XY 
 
 XY 
 
 4.- 
 
 XYorXY 
 
 o 
 
 XX 
 
 4 
 
 o 
 
 XXorXX 
 
 1 
 
 XY 
 
 XX 
 
 XY XY XY XX 
 
 Fig. 20. — Pedigree Chart of Colour-Blindness. 
 
 will be seen that his father and his mother's brother 
 were also colour-blind. His mother, though normal, 
 had a colour-blind son and daughter, and she must 
 therefore have been heterozygous for the character 
 (see Fig. 8, p. 23), which gives the history of the sex 
 chromosomes. Homozygous colour-blind mothers 
 transmit the defect to all their sons, as in generation 
 IV., while normal but heterozygous mothers transmit 
 it to half their sons. 
 
 Fathers, on the other hand, never transmit the 
 
PHYSICAL CHARACTERS IN MAN 113 
 
 defect to their sons ; but half their daughters by 
 normal mothers will, though normal, be transmitters 
 to half their sons by a normal father. Heterozygous 
 mothers with a colour-blind father will have 50 per 
 cent, of colour-blind daughters (while all the daughters 
 will transmit the defect), and half the sons of such a 
 marriage will also be colour-blind. Regarding the 
 deponent's grandparents there is no record, but the 
 grandmothers must both have been either colour-blind 
 or heterozygous transmitters of the defect, while the 
 grandfathers may or may not have been colour- 
 blind. 
 
 A shorter account of another case of colour-blindness 
 is given in a letter written in the previous year by 
 Mr. Joseph Huddart to the Rev. Joseph Priestley, 
 and published in the Phil. Trans., 1777. A shoe- 
 maker named Harris from Maryport, Cumberland, 
 was colour-blind, having discovered it at the age of 
 four years through being unable to distinguish a red 
 stocking from an ordinary (presumably black) one. 
 He also observed that " when young, other children 
 could discern cherries on a tree by some pretended 
 difference of colour, though he could only distinguish 
 them from the leaves by their difference of size and 
 shape." Colour-blindness consists essentially in the 
 failure to distinguish red from green. I'his man 
 " had two brothers in the same circumstances as to 
 sight; and two other brothers and sisters who, as well 
 as their parents, had nothing of this defect." Evi- 
 dently the mother was heterozygous, and transmitted 
 the defect to half her sons. According to Bateson 
 (1909), in European countries at least 4 per cent, of 
 the male population and less than 0-5 per cent, of the 
 females are colour-blind. 
 
 Bowditch (1922) describes three families related 
 through marriage, all showing the usual type of 
 sex-linked inheritance. In one of the families the 
 
 8 
 
1 14 HEREDITY AND EUGENICS 
 
 condition is present in the males of three generations, 
 being transmitted in one case through two genera- 
 tions of females before reappearing in a male. In 
 the second family there were two cases of colour- 
 blind females, one of whom had three sons, two of 
 whom were known to be colour-blind. 
 
 Little and Gibbons (1921) have recently considered 
 the inheritance of haemophilia and colour-blindness 
 in relation to the presence of sex-linked lethal factors, 
 which would, of course, follow the same line of in- 
 heritance. If there is linkage between a sex-linked 
 lethal factor and the normal allelomorph to haemo- 
 philia or colour-blindness (the latter being due to 
 different defects in one X chromosome, and the normal 
 to a non-defective X chromosome), then the authors 
 show that there should be an excess of abnormals 
 among the males in pedigrees in which these sex- 
 linked diseases occur, and a decreased proportion of 
 females in families in which an excess of affected males 
 does not occur. From the data of Bulloch and 
 Fildes (1910), as well as other data at the Eugenics 
 Record Office, they find these expectations fulfilled, 
 thus furnishing evidence of sex-linked lethal factors 
 in man.* 
 
 Congenital stationary night-blindness w^as recognised 
 as a Mendelian dominant b}^ Nettleship (1907). 
 It was in existence near Montpelier as early as 1637. 
 Data were afterwards obtained from the parish 
 records, and in 1836 Cuvier published a pedigree of 
 seven generations. The Abbe Capion completed 
 
 * Lethal factors have been most extensively studied in Dvoso- 
 phila. Their presence causes the normal development to go 
 astray, leading to the death of the organism at an early or a later 
 stage in its development. Enriques (191 9) has shown that in 
 the fly Calliphora erythrocephala, certain individuals produce 
 25 per cent, of non-vital offspring. The larvae cease to eat after 
 two or three days and then die. Some of the non-lethal offspring 
 in turn produce lethals in varying proportions. 
 
PHYSICAL CHARACTERS IN MAN 115 
 
 these records and added later ones, making; ten 
 generations. The night-blinchiess was first broiii^ht 
 to the village by Jean Nougaret, who was born 
 about 1637. It has therefore been handed down for 
 about 250 years through a large number of indi- 
 viduals. Bateson (1909, p. 220) gives a chart of this 
 pedigree. 
 
 In another family studied b}* Newman (191 3), 
 night-blindness (hemeralopia) is inherited like colour- 
 blindness, as a sex-linked character, being transmitted 
 through unaffected daughters of affected males to 
 some of their sons. This family is from Texas, having 
 originated in North Carolina. In one respect it 
 departs from the t3^pical scheme for sex-linked in- 
 heritance, in that there is " apparent non-inheritance 
 of the capacity to transmit night-blindness on the 
 part of the sisters of night-blind men." In F3 and 
 F5, if there were no consanguineous marriages, there 
 should be equal numbers of females carrying or not 
 carrying night-blindness. But none of the five 
 married sisters of F3 night-blind men show any 
 trace of night-blindness in their progeny. Newman 
 suggests that possibly night-blindness cannot be 
 inherited through two successive generations in the 
 female line, owing to prolonged association of the 
 defective X (sex) chromosome with a normal X. 
 The next generation will determine whether this is 
 the true explanation. 
 
 In its main essentials the character in this familv 
 behaves as a recessive located in the X chromosome, 
 but, as in haemophilia, there is an excess of abnormals. 
 Thus, of the 36 offspring of the night-blind-carrying 
 daughters of night-blind men, there were 22 (j", 14? , 
 and of these 22, 17 were affected and only 5 not. In 
 this family the night-blindness is usually accompanied 
 by m3^opia (short-sightedness), and almost invari- 
 ably by strabismus (squinting), Avith frequent occur- 
 
ii6 HEREDITY AND EUGENICS 
 
 rence also of pterygium.* It is believed that all 
 these conditions form one complex, and whether 
 all appear may depend on other factors present. 
 
 Nettleship (191 2) has also described a family in 
 which night-blindness was sex-linked and was as- 
 sociated with myopia. It would, therefore, appear 
 that the same condition may arise through an altera- 
 tion in the sex chromosome or in another chromosome. 
 
 The inheritance of manv other abnormalities of the 
 eye is known. For example, Folkar (1909) has traced 
 nodular opacity of the cornea through three genera- 
 tions, finding nine cases abnormal to nineteen normal 
 or unknown. 
 
 A bibliography of hereditary eye defects has 
 recently been published b}^ Howe (1921). Among 
 hereditar}^ defects are included corneal degeneration, 
 coloboma (congenital fissure) of the iris, aniridia 
 (absence of iris), glaucoma (a disease of the eye wdth 
 intense intra-ocular pressure, resulting in hardness of 
 the eye and blindness), cataract, congenital disloca- 
 tion of the lens, retinitis pigmentosa (inflammation 
 of the retina, with sclerosis, pigmentation, and atrophy 
 of the retina), atrophy of the optic nerve, micro- 
 phthalmus (abnormally small e3^es), myopia (short- 
 sightedness), astigmatism (a defect in the lens of the 
 eye, in which not all light rays are brought to a focus 
 at the same point), nystagmus (continuous rolling 
 movement of the eyeball), and ptosis (drooping of the 
 eyelid owing to paralysis). 
 
 Briggs (191 8) has studied the inheritance of ptosis 
 (paralytic drooping of the eyelid) through six genera- 
 tions from a w^oman having this ocular defect. The 
 lineage belongs to a family in the mountains of the 
 vSouthern States, and included 128 individuals, half 
 
 * Congenital pterygium or epitarsus is an abnormality of the 
 eye in which there is a fold in the conjunctiva or membrane lining 
 the eyelid and covering the front of the eyeball. 
 
PHYSICAL CHARACTERS IN MAN 117 
 
 of whom had the defect. Photographs are given, 
 and a chart indicating that the character is a 
 Mendehan dominant. 
 
 Nyctalopia or day-bhndness is also said to be 
 hereditary. Sedgwick (1861) cites a case of moment- 
 ary blindness after bending their heads in a father 
 and two sons. He also refers to the Le Compte 
 
 Q X % Blind at 35 
 n X % Blind at 19 
 
 1 
 
 4 4 A 6 i 
 
 bl.l3 bl.13 d-2 age 13 age 3 age I 
 
 Fig. 21. — Female Sex-Linked Blindness. 
 
 family, in which thirty-seven children and grand- 
 children became blind, like the grandfather, at the 
 age of seventeen or eighteen years. 
 
 Two interesting, because contrasted, pedigrees of 
 amaurosis or hereditar}^ blindness are given by 
 Sedgwdck (1863). In the first (Fig. 21) the condition 
 
 i * i i ii 6 6 6 
 
 Fig. 22. — Male Sex-Linked Blindness. 
 
 is apparently confined to the females, wdio go blind 
 before middle age. In the second the same con- 
 dition is confined to the males and skips a generation 
 in inheritance (Fig. 22). 
 
 Several pedigrees of sex-linked inheritance of excep- 
 tional interest are described or cited b}^ Sedgwick 
 (1861). One of them is a family with ichthyosis 
 
ii8 
 
 HEREDITY AND EUGENICS 
 
 (see also p. 122), which is evidentl}^ transmitted by 
 females to half their sons, as indicated in Fig. 23, 
 compiled from the data given. 
 
 In another family, cited from Cunier, thirteen 
 cases of ichthyosis occurred in five generations, and 
 all the affected individuals were females. Hence the 
 
 ^ o 
 
 n 
 in 
 
 IT 
 
 f 
 
 
 )xn 
 
 ri 
 
 7 
 
 Fig. 23. — Pedigree of Male Sex-Linked Ichthyosis. 
 
 condition is in this family female sex-linked. The 
 character must, therefore, behave as a dominant in 
 the females of the latter family and as a recessive in 
 the females of the former family. 
 
 An even more remarkable case of female sex-linked 
 inheritance is described by Cunier (1839), in which 
 
 F 
 
 4 
 
 ¥ 
 
 
 • 
 
 - 
 
 n 
 ni 
 
 1 
 
 2 
 
 4x 
 
 1 
 
 IV 
 V 
 
 |J-,3 rJ-, 
 
 4 rJL.5 X6 
 
 *f= 
 
 i'xD 
 
 1^ 4^xn d 
 
 i 
 
 8 
 
 Fig. 24. — Pedigree of Female Sex-Linked Colour-Blindness. 
 
 colour-blindness is inherited from mother to daughter 
 alone through five generations (see Fig. 24) in a 
 Belgian family. This again appears to be because 
 the character is behaving as a dominant instead of 
 a recessive. 
 
 The condition is transmitted from mother to 
 
PHYSICAL CHARACTERS IN MAN 119 
 
 daughter directly in the female line — that is, it is 
 sex-linked or, better, female sex-linked. It may be 
 spoken of as matrilineal in descent . The appearance 
 of the character in heterozygous females shows it to 
 be a dominant. We may think of such females as 
 having one affected and one normal X chromosome 
 (see p. 23). This would be transmitted to half the 
 sons, none of whom are affected, presumably because 
 the presence of the Y chromosome in some way 
 neutralises its activity.* Half the sons should then 
 be capable of transmitting colour-blindness to all 
 their daughters. Unfortunately the records of the 
 family furnish no data regarding the male lines of 
 descent in this famil3\ But it seems likely that if 
 such transmission had occurred it would have been 
 noticed, because the facts are evidently carefully 
 recorded. It is possible, therefore, that transmission 
 through the males may fail, just as it appears to fail 
 to be inherited through two successive generations 
 in the female line in the night-blind family studied 
 by Newman (191 3) (see p. 115). Another possible 
 explanation would be that only sons who have re- 
 ceived a normal X chromosome are viable. This 
 should lead to a deficiency of males in the offspring. 
 It is very interesting to find colour-blindness trans- 
 mitted as a sex-linked dominant in this family and 
 a sex-linked recessive in others. In this Belgian 
 
 family Madame Th (III. i. Fig. 24) and her aunt 
 
 and grandmother could not distinguish blue from 
 red (" rouge "), while her descendants confounded 
 blue with " cerise." The eyes of affected individuals 
 were very sensitive to light. 
 
 Sedgwick (1861) states that inability to distinguish 
 colours is often associated with inability to distinguish 
 
 * There is some evidence (see p. 94) that in man and in fishes, 
 unUke insects, the Y chromosome plays an active role in in- 
 heritance. 
 
I20 HEREDITY AND EUGENICS 
 
 sounds, and cites a famil}^ in which all the colour-blind 
 members were also stone-deaf. He also describes an 
 interesting famity, here thrown into pedigree form 
 (Fig. 25), having coloboma iridis or cleft iris. This 
 pedigree is difficult to explain, for it not only shows 
 transmission, as in an ordinary male sex-linked 
 character, through an unaffected mother to half her 
 sons, but also direct transmission from father to son in 
 two cases, unless the waves here happened to be trans- 
 mitters. One son (III. 7) only had the defect in one 
 eye. vSedgwick also describes cases of inheritance 
 of aniridia (absence of iris), amaurosis (blindness), 
 microphthalmia, absence of eyes, and squinting. 
 The latter is due to defective musculature of the 
 
 I Ox 
 
 i^ 
 
 nx6^ ¥ 
 
 n DxO bao 
 
 Fig. 25. — Family showing Cleft Iris. 
 
 eye, and is stated to be hereditary in some families 
 for many generations. In one family the five boys 
 squinted in the left eye or in both eyes, while the five 
 girls were normal. Their father and mother were 
 normal, but the mother's sister had a boy and girl 
 both squinting with the left eye. 
 
 A celebrated case which is often referred to in the 
 early literature is that of " the porcupine man," 
 Edw^ard Lambert. The first account appears to be 
 that of Machin (1733). A countr}^ labourer showed 
 his son, who was then fourteen, in London. The son 
 had a very scaly skin which did not bleed when cut, 
 but was callous and insensible. The skin was shed 
 every year in the autumn, a new skin growing up 
 
PHYSICAL CHARACTERS IN MAN 121 
 
 underneath. It had " bristly parts " about the 
 belly and flanks, which rustled like the quills of a 
 hedgehog. He was born normal, but the skin began 
 to turn yellow at the age of seven or eight weeks, 
 then by degrees changed to black, then thickened and 
 grew into its present condition. The parents were 
 apparently normal and had " many other children," 
 none of which showed this deformity, which seems 
 to have been an extreme form of keratosis. 
 
 Further details of this individual are given (Baker, 
 1755) w^hen he was about forty years old. The skin 
 most nearly resembled " an innumerable company of 
 warts," of a dark brown colour, and near an inch 
 in height when fully developed. His head and face, 
 palms and soles, alone were free from this condition. 
 He now had six children, all with the " same rugged 
 covering as himself," the condition making its first 
 appearance about nine weeks after birth. The 
 describer draws some interesting conclusions, which 
 we may quote in his own words : " It appears, there- 
 fore, past all doubt, that a race of people may be 
 propagated by this man, having such rugged coats 
 or coverings as himself; and if this should ever 
 happen, and the accidental origin be forgotten, 'tis 
 not improbable they might be deemed a different 
 species of mankind: a consideration which would 
 almost lead one to imagine that if mankind were all 
 produced from one and the same stock, the black 
 skins of the negroes, and many other differences of 
 the kind, might possibly have been originall}^ owing 
 to some such accidental cause." In modern language 
 we should call this individual a simple dominant 
 mutation, like so many of the other abnormalities 
 in man. 
 
 According to Sedgwick (1861), this condition was 
 perpetuated for two more generations, two brothers 
 of the fourth generation visiting Germany in 1802. 
 
122 HEREDITY AND EUGENICS 
 
 They had seven sisters who were normal, from which it 
 would appear that the character was male sex-linked — 
 in other words, recessive or suppressed in the presence 
 of the normal X chromosome in females, and 
 dominant or finding expression in the presence of 
 the Y chromosome in males. 
 
 A less extreme form of the same condition (Martin, 
 1818) was Jane Holden, aged three, whose whole skin 
 except the face w^as " covered with small scales, or 
 rather warty or bristle-like projections," light brown 
 to black in colour and constantly exfoliated. The 
 condition began at the age of three months. Her 
 mother was the same, except that the neck, breast, 
 and forearms, as well as the soles of the feet, were 
 free from this condition. Her parents were healthy, 
 and she was the only one of six children having the 
 disease. In this family, unlike the previous ones, 
 the condition is therefore not male sex-linked. 
 
 Still less severe forms of ichthyosis were formerly 
 said to be rather frequent on the Continent, and were 
 called "pellagra." Sedgwick (1861) quotes Itahan 
 statistics among the peasants of Lombardy, in which, 
 in 184 families, there were 671 healthy individuals 
 and 648 showing pellagra. From this it would appear 
 that the condition perhaps involved a simple Men- 
 delian recessive character. In modern studies of 
 pellagra (see Davenport, 191 6) in Italy, the United 
 States, and elsewhere the essential symptoms appear 
 to be inflammation and ulcerations of certain areas 
 (often symmetrically placed) of the skin, often accom- 
 panied by diarrhoea from ulcerations of the intestine. 
 These symptoms are due to the presence of a toxic 
 agent, which may also induce nervous and mental 
 disturbances in some individuals. Variations in 
 these symptoms are partly due to differences in the 
 hereditary constitution of affected individuals, leading 
 to differences in the susceptibility or resistance of 
 
PHYSICAL CHARACTERS IN MAN 123 
 
 various organs to the toxin. Davenport considers 
 that pellagra is probably communicable, but the 
 history of the disease will depend entirely upon the 
 constitutional conditions of resistance which it meets 
 in the organs of the body. When both parents are 
 susceptible to the disease, nearly half the children are 
 susceptible, while the disease affects less than i per 
 cent, of the whole population (statistics from Spartan- 
 burg Co., South Carolina). The high incidence in 
 certain strains will, then, be due partly to infection, 
 but also depends upon susceptibility, for susceptible 
 and non-susceptible children often occur in the same 
 family. Pellagra thus bears certain resemblances, 
 from an inheritance point of view, both to tuber- 
 culosis and cancer, and perhaps also to leprosy. 
 
 It was formerly widely held (Sedgwick, 1863) that 
 leprosy was hereditary, but that it descends by 
 collateral lines, and frequently skips a generation. 
 There is probably some basis for this view, which 
 deserves careful attention from modern students of 
 this disease. The lepra bacillus is known, just as 
 is the tubercle bacillus, but there may be constitu- 
 tional differences in the resistance to its attacks. 
 
 vSeveral other pedigrees showing sex-limited in- 
 heritance may be cited from a large mass of data 
 furnished by Sedgwick (1863). Pityriasis versicolor, 
 a skin disease, is confined to the males, but transmitted 
 by the females to their children in a family where the 
 grandfather, his three sons, and nine males of the next 
 generation all have it. In another family numerous 
 warts on the hands characterise the female line for 
 two generations, the mother and her three daughters 
 having them, the two sons normal. 
 
 In another family numerous sebaceous tumours 
 on the scalp occurred in a mother, her daughter, 
 and granddaughter, while the sons were free. The 
 brother's daughters, however, have them, '* as well 
 
124 
 
 HEREDITY AND EUGENICS 
 
 as several cousins of different degrees of relationship." 
 Hence the condition can be transmitted through 
 (unaffected) inales. This woman's mother, grand- 
 mother, and female relations backwards for seven 
 generations were similarly affected. " No female 
 who had attained her tenth year of age was without 
 them, whilst none of the males in the family ever had 
 them." In another family exactly the same manner 
 of inheritance occurred, a woman, the mother, 
 mother's mother, and so on, for two more generations, 
 all having scalp tumours, as well as several female 
 first and second cousins on the mother's side. Again 
 
 ixn 
 
 ¥ 
 
 ^n 
 
 i^i 
 
 W~¥^^.6^ 
 
 
 /<? 
 
 /2 
 
 d.3 9 
 
 2k. 15 
 
 13 
 
 D 
 
 5 
 
 Fig. 26. — Family showing Early Decay of Teeth. 
 The numbers beneath are the respective ages of the children. 
 
 all the females and none of the males developed the 
 condition. 
 
 A striking case of abnormal early decay and loss 
 of the teeth in three generations of a family is given 
 by Sedgwick (1863). It is confined to the females 
 (see Fig. 26), and there is no evidence as to whether 
 it is transmitted by the males. 
 
 Among family peculiarities which are known to be 
 inherited, one of the most notable is the large lower 
 lip and prognathous jaw of the Hapsburgs. Bateson 
 (1909) first suggested that this peculiarity was a 
 Mendelian dominant, and Haecker (191 1), from a 
 study of numerous portraits, confirms this conclusion. 
 The peculiarity dates back at least to Duke Ernst the 
 
PHYSICAL CHARACTERS IN MAN 125 
 
 Iron, who died in 1424, and it has been handed clown 
 continuously to the present time, hence for a period 
 of probabh^ more than 500 years, or fifteen to twenty 
 generations. The condition is less marked in the 
 women, and Haecker interprets it as the result of 
 the loss of an inhibitin£>: factor which normally reiiu- 
 lates in Europeans the development of the lower 
 lip and jaw. At least one other sporadic case of 
 prognathism is known to me, but I am not aware 
 of any other data concerning its inheritance. In 
 this case the father has the peculiarity, while one of 
 four children has it in an extreme degree and two 
 others to a less degree. This type of prognathism 
 suggests a mild form of the condition seen in the bull- 
 dog — a mutation which also occurs in cattle, foxes, 
 and other mammals. Donitz (1868), for example, 
 describes a fox skull shaped like a bull-dog's, w^ith 
 a short snout and the mandible turned up in front 
 of the premaxillse. See also Ktihn (1877) and Mivart 
 (1890), where much other information concerning 
 variations in dogs and other Canidae will be found. 
 
 Variations of the type just mentioned we now call 
 parallel mutations (see Gates, 1921, chap, v.), since 
 they result from similar changes in the germ plasm. 
 The list of such cases in mammals, given in Table IV., 
 is taken chiefly from Davenport (191 6), who further 
 points out that rabbits and guinea-pigs both show 
 agouti, yellow, chocolate, black, albino, and other 
 colours. Also the Angora t3^pe of coat is found in 
 rabbits, guinea-pigs, cats, dogs, goats, sheep (Lincoln), 
 and others. 
 
 The medical and anatomical literature on the subject 
 of the inheritance of abnormalities in man is much 
 too extensive to consider here. Only a few cases, 
 where the manner of inheritance through several 
 generations is known, are included. But in a great 
 number of other pathological and anatomical con- 
 
126 
 
 HEREDITY AND EUGENICS 
 
 ditions, no doubt, further research would disclose 
 equalty extensive pedigrees of inheritance. Hope and 
 French (1908) describe a family in which persistent 
 hereditary oedema (sw^elling due to the effusion of 
 water}^ liquid into the connective tissue) is traced 
 
 TABLE IV. 
 Comparative Table of Saltations. 
 
 
 I 
 
 2 '3 4 5 '6 
 
 7 
 
 8 19 10 
 
 II 
 
 
 
 Horses. 
 Cattle. 
 
 d 
 
 4= 
 C/3 
 
 
 
 c 
 
 Q 
 
 if. 
 
 a 
 1^ 
 
 
 
 
 1. Proopic brachycephaly, abbre- 
 
 viation of face 
 
 2. Sudden development of "horns" 
 
 on hornless races 
 
 3. Absence of horns on horned 
 
 races 
 
 4. Jaw appendages 
 
 5. Taillessness, absence of caudals 
 
 6. Short-leggedness, or limb ab- 
 
 breviation . , 
 
 7. Consolidation of paired hoofs, 
 
 syndactylism 
 
 8. Polydactylism . . 
 
 9. Epidermal thickenings 
 
 10. Mottled skin markings 
 
 11. Excessive hairiness or long 
 
 hair . . 
 
 12. Hairlessness, entire absence of 
 
 hair . . 
 
 13. Excessively fine or silky hair 
 
 14. Reversed hairs 
 
 15. Curled hair 
 
 XXXX X XXXX X XX X 
 
 * 
 
 X 
 X 
 
 X 
 X 
 
 X t X 
 
 X 
 
 X X 
 
 X 
 
 X X 
 
 X X 
 
 X X 
 X 
 X 
 
 X 
 
 X 
 X 
 X 
 
 X 
 X 
 
 X 
 
 X 
 X 
 
 X 
 X 
 
 X 
 
 X 
 X 
 
 X 
 
 X 
 
 X 
 X 
 
 X 
 X 
 
 X 
 
 X 
 
 X 
 
 X 
 X 
 
 X 
 X 
 
 X 
 
 X 
 X 
 X 
 
 X 
 
 y 
 
 X 
 
 * See p. 215. 
 
 I Chinese polo ponies. 
 
 through five generations, appearing in thirteen out of 
 forty-two individuals. This w^as accompanied by 
 nervous attacks in many cases. The inheritance, as 
 shown by the pedigree, is in accord with that of a 
 Mendelian dominant, except that one normal female 
 
PHYSICAL CHARACTERS IN MAN 127 
 
 has an abnormal child in a family of six. The swelling;- 
 of the legs, which was extreme in certain cases, was 
 usually kept down by w^earing bandages. vSeveral 
 individuals lived to over sevent}' with their legs 
 bandaged, having had the malady for sixty years or 
 more. This condition w^as first described by Milroy in 
 America, where it was traced through six generations, 
 and similar cases of hereditary oedema have been 
 described in France and England. Bulloch (1909) 
 gives nine pedigrees of trophcedema (with permanent 
 swelling of feet and legs), and finds it rather more 
 common in females than in males. In a total of 
 seventy-three affected individuals observed, forty-one 
 were of the former sex and thirty-tw^o of the latter. 
 Bulloch (1909) also describes angioneurotic oedema,* 
 or acute circumscribed oedema, in which there are 
 local swellings of the limbs, trunk, and face, and 
 the mucous membranes may also be involved. The 
 swellings are temporary, but often show remarkable 
 periodicity. There is direct inheritance in a number 
 of instances, or the disease may occur as a family 
 complaint. 
 
 Gossage (1908) cites many instances of inherited 
 abnormalities. Ichthyosis (a dry, rough, and scaly 
 skin), or keratosis (horny growths forming warts or 
 callosities) of the palms or soles is a Mendelian 
 dominant, and has apparentl}^ originated de novo 
 in two cases, one such woman having twelve chil- 
 dren, all, hke herself, abnormal. Multiple hereditary 
 telangiectasis (dilatation of the capillaries and minute 
 arteries) is apparently a dominant, but appears late: 
 fourteen abnormals to twenty-seven normals were 
 recorded. Other cases given are inheritance of 
 (i) tightly curled woolly hair; (2) epidermolysis 
 
 * This is a condition in which there is swelling in patches by 
 the accumulation of blood in the connective tissue owinj^ to a 
 disorder of the vasomotor system affecting the bloodvessels. 
 
128 HEREDITY AND EUGENICS 
 
 bullosa (a loosened state of the epidermis, with 
 formation of deep - seated buUse or blisters) ; 
 (3) bullosa; (4) early baldness with monilithrix (hairs 
 brittle and with bead-like enlargements); (5) hypo- 
 trichosis congenita familiaris (children born without 
 hair, or losing it a few months after birth) ; (6) enlarged 
 spleen; (7) polyuria or polydipsia (excessive secretion 
 of urine containing increased amounts of solid con- 
 stituents); (8) porokeratosis (a skin disease charac- 
 terised by hypertrophy of the corneous layer followed 
 by inward atrophy), etc. 
 
 Polyuria or diabetes insipidus is a condition in 
 which the kidneys fail to function properly, so that 
 the individual passes great quantities of urine of low 
 specific gravity. This causes excessive thirst, and 
 makes it necessary for the patient to drink gallons of 
 water dail}^ The condition may be either congenital 
 or acquired.* It is hereditary in a number of cases. 
 In Weil's case, cited by Bulloch (1909). J- ?• Schwarz 
 was born in 1772 in Oberhessen, and had 220 de- 
 scendants in four generations. Thirty-four of them 
 had diabetes insipidus. Three of his 5 children had 
 the affection, 7 of his 29 grandchildren had it, 13 of 
 his 66 great-grandchildren, and 11 of his 119 great- 
 great-grandchildren. In four of the larger families, 
 taken from the fourth, fifth, and sixth generations, the 
 numbers of normals and abnormals were respectively : 
 4:4, 2:4, 2:3, and 3:4, making a total of 11:15. 
 Hence the condition is, as usual, a Mendelian 
 dominant. In this pedigree it never skips a genera- 
 tion, except in one recorded instance of an affected 
 son (died age three) with normal parents. Occa- 
 sionally other instances of skipping a generation are 
 
 * This is an excellent example of the same peculiar character 
 being hereditary or not according to the manner of its origin — 
 i.e., as the result of a germinal change or an impressed modifi- 
 cation. 
 
PHYSICAL CHARACTERS IN MAN 129 
 
 recorded. Probably in such cases some favourable 
 condition in the transmitting parent prevents the 
 disease appearing. 
 
 Darwin, in his chapter on Inheritance, in the 
 Variation of Animals and Plants under Domestication, 
 refers to man}^ cases of inherited abnormalities in 
 man, but the knowledge of his time was insufficient 
 to explain them, as they can now be clearly under- 
 stood in the great majority of instances. He clearly 
 recognises this when he states, *' The laws governing 
 inheritance are quite unknown." 
 
 Differences essentially chemical are also involved 
 in many instances. The method of serum formation 
 and precipitation has been used as a means of testing 
 genetic relationships, both in animals and plants. 
 Learmonth (1920) has made certain interesting 
 observations in this connection. Human sera have 
 been classified into four groups, according to their 
 iso-agglutination* reactions. From a study of the 
 iso-agglutinins in the blood of forty families of 
 parents and children, it is concluded that tw^o 
 Mendelian factors, A and B, are concerned. Group I. 
 contains both factors, group II. contains A, group III. 
 B, and group IV. neither. These differences account 
 for the violent reactions which frequentl}'^ occurred 
 after blood-transfusion before the introduction of 
 blood-compatibility tests, since transfusion can only 
 take place safely between members of the same group. 
 With further experience the method will provide, in 
 many cases, a test of the paternity of a child. 
 
 Among hereditary abnormalities referred to b}' 
 Windle (1891) is polymastia or accessory breasts, 
 
 * An iso-agglutinin is an agglutinin capable of agglutinating 
 the red blood corpuscles of other individuals of the same species 
 as that in which it is developed. It is formed in the blood of an 
 animal by injection of the blood of another animal of the same 
 species. 
 
 9 
 
I30 HEREDITY AND EUGENICS 
 
 present in several cases in mother and child; hyper- 
 trichosis or excessive hairiness, which is said to be 
 usually associated with deficient dentition ; and gluteal 
 prominences, a racial character in Hottentot women. 
 Congenital luxation (dislocation) of the femur was 
 traced through five generations, and on both sides 
 of the house. Cleft-palate and hare-lip are said to be 
 undoubted^ hereditary, but many more data con- 
 cerning their inheritance are required. Rischbieth 
 (1910), in a study of these malformations, collated 
 the data regarding their incidence. They are often 
 associated. Frobelius examined 180,000 children in 
 the Foundling Hospital of St. Petersburg during 
 thirty years, and found one or both conditions in a 
 total of 1 1 8 cases, br o-o66 per cent. Among 67,945 
 children examined at London Hospital in 1908, 
 thirt3'-nine showed the deformity in one form or 
 another, hence a frequency of 0-057 P^^* cent. But 
 this figure is too low, because some children attended 
 more than once. The condition is said to be more 
 common among defectives, and it is often, though not 
 always, associated with other deformities. \ 
 
 Of similar origin are branchial fistula (failure of 
 the branchial clefts in the neck to close before birth), 
 and hypospadias (abnormal opening of the urethra), 
 both of which show signs of being hereditary. Eden- 
 tulism or partial absence of teeth, sometimes accom- 
 panied b}' a peculiarity of the hair, is hereditary, 
 and was traced through four generations in one family, 
 being accompanied by inherited polydactylism in 
 the fourth generation. Among malformations of the 
 eye, instances are quoted of microphthalmus, absence 
 of iris, coloboma (failure to close choroidal fissure), 
 congenital dislocation of the lens, and strabismus 
 (squinting) being inherited through several generations. 
 
 There are many early records of hermaphroditism 
 or allied conditions in man, many of which would 
 
PHYSICAL CHARACTERS IN MAN 131 
 
 now be classed as intersexual. Metchnikoff (1903) 
 concludes, from the presence in each sex of traces oi 
 the sexual organs belonging to the other sex, that at 
 a very remote period the ancestral vertebrates were 
 hermaphroditic, and that the sexes have only gradu- 
 ally become separated since. This is, however, a 
 ver}" doubtful line of reasoning. Bulloch ( 1 909) shows 
 that in man the condition may occur in several 
 members of a family or in several generations, a fact 
 which was known to Bauhin as earl}* as 161 4. But 
 the known pedigrees are incomplete, and little is 
 known of its inheritance. Blacker and Lawrence 
 (1897) and Lawrence (1906) discuss the cases of 
 " true hermaphroditism "in man. Thirty-three cases 
 of hermaphroditism (intersexualit}') are on record in 
 the medical literature. Of these only five, and one 
 which the authors describe, are regarded as true 
 hermaphrodites, defining the condition as one in 
 which the specific tissues of both ovary and testis 
 are present in any amount. Anatomical details of 
 these six cases, which vary greatly, are given. Xo 
 other cases are regarded as fully proven. Human 
 gynandromorphs, having male secondary sexual 
 characters on one side of the bodv, and female 
 secondar}^ sexual characters on the other, are not 
 unknown. Klebs classified " hermaphrodites " as 
 unilateral, bilateral, and lateral. 
 
 In these individuals there is frequenth' a tendency 
 for transformation from one sex towards the other 
 during the lifetime of the individual, as shown both 
 in behaviour and by anatomical examination. That 
 hens with diseased ovaries take on male characters 
 is, of course, well known. It is not our purpose to 
 discuss the various causes and phenomena of inter- 
 sexuality here, but it ma}' be pointed out that there 
 are several types of intersexualit}' in animals, in some 
 of which there is transformation from one sex to the 
 
132 HEREDITY AND EUGENICS 
 
 other, while in others the intersexual condition is 
 constant. Juhan Huxle}^ (1922) has discussed this 
 subject. In Drosophila (Bridges, 1921) the sexual 
 condition is shown to depend on a particular balance 
 between the XY chromosomes and the ordinar}^ 
 chromosomes (autosomes), as shown by the fact that 
 triploid individuals receiving only XX chromosomes 
 through non-disjunction are not females but inter- 
 sexes, while triploids with XXX chromosomes are 
 ordinary females. Banta (191 8), from his studies of 
 sex intergrades in Cladocera, concludes that maleness 
 and femaleness are not mutually exclusive states, but 
 that strains representing every quantitative intergrade 
 may be found. Crew (1921) and Witschi (1921)* 
 have shown that in frogs a real transformation from 
 females with ovaries to males occurs, and Crew in his 
 studies obtained the remarkable result that such a 
 transformed female mated with an ordinar}' female 
 produces only females (774 offspring examined in 
 tadpole and frog stage). This is, no doubt, because, 
 notwithstanding the somatic modification of a female 
 to a male, the structure of the germ plasm and the 
 chromosome content (XX chromosomes) remain 
 unchanged. It is not in this direction that any 
 practical application to the human race is to be 
 sought. 
 
 Shattock and Seligman (1906) describe a case of 
 hermaphroditism in a two-year-old Leghorn fowl. 
 The bird laid no eggs and did not crow, but it had 
 the comb, wattles, and spurs of a male, but not its 
 tail feathers. Both male and female genital ducts 
 w^ere present, with an ovotestis on the left side, and 
 apparently a testis on the right side. The authors 
 
 * Swingle (1922) controverts Witschi' s claim to have trans- 
 formed female frogs into males, showing that " appeal to the 
 somatic sex characters completely fails as proof of the trans- 
 iormation of female frogs into males." 
 
PHYSICAL CHARACTERS IN MAN 133 
 
 discuss the occurrence of hermaphroditic conditions 
 in reptiles, amphibians, fishes, and cyclostomata. 
 Hanna (1921) states several interesting facts regard- 
 ing hermaphroditism in seals. It is a rare condition 
 in mammals, and has not been previously recorded 
 in seals. Among 33,000 male seals killed on the 
 Pribiloff Islands of Alaska in 191 8, two were found 
 to be hermaphrodites. 
 
 An American family is described by Goldsmith 
 (1922) in which there are two round openings in the 
 parietal bones at the back of the skull. These 
 sometimes form a single opening in the younger 
 stages, and in some cases it may later close up entirely. 
 It is clearly a failure to complete development. In 
 five generations of this family sixteen cases are known. 
 The manner of its inheritance is not clear. Micro- 
 cephalic people occasionally occur in families (Bern- 
 stein, 1922). There is often more than one such 
 child in a family, but they seldom occur in successive 
 generations, and nothing appears to be known con- 
 cerning the inheritance of this condition. 
 
 Absence of the external ear is cited (Windle, 1891) 
 in a case where a normal father had a son with the 
 defect. The father's male cousin had the defect, 
 and two of his male children, but a daughter was 
 normal. A Mendelian dominant is suggested, a 
 result which is especially interesting in the light of 
 recent experiments with earless sheep, given below. 
 Sedgwick (i 861) cites a case of a boy with no external 
 left ear, the meatus being imperforate. This boy's 
 father had a male cousin whose tw^o sons exhibited 
 a deficiency of the cartilage of the left ear, while the 
 daughter was normal. The manner of inheritance 
 is not clear, except that it is from the original great- 
 grandparents, and it is confined to one side of the 
 head. In another case a woman, two of her daughters, 
 and two granddaughters had rudimentary lobules 
 
134 HEREDITY AND EUGENICS 
 
 to their ears, the male children and grandchildren 
 being normal. The rudimentary lobules probably 
 represent the heterozygous condition, but there is not 
 sufficient evidence of sex-linkage. Sedgwick (1863, 
 p. 457) describes a line of descent in three generations 
 with rudimentary ear-lobes adherent to the head. 
 The condition appears to have occurred onl}^ in the 
 women. It was present in the grandmother, in two 
 of her daughters, the third not being examined, and 
 one of the two sons examined being normal. One of 
 the daughters who had the peculiarity transmitted 
 it to her two daughters, the son being normal. No 
 doubt many other ear peculiarities are inherited. 
 The Kalmucks are said to have large and unsightly 
 ears as a racial character. 
 
 Lynch (1921) describes a mutation in the house- 
 mouse, in which the ears are about half the normal 
 length and somewhat narrower. They also differ 
 somewhat from the normal in outline, and are held 
 close to the head. The character behaves as a simple 
 Mendelian recessive. 
 
 Ritzman (1921) has found that short, thick ears 
 in a breed of sheep is a heterozygous condition, giving 
 equal numbers of both types of offspring in crosses 
 with the normal (sixteen short ear: sixteen long ear). 
 The mating together of short-eared individuals has 
 produced an earless ram, which therefore clearly 
 represents the pure recessive condition. Similar 
 results have been independently obtained by Wriedt 
 (191 9, 1 921), who adds that an earless ram mated 
 with normal sheep gave five offspring with short ears, 
 while an earless sheep mated with a normal ram pro- 
 duced one lamb with short ears. Earless individuals 
 mated together gave earless offspring. Short ears 
 in sheep were said to be very common formerl}^ in 
 Norway, and are still found in various parts of the 
 country. There is evidence that both the short-eared 
 
PHYSICAL CHARACTERS IN MAN 135 
 
 and earless conditions are found also in the Karakul 
 breed of Bokhara. 
 
 Lush (1922) describes the inheritance of a notch 
 in the lower margin of the ear in cattle. This character 
 is found in a Jersey bull at the Texas Agricultural 
 Experiment Station, and is inherited as a simple 
 dominant, the bull (Gamboge's Raleigh) being hetero- 
 zygous. Thirty of his calves were examined and 
 twelve found to be without the notch. There is much 
 variation in the degree of expression of the notch. 
 
 As an example of the inheritance of a slight 
 peculiarity may be cited the case of a bilobed ear 
 
 i 
 
 o 
 
 i 
 
 B^ 
 
 A 
 
 \ 
 
 B, 
 
 i 6 i i 
 
 A B2 B 
 
 Fig. 27. — Pedigree Chart showing Inheritance of Right 
 
 Bilobed Ear. 
 
 described by Schofield (191 7). In this family the 
 condition has been transmitted through four genera- 
 tions, only the right ear having the peculiarity. The 
 accompanying chart (Fig. 27) shows its incidence. 
 One generation or even two may be skipped, and the 
 condition varies considerably in different individuals. 
 Thus, in A there is a very marked deep cleft of 
 considerable length, while in those marked B the 
 cleft is not so well marked. In BB it was only a 
 furrow, while in B^ and B, there is a deficiency of 
 hearing in the bilobed ear. The family with pitted 
 ear-lobes, described by Jenks (191 6), is a similar case. 
 
136 
 
 HEREDITY AND EUGENICS 
 
 Kindred (1922) gives the pedigree of another family, 
 in which a pecuhar httle pit occurs in the skin at the 
 proximal end of the upper part of the helix of the 
 left ear. This is known to have occurred in four 
 generations, as is shown by the chart (Fig. 28). 
 
 The propositus (III. 7) has the pit, as well as her 
 father and father's father. Some of her father's 
 brothers and sisters probably had the mark, because 
 some of her cousins were known to have it. Three of 
 her sisters who married all had one or more children 
 showing the mark, although tw^o of them did not have 
 the pit themselves. One of the most remarkable 
 features of these slight peculiarities is their unilateral 
 
 n ,(> 
 
 5O 
 
 i © © ® © © 
 
 w 6, 6^ 6, k^ h, 6e 6, 4m^ 
 
 /O ^/l ^12 ^13 
 
 W ^// ^12 
 
 i, 
 
 14 
 
 *I3 
 
 Fig. 28. — Pedigree Chart showing Inheritance of a Small 
 
 Pit in the Left Ear. 
 
 occurrence, being confined to the right side in one 
 family, and the left in another. We are at present at 
 a loss to picture the hereditary mechanism by which 
 this comes about. 
 
 Of a similar nature is the case (Sedgwick, 1863) of 
 a Spanish nobleman who had one cheek bigger than 
 the other. His father and some of his uncles had 
 the same peculiarity. Another record of the same 
 writer (p. 464) is that of a patient in St. George's 
 Hospital in 1833. Neither he nor his father nor 
 grandfather had a patella (knee-cap). 
 
 Drinkwater (191 4) described an interesting case of 
 bimanual synergia, in which the individual is obliged 
 
PHYSICAL CHARACTERS IN MAN 137 
 
 to move both hands and arms in the same direction 
 at the same time. Only four other cases of this rare 
 condition are known in the medical literature, and 
 they were all recorded in Germany. In Drinkwater's 
 case, if the bo}^ held a pencil in each hand and wTote 
 with the right hand, the left would produce the 
 same words in mirror image form. Attempts to move 
 one hand when the other was held caused acute pain. 
 This case was unique in that the synergia was accom- 
 panied by similar sensations in both hands w^hen only 
 one was stimulated, the unstimulated member feeling 
 the sensation more intensely. Crossing of sensations 
 also occurred. Thus, when a hot test-tube was held 
 in the right hand, and a cold one in the left, the left 
 hand felt hot and the right cold. 
 
 The motor phenomena in this case were traced 
 through nine individuals occurring in four generations. 
 The manner of inheritance is in harmony with that of 
 a Mendelian dominant, except that one w^oman, four 
 of whose ten children showed the condition, did 
 not exhibit it herself. She probably, however, was 
 affected in infancy and outgrew it. Every infant has 
 to learn to use its right and left limbs independently, 
 and this power of unilateral control develops earlier 
 in some individuals than in others. One boy in this 
 pedigree w^as able to overcome the synergia at the age 
 of fifteen years, after repeated efforts. The condition 
 is, then, essentially one of failure in development of a 
 particular function. 
 
 Among many inherited peculiarities of the blood 
 system may be mentioned one cited by Windle (i 891 ) 
 from the Chicago Med. Joitrn. and Exa))i., 1879, 
 p. 475. The radial arter}' of a male in both arms 
 passed over the supinator longus muscle at 3 to 4 cm. 
 above the wTist, and ran over the radial extensors 
 above the styloid process to its normal distrilnition. 
 All his children had the same abnormalit}' on tlie left 
 
138 HEREDITY AND EUGENICS 
 
 side, and the daughters transmitted it better than the 
 sons. Amongst the grandchildren it occurred in four 
 on both sides, in four on one side, and was absent 
 in seven. 
 
 Bronchial asthma and hay fever form a closely 
 associated set of phenomena which are clearly inherited 
 in families, and have their basis in the nervous S3^stem. 
 Hay fever is a slight form of the condition, which may 
 develop asthmatic symptoms under special irritation 
 or lowered bodily vitality, and, as is wtH known, 
 may appear or disappear in an apparently capricious 
 manner at different ages or under different climatic 
 conditions. A considerable study of asthma from 
 the clinical and inheritance point of view has been 
 made by Adkinson (1920). She studied 400 cases, 
 and found a history of asthma in the family in 48 per 
 cent, of the cases. Of the total, 191 were sensitive 
 to proteins, as demonstrated by skin tests, while the re- 
 maining 209 w^ere negative to tests. There was a larger 
 percentage of inherited asthma in the former group. 
 
 The latter t^^pe or '' sensitive asthma " is more 
 like intensified bronchitis. Both types " run in 
 families," and both usually occur in different members 
 of the same familv. Asthma is found to be inherited 
 with equal frequency through either parent. Thirty- 
 eight family histories are presented, and the general 
 conclusion to be drawn from these is that the asth- 
 matic tendency is inherited as a Mendelian recessive. 
 Considering individual cases, " from the father's 
 family 66 patients ma}^ have inherited asthma, 
 39 directly, 8 skipping a generation, i skipping two 
 generations, and 18 collaterally. From the mother's 
 family, 64 patients may have inherited asthma, 
 25 directly, 22 skipping a generation, and 18 col- 
 laterally." It is found that " a nearly equal number 
 of men and women inherit asthma from the father, 
 but twice as many women as men inherit asthma 
 
PHYSICAL CHARACTERS IN MAN 139 
 
 from the mother, and 25 per cent, more women 
 than men inherit asthma directly from the parents." 
 
 It is concluded (i) that where both parents have 
 asthma or hay fever, all the children tend to show 
 the condition. (2) Where one parent has asthma 
 and one is normal (seventeen matings), all the chil- 
 dren (sixty) were normal. (3) When one parent is 
 asthmatic and one normal, but probabl}' carrying the 
 condition (simplex), then equal numbers of the off- 
 spring are affected or unaffected (sixt}^ asthmatic and 
 sixty-seven normal). (4) When both parents were 
 normal, but could be shown or must be assumed 
 to be carrying the condition (simplex), there were 
 three times as many asthmatic as normal children. 
 This is the reverse of expectation. It is partly ex- 
 plained by incomplete records of normals, and in part 
 by the addition of the non-transmitting type of 
 asthmatics. But it is at least possible that in a 
 character of this kind, in the cross DR x DR the 
 recessive character is able to express itself in some 
 instances in the heteroz3^gous condition. Whether this 
 is the case can be determined from further evidence, but 
 it appears probable that characters may depart from 
 strict recessive Mendelian behaviour in this respect. 
 
 Reference may be made here to the studies of 
 tuberculosis by Pearson (1907) and Goring (1909). 
 They compared the correlation between parent and 
 offspring as regards the incidence of the disease with 
 that between husband and wnfe, in order to determine 
 the relative importance of inheritance and infection 
 in the development of this disease. Pearson found a 
 correlation of 0-5 between parent and offspring, which 
 is about the same as for such characters as eye colour, 
 height, etc., indicating the same tendency to in- 
 heritance. Husband and wife, on the other hand, 
 gave a correlation of 0-24, and much of this was be- 
 lieved to be due to assortative mating. Pearson's data 
 
I40 HEREDITY AND EUGENICS 
 
 were taken from the upper classes. Goring studied 
 British convicts, and also found a correlation of o-; 
 for parent and offspring, but none for husband and 
 wife. 
 
 Wright and Lewis (1921) have made experiments 
 on guinea-pigs, in which they found marked differences 
 in resistance to tuberculosis in a number of inbred 
 families . The high resistance of one family was trans- 
 mitted b}^ either sex to the offspring in crosses with 
 other inbred families. It is found that the factors 
 determining resistance to tubercle are not closely 
 related to the other elements of vigour, such as growth- 
 ratio, adult weight, frequency and size of litter, per- 
 centage of 3'oung born alive, and percentage of young 
 raised to weaning. Inbreeding brings out differences 
 between families in these characters, as well as 
 independently in resistance to tuberculosis. 
 
 Nothing very definite appears to be known re- 
 garding the relation of cancer to inheritance in man. 
 In animals, however, many definite facts have been 
 determined. These are referred to by L. Loeb (192 1). 
 The inheritance of specific kinds of cancer in rats 
 and mice and other animals is known — e.g., cancer of 
 the inner canthus* of the eye in cattle, cancer of 
 the scrotum in rats, and sarcoma of the thyroid 
 in rats. Miss Slve has shown the inheritance of 
 cancer of the liver and other special forms of cancer 
 in certain families of mice. I am informed that the 
 late Professor Plummer recorded cancer in three 
 generations of wolves in the Zoological Gardens, oc- 
 curring always in the same place — viz., the shoulder. 
 In the fruit fly, Drosophila, Stark found two kinds 
 of inheritable tumour-like formations originating by 
 mutation. Others have since been found. Since 
 they cause death they are classed as lethal mutations. 
 Loeb concludes that the endemic occurrence of cancer 
 
 * 
 
 The angle next the nose where the eyelids meet. 
 
PHYSICAL CHARACTERS IX MAN 141 
 
 in animals is due to hereditary transmission of the 
 disposition to cancer. Infection from certain para- 
 sites may, in addition, act as an external stimulus, 
 comparable with Rontgen rays. 
 
 Probabl}^ in principle the conditions are similar 
 in man. Davenport {191 8) shows that the tendency 
 to neurofibromatosis* behaves as a dominant in 
 heredity, though it sometimes skips a generation. 
 It is a rare condition, being found in onh' one in 
 2,000 cases. Loeb believes that in man probably 
 one or more factors are hereditarily transmitted 
 which determine the intensity of the tendenc}^ to- 
 wards cancer development. In many cases, cross- 
 breeding appears to have equalised this tendency in 
 man. But in stationary or relatively pure popula- 
 tions, as in parts of Norway, there is evidence of 
 marked differences in the tendency to cancer in 
 different strains and races. 
 
 Stammering is due to an unusual excitability or 
 instability of cells in the speech centre of the cerebral 
 cortex. The tendency to stammer is clearly inherited, 
 although it not infrequently skips a generation. 
 Bryant (191 7), who has examined over 20,000 cases 
 in a practice extending over thirty-five years, states 
 that at least half had relatives who had suffered from 
 some nervous speech disorder. The condition begins 
 spontaneously in very young children beginning to 
 speak. A case is cited of stammering occurring in 
 four generations, but no other pedigrees are given. 
 
 The Jewish racialf physiognomy', which has been 
 
 * The formation of numerous tumours from necves, and con- 
 taining connective tissue. 
 
 t It is questionable in how far the Jews can be considered a 
 distinct race. Like most races, they have had a mixed origin, 
 probably from Armenoid and Hamitic stocks, as indicated by the 
 presence of both round heads and long heads among modern 
 Jews. The fair Jews evidently have an admixture of Nordic blood. 
 See also Salaman, Trans. Jewish Hist. Soc. Eng., ix. 163, 1922. 
 
142 HEREDITY AND EUGENICS 
 
 characteristic for over 2,000 3'ears, is believed by 
 Salaman (191 1) to show in marriages with Gentiles 
 incomplete or variable dominance and segregation. 
 Thus, from such marriages 328 children were classed 
 as Gentile in facial expression, twenty-six as Jew, 
 and eight intermediate. The subject is one which 
 invites more detailed study. Salaman points out 
 two other inherited peculiarities of the Jewish race: 
 (i) Amaurotic* family idioc}-, a disease whose victims 
 die in earl}^ childhood, and which is known onty in 
 Jews; (2) absence of alcoholism. 
 
 As our knowledge of the physiological controls of 
 development in the human individual increases, a 
 deeper anatysis of man}^ physical characters will 
 become possible. Various abnormalities in man, 
 such as brittle bones and blue sclerotics,t are already 
 believed to be due to an hereditary inferiority of 
 mesenchyme. J And the glands of internal secretion, 
 such as the pituitary, pineal, and thyroid, are alread}^ 
 known to control growth and to produce, by their 
 presence in excess or defect, various characteristic 
 conditions of the features or the limbs. Inherited 
 differences in these glands ma}' thus account for a 
 whole series of changes, not only in physical con- 
 formation, but in temperament as well.§ 
 
 What is often referred to as a remarkable feature 
 of human inheritance, which is observed also and 
 made use of in horse and cattle breeding (Hover, 
 1 91 6), is the occurrence of '' prepotency." Although 
 
 * Amaurosis is blindness without apparent lesion of the eye, 
 resulting from disease of the optic nerve, retina, brain, or spine. 
 
 J The hard, white, fibrous membrane forming the outer coat 
 of the eyeball, except at the front where it is replaced by the 
 cornea. 
 
 i The embryonic connective tissue, which forms not only 
 connective tissue, but also the bloodvessels and lymphatics. 
 
 § This subject will be referred to again more fully later (see 
 pp. 210, 219). 
 
PHYSICAL CHARACTERS IX MAN 143 
 
 there are facts which bear such an interpretation, 
 prepotency has not yet received a satisfactory 
 biological explanation, nor is it clear that the bio- 
 logical facts require one. Prepotency is believed to 
 be increased by inbreeding, and differences in vigour 
 or energy are also believed to be involved (Popenoe, 
 1 91 6). Mere dominance does not appear to be 
 sufficient to explain it, and the interactions of factors 
 may be concerned. The term should be used with 
 great care, as no case of individual prepotency has 
 yet been proved. Perhaps the most striking case in 
 man is to be found in the offspring of the Mormon, 
 Brigham Young (see Journal of Heredity, January, 
 1 91 6). In a photograph of some eleven of his 
 daughters by eight different wives each one seems to 
 have been stamped, as it were, with the father's own 
 image, though the resemblance is stronger in some 
 cases than in others, but the characters of the other 
 parent are by no means excluded. The resemblance 
 is particularly striking as regards the strong, firm 
 mouth, the ears, and the nose. But all the daughters 
 are said, by one who knew the family, to be also 
 musical, amiable, adaptable, genuine, sincere, w^arm- 
 hearted, generous, attractive, magnetic and S3'm- 
 pathetic, and temperamental yet reasonable. More- 
 over, all were good mimics and excellent cooks and 
 housewives, having also their father's voice and 
 temperament . This remarkable catalogue of qualities 
 is very well substantiated by an accompanying 
 photograph, which shows a group of motherl}-, kind- 
 hearted women with remarkable similarit}' of features, 
 although the mother's influence is also clear in the 
 differences which appear between half-sisters. This 
 resemblance is perpetuated in the grandchildren, 
 especially the girls, and may be partly attributable 
 
 to assort ative matmg. 
 
 Another question of heredity which I have not 
 
144 HEREDITY AND EUGENICS 
 
 touched upon here is the vexed question of functional 
 inheritance, which has been fully discussed by 
 MacBride (191 7), and has been considered elsewhere 
 (Gates, 1 921) in some of its evolutionary aspects. 
 The conceptions of Weismann regarding the insula- 
 tion of the germ plasm and its immunity from bodily 
 and environmental influence are now seen to have 
 been too extreme. Recent experiments of Guyer 
 and Smith (1920) are probably of significance in this 
 connection. B}^ injecting into fowls a finel}^ ground 
 suspension of the lenses of rabbits' eyes, the}' ob- 
 tained a serum from the fowl which was then injected 
 hypodermically into pregnant rabbits. The serum 
 contained a cytolysin* which in a few cases more or 
 less completely dissolved the lenses in the eyes of the 
 embryo rabbits, although those of the mother were 
 unaffected. Without any further treatment the 
 condition was intensified in later generations, and 
 was inherited through the male as well as the female. 
 If these results were actually due to the treatment, 
 as seems highly probable, the}^ have an important 
 bearing on the question of functional inheritance. 
 
 * A substance or antibody which produces dissolution of certain 
 cells. 
 
CHAPTER IV 
 
 INHERITANCE OF MENTAL CHARACTERS 
 
 IN MAN 
 
 When we consider mental and moral traits, the 
 
 evidence of inheritance in many cases appears sound 
 
 and beyond dispute, although in the matter of human 
 
 character it is less certain how far the accidents of 
 
 early environment ma}^ suppress or seriously modif\' 
 
 the expression of various inherited traits. Here 
 
 we are in a region where the structural basis of the 
 
 developed inheritance is so tenuous, and the contact 
 
 with the environment so intimate — character and 
 
 environment becoming so mutually involved and 
 
 interpenetrating — that it is conceivable that the laws 
 
 applying to structural characters are not applicable 
 
 with the same rigidit}- to the elements or methods 
 
 of reaction that go to make what we call human 
 
 character. Nevertheless, critical students of the 
 
 subject speak with one voice, and it is quite certain 
 
 that heredity plays an equally important role here 
 
 also. Indeed, the statistical results of Pearson (1904) 
 
 indicate that for siblings the intensit}' of resemblance 
 
 is as great for mental as for physical traits. He chose 
 
 eight physical characters — namel}^ health, e3'e colour, 
 
 hair colour, curliness of hair, cephalic index, head 
 
 length, auricular height, and athletic power — and 
 
 eight " mental " characters: vivacity, assertiveness, 
 
 introspection, popularity, conscientiousness, temper, 
 
 ability, and handwriting. While many of these 
 
 characters are not definite enough for anything 
 
 like accurate measurement, and therefore have no 
 
 decisive value, yet the coefficient of correlation 
 
 145 10 
 
146 HEREDITY AND EUGENICS 
 
 between brothers and sisters (siblings) comes out 
 0-51 for physical and 0-52 for mental characters. 
 Schuster and Elderton (1907), from a statistical 
 survey of Oxford class lists, attempted to determine 
 the correlation in mental ability between father and 
 son, and between brothers who attended the Uni- 
 versity. The}^ found r=o-3i2 for father and son, 
 and ^=0-405 for brothers. They agree with Pearson 
 that mental and physical characters are inherited 
 with the same intensity. 
 
 . Pearson has recently (191 9) considered the subject 
 again from different data, comparing the results of 
 applying the Binet-Simon test (a) to children in 
 orphanages in California, hence under nearty uniform 
 conditions ; (b) to children in schools of Great 
 Britain, under the greatest variety of conditions of 
 education and home training. Although the mental 
 environment w^as relatively uniform in one set of 
 data and diversified in the other, yet the correlation 
 of intelligence betw^een siblings w^as the same in both 
 groups, the resemblance, r =0-508 in the Californian 
 and r=0'5i5 in the English data, indicating that 
 heredit}' and not environment determined the differ- 
 ences in all cases. 
 
 But the situation as regards some ps3^chical charac- 
 teristics is beyond our present powders of accurate 
 anal3^sis. This is probably because we have not yet 
 learned to define ps^^chic characters in biological 
 terms. That psychologists are beginning to recognise 
 the necessity for an analysis of the mind from the 
 point of view of the inheritance of mental traits, is 
 shown particularly b}^ McDougall's book. Psychology, 
 the Study of Behaviour {e.g., p. 187). In writing of 
 the very close resemblances in intellect and character 
 which twins often show, he says : " The more children 
 are studied from this point of view, the more far- 
 reaching does the influence of heredity appear." At 
 
MENTAL CHARACTERS IN MAN 147 
 
 the same time, he finds it impossible to define, except 
 in the roughest way, the innate bases of these heredi- 
 tary pecuharities. He concludes that we are com- 
 pelled to believe the}' consist in " inherited mental 
 structures of very considerable degrees of specialisa- 
 tion." McDougall points out that biologists and 
 statisticians, in studying the inheritance of mental 
 qualities, have frequently used crude and non- 
 psychological popular distinctions, such as good 
 temper, courage, conscientiousness, or popularity, 
 and emphasises the need for accurate psychological 
 anal3'sis of the constitution of the mind as a basis for 
 the study of mental inheritance. Biologists must 
 undoubtedly look to psychologists for aid in this 
 direction. In speaking of ps3'chic characters we are 
 not merely referring to the grosser mental differences, 
 such as feeblemindedness and the presence or absence 
 of musical, mathematical, or general ability, whose 
 inheritance is almost universallv admitted ; but to 
 the less readil}' definable traits which go to make up 
 what we call temperament, disposition, and character. 
 These have not yet received adequate biological 
 classification, treating them as methods of reaction ; 
 but such a scheme, combined with observations and 
 comparison of the elements of human characters, 
 would certainly help to clarify our conceptions con- 
 cerning the basis of the differences involved. 
 
 May it not be also that in individuals who are 
 heterozygous for various character traits which are 
 alternative in inheritance, either method may come 
 into expression according to circumstances ? And 
 since every individual may be supposed to be hetero- 
 zygous for many pairs of traits of human character, 
 it appears possible that mental traits generally difiVr 
 from structural characters in that , in the former, all the 
 alternative possibilities may come into expression in 
 the same individual at different times, thus adding to 
 
148 HEREDITY AND EUGENICS 
 
 the complexit}^ of the result. What we call human 
 character in its developed form appears to consist 
 in the acquired habit of inhibiting certain inherited 
 tendencies, and giving free expression to others. 
 But then, again, differences in powers of inhibition 
 are undoubtedly inherited, and weakness in such 
 powers ma}^ lead in the one extreme to vicious 
 tendencies, and in the other to a free expression of 
 the other elements of the inheritance. Nevertheless, 
 there is always a choice of ideals to be aimed at, 
 and it is necessary to distinguish in conduct between 
 those who fail to reach their ideals and those who 
 deliberately pursue non-moral ends. 
 
 The lay mind frequently goes astray on the question 
 of the inheritance of abilit}^ by assuming that if the 
 sons of an able father do not themselves show ability, 
 this is a case of " failure of inheritance." In a 
 scientific view of inheritance in such a case, one of 
 the alternative factors has been inherited instead of 
 that which conditions ability — an undesirable instead 
 of a desirable quality has been handed on — or at 
 least one of the necessary elements for the expression 
 of abilit}' is missing. In types of ability where the 
 correlated action of several independent qualities 
 or factors is required, the appearance of the same 
 combination of exceptional qualities in the offspring is 
 very likely to be infrequent, because of the presence 
 of alternative characters in the germ plasm. 
 
 That the tendency to perform certain tricks when 
 in a particular frame of mind may be inherited, was 
 show^n in a case cited by Darwin {Animals and Plants, 
 chap, xii.) of a man who, as a bo}^, had the habit, 
 when pleased, " of rapidly moving his fingers parallel 
 to each other, and, when much excited, of raising 
 both hands, with the fingers still moving, to the sides 
 of his face on a level with the eyes." As a grown 
 man the trick was with difficulty suppressed, but one 
 
MENTAL CHARACTERS IX MAX 149 
 
 of his eight children, a girl of four and a half years, had 
 exactly the same trick. Darwin states that imitation 
 was out of the question. 
 
 Considering now the inheritance of various forms 
 of mentality, Galton (1869), in his classical work, 
 Hereditary Genius, first dealt with the inheritance of 
 mathematical and various other forms of ability. 
 This and the subsequent studies are too well known 
 to require treatment here. Hurst first pointed out the 
 probabilit}^ that musical ability was a Mendelian 
 recessive. The same is apparently true of feeble- 
 mindedness, at least in its extreme form, two feeble- 
 minded parents almost invariably having only feeble- 
 minded children. The exceptions to the rule are 
 probably explainable by illegitimacy. The literature 
 of feeblemindedness is too well known and too 
 extensive for full discussion, but reference may be 
 made to some of the results. For the Mendelian 
 interpretation Goddart (191 2, 1914) and Estabrook 
 (191 6) may be cited. 
 
 Goddart (191 4) finds that at least 50 per cent, of 
 the paupers cared for in American institutions are 
 feebleminded, and at least 50 per cent, of the pros- 
 titutes are estimated to be in the same condition. 
 Many criminals come in the same class, and there is 
 also a close relation between feeblemindedness and 
 alcoholism. On the basis of graded mental tests of 
 the Binet-Simon Measuring Scale of Intelligence, in- 
 dividuals are classed as idiots when their mental age 
 is 1-2 3^ears, imbecile when it is 3-7 3'ears, and morons 
 when it is 8-12 years. The latter would be called 
 feebleminded in England. The mental development 
 may stop at any age, and feeblemindedness is 
 essentially a condition of early suspension of mental 
 development. Various accidents and certain diseases 
 in childhood may result in feeblemindedness, but 
 it would appear that the great majorit}- of cases 
 
ISO HEREDITY AND EUGENICS 
 
 are hereditary. In hereditar}^ feeblemindedness the 
 children tend to have about the same grade of 
 mentality as the parents. Sometimes accidents in 
 childhood reduce an hereditary moron to imbecility 
 or idioc}^ When their mentality is under five years, 
 individuals rarely become parents, but parenthood 
 with a mental age of seven or eight is common. 
 
 The careful training methods of the Vineland In- 
 stitution show that it is impossible to develop a mind 
 beyond its inherited capacity. The mental develop- 
 ment may stop at any point, and training cannot push 
 it any further, although the most patient and per- 
 sistent efforts have evidently been made in this 
 direction. When mental progress ceases, it is neces- 
 sary to turn to manual training for any further 
 development of the individual. 
 
 As regards inheritance, Goddart cites 42 matings, 
 NF? xFFc^ — i.e., a heterozygous but normal mother 
 and a feebleminded father — producing 144 children 
 whose mentality is known. Of these, 71 were feeble- 
 minded and 73 normal, almost exactly in accord with 
 the Mendelian expectation of equality. On the other 
 hand, from 6 matings FF ? xNFr? there were 193 
 children whose mentality is known, and they were 
 122 feebleminded to 71 normal. Hence it appears 
 that the number of feebleminded considerabl}^ exceeds 
 expectation w^hen the mother is feebleminded. Again, 
 in NFxNF matings (26) there were 185 offspring, 
 and the mentalit}^ of 122 was determined, 83 being 
 normal to 39 feebleminded (expectation for one 
 Mendelian difference, 91 -5: 30-5). Among 476 chil- 
 dren from FF x FF matings, only 6 are recorded 
 as normal, and these were no doubt border-line cases, 
 or perhaps illegitimate. Hence the evidence clearl}- 
 favours the interpretation of feebleinindedness as a 
 simple recessive. 
 
 Holmes (1921) and other writers are less willing 
 
MENTAL CHARACTERS IX MAN 
 
 I ; I 
 
 to grant this conclusion. Holmes agrees with 
 Pearson and Heron that feeblemindedness varies 
 continuously, but he admits that this does not 
 imply " that the various kinds of mental defect are 
 not transmitted according to Mendel's law." He 
 nevertheless concludes (p. 39), '' I very much dcjubt 
 if the facts concerning the inheritance of mental 
 defect are as yet known with sufficient precision to 
 warrant our tr34ng to force them into simple Mendelian 
 formulae." We cannot agree with his statement that 
 " it seems improbable a priori that the inheritance 
 of general mental development would follow the 
 simple Mendelian formula for the inheritance of two 
 contrasted characters." All sorts of ph3^sical defects 
 in man and other animals, and in plants, are known 
 to follow the behaviour of a simple recessive character. 
 This appears to be due in each case to the fact that 
 an altered element (gene) is present in a particular 
 locus of a chromosome, and we find no difficult}' in 
 applying the same view to mental defects, which must 
 have a physical basis. 
 
 We may, however, point out an inference which 
 follows, and has not yet been generall}^ recognised. 
 If feeblemindedness is inherited as a ]\Iendelian 
 recessive, this in itself furnishes evidence that it has 
 arisen as a defect mutation from the normal con- 
 dition. It has sometimes been suggested that feeble- 
 mindedness represents the primitive condition of 
 palseolithic man, which has persisted in certain strains 
 through crossing w^hile the gradual mental evolution 
 of the remainder of mankind has continued. If the 
 latter h3'pothesis were true, it is unlikely that simple 
 alternative inheritance would result. On the whole, 
 it appears most likely that feeblemindedness has 
 arisen many times, and may still arise, as a defect 
 mutation in various stocks, although the condition 
 itself may resemble in some respects the mental 
 
152 HEREDITY AND EUGENICS 
 
 condition of primitive man. Goddart cites a family 
 of eleven feebleminded children from two white feeble- 
 minded parents. There were also two " normal " 
 children, but they were black. The mentality of 
 the negro is distinct from that of the feebleminded. 
 The latter presumably occur also in primitive races. 
 The evidence, so far as it goes, also appears to indi- 
 cate the gradual evolution of the mentality of normal 
 civilised man, involving man}' steps, whatever may 
 have been the forces involved. 
 
 Holmes points out that where a normal person 
 married to a feebleminded one has some feebleminded 
 children, it is too easily assumed that the normal 
 parent was heteroz3^gous for this defect. If this were 
 always true, it would give a ver}- high frequency for 
 the occurrence of this latent defect (see p. 159). It 
 seems much more likely, as Holmes points out, that 
 the normal mentalit}^ show^s variable or incomplete 
 dominance, especially when, as is usual in such 
 matings, the normal parent is also intellectually 
 below par. 
 
 Goddart estimated the number of feebleminded 
 in the United States at 300,000 to 400,000. He 
 thinks it important that the public should understand 
 the mentality of a moron (mental age ten), and employ 
 him accordingl}', recognising his limitations. The 
 moron has a lifetime in which to learn to do efficiently 
 things that can be done by a boy of ten. Goddart 
 suggests that their training should be carefully 
 arranged according to mental age tests, that as many 
 as possible should be " colonised," some sterilised, but 
 the great mass " educated " for their proper work. 
 
 The *' Mongolian " is a well-defined type of mental 
 defectiveness, which has generall}' been regarded as 
 non-inherited. The oblique eyes and round faces of 
 Asiatics are combined wath short stubb}' fingers, 
 rather dry rough skin, poor circulation, lack of 
 
MENTAL CHARACTERS IX MAN 153 
 
 occipital prominence, and usuall}' in older cases a 
 deeply furrowed tongue. The mentality is nearly 
 always that of a four-year-old child. Mongolians 
 usually appear in good-class families, they are not 
 associated with feeblemindedness, and are frequently 
 the last born in large families. The}' probably result 
 from derangement of function (uterine exhaustion) 
 leading to arrest of development, beginning at a 
 definite point in the prenatal development. The 
 causation of the type according to Goddart {191 4) 
 appears to be purely physiological, without any 
 element of inheritance. Probably defects of certain 
 internal secretions are involved. It has recently been 
 claimed, however, that there is some reason for 
 regarding Mongolianism as a recessive Mendelian trait 
 (see Davenport, 1920). There is evidence also that 
 idiocy frequent!}' results from a severe infection, 
 from cerebro - spinal meningitis, or from S3'philis, 
 alcoholism, or addiction to drugs on the part of 
 the parents. But, according to Davenport (1920), 
 statistics show that the great mass of idiots arise 
 from feebleminded parents. 
 
 The controversy between the schools of Pearson 
 and Davenport turned on the terms in which the 
 inheritance of feeblemindedness is to be stated. 
 Both agree that the condition is inherited. It is 
 possible that the inheritance is not always strictly 
 Mendelian, although it appears to be usually in con- 
 formity with the simple Mendelian scheme. It would 
 appear that occasional departures from strict con- 
 formit}' with the Mendelian scheme may be expected 
 in connection with the inheritance of mental charac- 
 teristics. Nevertheless, it must be remembered that 
 with feeblemindedness, as with other Mendelian 
 characters, the expression of the inheritance may be 
 modified by the presence of other deternuners. It is 
 also possible that the inheritance follows diflferent 
 
154 HEREDITY AND EUGENICS 
 
 rules in certain families, as is known to be the case 
 with other Mendelian characters. For example, if 
 a defect has arisen in an ordinary chromosome, it will 
 be inherited probably according to the simple scheme 
 of a Mendelian dominant or recessive, but if it has 
 arisen in a sex chromosome it will be sex-linked. 
 
 We have already seen that feeblemindedness is 
 essentially a condition of arrested mental develop- 
 ment. Epilepsy is a closely related neuropathic con- 
 dition. Insanity is more variable in its causes, and 
 is not always inheritable. Many data on the inheri- 
 tance of mental defects are given by Guyer (191 6). 
 
 The relations between feeblemindedness and in- 
 sanity have frequently been misunderstood. From 
 
 ^ ^'xD "S^D 5^0 i)"^ D 
 
 H A' . r-l A^ A.3 rJ^4 ^^r^6^7 16 ±9 1,0 ^,/ 
 
 
 m |-h/ X2 X3 
 
 Fig. 29. — Hereditary Imbecility in the Female Line. 
 
 the point of view of the Binet-Simon tests, while 
 feeblemindedness gives general arrested development 
 at a certain level, insanity and epilepsy show '' scat- 
 tering " in the tests — i.e., in the diseased brain some 
 questions in various years will be missed. '' Scat- 
 tering " in tests of the feebleminded indicates the 
 oncoming of insanity, w^hich may not become evident 
 for several years. In many respects feeblemindedness 
 and insanity are at opposite ends of the mental scale, 
 although an unusually high percentage of feeble- 
 minded become insane. Psychiatrists maintain that 
 insanity comes in highly developed nervous systems, 
 which are easily thrown into an abnormal condition. 
 Morons, on the other hand, represent often a vigorous 
 
MENTAL CHARACTERS IN MAN 153 
 
 organism of low intellect and strong physique. They 
 often have exceptional strength, but cannot show 
 it on a dynamometer because of lack of will power. 
 They represent a more primitive type, with dullness 
 to pain, etc., but under exceptional conditions they 
 may perform surprising feats of strength. 
 
 Sedgwick (1861, 1863) records many instances of 
 the inheritance of insane diatheses. In one familv 
 (Fig. 29) hereditary imbecility appears in nearly 
 all the females of two generations, while the sons 
 were normal. No. II. 3 was eccentric and silly, 
 while No. II. 11, though not an imbecile, was a 
 religious fanatic and became a Mormon. 
 
 Inspection of charts does not convince one that 
 insanity in the ancestry has any potent influence 
 towards causing feeblemindedness. On the other 
 hand, the feebleminded not infrequently have insane 
 offspring. Insanity is a symptom of nervous de- 
 rangement which will occasionally give rise to feeble- 
 mindedness. Thus, Goddart cites the case of Nora T., 
 age thirteen years, mentality three. Her father and 
 mother were both normal, but the feeblemindedness 
 in the father's family and the insanit}^ in the mother's 
 family apparently brought about the result in Nora. 
 Again, Bessie X. has a cousin who is epileptic and 
 a number of distant relatives who are insane or 
 epileptic, while others are " queer "or'' peculiar." vShe 
 is fifteen, with a mentality of two, and her condition 
 is looked upon as a summing-up of various morbid 
 tendencies which have appeared sporadically in 
 several generations of her ancestors. 
 
 It is worth noting that the drawings of animals 
 by the feebleminded sometimes remind one in style 
 and method of some of the cave drawings of early man. 
 
 While feeblemindedness is certainl}' far removed 
 from genius in the mental scale, representing a 
 primitive undeveloped mental condition, it is often 
 
156 HEREDITY AND EUGENICS 
 
 but a step from insanity to genius. Indeed, many 
 geniuses would pass with any psychiatrist as true 
 insanities. The diagnosis may depend on whether 
 the aberration is useful or dangerous. But it is 
 impossible to graft genius on to feeblemindedness, and 
 the loss of a whole feebleminded stock would not 
 involve the suppression of a single genius. For in 
 feebleminded families even the " normals " are 
 usually of low-grade intelligence, and they are as a 
 rule correspondingh' low in social grade. Notwith- 
 standing this, it is clear that the condition of the 
 feebleminded does not result from their environment, 
 but rather that their lack of capacity causes them to 
 gravitate into squalid conditions, since the}- cannot 
 grapple adequately with the complexities and subtle- 
 ties of modern civilised life. Urquhart (1909) 
 classifies insanitv as melancholia, mania or dementia 
 which are acquired, and idioc}^ and imbecility which 
 are congenital. The latter conditions are, usually 
 at least, accompanied by gross physical deficiencies. 
 The pedigrees of insanity are usually unsatisfactory 
 in failing to distinguish betw^een different types, and 
 so they give no general rule of inheritance, although 
 many of them run through three generations. 
 
 Holmes (1921) has pointed out that the germ plasm 
 of neurotic stocks may be affected in a variet}" of 
 wa^^s in different individuals. He says (p. 49): 
 " Charts of the inheritance of insanity show that the 
 afflicted individuals exhibit a great diversity of 
 symptoms in successive generations." Particular 
 types of insanity, however, tend to run in certain 
 families. This is particularl}- true of dementia 
 prsecox (see p. 158) and periodical insanity. Unlike 
 most forms of insanity, Huntingdon's chorea* appears 
 
 * Chronic chorea or St. Vitus' dance is a convulsive nervous 
 disease with irregular movements, dementia, and disturbance of 
 speech. 
 
MENTAL CHARACTERS IX MAN 157 
 
 to be usually a typical dominant character in in- 
 heritance. While the feebleminded may be con- 
 sidered to form a graded series, insanity is much 
 more varied in its manifestations, and is to be regarded 
 as a pathological condition working havoc with the 
 normal mental mechanism, rather than a simple 
 defect of mental machiner}^ Some types of insanity 
 may only appear late in life and yet are inherited, 
 showing that the seeds of ultimate derangement aru 
 present in the germ plasm. In other cases, an 
 exceptional mental or physical strain may bring out 
 phenomena of insanity which would never appear 
 under ordinary circumstances. 
 
 Ordahl (191 9) made a study of fifty families in 
 California containing feeblemindedness. He con- 
 cludes that the parents of the feebleminded are often 
 borderline cases and escape detection by ordinar}- 
 means. Seventy-two per cent, of the fifty families 
 showed defective inheritance. Of the living children, 
 5*6 per cent, were idiots, 15-6 per cent, imbeciles, 
 26-2 per cent, morons, 3-1 per cent, dull normal, 
 1-2 per cent, psychopathic, 48-1 per cent, normal. 
 Ordahl believes that the moron and dull normal can be 
 detected by expert means in the earl}' school 3'ears. 
 Otis (191 6) aims to reconcile the views of Pearson and 
 Davenport. He considers it important to distinguish 
 between intelligence and " brightness " — i.e., the 
 degree the child is in advance of the normal develop- 
 ment of intelligence. Pearson showed that all degrees 
 of intelligence (meaning brightness) exist, but thi> 
 does not exclude the Mendelian inheritance of any 
 degree when mated with feeblemindedness. Otis 
 concludes that " the existence of all grades of bright- 
 ness, and the possibility of the universal ]\Iendelian 
 inheritance of different grades of brightness, arc- 
 therefore seen to be entirely compatible." This is in 
 accord with much other Mendelian behaviour. 
 
158 HEREDITY AND EUGENICS 
 
 A mental disorder which appears to be confined to 
 Russian Jews (see Davenport, 1920) is amaurotic 
 famil}^ idioc}', which runs in famihes and appears to 
 be a simple Mendelian recessive. Myoclonic epilepsy 
 (see p. 108) has been shown by the extensive pedigrees 
 compiled by Lundborg in Sweden to be inherited 
 in the same wa}'. It is recognised that epilepsy occurs 
 in a great variety of forms, and the pedigrees studied 
 by Davenport and Weeks and others indicate that 
 the common form at any rate follows the same rule 
 of inheritance. A relation between epilepsy and 
 feeblemindedness is also indicated, such that if one 
 parent is epileptic and the other feebleminded, all 
 the children will be either epileptic or feebleminded. 
 Various investigations indicate (Davenport, 1920) that 
 dementia praecox* maybe also a Mendelian recessive. 
 According to F. W. Mott {Proc. Roy. Soc. Med., June, 
 1920), this condition is accompanied by a complete 
 arrest of spermatogenesis. Riidin (191 6) finds that 
 various other psychoses accompany dementia praecox, 
 and thinks that a Mendelian explanation is possible. 
 Hoffman (1921), in a stud}'^ of dementia praecox and 
 the manic depressive condition, concludes that two 
 factors are involved in the former, while in the latter 
 a dominant character in some form is concerned. 
 Siemens (1921) gives a list of inherited abnormal 
 physical and psychical conditions. 
 
 The appalling frequency of feeblemindedness in 
 some parts of America is to be seen from statistics 
 collected (Sessions, 191 7) in one county in Ohio, 
 where the feebleminded number i per cent, of the 
 population. An equal frequenc}^ throughout the 
 State of Ohio would mean 47,000 feebleminded within 
 its borders. The rapidity with which the problem 
 is becoming still more serious is to be seen from the 
 
 * Adolescent insanity marked by melancholia and other 
 emotional states. 
 
MENTAL CHARACTERS IN MAN 159 
 
 fact that " one feebleminded man left at large five 
 generations ago is responsible for seventy-five feeble- 
 minded persons living at the present time." The 
 normal population of the country, apart from immi- 
 gration, can hardly have increased to anything like 
 the same extent during this time. 
 
 But even if all feebleminded individuals were 
 prevented b}- segregation from multiplying, the most 
 difficult part of the process of eliminating feeble- 
 mindedness from the germ plasm of the population 
 would scarcety have begun. For, as East (191 7) has 
 pointed out, while the number of feebleminded in the 
 whole population of the United vStates may be 
 estimated at 3 per 1,000, the number which are 
 carrying feeblemindedness as a recessive defect must 
 be nearer i in 14. Punnett (191 7) puts the number 
 even higher, and emphasises the impossibihty of 
 greatly reducing feeblemindedness in the population, 
 except by segregating also those who are carriers of 
 the disease as a recessive quality. He shows that if 
 the proportion of the feebleminded in the United States 
 is now 3 per 1,000, then it would require 250 genera- 
 tions, or about 8,000 years, to reduce the proportion 
 to I in 100,000 b}- the method of merely segregating 
 or sterilising those who show the character. It is 
 evident, then, that the elimination from reproduction 
 of those showing any recessive racial defect merely 
 prevents the problem from becoming more serious, 
 while marked improvement in the germ plasm of the 
 population can only be effected by selection against 
 the heterozygotes, who are carrying the defect in half 
 their germ cells. More accurate mental tests ma>' 
 make it possible to distinguish such heterozygous 
 individuals from the fully normal members of the 
 population. This has happened in the history of the 
 study of many Mendelian characters. From this 
 point of view, any tendency for those transmitting 
 
i6o HEREDITY AND EUGENICS 
 
 feeblemindedness to intermarry will have the desirable 
 effect of bringing it to the surface where the individual 
 can be segregated, rather than spreading the condition 
 subterraneoush^ by marriage with sound stocks. 
 
 That even the most degraded family is not entirely 
 incapable of better things in any of its members is 
 shown b}^ the recent histor}- of the notorious " Juke " 
 family (Estabrook, 191 6). This family, whose history 
 has been a continuous record of crime, vice, and feeble- 
 mindedness, dates from 1720-40, and has been an 
 untold burden upon the State. Dugdale published 
 a histor}^ of it in 1877. Estabrook shows that, in their 
 history, out of 399 fertile marriages about 176 might 
 be classed as eugenic matings and 223 as cacogenic. 
 Fifty-five per cent, of these matings should have been 
 prevented, even putting the eugenic standard as 
 regards intelligence very low. Had this taken place, 
 the remainder would now show less than 5 per cent, 
 of offspring wdth undesirable traits. In fact, over 
 half the total offspring are mentally defective or have 
 antisocial traits. The occurrence of both desirable 
 and undesirable individuals in the same sibship is 
 often startlingly clear in these families. 
 
 Eugenic studies have been made in America of the 
 Edwards, Jukes, and Kallikak families, the Hill Folk 
 and the Nam family. A more recent study of a 
 Pennsylvania family containing good and bad elements 
 has been made by Miss Key (1920). Two pioneer 
 families of German descent are traced through five 
 and six generations on American soil. They mostly 
 belong to the great middle class, containing no 
 eminent members and no notorious criminals. The 
 study began with four young feebleminded in a 
 Pennsylvania Institution. The history of this family, 
 with a network of descent including i ,822 individuals, 
 shows the establishment of lines which var}^ greatly 
 in social efficiency. Marriage selection has given 
 
MENTAL CHARACTERS IX MAX i6i 
 
 rise to three strongl}^ contrasting; lines, the original 
 defects persisting or becoming accentuated in some 
 hnes, while marriage into better strains has produced 
 other hnes socially more efficient. One famil\' l)egan 
 with a German and his wife, who innnigrated into 
 Western Pennsylvania in the latter part of the 
 eighteenth century. He was a fair specimen of the 
 pioneer type, but his wife was totally- lacking in any 
 sense of nuinber or quantity, and could neither sew, 
 spin, nor w^eave acceptably. They had children, 
 three of whom were apparently feebleminded, while 
 the others, through marriages with different types, 
 established various lines, some of which split up into 
 divergent branches. Five separate strains are traced 
 in this family. Another German immigrant and his 
 wife, about the same time, had twelve children. 
 They were very tall and possessed great strength, 
 qualities which some of their descendants perpetuated. 
 Six of the children formed socially efficient strains, 
 four died without marrying, while two daughters, 
 the dullest and slowest of the fraternitv, but with 
 great strength and endurance, married into defective 
 stock belonging to the previous family, and gave rise 
 to an undesirable strain. 
 
 The characteristics of the various lines are deter- 
 mined by the combination of traits carried by their 
 founders, together with the leading traits of the 
 strains into which they married. There is a sifting 
 out in every generation. Where weakness marries 
 strength the defect may appear, but in lessened degree. 
 This results in the practical elimination of some 
 defects (in their external expression), and in increased 
 efficiency. The intermarriages of defectives, on the 
 other hand, give a continuous line of defectives 
 requiring institutional care. Two of the lines con- 
 tinue to be mixed, showing defectives, degenerates, 
 and socially fit. The degenerate branches gravitate 
 
 II 
 
i62 HEREDITY AND EUGENICS 
 
 downwards, and produce nothing but degeneracy. 
 The rapid multiphcation of these people is most 
 serious. Miss Ke}^ points out that pubhc opinion is 
 helpless to prevent marriages between them, and 
 suggests State control of marriages through a State 
 Eugenics Board, with power to prohibit certain 
 unions under penalty after studying the hereditar}' 
 defects of the proposed parties to a marriage. But 
 it is not to be expected that a ban on marriage would 
 prevent people of this type from reproducing them- 
 selves. It is noticeable that while defective members 
 of these stocks remain for the most part within a 
 few miles of their place of origin, and hence tend to 
 establish a defective group in the community, the 
 better members, by marriage or otherwise, remove to 
 greater distances and a new^ environment. 
 
 Various attempts to analyse temperaments and 
 their inheritance have been made, notabl}^ by 
 Davenport (191 5). He divides temperaments into 
 h3^perkinetic or nervous and hypokinetic or phleg- 
 matic, and recognises tw^o grades of each. A dualism 
 of this kind, romantic and classic types, radical and 
 conservative, feebly and strongly inhibited, he finds 
 running through the whole population ; also a tendency 
 for matings to take place between unhke tempera- 
 ments. He hypothecates a factor E producing 
 periodic excitement, its absence e producing calmness. 
 Another factor C makes for cheerfulness, while c 
 permits more or less periodic depression ; and he finds 
 that C and E are independently inherited. As a 
 modern attempt in the anatomy of melancholy, this 
 shows courage in the effort to explore a field which 
 is notoriously full of pitfalls. That it is inadequate 
 as a complete analysis appears obvious. The desira- 
 bility of creating '' factors " for calmness and cheer- 
 fulness appears very doubtful. 
 
 Nomadism, or the wandering instinct, Davenport 
 
MENTAL CHARACTERS IN MAN 163 
 
 (191 5) treats as a fundamental lunnan instinct, 
 which is typically inhibited in intc^llii^cnt civilised 
 adults. It appears to be a sex-linked recessive 
 monoh3'brid trait. Sons are found to be nomadic 
 only when their mothers belong to nomadic stock. 
 Daughters are nomadic only when the mother belongs 
 to such a stock and the father is also nomadic. 
 The impulse occurs frequently in families showing 
 such periodic behaviour as depression, migraine,* 
 epilepsy, and hysteria. Nomadism would appear to 
 be more widespread in the Anglo-Saxon population 
 of North America than in the resident population of 
 Britain. This is probably because emigration has 
 always been more largely of the roving types, the 
 more sedentary elements of the population preferring 
 to remain behind. This difference probably applies 
 chiefly to the labouring and agricultural classes, the 
 higher classes being able to satisfy their nomadic 
 instincts by travel. 
 
 The relation of criminality to inheritance is often 
 debated. Obviously it cannot be a simple one. 
 Davenport (1920) classifies antisocial behaviour as 
 due to one of the following four sets of conditions : 
 (i) Ignorance of the mores (or social requirements), 
 merely through lack of opportunity to learn the 
 mores. This condition would apply partially to the 
 foreigner, or to the improperly or insufficiently taught 
 offender. (2) Ignorance of the mores through lack 
 of capacity to understand what society expects. 
 This is characteristic of the feebleminded. (3) Know- 
 ledge of the mores, accompanied by a social blindness 
 and inability to have the action controlled b}' a 
 knowledge of w^hat society expects of one, because 
 of lack of gregarious, social, or altruistic instinct. 
 
 * A nervous affection marked by periodic headache, often 
 confined to one side of the head, and accompanied by nausea 
 and other symptoms. 
 
1 64 HEREDITY AND EUGENICS 
 
 Here belong the extreme individualists and anarchists. 
 (4) Knowledge of the mores with presence of the 
 social instincts, but with inability to meet the ex- 
 pectations of society through insufficient inhibition 
 or self-control. This insufficiency may be general 
 and permanent, or it may be temporary (periodic). 
 This would include the hyperkinetic, the hysterical 
 and epileptoid offenders. It is thus evident that 
 a tendency to the inheritance of criminality will vary 
 according to its type. 
 
 Another work by the same author (191 9), on 
 heredit}^ in naval officers, contains genealogical and 
 biographical data of many English and American 
 naval officers, including Raleigh, Hardy, and 
 Nelson. Its attempt to treat thalassophilia, or love 
 of the sea, as an inherited trait is not very happy 
 as a means of analysing the inheritance of men who 
 were, in many cases, remarkably diverse in their 
 exceptional qualities. The Mendelian conception is 
 valuable in connection with so many human traits, 
 that it w^ould be unfortunate if any loose and un- 
 justified usage of it, as in the present instance, with- 
 out any adequate understanding of the nature of 
 the differences involved, should have the effect of 
 throwing doubt on the man}^ cases, mental as well 
 as physical, of Mendelian inheritance in man. It 
 is clearly a matter of greater difficulty to prove 
 the Mendelian inheritance of a mental than of a 
 physical trait, and correspondingly increased caution 
 is necessary. 
 
 A very good summar}'' of the general arguments in 
 proof of the inheritance of mental traits is given by 
 Popenoe (191 6). Failure to recognise the fact of 
 mental inheritance comes largely, now, from certain 
 psychologists and educationists whose biological 
 ignorance and lack of understanding of heredity are 
 a matter for commiseration. Many psychologists, 
 
MENTAL CHARACTERS IX MAX 165 
 
 however, now clearly recognise the inheritance of 
 mental traits. That mental traits are inherited in 
 animals has been clearly shown in one case by Castle, 
 who proved that in crosses between wild and tame 
 rats wildness is transmitted by the father to offspring 
 who have never .seen their father or had experience 
 of any behaviour but that of their tame mother. 
 Those who deal with psychological tests of such 
 animals as rats and mice soon learn to recognise 
 individual differences in psychology which make 
 the simple tests of efficiency, such as maze-running, 
 appear entirely inadequate unless careful allowance 
 is made for such temperamental differences. 
 
 Modern psychology has developed in two directions, 
 which tend to make it more biological and are of 
 interest in connection with the present discussion : 
 (i) The theories of Freud and Jung dealing with the 
 formation of mental complexes, unconscious sup- 
 pression, mental conflicts, etc., and tending to show 
 that mental experiences very early in life, and quite 
 unperceived at the time, ma}^ have a profound in- 
 fluence on the later mental development ; (2) be- 
 haviourism, which has grown out of the purety 
 zoological experimental study of animal behaviour, 
 from protozoa to the anthropoid apes. The second 
 phase need not particularly concern us here. Avery 
 good summary of the Freudian phase has been written 
 by Tansley (1920). Instead of man being the rational, 
 thinking being the older psychology pictured him, 
 his mentality is seen to be built up on a mass of 
 instincts inherited from his animal ancestry, giving 
 him tendencies or instincts which constantly require 
 to be altered or repressed under the conditions of 
 civilised life. When not repressed, he acts first, and 
 rationalises his action afterwards. This repression, 
 often unconscious, ma}' lead to subconscious mental 
 conflicts and other difficulties. Kempf (1921) shows 
 
i66 HEREDITY AND EUGENICS 
 
 how the bodily functions have their effect on the 
 mind, and an\^ defect is unconsciously compensated 
 for b}^ the individual. This may ultimately lead to 
 a pathological condition of the mind, in other words, 
 insanity, particularly in a time of mental stress, 
 and under some conditions a psychoanalysis may 
 restore the mental balance. The development of 
 insanity is thus closely wrapped up with bodily con- 
 ditions. That there is also an element of inheritance 
 in man}^ cases of insanit}- is undeniable, but it remains 
 to be determined precisely what that element is in 
 different cases. The situation is obscure in com- 
 parison with feeblemindedness where the nature of 
 the inheritance is clear. Insanities also show a 
 greater variety of types, and they cannot be graded 
 in a simple series like the mental-age series of the 
 feebleminded. The compelling force of the excessive 
 development or derangement of some autonomic 
 bodily function will usually furnish the immediate 
 cause of an insane manifestation. Various inherited 
 derangements of the nervous control of the bod}' 
 may then provide the basis for the development of an 
 insane diathesis. 
 
 Inherited mental differences, no doubt, go back 
 to germinal changes affecting the nervous system. 
 Traced backwards in the ontogeny, they must have 
 a purety physical basis like other germinal changes.* 
 The description of a breed of goats in Kentucky 
 (Hooper, 191 6) is instructive in this connection. 
 When frightened, their forelegs become stiff, and 
 they hop along, dragging their hind legs. If much 
 frightened, the latter also become stiff, and the animal 
 falls over. Such a breed must have arisen through a 
 germinal change affecting chiefly the nervous system. 
 
 * Yerkes has shown that in crosses between wild and tame rats 
 wildness will appear in the offspring even when the father was 
 wild and the young were reared by tame mothers. 
 
MENTAL CHARACTERS IN MAN 167 
 
 A very similar condition appears in sheep, and also 
 in horses and cattle, as a result of feeding too freely 
 on pampas grass, Poa argentina (Jones and Arnold, 
 191 7). But it is a form of intoxication, and is not 
 inherited. Cole (1920) describes in guinea-pigs a 
 form of congenital palsy which is not exactly like 
 any nervous disorder in man, though it resembles 
 ataxia in pigeons, which Riddle finds is a recessive 
 character with some irregularities in inheritance. 
 Congenital palsy in guinea-pigs runs a brief course, 
 ending in death at an early age. The neurosis 
 appeared in 191 4, and is characterised by clonic 
 spasms,* particularly of the legs, in which the animal 
 lies helpless. It is inherited as a simple Mendelian 
 recessive, heterozygotes being entirely normal. 
 Hurst states that '' feeblemindedness " in pigeons is 
 a recessive. Tumbling in pigeons and *' waltzing " in 
 inice and rats (again recessive) are other examples 
 of inherited nervous disorders in animals. These 
 defects have been shown to be due to defective 
 semicircular canals. 
 
 The inheritance of wildness in rats has been referred 
 to elsewhere. Yerkes (191 3) made a study of wild 
 and tame rats and their Fi and Y^ hybrids. He 
 proved that wildness, savageness, and timidity are 
 inherited, although wildness and timidit}' are very 
 difficult to distinguish. Coburn (1922) has made a 
 study of 1,300 mice, hybrids between wild and tame, 
 in three generations. He made careful psychological 
 tests of his animals, and concludes that the in- 
 heritance of wildness and savageness in mice is 
 Mendelian of the " blending " or multiple factor type, 
 but much more work is needed before the precise 
 manner of inheritance can be stated. He thinks, 
 however, that the two behaviour complexes, wild- 
 ness and savageness, result from several different 
 
 * Spasms in which rigidity and relaxation succeed each other. 
 
i68 HEREDITY AND EUGENICS 
 
 inheritance factors which appear to follow Mendelian 
 rules. 
 
 Modern psychology is only beginning to recognise 
 the importance of the inheritance element in mental 
 differences . McDougall ( 1 9 1 9) clearly recognises such 
 an element in inheritance, but many psychologists 
 are still too engrossed with the mind itself to recognise 
 the genetic relationships of its various elements to 
 the minds of relatives. Psychopathologists also 
 frequently fail to appreciate that any element of 
 mental inheritance exists. For example, Kempf 
 (1921) studies the development of the mind with a 
 complete disregard of the facts of mental inheritance. 
 He devotes forty pages to an analysis of Darwin's 
 mental development from the psychoanalytical point 
 of view. We hear nothing at all of the inheritance 
 of mental traits, but everything is explained on the 
 basis of the mental relationships between Charles 
 Darwin and his father, the early influence of his 
 mother (who died when he was eight years of age), 
 and afterwards of his wife. He sees in Darwin's 
 mother's " charming interest in nature," her 
 " romantic fondness for flowers," her keeping of 
 pigeons, and her interest in the theories of her father- 
 in-law, Erasmus Darwin (author of Zoonomia), a 
 basis for Darwin's interest in nature. This inspired 
 her son to search for '' the secret of her fascination." 
 At the age of eight he had alread}^ begun to collect 
 " all sorts of things." The writer mentions that 
 collecting was a characteristic of several of Darwin's 
 uncles, but fails to recognise any element of in- 
 heritance in the reappearance of this trait. It seems 
 more probable that Darwin inherited this quality, 
 than that it was based on the development of a 
 childish fantasy which originated through his mother's 
 influence on his early mental development. 
 
 Granting that Darwin's mother's '' charming in- 
 
MENTAL CHARACTERS IN MAN 169 
 
 terest in nature " was a fact, this interest may have 
 been a portion of her son's inheritance. Kempf 
 (p. 216) impUes that the mother had unconsciously 
 '' named her wish for her boy's destiny," and that 
 this early attachment to his mother had influenced 
 the whole course of his life, preventing him from 
 following his father's and grandfather's profession 
 of a physician. But Darwin's attachment to his 
 father, who survived to influence him throughout his 
 development, seems to have been equally strong. 
 It seems, at least, very unlikely that Darwin's mother- 
 attachment was the basis of his attraction to natural 
 histor\^. Rather his taste for natural history appears 
 to have represented the inevitable expression of an 
 inherited tendenc}^ a tendency which finally overcame 
 all obstacles and found an environment (the Beagle 
 voyage) where it could develop freely. There are 
 many similar instances of exceptional men whose 
 development necessitated the overcoming of parental 
 wishes. The recognition of Darwin's inheritance, 
 which made his greatness possible, does not lessen 
 the importance of parental attachment as a guide 
 in development, or in some cases a hindrance if 
 unwisely exercised. 
 
 Kempf goes on to consider Darwin's later chronic 
 ill-health. He thinks Darwin suffered from an 
 '' anxiety neurosis, due to consistent affective sup- 
 pression," from anticipation of what his work would 
 mean to civilisation, the criticisms and opposition it 
 would arouse. Although Darwin suffered from sea- 
 sickness and dizziness during the voyage, yet his first 
 experience of becoming " unwell " was after his 
 return, and in his early life he was very vigorous and 
 fond of sports. " The later course of his anxiety 
 indicates that it was a reaction to his efforts to adjust 
 himself to his career, his father (who had opposed the 
 voyage on the Beagle, and wished him to take up 
 
I70 HEREDITY AND EUGENICS 
 
 a church career after his failure to be interested 
 in medicine, and on whom he was economically 
 dependent), and his mating." The necessity for 
 avoiding conflicts in order not to be distracted from 
 his researches was another element in his adjustment. 
 Of course, Darwin's ill-health has been much written 
 about. This brief account is given as a typical 
 example of the psychoanalytic method applied to a 
 man of genius. It w^ould gain greatly in value if it 
 recognised the importance of inheritance as furnishing 
 the potentialities on which environmental influences 
 play. It ought to be obvious that if Darwin had been 
 a person of mediocre abilit}^, neither his mother 
 attachment nor anything else could make of him a 
 great naturahst. It is this fact which the psycholo- 
 gist too often overlooks. 
 
 As regards the inheritance of mental aptitudes, that 
 musical ability " runs in families," and is more 
 frequent in some races than in others, is well known. 
 Not onty is this true of such groups as the Bach 
 family, but also of innumerable other families of less 
 exceptional musical ability. Hurst first suggested 
 that this characteristic w^as a Mendelian recessive. 
 A study of five musical families by Drinkwater (191 6) 
 partly supports this conclusion. A family of organists 
 was traced through several generations, and in every 
 case where both parents were musical all the children 
 showed musical ability. In another branch of this 
 family, where both parents lack musical ability, all 
 the children lack it. These families w^ere united by 
 marriage, but instead of all the children being non- 
 musical, exactly 50 per cent, of them w^ere musical, 
 two being professionals of great abilit}-. It therefore 
 appears that musical ability may be a recessive w^hich 
 may nevertheless appear in some cases in the 
 heteroz^^gous condition. Artistic abilit}^ was also 
 traced through four generations as a recessive 
 
MENTAL CHARACTERS IN MAN 171 
 
 character. But further evidence is required for 
 clear conclusions regarding the inheritance of musical 
 and artistic ability. 
 
 Miss Stanton (1922) has made records of the 
 musical capacities in various American families con- 
 taining one or more distinguished musicians. The 
 measures of musical capacity used were (i) sense of 
 pitch, (2) sense of intensity, (3) sense of time, (4) tonal 
 memory. These are believed from extensive experi- 
 mentation to be basic qualities in connection with 
 musical ability, being little affected by practice, age, 
 musical training, sex, or general intelligence. Dis- 
 crimination tests were made on the basis of phono- 
 graphic records and standard laboratory apparatus, 
 531 individuals being classed as poor, average, 
 superior, etc., on the basis of each test. As regards 
 inheritance, the results are not extensive enough to 
 warrant any very definite statement of laws. It is 
 nevertheless suggested that the data indicate the 
 dominance and segregation of superior capacity from 
 average and poor capacities. It is concluded that 
 " the inheritance of musical capacities seems, indeed, 
 to follow Mendelian principles, but the method of 
 inheritance is so complex that it is impossible now to 
 state how many factors may be present." It is 
 doubtful if such a result has much value, beyond the 
 recognition of the fact that degrees of musical capacity 
 are probably inherited. 
 
 Pearson treats handwriting as a mental charac- 
 teristic. There is no doubt that it is an extraordinary 
 index of human character,* and can be used for an 
 intimate analysis of the character by one who is 
 expert in the comparison and analysis of different 
 types of cheirograph3^ There is nothing mystical 
 in this relationship. The handwriting is an ex- 
 
 * This statement has often been disputed, but from personal 
 experience I am convinced that it is a fact. See also p. 172. 
 
172 
 
 HEREDITY AND EUGENICS 
 
 pression of one's manner of doing things. It may be 
 neat or slovenly, run together or disconnected, large 
 and sho\\y or small and carefulh^ formed, with long 
 loops, precisely crossed t's, large capitals, long 
 flourishes, etc. In the hands of an expert these, and 
 many much more minute details, yield a remarkably 
 accurate analysis of the character and capacities of 
 the individual. The autograph is truly the product 
 of the whole man. If you write another man's name 
 you will write it differently from his autograph, unless 
 your characters reseinble each other, in w^hich case 
 3^ou ma}^ form the letters in a very similar way. 
 There is one man whose name I write almost exactly 
 as he does, and I know that our characters have many 
 points of resemblance. 
 
 The anatysis of this relationship between character 
 and handwriting, a relationship which extends to the 
 minutest details, is worthy of scientific study. I 
 know of one woman, a teacher, who is almost in- 
 fallible in delineating the character of any person 
 whom she has never seen, from only a few lines of the 
 handwTiting. It seems to be a matter of sensing the 
 significance of different t3^pes of curves and various 
 other features of handwriting, as they blend together 
 in the expression of the character of the individual. 
 The mood of the individual, whether elated or suffering 
 from depression, is also registered in the hand- 
 writing. Indeed, the method is so accurate that 
 specimens of the handwriting could undoubtedly be 
 used to determine the character-traits of deceased 
 persons concerning w^hom insufficient evidence is 
 available in the study of mental inheritance. The 
 striking resemblances one sometimes sees in the hand- 
 writing of relatives is associated with inherited 
 similarities in character. Identical twins, however, 
 sometimes show fairl}^ marked differences in hand- 
 WTiting. This subject of the handwriting of twins 
 
MENTAL CHARACTERS IN MAN 173 
 
 is worth}' of further investigation. It should throw 
 hght on (1) the similarities between twins; (2) the 
 limits of relation between handwriting and character. 
 
 Another important fact which the student of 
 eugenics must needs bear in mind is not only that a 
 vast array of biological character-differences exist, 
 which are being reshuffled from generation to 
 generation, but that in the individual the greater 
 number of these characters will be in the heterozygous 
 or hybrid {i.e., inconstant or splitting) condition. 
 This has both advantages and disadvantages from 
 the point of view of selective mating and offspring. 
 Among the advantages may be reckoned the fact 
 that the offspring are sure to show a variet}^ of mental 
 and physical characteristics — i.e., to differ markedly 
 from each other (except in the case of identical twins) ; 
 while the disadvantage is measured by the number of 
 unfavourable recessive characters carried bv both 
 parents. The fact that both parents may be carrying 
 some of the same unfavourable or deleterious recessive 
 characters is the chief and probably the only sound 
 biological argument against cousin marriages. Here it 
 may be pointed out, that w^hile it is impossible to know 
 with certainty from a human pedigree all the recessive 
 characters which are carried by an individual, yet it 
 will be possible to determine some of them from a study 
 of the ancestors, and particularly of the collateral 
 lines, such as uncles and cousins and their families. 
 
 Eugenic action should, then, be based upon four 
 separate factors: (i) Positive selection for desirable 
 qualities, w^hich are frequently dominant ; (2) negative 
 selection against undesirable recessive qualities which 
 appear in collateral or ancestral lines, and may 
 therefore be carried in the family germ plasm ; 
 (3) isolation of individuals having undesirable 
 dominant qualities ; (4) correlated with this should be 
 an effort to foster matings between individuals 
 
174 
 
 HEREDITY AND EUGENICS 
 
 showing the same desirable recessive quahty. All 
 this implies an array of information more elaborate 
 than anyone possesses concerning his own ancestors 
 and more distant relatives, unless he has made 
 exceptional efforts to collect and compile the necessar^^ 
 data from ancestral records, portraits, and other 
 sources. It w^ill also be understood that although 
 I have here spoken of dominant and recessive 
 characters as though the difference betw^een them 
 were absolute, yet it is well known that in many 
 instances this is not really the case. It is quite likely 
 that in man the interrelations with other germinal 
 qualities may bring about variable dominance; and 
 the heterozygous combination of a pair of characters 
 much more often gives an intermediate result, or at 
 least one in which the recessive exhibits some tangible 
 effect of its presence. Even in the case of such 
 abnormalities as brachydactyly, which are commonly 
 treated as dominants, there is some evidence that the 
 homozygous condition of the abnormality is much more 
 extreme, and indeed non-viable (see p. 90). If this is the 
 case, it shows incidentally that the original mutation 
 must have been itself heterozygous. It also follows 
 that the heterozygous condition is intermediate be- 
 tween the normal and the homozygous condition of 
 the abnormality, although the latter is non-viable 
 and cannot reach mature development. Abnormali- 
 ties in which the heteroz3^gous condition alone exists, 
 since the homozygous is non-viable, are not perhaps in 
 the strict sense dominants, although they are usually 
 referred to as such. Factors which can only bring 
 about development when in the heteroz^^gous con- 
 dition are one t3^pe of the class of factors now spoken 
 of as lethals (see p. 196). Such mutations, which 
 are commonly spoken of as dominants in the hetero- 
 zygous condition, are really defects which affect the 
 offspring when present on only one side of the house. 
 
CHAPTER V 
 
 THE LIMITS OF HEREDITY 
 
 Another subject of great interest in connection with 
 human inheritance is the question of its hniits. 
 Are there any details of structure so small, or of such 
 a nature, as to be beyond the reach of heredity ? 
 Galton considered this subject, and in his book on 
 Finger Prints (1892) found such structures in the 
 more minute details or minutiae of the individual 
 ridges of the finger-print patterns.* We have already 
 considered another case (p. 74) in right and left- 
 handedness of cereals. Obviouslv the observation 
 of human duplicate twins should throw much light 
 on this subject, and since Galton 's studies, in which 
 he classified finger-tip patterns as loops, whorls, and 
 arches, a considerable literature has grown up which 
 
 * I cannot refrain from pointing out again how closely Galton 's 
 views agreed with some of the current conceptions of continuous 
 and discontinuous variation. He says [I.e., p. 211): "Not only 
 is it impossible to substantiate a claim for natural selection, that 
 it is the sole agent in forming genera, but it seems, from the 
 experience of artificial selection, that it is scarcely competent to 
 do so by favouring mere varieties, in the sense in which I under- 
 stand the term. 
 
 "My contention is that it acts by favouring small sports. 
 Mere varieties from a common typical centre blend freely in the 
 offspring, and the offspring of every race whose statistical charac- 
 ters are constant, necessarily tend, as 1 have often shown, to 
 regress towards their common typical centres. Sports, on the 
 other hand, do not blend freely; they are fresh typical centres 
 or sub-species, which suddenly arise, we do not yet know precisely 
 through what uncommon concurrence of circumstances, and which 
 observations show to be strongly transmissible by inheritance." 
 
 175 
 
176 HEREDITY AND EUGENICS 
 
 can onh^ be touched upon here. A full bibliography 
 is given b}- Wilder (191 6). The results have shown 
 that not onh^ the ridge patterns of the linger tips, 
 but also those of the palms of the hands and the soles 
 of the feet, tend to be inherited. Wilder gives some 
 striking instances of pecuhar and unusual palm and 
 sole patterns appearing in parents and offspring. 
 Thus, a man with a calcar loop on both feet married 
 a woman with a calcar loop and a divergence. Of 
 their three children, one has a loop on both feet, two 
 have a loop on one foot and a divergence on the other, 
 the loop being on the right foot in one case and the 
 left in the other. Yet the calcar loop is so rare as to 
 have been found only four times (aside from this 
 famil}") in 1,000 or more individuals examined. 
 
 Twins. 
 
 In the case of duplicate or identical twins (Wilder, 
 1904) these patterns show great similarit}'", though 
 not identity, and there is a distinct tendenc}^ for 
 mirror-image patterns to appear, especially on the 
 forefingers. Light has been thrown on the subject 
 of inheritance in twins by the studies of Newman 
 and Patterson (191 1, 191 6) on development and 
 variation in the armadillo. This animal always 
 produces four \^oung at a birth (some species more), 
 and these are invariably of the same sex, and have 
 been shown by Patterson (191 3) to arise by a process 
 of embryonic budding in the embryo derived from 
 a single egg. 
 
 Stockard (1921) has recently suggested an ex- 
 planation of this condition of polyembryony in the 
 armadillo. The Texan species invariably produces 
 four young at a birth, a South American species 
 regularl}^ produces eight, while in certain species as 
 many as twelve 3^oung may be produced, apparent ty 
 
THE LIMITS OF IIEREDTTY 177 
 
 from tertiary Imclding. Some other species of 
 armadillo produce only one embr^-o from the e^g. 
 In the Texas species {Tatusia novcnicincta) Patterson 
 has shown that two buds grow out, each of which 
 immediately divides into two. In the species in 
 which eight young are produced, these four buds 
 presumably divide again, while tertiary budding of 
 the embryo produces a higher number. 
 
 Patterson (191 3) found a " period of quiescence " 
 in the development of the young blastocyst, which 
 Newsman believes to be connected with the cause of 
 the budding. In the gastrula stage the embryo 
 remains quiescent for several weeks. Then placenta- 
 tion takes place, and the development is resumed. 
 Stockard (1921) suggests that while the blastoc^^st is 
 lying free and unattached in the uterine cavity, the 
 consequent absence of an oxygen supply {via the 
 blood) inhibits development. This condition of an 
 unattached blastocyst is found in no other mammal 
 except the deer. It is not known wh}'- the delay in 
 implantation of the blastoc3'^st occurs, but from 
 studies of other mammals it is suggested that it may 
 be due to some peculiarit}^ in the formation of the 
 corpora lutea.* In other animals, for example 
 birds, the deer, and lower animals, arrest of develop- 
 ment does not lead to pol^^embryony. But Stockard 
 finds from experiments with certain fish eggs that, 
 if development is arrested early (before gastrulation), 
 twins and double embryos are frequently produced. 
 Hence the interruption must occur at a critical time. 
 Also there must be present in the Qgg, as in that of 
 the armadillo, a decided tendcmcy to form buds under 
 conditions of arrest. .Ihus it appears that the 
 interaction of certain external and internal forces is 
 
 * A yellow mass of cells in the ovary in place of a discharpjcd 
 
 ovum. If the ovum is fertilised the corpus luteum persists and 
 
 grows for several months. The number of corpora lutea therefore 
 
 corresponds with the number of developing embryos. 
 
 1 2 
 
178 HEREDITY AND EUGENICS 
 
 necessar}?- to produce polyenibryony.* In the deer 
 it is not known when the arrest occurs, but failure of 
 budding (twins) may be due to (i) arrest being at 
 the wrong stage of development, or (2) lack of a 
 tendency" for the embr3^o to bud. Possibly delayed 
 implantation of the blastocyst, which may in turn 
 be controlled by the condition of the corpora lutea, 
 may account for the production of identical twins in 
 man. A peculiarity^ in the activity of the corpora 
 lutea would be as likely to be inherited as are 
 differences in other glands of internal secretion, and 
 such a difference would then become a factor in the 
 inheritance of twinning. 
 
 Newman, who has investigated twinning for a 
 number of 3^ears, published a little book on the 
 subject (191 7), and has recently (1921) taken up 
 experiments on the production of twin embryos. 
 He used a Californian starfish, and studied the 
 twinning which may occur in spontaneous^ partheno- 
 genetic larvae and in hybrids with another species. 
 He looks upon twinning as a process which involves 
 the duplication of originally single structures. The 
 first step involved is retarded development, followed 
 by loss of organisation or dedifferentiation. Re- 
 cover}^ results in the formation of new apical points, 
 which form the anterior ends of new individuals. In 
 the starfish Patiria such arrested development may 
 result in physiological isolation of blastomeres in 
 
 * Regarding the interpretation of polyembryony in the 
 armadillo, Professor MacBride suggests that all the South Ameri- 
 can Edentates are originally descended from tree-living animals, 
 in which it is an advantage to have only one young at a birth, 
 and a dome-shaped placenta as in the apes. The armadillos 
 have taken to the ground where the risks are greater, but have not 
 been able to recover the habit of laying more than one egg. They 
 have, however, substituted the method of multiplication by 
 budding from the single egg. The fact that in man also identical 
 twins occur may similarly be a result of his arboreal ancestry. 
 
THE LnriTS OF TTEREDTTY 179 
 
 the two- or four-cell stage, or the formation of double, 
 triple, or multiple monsters in the blastula, gastrula, 
 or larval (bipinnaria) stage. 
 
 It is of interest to note in this connection that 
 pol^^embryon}^, through division of the proembr^-o 
 into four cells which undergo separate development, 
 is a common feature in the pines and in some other 
 Abietineae, although in Pinus laricio it has been 
 observed that a single embryo sometimes develops 
 from these four cells owing to their failure to separate. 
 In an}^ case only one embryo reaches maturity, the 
 others aborting at various stages of their develop- 
 ment. It is unknown what determines the cohesion 
 or separation of the four proembryonic cells. 
 
 Reversed symmetry and mirror-imaging are the 
 result of a unit}' in development, and the degree in 
 which these phenomena appear in twins furnishes 
 evidence as to the length of time which the embryos 
 remain in contact during development. It is now 
 generally agreed that double monsters are simply 
 conjoined twins which have failed to complete their 
 separation. Wilder (191 6) describes a remarkable 
 case of double twins (girls) of the extremely rare 
 pygopagous* type. Their four palms are practically 
 alike in ridge pattern. Three of the soles are also 
 alike, but the fourth is radically different. Curiously 
 enough, the data concerning the palm and sole 
 patterns of the parents, which are necessary for an 
 evaluation of the inheritance, are not mentioned, and 
 this limits the interpretation of the facts. One cannot, 
 therefore, say that the aberrant pattern is beyond 
 hereditary control. 
 
 The famous Blazek twins, who were born in 
 Bohemia and recently died in Chicago at the age of 
 forty- four, are apparently another case of pygopagy. 
 One of them was married and gave birth to a son, 
 
 * Joined by the buttocks. 
 
i8o HEREDITY AND EUGENICS 
 
 now eleven years of age. Whether they were of the 
 identical type is not stated, but they were said to 
 differ in disposition and tastes, although they are 
 stated to have had only one set of digestive and pro- 
 creative organs. The\^ both nursed the infant son, 
 and food eaten b}^ one benefited the other. As they 
 left no wills, litigation is now pending to determine 
 whether the}^ should be legally considered one or two. 
 
 A similar case of united twins is described by 
 Sullivan (191 9). These twin bo3^s were ten ^^ears old 
 when examined, and w^ere born in Samar Island, 
 Philippines. They are identical twins in which the 
 separation has been incomplete, the right buttock of 
 one being in juncture with the left buttock of the 
 other, and the terminal part of the alimentary canal 
 is a single structure. The}^ are otherwise normal 
 and intelligent, having yellowish-brown skin colour, 
 straight black hair and dark brown eyes. But the 
 left twin is right-handed and the right twin left- 
 handed. The latter also has more rounded ears closer 
 to his head, is somewhat taller, and probably more 
 often takes the initiative. There are marked 
 differences in the proportions of the head and face, 
 both being somewhat asymmetrical and laterally 
 distorted to the right in the right twin and to the left 
 in the left twin. Hence the distortion is probably due 
 to external influences and developmental disturbances. 
 The finger prints are very similar, but with minor 
 differences in configuration. 
 
 Danforth (191 9) has dissected the left hands of a 
 pair of poly dactyl negro infant tw^ins, and compared 
 them with a normal white infant. It is uncertain 
 whether they were identical (uniovular) twins. The 
 polydactylism consisted in a small, nearly globose, 
 mass on each hand w^ith a slender attachment to the 
 little finger. This extra digit bore a nail and friction 
 ridges. It is thought that Polydactyly of this type 
 
THE LIMITS OF HEREDITY i8i 
 
 may have its greatest expression early in ontogeny, 
 before birth, and that it may be induced either by 
 hereditary or other factors. The twins showed 
 marked similarit}^ in their friction ridge patterns, 
 also in the muscular and arterial systems of their 
 hands, some similarity in nerve distribution, but 
 practically no resemblance as regards the veins. 
 Compared with the control hand, these resemblances 
 indicate that heredity is the chief factor involved in 
 the variations observed. 
 
 Newman and Patterson (191 1) have made a study 
 of the inheritance of peculiarities in the scutes or scales 
 on the nine bands of the armadillo, and similar 
 phenomena to those above mentioned (p. 179) appear 
 in their quadruplets, but in all these cases the father 
 is unknown. Thus, in one set of quadruplets three 
 show a double or abnormal scute, and one lacks it ; 
 in another set three have the scapular double scute, 
 and one lacks it. Other sets of quadruplets show 
 more variation in the position of. abnormal scutes, 
 but the evidence indicates that the latter are, at any 
 rate, blastogenic or predetermined in the egg. The 
 authors attribute these divergencies to inaccuracy 
 in the bilateral distribution of hereditary materials 
 during development — in other words, to somatic 
 segregation. The element of heredity cannot be 
 accurately judged without a knowledge of the male 
 parents. The process of scute alignment is shown to 
 be largely mechanically determined, and hence beyond 
 the limits of hereditary control. 
 
 Newman (191 6) finds in armadillo quadruplets a 
 condition of symmetry between that observed in 
 double monsters (whose whole development has been 
 in contact), and human duplicate twins. Hence he 
 concludes that the latter become ''physiologically 
 isolated " (this may imply asymmetrical nuclear 
 divisions of cells whose descendants remain tor some 
 
I 82 
 
 HEREDITY AND EUGENICS 
 
 time in contact) considerably earlier in development 
 than do armadillo quadruplets. Indeed, the amount 
 of mirror-imaging is so small in human duplicate twins 
 that it appears probable that the separation (actually 
 of cells or ph3^siologically of nuclear elements) takes 
 place early in the cleavage, though not necessarily 
 
 Fig. 30. — ^TwiN American Sailors of Irish Birth. 
 
 at the first cleavage of the egg, as was formerly 
 supposed. It should be pointed out that this line of 
 reasoning, while attractive, is not necessarily con- 
 clusive according to the present state of our know- 
 ledge. 
 
 A typical case of finger-print patterns in duplicate 
 
THE LIMITS (3F HEREDITY 
 
 183 
 
 twins is given in the Journal of Heredity, November, 
 1 91 6 (see Figs. 30, 31). The patterns are ahke in 
 these two men, except that the thumb of the left hand 
 has a loop in one twin and a whorl in the other, while 
 the middle finger in the former has an arch, and in the 
 latter a loop. Moreover, in each twin the patterns 
 on the fingers of the left hand are in nearly every case 
 mirror-images of the patterns on the corresponding 
 
 UEF-T ►-< AN O. 
 
 UEF-X MAMO. 
 
 7 ,"■{ 
 
 £r ^^ '=iM> ■'* 
 
 
 ^x^- 
 
 RIO WT M A^J O. 
 
 % 
 
 '■\ 
 
 RIOMT H AM O. 
 
 m 
 
 Fig. 31. — Finger Prints of the Twins in Fig. 30. 
 
 The thumbs of their left hands and the middle fingers of their 
 right hands are clearly distinguishable in pattern. 
 
 fingers of the right hand. Another evidence that 
 these friction-skin patterns are on the borders of 
 hereditary control is found in the fact that in a 
 congenitally split finger observed b}' Wilder the 
 patterns of the two finger tips were not identical. In 
 all hands the minutiae of the ridges, such as forkings, 
 interruptions, and isolations, remain constant through- 
 out life, and these form the basis for the identification 
 
1 84 
 
 HEREDITY AND EUGENICS 
 
 systems. These details are clearly not inherited, 
 for no two patterns are alike in these particulars, 
 and Galton concluded that the chance of two finger 
 prints being identical was less than i in 64,000,000,000. 
 The inheritance of finger-print patterns is the 
 subject of a paper by Miss Elderton (1920). The 
 arch, loop, whorl, and composite are the types of 
 pattern used for criminal classification. But this is 
 inadequate for scientific distinctions. Galton in- 
 creased his four or five original categories up to fifty- 
 three. He was led to assume continuity between 
 
 Fig. 32. — Twins, Eighteen Years of Age, from York, 
 
 Pennsylvania. 
 
 types, and for years sought quantitative measures 
 for the finger print. Miss Elderton adopts the follow- 
 ing order, arch, small loop, large loop, composite, 
 whorl, as a natural order in passing from type to type. 
 An effort was made to state the inheritance in 
 Mendelian terms. The difficulties were (i) in the 
 presence of transitional forms; (2) there is probable 
 inheritance of pattern with change of finger. As- 
 suming that inheritance was on the same finger from 
 parent to offspring, and classifying Galton 's data, she 
 found that : (i) Arch x arch and arch x composite ap- 
 pear to give no whorls ; (2) whorl x whorl and whorl 
 
THE LIMITS OF HEREDITY 
 
 i8 
 
 X composite give no arches; (3) arch x loop, whorl 
 X loop, composite x loop, and loop X loop can give 
 all four types ; (4) composite is rare, but it may be 
 that composite x composite cannot give arches ; 
 (5) arch X whorl can give all types. These results 
 suggest that loop is '* much more heterozygous " than 
 arch or whorl. If composite is combined with loop, 
 simpler ratios are obtained. But the Mendelian 
 
 Fig. 33, — ^TwiNs having the same Height, Weight, Tastes, 
 
 Disposition, and Talents. 
 
 They have worked together for twenty-five years and have never 
 
 been separated. 
 
 interpretation is unsatisfactory (i) because it is 
 unjustifiable to combine composite with loops; (2) be- 
 cause the categories are really not sharp, but a great 
 variety of transitional forms occurs; and (3) there is 
 good reason to believe that inheritance is not neces- 
 sarily from one finger of the parent to the same finger 
 of the child. The coefficient of inheritance method 
 of treatment gives low values of inheritance. 
 
I 86 
 
 HEREDITY AND EUGENICS 
 
 The brain convolutions in duplicate twins have 
 also been compared. For example, Sano (191 6) 
 studied the brains of stillborn twin boys. One boy 
 
 Fig. 34. — ^TwiNs from Battle Creek, Michigan. 
 
 They were separated when three years of age, and have always 
 lived apart. Even their best friends cannot distinguish 
 them when they meet. 
 
 was somewhat larger throughout than the other, 
 and this applied also to the brains, the larger brain 
 being more highly developed, with more sulci. But 
 
 Fig. 35. — Twin Sisters from Romanshorn, Switzerland. 
 
 there was a very remarkable similarity in the dis- 
 position of the furrows, and all the differences were 
 of secondary importance, thus indicating the in- 
 heritance of similar mentalities. 
 
THE LIMITS OF HEREDITY 187 
 
 Galtoii (1883) made a study of twins, which con- 
 tains many facts of great interest. In response to 
 inquiries he obtained descriptions of about eighty 
 pairs of closely similar twins, thirty-live of which 
 entered into full details. He says (p. 21C): " In a 
 few of these not a single point of difference could be 
 specified. In the remainder the colour of the hair 
 and eyes was almost always identical; the height, 
 weight, and strength were nearly so. Nevertheless, 
 I have a few cases of a notable difference in height, 
 weight, and strength, although the resemblance was 
 otherwise very near. The manner and personal 
 address of thirty-five pairs of twins are usually 
 described as very similar, but accompanied by a 
 slight difference of expression, familiar to near 
 relatives, though unperceived by strangers. The 
 intonation of the voice when speaking is commonl}' 
 the same, but it frequently happens that the twins 
 sing in different keys. Most singularly, the one 
 point in which similarity is rare is the handwriting. 
 I cannot account for this, considering how strongl}' 
 handwriting runs in families, but I am sure of the 
 fact. I have only one case in which nobody, not 
 even the twins themselves, could distinguish their 
 own notes of lectures, etc., barely two or three in 
 which the handwriting w^as undistinguishable by 
 others, and only a few in which it was described as 
 closely alike. On the other hand, I have many in 
 which it is stated to be unlike, and some in which 
 it is alluded to as the only point of difference. It 
 would appear that the handwriting is a ver}- delicate 
 test of difference of organisation— a conclusion which 
 I commend to the notice of enthusiasts in the art ol 
 discovering character by handwTiting."* 
 
 Galton cites a number of remarkable similarities 
 in these thirt3'-five pairs of twins and others. In 
 
 * Cf. p. 172. 
 
1 88 HEREDITY AND EUGENICS 
 
 seven of the thirty- five, both twins " suffered from 
 some special ailment or had some exceptional 
 peculiarity. Two twins at the age of twenty-three 
 were attacked by toothache, and the same teeth had 
 to be extracted in each case." A pair of French twins 
 who travelled as business men and were asthmatic 
 always had attacks in the same cities. They were 
 taken simultaneously with rheumatic ophthalmia 
 (an inflammation of the eye), one in Paris, and the 
 other in Vienna. In another French case the twins 
 were monomaniacs, melancholy, morose, suffering 
 from imaginary persecutions, etc. They showed 
 precisely the same symptoms, although always kept 
 apart and never communicating with each other. 
 At intervals of months the same mental changes 
 would spontaneously come over them both inde- 
 pendently, even when they w^ere in institutions some 
 miles apart. 
 
 In eleven of the thirty-five pairs of twins cited by 
 Galton there was the same association of ideas, twins 
 often making the same remarks on the same occasion, 
 or beginning to sing the same song at the same time. 
 One twin visiting Scotland bought a set of champagne 
 glasses as a surprise for his brother B. The brother 
 in England at the same time bought a set of precisely 
 the same pattern for his brother A. In sixteen cases 
 the twins were closely similar in tastes and dis- 
 positions. The differences in the others were merely 
 in intensity or energy, one being more vigorous, the 
 other more gentle, etc. The mental similarities 
 evidently extended to the fundamental structure of 
 the mind, and were not merely superficial. In only 
 two cases was a strong bodily resemblance accom- 
 panied by mental diversity, and the converse occurred 
 only once. Clearly a more extended study of the 
 mental differences between identical twins will throw 
 valuable light on questions of mental inheritance. 
 
THE LIMITS OF HEREDITY i <S9 
 
 The records of similar twins show that ilhicsses 
 clearly retard i^rowth, and may thus cause permanent 
 differences between twins. Some inherited differences 
 also first develop late in life. 
 
 The number of the Journal of Heredity for December, 
 1 91 9, is devoted entirely to twins, and contains 
 thirty figures, chiefly photographs of twins, which 
 show remarkable degrees of resemblance. One ]jair 
 of grown-up brothers have not only identical features, 
 but the same height and weight, the same tastes, 
 disposition, and talent. Another pair of identical 
 twins of exceptional abilit}" have never differed 
 more than a pound in weight, never varied more 
 than o-i per cent, in their college marks, and although 
 absolutely dependent upon glasses, can wear each 
 other's. Their illnesses have often coincided, and 
 most of their tastes are similar. But their tailor says 
 that one of the twins has a short left arm and the 
 other a short right arm — a mirror-image difference 
 such as frequently occurs in twins. Several pairs of 
 these twins are illustrated in Figs. 30 to 35. 
 
 The record of identity in another case extends to 
 size, voice, and tastes in music, but they differ in 
 their taste for mathematics. Twins which were 
 separated at three years of age (Fig. 34), and have 
 since remained apart, show^ an equall}' striking 
 identity of features. The handwriting, which is 
 known to be an index of character, is closely alike 
 in many twins, in one case " virtually identical," 
 but differences are also recorded. 
 
 There are clearly differences in the degree of 
 resemblance between *' identical " twins. One pair 
 of men twins agree in features and in their likes and 
 dislikes, diversions, foods, and intellectual interests. 
 They both suffer from night-blindness, but their hand- 
 writing is " very different." Another pair have 
 similar tastes for poetry and music, and enjoy the 
 
I go HEREDITY AND EUGENICS 
 
 same sports, but differ in their mathematical tastes 
 and in their gait. One was left-handed as a child, 
 but their writing is strikingly alike, and they both 
 have the same peculiarity of the left thumb joint. 
 They differ in application and in nervousness. This 
 is a striking combination of similarities with minor 
 differences and an unaccountable left-handedness 
 in one. 
 
 Still another pair of men of fift3^-nine show less 
 identity of feature, but similar gait and bodily 
 weaknesses, the same dislike for strawberries and acid 
 foods, and a congeniality for each other which appears 
 to be characteristic of identical twins . But their ocular 
 defects pertain to the right eye in one and the left eye 
 in the other, and their handwTiting is not strikingly 
 similar, though showing marked resemblances. 
 
 Popenoe (1922) has recently described a case in 
 which twin girls were reared separately and have led 
 very different lives yet maintain their physical and 
 mental identity. The mother died, and they were 
 separated at the age of eight months. They did not 
 see each other again or correspond until they were 
 eighteen, and have only been together for about ten 
 months in all their lives. One married and taught 
 in a school, the other travelled and has followed 
 a business career in various parts of the country. 
 Yet they remain of exactly the same height and can 
 wear each other's clothes. Their hair and voices are 
 the same and people cannot tell them apart. They 
 even both had their hair bobbed at the same time, 
 each without the other knowing it. Their intellectual 
 capacities appear to be very similar, as well as their 
 tastes. Like many twins, their illnesses also usually 
 came at the same time. Here is an excellent example 
 showing the overpowering importance of nature, 
 and the insignificance of environment and experience 
 m producing differences. 
 
THE LIMITS OF HEREDITY 191 
 
 One of the interesting facts concerning " identical " 
 twins which emerges, and has already been shown in 
 other data, is (i) that they differ in their degree of 
 resemblance; (2) that they ma}^ show exceptional 
 similarity in most respects, and marked divergence 
 in a few. The former fact can probably be accounted 
 for, as explained above, on the basis of an earlier or 
 later separation of blastomeres, or of the budding 
 rudiments of separate embryos. Marked divergence 
 in certain characters was also obtained in armadillo 
 quadruplets, together with mirror- image effects. 
 The explanation is doubtless the same in both cases, 
 but is not clear at the present time, unless it be that 
 the}^ are biovular twins from parents heterozygous 
 only in these characters. A certain amount of 
 divergence must be expected even between identical 
 twins, just as the two sides of the face, or the measure- 
 ments of any bilaterally symmetrical organs of the 
 body ma}^ show differences. It is a more puzzling 
 fact that this bilateral asymmetry is itself inherited, 
 as shown b}^ identical twins whose faces show exactl}' 
 the same asymmetries (Fig. 34). 
 
 A fact in this connection which is frequently for- 
 gotten is that the only reason why human identical 
 or monozvsfotic twins more closelv resemble each 
 other than ordinary brothers and sisters is because 
 man is usually heterozygous for so many characters 
 that the chances of two different germ-cells from the 
 same parents furnishing exactly the same combination 
 of characters is remote. Nevertheless, it is un- 
 doubtedly the fact that in some families in which both 
 parents are homozN'gous for many characters, brothers 
 or sisters ma}', and do, occasionally occur from 
 separate births, and yet resemble each other as much 
 as identical twins, except that there is always an age 
 difference. Biovular twin births in such families 
 may be expected to give rise occasionally to twins 
 
192 HEREDITY AND EUGENICS 
 
 which appear to be of the " identical " type, except 
 in one or two, or a few characters in which the 
 parents were heteroz3^gous and the germ cells con- 
 cerned happened to carry the corresponding allelo- 
 morphic characters. 
 
 We are so accustomed to seeing diversity in the 
 offspring from a single pair of human parents that 
 we forget what always happens in crosses of homo- 
 zygous types. Any plant breeder will have made 
 numerous crosses in which the F^ offspring are so 
 absolutely alike as to be indistinguishable by any 
 visible differences, or probabh^ even any constant 
 measurable difference. There is no doubt that, for 
 similar reasons, what appear to be identical or 
 monozygotic twins occasionally appear in human 
 families when they are really dizygotic or ordinary 
 twins of the same sex. This clearly helps to account 
 for the occurrence of intermediates between identical 
 and fraternal twins — i.e., twins of the same sex which 
 differ only in a very few characters. 
 
 Windle (1892) has collected numerous cases of 
 identical malformations in twdns, many of which 
 were known to be of the identical type, although, 
 unfortunately, the sex is specifically mentioned in only 
 one or two. A case is described of twins enclosed in 
 the same membranes, in both of which there was a 
 deficiency of the anterior abdominal wall, the in- 
 testines and part of the liver being contained in a thin 
 membranous sac. Another sac, the size of a walnut, 
 hung posteriorly from between the thighs. The 
 latter was probably due to persistence of the neuren- 
 teric canal, dilated by the rachidian fluid to form a 
 sac. Instances in which both twins have the same 
 malformation are said to be not uncommon. But in 
 Rotunda Hospital, Dublin, in the years 1 847-1 854, 
 there were 13,748 women delivered, of whom 233 
 had twins ( = 1 in 59), none, however, showing similar 
 
THE LIMITS OF HEREDITY 193 
 
 malformations. Windle cites numerous instances 
 from the literature, including two cases of twins, both 
 showing hypospadias; (3) one pair with hermaphro- 
 ditismus masculinus ; (4) one with occipital meningo- 
 celes* of the same size, and hypospadias as well; 
 (5) one of spina bifida ;t (6) occipital meningocele with 
 the upper and low extremities one-quarter their normal 
 length (considered phocomeliaj) ; (7) anencephali 
 (without a brain), the palates 1 also having a deep 
 longitudinal furrow; (8) male twnns, both with right- 
 sided congenital hydrocele ;§ (9) twins with cyclopia 
 (one median eye); (10) twin girls with abnormally 
 developed sex organs, christened as boys; (11) twins 
 with six digits on hands and feet (in one amnion) ; 
 (12) twins with a supernumerary pollex (thumb) on 
 the right hand; (13) one twdn with six fingers, the 
 other with six fingers and six toes; (14) twans with 
 a sternalis muscle, the mother also having one; 
 (15) twins with a remarkable conformation of the left 
 parietal bone; (16) cited b}^ Galton, a pair of twins 
 with slight congenital flexure of one of the joints of 
 the little finger. The condition was inherited from 
 a grandmother, but neither parents nor sisters nor 
 brothers show any trace of it. (17) Twins with a 
 peculiar way of bending their fingers. There is a 
 faint tendency to the same peculiarity in the mother, 
 but in no other member of the family. (18) Cited 
 b}^ Darwin, twins with a crooked little finger, but 
 no know^n family tendency to this peculiarity. 
 
 * Hernial protrusion in the occipital region of the three 
 membranes surrounding the spinal cord. 
 t Congenital cleft of the vertebral column. 
 j A condition with hands and feet, but no arms or legs. 
 § A collection of fluid, occurring especially in the scrotum. 
 
 13 
 
194 HEREDITY AND EUGENICS 
 
 Inheritance of Twinning. 
 
 Interesting studies have recently been made on 
 the inheritance of twinning. It is well known that 
 a tendency to produce twins is inherited in sheep, 
 certain breeds nearly always bearing twins. Daven- 
 port (1920) places the frequenc}^ of twin births at 
 about II per cent., and Bonnevie (1919^) finds, from 
 statistics of human births in Norway, that i -34 per 
 cent, of births are twins. In one Norwegian family, 
 however, the frequenc}^ of twin births was as high as 
 19-5 per cent., showing a strong tendenc}^ to in- 
 heritance. It is significant that twinning occurs more 
 often in large than in small families. In the families 
 investigated, 20 per cent, of the twin births were 
 believed to be uniovular — i.e., derived from a single 
 impregnated Qgg. It is suggested that the tendency 
 to produce biovular or non-identical twins is a 
 recessive character, but this conclusion does not 
 appear very probable. 
 
 In a statistical stud}^ of twinning in families, 
 Davenport (1920) considers families in which twin 
 births had occurred more than once. The mothers 
 and fathers of such families are spoken of as repeaters. 
 If inheritance of twinning were onl}^ through the 
 mother, then the relatives of repeating mothers should 
 show a higher proportion of twins than the relatives 
 of repeating fathers. It was found, however, that of 
 355 labours occurring to the mothers of repeating 
 mothers, 16 or 4-5 per cent, were twin labours; while 
 of 289 labours occurring to the mothers of twin- 
 repeating fathers, 12 or 4-2 per cent, produced twins. 
 Thus, twins occur with nearly equal frequency in the 
 fraternities of repeating fathers and mothers, and with 
 about four times their frequency in the general popu- 
 lation. These and similar statistics indicate that, in 
 strains bearing two or more pairs of twins to a family, 
 
THE LIMITS OF HEREDITY 195 
 
 the hereditary influence of the father on twin produc- 
 tion is approximately equal to that of the mother. In 
 thirty families containing twins classed as identical, 
 both the fathers and the mothers belonged to fra- 
 ternities in which there were 13 per cent, twin births. 
 Hence the inheritance factor in the production of 
 identical twins is nearly three times as strong as in 
 the production of twins in general, and again the in- 
 fluence of the father appears to be as great as that 
 of the mother. 
 
 The sex of twins is also used as a means of deter- 
 mining how many are probably biovular or uniovular 
 in origin. In 160 pairs of twins in repeater families 
 (having two or more pairs of twins), in which the sex 
 was given, fifty- four w^ere of unlike sex and 106 of 
 like sex. Since the expectation for two-egg twins 
 is an equalit}' of like and unlike sexed twins, the 
 excess of fifty-two pairs of like-sexed twins was 
 probably uniovular in origin. This indicated that 
 about I in 3 of the twin births are of identical twins. 
 Davenport has also examined families in which one 
 parent of twins has married twice. In fourteen cases 
 the father married twice, in fifteen the mother, and 
 in one family both father and mother. Where the 
 father had married twice, there were twins of both 
 marriages in tw^o cases, or 14 per cent., and the corre- 
 sponding figure where the mother had remarried was 
 21 per cent., again indicating by these high values 
 the hereditary- nature of twinning. 
 
 Until recently it would have appeared absurd that 
 the father could have any hereditary' influence on 
 twinning, but Davenport points out how our present 
 knowledge provides the basis for such a result, at least 
 as regards biovular or fraternal twins. In the first 
 place, there is evidence to show that the simultaneous 
 release of two eggs is much more frequent than are 
 twin births. There is statistical evidence from the 
 
196 HEREDITY AND EUGENICS 
 
 examination of corpora lutea (see p. i 'j'j) that 5 to 6 per 
 cent, of ovulations are probably double. When the 
 number of corpora lutea of pregnant rabbits and pigs is 
 compared with the number of embryos, there is found 
 to be always an excess of the former, indicating 
 that some eggs fail to be fertilised after ovulation. 
 Blighted embr3^os are also repeatedly found. They 
 account for some of the human cases of earh' mis- 
 carriages. Such cases are by no means always due 
 to physiological causes, but are often to be explained 
 by inability of the embryo to complete its develop- 
 ment. Lethal factors w^hich kill the embr3^o or 
 inhibit its development beyond a certain point when 
 present in homozygous condition are now^ well known 
 through the work of Morgan and his pupils with the 
 fruit fly Drosophila. It has long been known that 
 onty mice heterozygous for yellow body colour can 
 live, and it has recently been shown that when such 
 3^ellow mice are crossed with each other, 25 per cent, 
 of the embryos — i.e., the homoz^^gous yellows — are 
 atretic and fail to develop. 
 
 Such evidence makes it certain that double ovula- 
 tions are much more frequent than twin births. This 
 will be due, as Davenport points out, to (i) a failure 
 of fertilisation of one egg, or (2) a failure of develop- 
 ment of one egg. Of course, lethal factors may be 
 present in both ^gg and sperm, and their presence 
 will probably account for many cases of sterilit}' in 
 mankind. Thus a woman may be sterile with one 
 husband and fertile with another, or a man may have 
 children by one wife and not by another. Couples 
 desiring children not infrequenth' fail to produce 
 them. In some of these cases the germ cells of both 
 ma}^ contain the same lethal factor, or a combination 
 of factors which are incompatible with development. 
 It is w^ell known that dairy cattle show similar 
 phenomena, a particular bull being sterile with 
 
THE LIMITS OF HEREDITY 197 
 
 certain cows. Gynecological literature abounds with 
 cases of blighted twins, or of single births accom- 
 panied by an undeveloped foetus. Probably the 
 presence of lethal factors in some of the germ cells 
 accounts for many such cases. We have already 
 seen (p. 90) that brach3^dactyh' is perhaps lethal in 
 its effects w^hen present in the homozygous condition, 
 and the same is probably true of various other 
 abnormalities. Ihe conception of lethal factors is 
 thus destined to play an important part in the ex- 
 planation of many phenomena of reproduction in 
 man, and to furnish an explanation of sterility in some 
 cases where there has been no voluntary prevention 
 of children. 
 
 A remarkable instance of a strain producing multiple 
 births has recenth^ been described (Davenport, 191 9). 
 A woman living in Cleveland, Ohio, has in three 
 successive marriages never had a single child at a 
 birth. She was born in Paris, and her mother and 
 her mother's mother are both said to have had only 
 twins, triplets, or quadruplets. By her first husband 
 she had twins. When he died she married a French- 
 Canadian, and bore twins, a boy and a girl. The girl 
 married and bore first a single child, and then twins, 
 who died with the mother shortly after birth. The 
 original mother next bore triplets ? ? c^ who died young. 
 Two years later twins ? S were born, and again the 
 following year twins ? S • By a third husband of 
 English and Scotch descent she had twins S c^ , who 
 died young, then triplets c^ ? ? , a boy still living and 
 two others born dead. This was followed by a 
 miscarriage of triplets ^ ? 5 , then twins ? c^ , the girl 
 dying shortly after birth. Next followed a mis- 
 carriage of quadruplets (^ c? ? ? , caused by poor health 
 of the mother. Twins ^ ? followed, the girl dying in 
 ten days, then triplets were born c? ? ? , the boy sur- 
 viving. In 1912 quadruplets, girls, were born; the 
 
198 HEREDITY AND EUGENICS 
 
 same year occurred a miscarriage of four boys, and 
 the following year a miscarriage of three girls. This 
 makes a total of fort3'-two births and miscarriages 
 from the one mother. In this remarkable case the 
 tendency to multiple births has been traced in four 
 generations. 
 
 Hayden (1922) describes a case of a pure-bred 
 Holstein-Friesian cow in the herd of the Ohio 
 Agricultural Experiment Station which has had twin 
 calves five times out of seven by three different bulls. 
 A more remarkable case is described by Pearl (191 2), 
 who remarks that: ''It is well established that a 
 tendency to multiple gestation in normally uniparous 
 forms may be inherited." A Guernsey cow pro- 
 duced fourteen calves in her first eight pregnancies, 
 bearing triplets twice, twins twice, and single 
 young four times. The triplets were two females 
 and a male, the former probably free-martins. 
 The male closeh' resembled the mother, while the 
 females were of different colour and pattern like the 
 father. 
 
 That there are two types of twins — identical or 
 uniovular, of the same sex, and showing exceptionally 
 close resemblance; and biovular or fraternal, show- 
 ing no greater resemblance than ordinary brothers 
 and sisters — has, of course, long been recognised. 
 Occasionally attempts have been made to show that 
 twins do not fall into such categories, but without 
 success. Fisher (191 9), from a mathematical treat- 
 ment of some earlv data of Thorndike, thinks it 
 necessary to conclude that differences in the degree 
 of resemblance between twins could be accounted 
 for by assuming that the egg divides into two 
 halves, each of which is fertilised by a different 
 spermatozoon. vSuch an hypothesis seems to have 
 no biological or experimental evidence in its favour, 
 while the evidence for the existence of both biovular 
 
THE LIMITS OF HEREDITY 199 
 
 and uniovular twins in mankind is strong and un- 
 equivocal.* 
 
 It was formerly supposed that identical twins were 
 produced by separation of the first two cells formed by 
 the division of the fertilised egg, the first two cells into 
 which the egg divides becoming separated after the egg 
 has been fertilised by a single sperm. There is experi- 
 mental evidence of the production of two embryos 
 or of double monsters from invertebrate eggs by this 
 method. But since the investigations of Newman 
 and Patterson on the armadillo, in which the latter 
 showed that the four embryos at a birth are produced 
 by budding at an early stage of development, it has 
 seemed much more probable that identical twins 
 (surrounded by a common chorion) in man are pro- 
 duced in a similar way. Moreover, the number of 
 buds in the nine-banded armadillo is occasionally 
 three or five, and varies more widely in other species ; 
 and probabl}^ in man also the number is not abso- 
 lutely fixed, but may occasionally be three, thus 
 accounting for some cases of triplets of the same sex. 
 
 Zeleny (1921) finds a definite relation between the 
 number of twin births and triplet births in mankind. 
 
 Thus, if - is the number of twin births, then the 
 n 
 
 number of triplet births will very nearly approximate 
 2- In Prussia during the years 1826-49 the 
 
 ft' 
 
 * A recent case (Arey, 1921) proves directly the origin of 
 identical twins from a single ovum. Twin embryos are described, 
 each 12*3 mm. long, and contained in a single amnion and chorion. 
 The two umbilical cords and yolk-stalks were inserted in a common 
 yolk-sac. In a second pair of monochorionic twin embryos with 
 separate amnions, one of the embryos had neither yolk-stalk nor 
 sac. It is suggested that the human embryo probably shows 
 rather rigid determinate cleavage, and that monozygotic or 
 identical twins result not from the separation of blastomeres or 
 blastomere clusters in early cleavage, but " from later fission of 
 the inner cell mass." 
 
200 HEREDITY AND EUGENICS 
 
 number of births was 13,360,557. The frequency of 
 twin births was i in 89-1, and of triplets i in (88-9)^. 
 For quadruplets, however, there is an excess over 
 expectation, the number being i in (71 -9)^. Again, 
 in the United States birth-registration area in 191 7 
 the number of births is recorded as 1,339,975, the 
 number of twins being i in 93-1, and of triplets i in 
 (93-0)2. From these statistical relations it would 
 follow that " triplets are produced by the coincidence 
 of two independent processes occurring with equal 
 frequencies." One of these processes gives rise to 
 twins. This relation w^ould hold whether multiple 
 births occurred through multiple ovulation or budding 
 of a monoz3^gotic embryo or both, provided that each 
 followed the rule. This result is remarkable when 
 one considers the number of conditions, both bio- 
 logical and human, which contribute to produce the 
 registration statistics. 
 
 Man appears to be unique among animals, as 
 Davenport points out, in that he produces both types 
 of multiple births: (i) by the budding method found 
 in the armadillo; (2) multiple births from separate 
 eggs, as found in carnivora, herbivora, and rodentia 
 generally. Differences in the degree of resemblance 
 betw^een identical twins may depend in part on the 
 stage at which budding of the original embryo takes 
 place. Much more information is required regard- 
 ing human multiple births, particular^ data from 
 obstetricians on such matters as the number of 
 chorions present, the presence of blighted embryos 
 in the afterbirth, and the relation between the number 
 of corpora lutea and the number of embr3^os at a 
 birth. The study of twins presents many sides, 
 and will furnish evidence on a variety of questions 
 connected with heredit}^ and reproduction in the 
 human race. 
 
 The recent study of the so-called free-martin or 
 
THE LIMITS OF HEREDITY 201 
 
 sterile female in cattle has thrown a good deal of 
 light on questions of sex alteration, and also on the 
 production of twins in cattle. John Hunter (1779), 
 in an early account of the free-martin, states that it 
 was a type well recognised b}^ the farmers at that 
 time. Such barren cows in Roman times were called 
 taurce, but apparently the Romans did not understand 
 the manner of their production. Hunter says: '* It 
 is a known fact, and, I believe, is understood to be 
 universal, that when a cow brings forth two calves, 
 and that one of them is a bull-calf, and the other a 
 cow to appearance, the cow-calf is unfit for pro- 
 pagation; but the bull-calf becomes a very proper 
 bull." This clearly states the general facts regarding 
 the production of free-martins. Hunter dissected 
 three such animals and considered them hermaphro- 
 dites, but found that they differed from one another. 
 He gives the anatomical details of his dissections, 
 and states that free-martins are " much larger than 
 either the bull or the cow, and the horns grow longer, 
 being very similar to the horns of an ox." 
 
 The important investigations of Lillie (191 7) on the 
 foetal development of twins in cattle has furnished 
 a clear explanation of the fact that the free-martin 
 is nearh^ always sterile. The internal reproductive 
 organs of the free-martin are found to be usually 
 predominantly male, while the external organs are 
 at least usually female, but there are considerable 
 variations. Lillie 's main disco verv was that in the 
 production of twin embryo cattle there is a secondary 
 fusion of the two chorions and anastomosis of the 
 circulation of the two foetuses. The free-martin is a 
 female transformed by the action of hormones derived 
 from the male twin, which pass through the anasto- 
 mosed bloodvessels into the circulation of the female 
 embryo. Nearl}- all twins of cattle are monochorial, 
 with the chorions more or less completely fused. 
 
202 HEREDITY AND EUGENICS 
 
 About 1 3 per cent, of free-martins (z.^., females twinned 
 with a male calf) are fertile. This happens when the 
 fusion of chorions does not take place, and there is 
 hence no opportunity for the male embryo to influence 
 the development of the female. It is also found that 
 there are always in cattle two corpora lutea present 
 when twins are born, and a single one at single births. 
 This shows that the vast majority, at least, of twins 
 in cattle are derived from two separate eggs. There 
 is no certain evidence that monozygotic twins ever 
 occur in cattle. This is contrary to the condition in 
 man, where both monozygotic (identical) and dizygotic 
 (fraternal) twins are now known to occur. 
 
 That monozygotic twins occur but rarel}', if at all, 
 in cattle and sheep, is shown b}^ the ratio of the sexes 
 in twin births. This ratio closel}^ approximates 
 ic?c^:2?c^:i$ ?, which would occur if all tw^ins were 
 derived from separate ova. The data on this subject 
 have been considered by Go wen (1922). In human 
 twin births there is a wide departure from this ratio, 
 owing to the occurrence of " identical " twins derived 
 from a single ovum. Thus, in statistical records of 
 Nichols, the proportions of the sexes in human twin 
 births is males, 234,497; male and female, 264,098; 
 females, 219,312. This represents a ratio of 
 I -07 : I -20 : I . These statistics are clearly in harmony 
 with the view^ that both uniovular and biovular twins 
 occur in man. 
 
 Gowen has also compared the colour markings of 
 cattle twins, taken from the Herd Books of the 
 American Jersey Cattle Association. These records 
 included 749 twin females, 168 twin males, and 207 
 male and female. Compared as regards colour mark- 
 ings, tongue colour, and switch colour, there was found 
 to be little if any significantly greater resemblance 
 in favour of twins of like sex. There w^as, however, 
 5 per cent, greater resemblance in favour of male 
 
THE LIMITS OF HEREDITY 203 
 
 twins as compared with twins which are male and 
 female, and this might be due to the occurrence of 
 monozygotic twins. But in no case is this difference 
 greater than twice the probable error, so it really 
 furnishes no eyidence in fay our of the occurrence of 
 monozygotic twins in cattle. 
 
 Lush (1922) describes a pair of twin Jersey heifers 
 which he thinks are identical. They both haye a 
 moderate notch (see p. 135) in their ears; their noses, 
 tongues, switches, and general shade of body colour 
 are the same; and they each haye a single spot on 
 the right hind foot. This indicates that monozygotic 
 twins occasionally occur in cattle. It is hardly 
 likely that both parents would be homozygous for 
 all these characters. 
 
 In pigeons, two pairs of female monozygotic twins 
 haye been described (Riddle, 191 8). They were both 
 deriyed from eggs with yery large yolks, but not 
 " double-yolked," the embryos haying a single 3^olk 
 sac. It is belieyed that they were formed by the 
 separation of the first two blastomeres in the fertilised 
 egg, this separation being a result of the yery large 
 initial size of the e.gg. 
 
CHAPTER VI 
 
 SOCIAL AND WORLD ASPECTS OF 
 
 EUGENICS 
 
 While the observation and study of the innumerable 
 alternative differences in man is a theme of great 
 interest, yet it lies for the most part outside the range 
 of practical eugenics, for great numbers of these 
 differences, aside from abnormalities, are, as far as 
 our present knowledge goes, innocuous in nature, 
 being neither advantageous nor detrimental in their 
 effects, but lending a pleasing and desirable variety 
 to the huinan race. The aim of practical eugenists 
 would, then, be rather so to direct selection by con- 
 trolling the conditions w^hich determine selection 
 as to eliminate the obviously undesirable or anti- 
 social traits ; and to improve, through public opinion 
 or otherwise, the chances of perpetuation and in- 
 crease of their kind on the part of the better qualified 
 members in every stratum of society. This aim, 
 though easily stated, is obviously almost infinitely 
 difficult of achievement in a complex civilisation. 
 And it is rendered all the more difficult by the fact 
 that eugenics aims, not to establish and improve a 
 single type, as in breeding, for example, racehorses, 
 but at the infinitely more complex result of improv- 
 ing innumerable more or less inter-breeding strains 
 simultaneously, weeding out their more defective 
 members or qualities, and at the same time main- 
 taining the diversity of t3^pes in the whole population. 
 A world of Shakespeares or Newtons or Goliaths, 
 even if attainable, would not be an econgmic success. 
 
 204 
 
SOCIAL AND WORLD ASPECTS 205 
 
 Differentiation of types is one measure of civilisation, 
 and no high type of culture could long be maintained 
 without it. The miner and the professor, the peasant 
 and the banker, each in his sphere makes his contri- 
 bution to civilisation, and so widens its boundaries 
 and increases the richness (mentally and morally, as 
 w^ell as economically) of the social inheritance of 
 tradition which makes the maintenance of culture 
 possible and the development of culture cumulative. 
 
 Nevertheless, there is great need for improvement 
 in the general mental and ph3^sical level of our race 
 through some form of selection. Probabl}" no race 
 has ever rivalled the Greeks in the number of great 
 men they produced in a relatively small population 
 during a period of a few centuries. It should be 
 possible to devise some more effective means of 
 discovering the youths of exceptional quality in 
 every stratum of societ}', and giving them larger 
 opportunities of self-expression. Mere advocacy of 
 an indiscriminately higher birth-rate, fostered by 
 artificial doles to the poorer classes of society, \wi\\ 
 only achieve a dysgenic result. An able discussion 
 of these problems is to be found in Bateson's presi- 
 dential address to the British Association in Sydney, 
 Australia, 1914. 
 
 The presence of various pairs of alternative 
 characters in the same individual probably has the 
 same stimulating effect in man that it has been 
 experimentally shown to have in such organisms as 
 maize and wheat. The frequently increased vigour 
 of hybrids was known to Darwin and other early 
 writers, but modern genetic experiments have given 
 the facts a much more precise orientation, although 
 its cause cannot yet be said to be fully understood. 
 The phenomenal growth of certain hybrid walnuts, 
 and the remarkable hardiness and vigour of such 
 hybrid trees as the London plane, are well known. 
 
2o6 HEREDITY AND EUGENICS 
 
 But, on the other hand, inbreeding by no means 
 necessaril}^ leads to deterioration. Among plants, 
 garden beans (Phaseolus vulgaris) and the small- 
 flowered evening primroses (of which there are many 
 species) are regularly self-pollinated, and probably 
 are crossed only at long intervals under exceptional 
 circumstances. Yet they are not lacking in vigour, 
 and, indeed, the small-flowered (Enotheras are much 
 more widespread in their wild condition in North 
 America than the large-flowered forms which are 
 open-pollinated, and hence give greater chances for 
 crossing. The former have been more successful in 
 an evolutionar}- w^ay, despite their self-pollination. 
 The advantages of ensured seed production for 
 every flower have more than counterbalanced any 
 advantages derived from crossing. 
 
 In this connection it is necessary to remember 
 several points. First, the h^^brid vigour or heterosis 
 arising from crossing both in plants and in animals 
 is confined very largely, or in some cases entirely, to 
 the first hybrid generation. It is therefore a purety 
 temporary phenomenon, unless the crossing is con- 
 tinued in each generation. It is apparently not even 
 a constant accompaniment of the heteroz3^gous con- 
 dition, but is speciall}^ characteristic of the F^ 
 generation. Another point to remember is that in- 
 breeding, which must always occur to some extent 
 even amongst wild animal species, tends to reduce 
 the amount of heterozygosity in each generation. 
 Probably in man, in whom a host of character- 
 differences are being redistributed in each generation, 
 a homoz3^gous condition is seldom reached, except as 
 regards a relatively small number of characters. 
 The degree to which the homozygous condition exists 
 in any family may be to some extent measured by 
 the amount of diversity between sibs (brothers and 
 sisters) and their parents, grandparents, and collateral 
 
SOCIAL AND WORLD ASPECTS 207 
 
 relations. Obviously, if they all resemble each other 
 in a particular character, the family will be homozygous 
 for that character. But it appears that in inodern 
 civilised races, at any rate, this is seldom the case, 
 even for a single character. Nevertheless, many 
 Scandinavian families are probably homozygous for 
 blue e^^es, and other similar cases might be mentioned, 
 but they are obviously exceptional. This brings us 
 to consider briefly some of the mathematical laws 
 connected with in-breeding and cross-breeding. 
 
 A considerable mathematics has grown up about 
 the stud}' of Mendelian characters. It is not my 
 purpose to deal with that literature here, but a few 
 of the consequences of Mendelian inheritance as 
 regards the whole population may be pointed out. 
 There is considerable evidence that man}' trivial 
 characters in plants and animals, as well as in man, 
 are quite innocuous as regards the welfare of the 
 organism, at least under usual conditions. It is 
 difficult to believe that a long nose or blue eyes is of 
 an}^ direct biological advantage to their possessor 
 in a civilised communit}^ in temperate countries. 
 But under a burning sun in a condition of nature 
 it is at least highly probable that a pigmented iris 
 as well as a pigmented skin are a distinct protection. 
 This is, perhaps, why such mutations in loss of pig- 
 mentation as have occurred to native races in the 
 tropics, have never been able to establish themselves 
 or give rise to a distinct type. 
 
 While natural selection as regards blue or brown 
 eye colour is therefore probabl}' inoperative in 
 temperate countries,* it might easity become opera- 
 tive under wild conditions in the tropics. W^arren 
 (191 7), in a paper on the numerical effects of natural 
 selection acting upon Mendelian characters, shows 
 the number of generations which would be required 
 
 * What sexual selection may do is another matter. 
 
2o8 HEREDITY AND EUGENICS 
 
 to eliminate a dominant or a recessive character. 
 He finds that in a Mendehan population in which the 
 numbers tend to double in each generation, and in 
 which a dominant character has twice the viability 
 of the corresponding recessive, then the recessive will 
 be eliminated in the eleventh generation. On the 
 other hand, if the recessive is twice as viable as the 
 dominant, then the latter will be eliminated in eight 
 generations. Hence, other things being equal, the 
 elimination of a deleterious dominant character is 
 more rapid than of a recessive. 
 
 The subject of the Mendelian proportions in a 
 mixed population was first considered by Pearson 
 (1904). He showed that with random mating of two 
 forms A A and a a and their progen}^, the formula 
 AA -\- 2 Ka-\- 2 aa will apply to the proportions in every 
 later generation — i.e., the population will remain 
 stable. Hard}^ (1908) pointed out the same thing. 
 Pearl (191 3, 1914) has worked out formulae for differ- 
 ent types of inbreeding, and determined coefiicients 
 for different degrees of relationship among inbred 
 pedigrees. Jennings (191 6) has elaborated eight}"- 
 two formulae, from which can be calculated, in many 
 cases directly, the results of various systems of 
 breeding in a Mendelian population. The results 
 vary, of course, not only according to the system of 
 breeding followed, but also according to the com- 
 position of the population at the beginning. The 
 systems of breeding analysed include random mating, 
 assortative mating, self- fertilisation, and various 
 systems of inbreeding, and from the formulae obtained 
 the relative proportions of the various t3^pes in any 
 generation may be determined. 
 
 With random mating the resulting population 
 generally remains stable, but with inbreeding or 
 assortative mating it may alter progressively in a given 
 direction. Inbreeding wall also, of course, gradually 
 
SOCIAL AND WORLD ASPECTS 209 
 
 transform any heteroz3"gous population into a homo- 
 zygous one, the rapidity with which the completel}' 
 homozygous condition is reached depending on the 
 system of inbreeding employed and the degree of 
 heterozygosity in the original population. Self- fertili- 
 sation, which is not uncommon in plants, is, of course, 
 the most stringent form of inbreeding, and it quickly 
 reduces any heterogeneous heterozygous population 
 to a completely homoz^'gous (but heterogeneous) con- 
 dition, unless some condition in the germ plasm, such 
 as balanced lethal factors, or some method of repro- 
 duction, such as apogamy. prevents the gametic 
 representatives of the different characters being freel}' 
 redistributed to the next generation. In wild species, 
 also, some of the Mendelian characters in the popula- 
 tion may be subject to natural selection, positiveh' 
 or negatively, and thus alter their proportions in the 
 population. This would lead to the elimination of 
 certain characters, even in a population mating at 
 random, although such characters are more dithcult 
 to eliminate from the germ plasm when recessive than 
 when dominant. In the same way the action of 
 natural selection would lead to the more rapid 
 multiplication and spread in the population of a 
 favoured character whether dominant or recessive. 
 
 Laughlin (1920) has worked out the conditions of 
 ancestral inheritance in man, assuming twelve pairs 
 of chromosomes representing as man}^ pairs of linked 
 genes. Galton's original law of ancestral inheritance 
 is well known — namely, that the two parents con- 
 tribute 50 per cent. (0-5) of the inheritance, the four 
 grandparents 25 per cent, or (0-5)^, the eight great- 
 grandparents 12*5 per cent (0-5)^, etc., the total 
 heritage being (0-5) +(0-5)^ + (0-5)^+ . . . = 1. Karl 
 Pearson later modified this scheme, on the basis 
 of statistical data of correlation between father and 
 son, finding that the resemblance varied from 30 per 
 
2IO HEREDITY AND EUGENICS 
 
 cent, or more for some characters to 50 per cent, 
 or more for others. Laughhn's scheme is based upon 
 the known constitution of the germ plasm — i.e., its 
 division into chromosomes, each bearing its group of 
 genes ; and ancestral influence is measured by tracing 
 individual chromosomes backwards through previous 
 generations. The " trail " of a given chromosome 
 in the ascendant or descendant generations will depend 
 upon the laws of probability and recombination, and 
 these laws will differ for the ordinary chromosomes 
 and the X and Y chromosomes. On this basis various 
 mathematical formulae are developed for calculating 
 ancestral influence. 
 
 The Basis of Racial and Temperamental 
 
 Differences. 
 
 In discussing questions of elimination or increase 
 of certain types or characters, it is very desirable to 
 know not only what relation these characters bear 
 to the economy of the organism, but also what are 
 their sources and controls in its development. The 
 ductless or endocrine glands, which have been studied 
 in recent 3^ears, are of the utmost importance in this 
 connection. The}' pour direct h' into the blood in 
 minute quantities hormones which influence and con- 
 trol directly the activities of various organs of the 
 body. They also form a system of checks and 
 counterchecks to each other, and so constitute a 
 sort of interlocking directorate, exercising the most 
 complete control over the bodily activities, as a whole, 
 through the medium of the substances they discharge 
 in minute traces into the blood. These glands have 
 a very long evolutionary history, being derived 
 from totalh^ different organs having other functions, 
 which are present in the lower vertebrates (Chordates) 
 such as Amphioxus . 
 
 In his presidential address to the Anthropological 
 
SOCIAL AND WORLD ASPECTS 211 
 
 Section of the British Association, Sir Arthur Keith 
 (1920) discusses the basis of differentiation of man- 
 kind into racial types, and shows how the character- 
 istic racial differences are probably connected with 
 differences in the secretions of the endocrine glands. 
 He points out that the characteristic differences of 
 feature, build, and colour cannot (for the most part) 
 have been evolved directh^ by natural selection of 
 variations, and elaborates the view that the differences 
 observed are a result of variations which have arisen 
 in the organs of internal secretion. These glands are 
 now known to control in a marvellous manner the 
 processes of development and functioning of the body. 
 The principal of these organs are as follow^s : (i) The 
 thyroid (a gland in the neck, astride the trachea); 
 (2) the parathyroids (four small glands close to the 
 thyroids); (3) the pituitary (a small reddish organ at 
 the base of the skull), of which the anterior and 
 posterior lobes have different functions ; (4) the pineal 
 body;* (5) the suprarenal capsules, over the kidney's, 
 consisting of cortex and medulla, with different origins 
 and diverse functions ; (6) the islets of Langerhans 
 in the pancreas ; (7) the interstitial tissue of the gonads . 
 These glands pour directly into the blood which 
 bathes them extremely minute quantities of their 
 various secretions, and the latter control in remark- 
 able fashion both the development and functioning, 
 not only of the body, but also to some extent of the 
 brain and mind. 
 
 The first instance in which the form of the body 
 was found to be influenced by an internal secretion 
 was that in which a pathological condition of the 
 pituitar}^ was shown to be the cause of the condition, 
 known as acromegaly, in which there is enlargement 
 of the bones and flesh of the hands, feet, and face. 
 
 * A small gland, about the size of a pea, under the brain, 
 resting on the anterior corpora quadrigemina. 
 
212 HEREDITY AND EUGENICS 
 
 Enlargement of the pituitary is also frequently 
 associated with gigantism. Dwarfism may result 
 from an invasion of the pituitary by tumours, and 
 also from a failure of functioning on the part of the 
 thyroid. If such conditions are induced by deranged 
 functioning of these glands, it is reasonable to suppose 
 that corresponding racial (inherited) differences would 
 arise from germinal changes, w^hose effect is to alter 
 the cjuantity (or quality) of these secretions. The 
 Caucasian,* according to Keith, shows a greater pre- 
 dominance of the pituitary than the Negro or Mongol, 
 as indicated by the pronounced nasalisation of the 
 face, the tendency to strong eyebrow ridges, prom- 
 inent chin, and the tendenc}^ to greater stature 
 and bulk of body. It is also suggested that the 
 beardless face and almost hairless body of the repre- 
 sentative Negro and Mongol types is due to a lesser 
 activity of the interstitial glands, the long stork-like 
 legs of Nilotic and other tribes resulting from a greater 
 abeyance of the same glands. 
 
 In the same way, differences in the pigmentation 
 of the skin, which characterise the various races of 
 mankind, may be reasonably assumed to be due to 
 inherited differences in the activities of the suprarenal 
 bodies, since it is known that Addison's disease, in 
 which, among other symptoms, there is a darkening 
 of the skin through pigmentation, is the result of a 
 pathological condition of the adrenal cortex. Thus, 
 the great colour varieties of mankind are probably 
 determined in part by differences in the activity of 
 the adrenal bodies ; but it is probable that other 
 
 * Of course, anthropologists now recognise that there is no 
 Caucasian race, but that modern European populations are a 
 mixture in various proportions of three distinct races: (i) Nordic 
 tall, blue-eyed, and long-headed (dolichocephalic); (2) Alpine, 
 short and stocky, brown-eyed and broad-headed (brachycephalic) ; 
 (3) Mediterranean, small and slender, brown-eyed and long- 
 headed. 
 
SOCIAL AND WORLD ASPECTS 213 
 
 glands as well are concerned in the determination of 
 skin pigmentation, and we have already indicated 
 some of the other racial differences which they 
 probably control as well. If, then, in the various 
 races hereditary differences in the activities of these 
 glands of internal secretion are concerned, it may be 
 expected that the results of racial crosses will be 
 very different from what they would be if there were 
 direct determiners for the various individual visible 
 characters. For each endocrine (ductless) gland 
 has various activities and affects the development oi 
 many parts of the body. In crosses between races, 
 whole complexes of characters w^ould then be ex- 
 pected to be inherited or modified together. If the 
 difference between a white and a black skin is due to 
 the greater activity of the suprarenals in the white 
 race, then it would appear that quantitative differences 
 in the activities of these organs are the units really 
 involved in white-black crosses. The laws of quan- 
 titative inheritance are by no means clearl}^ under- 
 stood at the present time, nor are even the facts of 
 colour inheritance in mankind entirely agreed upon 
 (see p. 52) ; but if they are due to inherited differences 
 in endocrine activitv, we have here the basis for a 
 further analysis and understanding of the combined 
 phenomena of blending and segregation in the colour 
 inheritance of racial crosses. 
 
 The thyroid is considered by Keith to be anthro- 
 pologically the most important of all the endocrine 
 glands. The thyroid, like all these glands, is believed 
 to throw off two types of substances,* one which is 
 
 * It may be questioned whether there are really two types of 
 substances given off, one early in development and the other 
 after maturity. It appears rather that a germinal change in, for 
 example, thyroid production causes morphogenetic changes 
 which will be inherited, while a functional derangement of the 
 same kind occurring later will produce different results and not 
 be inherited. 
 
214 HEREDITY AND EUGENICS 
 
 morphogenetic and affects the development, the other 
 which controls and regulates in a remarkable manner 
 various activities of the body through the minute 
 traces of certain substances which it pours into the 
 blood. This latter substance in the case of th3'roid 
 is known as thyroxin. It has been isolated and its 
 chemical structure determined, the molecule being 
 found to contain iodine and arsenic. About 150 
 grains were obtained from some 6,000 pounds of ox 
 thyroid, so that the amount of thyroxin poured daih' 
 into the blood of a man must be almost too infini- 
 tesimal for computation. The condition known as 
 myxcedema, which is accompanied by peculiarities of 
 the skin and hair, disappears when thyroid extract 
 is administered. Berman (1921) cites the fact that, 
 as early as 1891, sheep th3^roid was administered to a 
 woman with myxcedema.* The symptoms disap- 
 peared, but she was obliged to continue taking thyroid 
 extract until her death, in 191 9. In this period of 
 twenty-eight years she consumed nine pints of 
 thyroid, equivalent to the extract from the glands 
 of 870 sheep. 
 
 Hence, the thyroid acts directly on the skin and 
 hair, which are the chief structures used in the classi- 
 fication of the races of mankind. It also affects the 
 skeleton, and when deficient, causes, according to 
 Keith, arrested development of the basal part of the 
 skull, the root of the nose appearing to be flattened 
 and drawn backw^ards between the eyes, the upper 
 forehead projecting or bulging, the face being flattened, 
 and the bony scaffolding of the nose greatly reduced. 
 These are all characteristic features of the Mongohan 
 
 * A condition with dropsy-like swelling caused by failure of 
 nutrition from defective nerve influence. It is associated with 
 atrophy of the thyroid, and is probably directly due to excess 
 of mucin in the system. It is accompanied by sluggish move- 
 ments, thick speech, and dull mental condition. 
 
SOCIAL AND WORLD ASPECTS 215 
 
 face, and to a lesser degree of the Negro face. Hence, 
 it is concluded that a reduction or alteration in th^Toid 
 activity has been a factor in determining some of the 
 characteristics of these races. The Mongol might be 
 characterised as subthyroid relatively to the white 
 man, while the negro is relatively subadrenal. 
 Similarly such Eastern races as the Malays, Siamese, 
 Chinese, and Japanese, having nearl}^ hairless faces 
 and little hair on their bodies, may be classed as 
 in some respects eunuchoid, with a weak secretion 
 from the adrenal cortex. They are, however, vigorous 
 and prolific, and these are not eunuchoid charac- 
 teristics. The social dominance of the white man 
 might, then, be said to be due to the greater concen- 
 tration of certain hormones in his blood. 
 
 Achondroplasia (see pp. 34, 39) is a form of dwarfing 
 due to hypothyroidism, and is inherited. In man it 
 may be accompanied by shortening of the face 
 (prosopia), as in the bull-dog, or the face may be 
 unaffected, as also in the dachshund. The latter 
 condition is much less common. Short limbs and a 
 long trunk, accompanied by retraction of the nasal 
 region of the face, are all, according to Keith, 
 Mongolian characteristics. The so-called ^Mongolian 
 idiots (see p. 152) are stunted individuals, imbeciles 
 with Mongoloid features. Their occurrence among 
 Caucasian offspring is not an indication of ^longol 
 ancestr}^ outcropping, but is a form of hypothyroidism. 
 On the other hand, enlargement of the th3Toid causes 
 goitre, and there are particular regions, as the vicinity 
 of the Great Lakes of North America, where goitre is 
 more frequent owing, apparently, to insufficiency of 
 iodine in the water.* According to Berman (1921), the 
 thyroid also controls the speed of living. With more 
 
 * There is some evidence that goitre is concerned with a 
 specific bacillus, one host of which is the goat, and that it may 
 be conveyed by contamination of drinking-water. 
 
21 6 HEREDITY AND EUGENICS 
 
 thjToid one thinks and acts more quickly. One 
 milligram of th3'roxin is found to increase the rate of 
 metabolism 2 per cent. Cretin babies fed on th^-roid 
 undergo a remarkable mental and physical transforma- 
 tion to normal human beings. But the}^ must be fed 
 on it all their lives, or they relapse into their former 
 condition, because they are incapable of producing 
 the secretion themselves. More recently Keith (1922) 
 has elaborated his views on this subject in an extremely 
 interesting way, discussing such subjects as the 
 Neanderthal skull, acromegaly, dwarfism, and many 
 other anatomical alterations from the point of view 
 of hormone control. 
 
 Seligman (1904) has described the frequent oc- 
 currence of " cretins " in Dexter Kerry cattle. The 
 breed appears to have originated, at Kerry at least, 
 as earh^ as the middle of the eighteenth centur3^ 
 One of its most striking features is the very short 
 legs, which suggest a condition of h^'pothyroidism. 
 In one herd fourteen cretins were produced among 
 fift^^-five calves in seven years. Another herd pro- 
 duced five cretins among tw^ent\'-seven calves in three 
 3^ears. These " bull-dog monsters " are non- viable, 
 and abnormal in man}^ respects. Their chief 
 peculiarities are their short trunk and extremely 
 dwarfed limbs (humerus onl}^ 1 3 millimetres in length), 
 the extreme brachycephaly of the head with its 
 rounded forehead bulging over the ver}' depressed 
 nose and upper jaw, while the lower jaw is normally 
 developed. There is always a gap in the abdominal 
 wall through which the internal organs protrude. 
 The palate is cleft, the tongue long and protruding, 
 while the thyroid is irregularly developed, and shows 
 the same histological peculiarities as the thyroid of 
 cretin children. It w^as probably devoid of proper 
 secretion, as the extract of such glands produced little 
 or no fall in blood pressure when injected intravenously. 
 
SOCIAL AND WORLD ASPECTS 217 
 
 This condition of cretinism is said to be constantly 
 associated with placental disease, which would pre- 
 vent the thyroid hormones of the mother from acting 
 properh' upon the young. The frequent occurrence 
 of cretinism in this breed of cattle may, then, perhaps 
 be accounted for by a diseased placenta preventing 
 the already hypothyroid mother from furnishing her 
 offspring with sufficient thyroid secretion. There is 
 another explanation, however, which appears more 
 probable. In at least one case a cow is known to 
 have produced a normal calf following a cretinous 
 one. Any defect in the placenta would then probably 
 not be the result of a diseased condition of the cow, 
 but rather the initial defect would be in the developing 
 foetus. Another fact which may be significant is the 
 occurrence of 25-4 per cent, of " cretinous " offspring 
 in the larger herd already referred to. This clearly 
 suggests that the condition is a Mendelian recessive, 
 due to a lethal mutation carried in the germ plasm 
 of the breed, or in some of them. Further data would 
 be required in order to verify this h^'pothesis. 
 
 Sir Arthur Keith applies the same conceptions of 
 hormone determination to the anthropoid apes and 
 other vertebrates, holding that in the orang there is a 
 predominance of thyroid, while in the gorilla the 
 pituitary is predominant. However this may be, the 
 view seems well founded that raciiil differences in 
 man, including the colour and character of the skhi 
 and hair, differences in physiognomy and in stature 
 and the relative length of limbs, are related to inherited 
 differences in the activities of various endocrine 
 glands. This thesis will, no doubt, be further 
 elaborated with increasing knowledge. 
 
 The bodily changes associated with pain, fear, and 
 rage have been particularly studied by Cannon (191 6), 
 who showed how in a state of fear or anger adrenahn 
 is poured into the blood, which causes reactions, 
 
21 8 HEREDITY AND EUGENICS 
 
 putting the body into a state of defence in the most 
 marvellous wa\^ The substance adrenalin is derived 
 from the medulla of the adrenal glands. It has been 
 chemically synthesised, and Schaefer showed that 
 when injected into the veins it raises the blood- 
 pressure. Its concentration in the blood is only about 
 I part in 20,000,000, and 100,000 times this quantity 
 is held in the gland ready for emergencies. Cannon 
 showed that w-hen secreted into the blood, as a result 
 of the emotions of fear or anger, it prepares the body 
 for mortal combat by summoning its reserves and 
 increasing its defences. It stimulates the liver to pour 
 out more carbohydrates. The blood is thus flooded 
 with sugar which can immediately be used as fuel for 
 the body in exertion. The number of red corpuscles 
 in the blood is also increased, the blood is withdrawn 
 from the skin and viscera and sent to the muscles, 
 heart, lungs, and central nervous system. The limbs 
 actually grow larger wdth their increased blood suppl}^ 
 the heart beats faster, and the senses are keener; the 
 effects of fatigue are abolished, and the blood is 
 rendered more coagulable. All these purposive re- 
 actions of the body depend upon the presence in the 
 blood of a shghtly increased amount of adrenalin. 
 The administration of adrenalin to animals also 
 causes their blood to clot more quickly, erects their 
 hair, and dilates their pupils. Adrenal excess, due 
 to hypertrophy of the cortex, causes high blood 
 pressure, and in w^omen a tendency to masculinity. 
 Depletion of the adrenal reserves, on the other hand, 
 leads to the conditions know^n as neurasthenia, 
 nervous breakdown, chronic fatigue, and shell shock. 
 If differences in endocrine activity are characteristic 
 of the races of mankind, then such differences are 
 inherited. Are smaller glandular differences between 
 the individuals of the same race inherited ? This 
 thesis is supported by Berman (i 921) in a book on the 
 
SOCIAL AND WORLD ASPECTS 219 
 
 Glands Regulating Personality. The qualities con- 
 stituting personality have long eluded analysis. In 
 the Middle Ages the problem was viewed as one 
 of humours in the blood, giving rise to a bilious, 
 lymphatic, nervous, or sanguine temperament. If 
 personalities are determined by the quantities of 
 various hormones poured into the blood by the 
 endocrine glands, then the old conventional view 
 was not so very far wrong after all, although, of course, 
 the views of the Middle Ages had no such definiteness 
 It is not improbable, as Berman holds, that each 
 individual has inherited a certain constellation of 
 endocrine activities, but it seems likely that he has 
 exaggerated their all-importance in the determination 
 of the personality. He recognises three types of 
 personality, thyroid-centred, pituitary-centred, and 
 adrenal-centred, regarding all personalities as com- 
 binations of these. Each of the three t^'pes, he says, 
 is " stamped with a significant figure, height, skin, 
 hair, temperament, ambition, social reactions, and 
 predisposition to certain diseases." Individual facial 
 types are also regarded as the expression of endocrine 
 differences. Whether the forehead is broad or narrow, 
 the distance between the e3"es great or small, the 
 character of the eyebrows, the shape, size, and 
 appearance of the eyes, the mould of nose and jaws, 
 and peculiarities of the teeth — all are regarded as 
 determined by hormone differences. Indeed, the 
 individual is looked upon as a complicated pattern of 
 designs traced by the hormones. Onl}' after a further 
 analysis of the relation of hormones to the hereditary 
 determiners which produce fixed quantitative dif- 
 ferences in their activities can it be determined 
 whether such a view is too extreme. It has to be 
 remembered, in any case, that differences in the 
 nervous system are also inherited. 
 
 Shelley's face is characterised b}' Berman as hypo- 
 
220 HEREDITY AND EUGENICS 
 
 thyroid, with its oval shape, dehcate features, wide, 
 high brow, large, proininent, and vivacious eyes, and 
 sensitive lips. A hyperpituitar}^ face, on the other 
 hand, is distinguished by its low and narrow shape, 
 square protruding jaw, high, thin, straight nose, 
 marked cheek-bones and eyebrow^s ; while a subpitui- 
 tary face is round with receding chin, fat cheeks, and 
 broader and flatter nose. The physiognomy and 
 character of various men are also analysed in terms 
 of internal secretions. Napoleon and Nietzsche are 
 regarded as pituitocentric, Darwin as a neurasthenic, 
 pituitocentric genius, Caesar as a pituitocentric 
 epileptic with too much adrenal and post-pituitary^ 
 secretion. This method seems at present something 
 like the older phrenology, where much latitude was 
 left to the imagination. But it seems clear that 
 various differences in endocrine activity are inherited, 
 and with further knowledge this may form a satis- 
 factory basis for the analysis of personahties and 
 their inheritance. It is eas}- to understand that if 
 a personality is in part determined by the relative 
 activity of several endocrine glands, these being in 
 turn determined by various factors or genes located 
 in different chromosomes of the germ plasm, then the 
 recombinations of such factors in later generations 
 would give a complicated situation very difficult to 
 analyse, but one in which various elements of 
 personalit}^ might still be said to be inherited. Even 
 if the personality depended entirely upon shifting 
 cross-currents of hormone control, it would be 
 extremely difficult to investigate the inheritance of 
 the germinal factors w^hich, in turn, determined plus 
 or minus variations in the activities of the various 
 endocrine glands, because each gland produces many 
 effects, and some of these effects overlap or reinforce 
 each other. If the hormone view of personality has 
 any sound basis, then each personality, both in 
 
SOCIAL AND WORLD ASPECTS 221 
 
 physical configuration and ni mental activities, is 
 a palimpsest of cross-patterns and developmental 
 currents blended into a unified whole. But many 
 elements of the personality must also be determined 
 by mental differences based on inherited differences 
 in the nervous system. 
 
 The Results of Crossing between Races. 
 
 Eugenic wTiters differ, according to their social 
 and political bias, in the stress they lay upon a 
 democratic or an aristocratic society as the basis f(jr 
 eugenic improvement. This difficult question we 
 need not touch upon here, except to point out that the 
 methods of eugenic selection may differ somewhat 
 in the tw^o cases. The stratification of society in older 
 civilisations appears to be a natural process {cf. 
 Flinders-Petrie, 191 1), which has often been at first 
 acquiesced in rather than promoted by human arrange- 
 ments, though ultimately petrified and perpetuated 
 b}^ some form of caste. An aristocratic society might 
 be supposed to be composed of strains which wert- 
 more or less " pure lines " as regards their distin- 
 guishing characteristics, but this is seldom, if ever, 
 the case. The chief reason, of course, is that society 
 is so largely founded upon monetar}^ considerations, 
 and each class is therefore continually receiving- 
 recruits from other classes. In a population of real 
 pure lines, such as wheat or garden beans, the process 
 of selection for any given quality is simpler than in 
 a hybrid population, for it consists merely in finding- 
 one or a few individuals with the desired qualities, 
 and giving them the opportunity of increased pro- 
 pagation. 
 
 On the other hand, an obvious weakness of an 
 aristocratic society from the point of view of eugenics 
 and heredity is the fact that while titles arc usually 
 
222 HEREDITY AND EUGENICS 
 
 conferred in the first instance as a recognition of 
 exceptional ability or initiative, ^xt the inheritance 
 of that abilit}' will probabl}' follow different rules in 
 different cases, and eldest sons are as likely as not 
 to receive other qualities from their father, but not 
 his abilit}'. Ability, like genius, is probably often 
 due to a fortunate concatenation of favourable 
 elements, and if these are independently inherited 
 the chances of their reappearance in the offspring are 
 small. Nevertheless, it must be admitted that the 
 exceptional individual has a much better chance of 
 transmitting his qualities, or some of them, than the 
 average individual can possibh^ have. Yet titles, 
 no doubt, often long survive any expression of 
 exceptional qualities in their holders. And once the 
 quality is gone, through having failed to be inherited, 
 cross-breeding alone can bring it back. Would it not 
 seem, then, that societ}' founded upon ability and 
 quality, and not upon wealth, in which there was 
 also a measure of latitude in intermarriage, would 
 be in consonance with the eugenic ideal ? 
 
 While, therefore, intermarriage of diverse strains 
 is important, both from the point of view mentioned 
 above and on account of the increased vigour resulting 
 from a heterozygous condition, yet there are important 
 limitations to the width of the crosses which are desir- 
 able. In the newer countries, such as North and 
 South America and parts of Africa, the cross-bred 
 races which have sprung up through miscegenation 
 between Europeans and more backward peoples are 
 at a disadvantage from almost every point of view. 
 Physical disharmonies result, such as the fitting of 
 large teeth into small jaws; or as Davenport (igiyb) 
 points out, large men with small internal organs, or 
 inadequate circulator}^ s^'stems, or other disharmonies 
 which tax the adjustability of the organism, and may 
 lead to earl}- death. (But see p. 29.) Segregation 
 
SOCIAL AND WORLD ASPECTS 223 
 
 of characters thus results in a motley assortment of 
 types, with some primitive and some advanced 
 mental, moral, or physical qualities in place of the 
 original more or less blended condition in the first 
 generation of the cross. It is questionable even if 
 marriages between North and South European races 
 are always wholly desirable in their results ; although 
 history shows, on the other hand, that the inter- 
 mixture of more closely related races is beneficial 
 as supplying increased vigour and a greater range of 
 alternative characters, to increase the potentialities 
 of the population or for selection to play upon. 
 
 Not only within the historical period (see, for 
 example, Haddon, 191 9), but also among the races 
 of Neolithic and Palaeolithic man there is evidence 
 of the frequent shifting of peoples in various parts of 
 the world. Sometimes the defeated race was driven 
 out or exterminated, but ver}- often such migrations 
 resulted in the fusion of two races into a new unit 
 ultimately having certain uniform and distinctive 
 features. It is evident that h^'bridisation has been 
 going on in this way at intervals throughout the 
 histor}- of man. It does not follow, as some writers 
 assume, that crossing is the cause of the evolution, 
 but it does follow that the great majority at least of 
 modern races are hybrid in origin, although they may 
 have become quite uniform through isolation and 
 inbreeding. The fact is that any racial unit contains 
 the potentialities of innumerable minor races if these 
 could be separated out and inbred. The range of 
 migration of a people is an important element in 
 determining how many distinct types will occupy a 
 given area of territor}'. When the Indian tribes of 
 the central plains of North America took to a nomadic 
 life after the introduction of the horse, many of the 
 tribal differences between them quickly disappeared. 
 Differences can only grow up in a condition of 
 
224 HEREDITY AND EUGENICS 
 
 isolation. This evolutionary principle of isolation 
 is of enormous importance and has usually been 
 overlooked by anthropologists. 
 
 The question is often discussed as to whether 
 modern man is a single species or more than one. 
 The fact that all the races of mankind are fertile with 
 each other is no longer a sufficient reason for class- 
 ing them as one species. The present generation of 
 naturalists is describing innumerable species of plants 
 and animals as distinct species, although they are 
 perfecth^ fertile with each other. Sterility as a 
 criterion of species has almost completely broken 
 dow^n. The origin, causes, and nature of inter- 
 specific sterility are still largely obscure. On the one 
 hand, species of Drosophila, so closely similar that 
 they are scarcely distinguishable even by experts, 
 may show complete sterility with each other or, at 
 least, provide onl}' sterile hybrids ;* while, on the other 
 hand, all the species of cattle {Bovidce) are inter- 
 fertile, although man}^ of them show striking 
 differences. In mankind the differences between the 
 five great colour varieties are not merely in the skin 
 colour, but also in such points as stature, hair colour 
 and shape, cranial conformation, facial peculiarities, 
 skin secretions, and intelligence. These differences 
 are quite as distinctive and varied as those betw^een 
 many described species of higher animals. Such 
 differences could only have grown up during long 
 periods of isolation, and can only be maintained by 
 isolation or an absence of crossing. The five colour 
 types of mankind also occupied, until modern trans- 
 portation began, more or less marked^ separated 
 
 * Even more extreme are the various cases of self-sterility in 
 plants, in which many of the individuals are sterile with their 
 own pollen. In such cases as Primula, crosses between individuals 
 of the same species but having different types of flower are more 
 fertile than self-fertilised plants. 
 
SOCIAL AND WORLD ASPECTS 225 
 
 areas of the earth's surface, althoui^h where the yellow 
 and brown races, for example, are in contact in south- 
 eastern x\sia a gradual transition occurs between them. 
 Where evolution has been going on independently in 
 these races for such long periods, and some races have 
 progressed far beyond others, both mentall}' and 
 culturally, it is foll}^ to suppose that crosses between 
 a progressive and a primitive race can lead to a desir- 
 able result from the point of view of the advanced 
 race, or even of the primitive race. Many native 
 African and other tribes are in the Stone Age, so far 
 as their culture is concerned, and it cannot be ex- 
 pected that their mentality has advanced beyond 
 that period. The mental status of the average 
 Palaeolithic man is difficult to determine. Although 
 the mental capacity of modern man has not increased 
 during the historical period, yet it is necessary to 
 suppose that the development of the human mind 
 has consisted in something more than the mere 
 accumulation of tradition. In other words, there 
 has been a real evolution in which the mind has been 
 one of the reacting elements. The mental level of 
 the average Palaeolithic man can hardly have been 
 higher than that of our modern feeble-minded. The 
 Australian black-fellow appears to be an earh' Pakeo- 
 lithic survival, resembling Mousterian man, and 
 wholly incapable of coping with the white man's 
 civilisation. It is clear that other races represent 
 different stages of mental development. 
 
 This, of course, is often disputed, and it is frequently 
 held that Palaeolithic man was potentially the mental 
 equal of modern civilised man. This depends on the 
 sense in which the term " potential " is used. The 
 important point is that primitive races are largely 
 incapable of taking hold of the white man's civilisa- 
 tion and profiting by it, or adapting it to their own 
 use, except in a primitive way. No doubt, as Carr- 
 
 13 
 
226 HEREDITY AND EUGENICS 
 
 Saunders (1922) holds, man's mental evolution has 
 consisted largely in the handing down of accumulated 
 tradition, but there must also have been a reaction 
 of man's mind' — that is, a mental evolution — in order 
 to make the continued accumulation and advance of 
 tradition possible. That such a mental evolution has 
 accompanied the accumulation of tradition is evident 
 from the recent history of the Japanese. They were 
 able in one generation to absorb a great part of 
 Western science and begin making independent 
 contributions to that science. This remarkable 
 phenomenon, resulting from contact with Western 
 civilisation, has not been approached by any truly 
 primitive people, which shows that primitive peoples 
 w^ould require a long period of mental evolution before 
 they were capable of grasping or profiting by the 
 views of nature held in the civilised world. 
 
 As we have already pointed out, crossing between 
 more or less related races or tribes of mankind has 
 been going on at intervals throughout the whole of 
 historical and prehistoric time. Nevertheless, at any 
 given period it has usually been confined to definite 
 areas of contact between tribes, and has been very 
 limited in its scope, except at times of migrating or 
 shifting populations. Primitive man, in particular, 
 was far less of a roving animal than is commonly 
 supposed. This is shown by the great number of 
 local native tribes which existed among the Indians 
 of North and South America at the time of their first 
 contact with European civilisation. Such differentia- 
 tion, like that of any other species, could only have 
 occurred under conditions of relative isolation and 
 segregation — i.e., absence or infrequency of inter- 
 marriage. Carr-Saunders (1922) has pointed out that 
 as soon as early man began to have am^ social organ- 
 isation at all, probabty even as earty as the Upper 
 Palaeolithic, families and groups began to develop 
 
SOCIAL AND WORLD ASPECTS 227 
 
 hunting and fishing and general food-getting rights 
 over fixed hniited areas. Among the primitive races 
 of modern times these conditions continue. For 
 instance, in parts of former German South-West 
 Africa, where the chief Hottentot food-plant on parts 
 of the coast is a gourd, Acanthosicyos horrida, growing 
 on the sand-dunes, individual families and groups 
 have vested rights over the fruits of this plant in 
 local areas, and it annually saves their lives and 
 serves as a source of both food and water until other 
 food is obtainable. Native groups are, then, not free 
 to wander at will wherever fancy dictates, but each 
 party is confined to a limited area, whose boundaries 
 are definitely known to them. This fact, that each 
 group is definitely tied to a local area by recognised 
 custom and is often at war with its neighbours, adds 
 greatly to the stabilit}^ of any savage population, 
 and probably lessens the amount of exogamy between 
 unrelated families. These are the conditions under 
 which local tribes and differentiated groups might 
 be expected to grow up. Such a process of differentia- 
 tion is, however, ver}^ slow, and the spread of culture 
 from group to group will also tend to the maintenance 
 of uniformit}'. Nevertheless, cultural differences, 
 owing to local environmental conditions, will arise 
 long before structural differences appear, and in the 
 tribes of North American Indians such structural 
 differences seem to have been ver}^ few. Languages, 
 on the other hand, were many and often widely 
 different (though showing evidences of a common 
 origin), w^hich implied a long period of cultural 
 isolation. 
 
 The results of crosses between such related tribes 
 are relativel}' insignificant, the differences involved 
 being less than those between the peoples of European 
 nations. Crosses between equally primitive or equally 
 advanced peoples of similar culture involve no very 
 
228 HEREDITY AND EUGENICS 
 
 serious problem. Inter-crossing between races more 
 remotely related, especiall}' when one is primitive 
 and the other advanced, immediately involve prob- 
 lems of the utmost difficulty — problems which may 
 be said to have arisen seriously onl}^ in modern times. 
 These problems require study in three separate 
 aspects : (i) In crosses between primitive races; (2) in 
 crosses between a primitive and an advanced race ; 
 (3) in crosses between advanced races. In each case 
 the results of the particular cross must be taken into 
 account. For instance, crosses between Europeans 
 and Bantu peoples might be undesirable from am^ 
 point of view, while marriages between Europeans 
 and Polynesians might conceivably- produce a more 
 felicitous result. 
 
 Wallace (Alalay Archipelago, p. 335) states that 
 *' Everywhere in the East where the Portuguese 
 have mixed with the native races the}- have become 
 darker in colour than either of the parent stocks"; 
 but that " the reverse is the case in South America, 
 where the mixture of the Portuguese or Brazilian 
 with the Indian produces the ' Mameluco,' who is not 
 unfrequently lighter than either parent, and always 
 lighter than the Indian." Such results might be 
 expected if skin colour were controlled by differences 
 in the activity of various endocrine glands. 
 
 Very few serious studies of the results of racial 
 crossing have been made, and probably no field of 
 anthropology could be more profitably explored at the 
 present time. The Pitcairn and Norfolk Islanders 
 w-ould form a valuable basis for such a study. They 
 are descended from ten English sailors, who mutinied 
 in a voyage to Tahiti in 1788, and with eighteen 
 native Polynesians (six men and twelve women) 
 formed a colony on the little island of Pitcairn. In 
 1856 the resulting population of 200 overflowed to 
 Norfolk Island, and the descendants of this crossed 
 
SOCIAL AND WORLD ASPECTS 229 
 
 race on the two islands now number about a thousand. 
 They should form excellent material for an anthro- 
 pometric study of a population descended through 
 several generations from original crosses between 
 English and Polynesians. 
 
 The most ambitious of such studies which has yet 
 been made is probably that of Fischer (191 3) on the 
 Reheboth hybrid people inhabiting a portion of the 
 area which was formerly German South- West Africa. 
 These people were derived from crosses between 
 Hottentot women and Boer men, which began over 
 a century ago. They now number, perhaps, 3,000. 
 In a general anthropological and ethnographical study 
 of these people, Fischer concludes that they are a 
 well characterised but very variable group. The 
 characters of the parent races are combined in the 
 greatest variety of ways, showing continued segrega- 
 tion, and not a permanent blend. The first crosses are, 
 in general, intermediate, and when crossed back with 
 either race, they resemble more the race with which 
 they were recrossed. They are said to be sound, 
 strong, and ver}^ fertile, having an average of 7-4 
 children per famil}^ The inheritance of individual 
 characters, such as hair form and colour, eye colour, 
 skin colour, shape of nose, nasal index, form of eyelid, 
 breadth of forehead, etc., was studied and found to 
 show alternative inheritance; but the observations, 
 while valuable, are scarcel}' sufficiently detailed to 
 furnish critical evidence on all these points. Never- 
 theless, a body of valuable data of inheritance is 
 brought together. An important conclusion reached 
 is that the size of body and length of face is greater 
 than in either parent race, while the fertility is found 
 to be undiminished and the sex ratio unaltered. 
 
 The latter conclusion is, however, not in harmony 
 with the statistical data on the sex ratio in hybrids 
 obtained by other investigations. Thus, Pearl and 
 
230 HEREDITY AND EUGENICS 
 
 Pearl (1908) examined the vital statistics of the city 
 of Buenos Ayres, where Italian, Spanish, and Argentine 
 crosses take place, the last being itself a mixed race. 
 The data extended over a period of ten years, and 
 made possible the comparison of the sex ratio in pure 
 matin2:s with that in crosses. In the former case the 
 ratio was 102-21 : 100, in the latter 105-99: 100, hence 
 a greater excess of male offspring from cross-matings. 
 Little (19 1 9) has made a similar study of the sex 
 ratios from the records of a lying-in hospital in New^ 
 York. These records, unlike the previous ones, in- 
 cluded still-births, and the types of matings included 
 (i) those within each of the following nationalities: 
 English, Irish, Scotch, Italian, Russian, Greek, 
 Austrian, and German; (2) all possible first genera- 
 tion matings between members of these nationalities. 
 The results gave a sex ratio of 106-27 for the pure 
 stocks, and 121-56 for the crosses. This indicates 
 an even more marked increase of male births in the 
 hybrid stocks than the Argentine statistics. Separate 
 examination of the data for still-births indicated 
 that they were more frequent in the pure races than 
 in the crosses. These results indicate that in crosses 
 betw^een European races there is a higher ratio of 
 male births and a lower frequency of still-births, at 
 least in the first generation. The latter is probably 
 a result of hybrid vigour. That crossing a species 
 may alter the sex ratio of the offspring in very 
 marked degree has also been shown in the case of 
 pigeons and other animals. 
 
 Returning to the subject of racial crossing, re- 
 ference may be made to a short study of racial 
 mixture in Hawaii (MacCaughey, 191 9). In these 
 islands intermarriages of Portuguese, Spanish, 
 Haw-aiian, Chinese, Japanese, Americans, English, 
 and other Europeans are taking place. The popula- 
 tion containing this remarkable diversity of races 
 
SOCIAL AND WORLD ASPECTS 231 
 
 numbers about 246,500, the Japanese predominating 
 in numbers. From a decade of observation of this 
 microcosmic mehing-pot, the conclusion is reached 
 that such racial intermingling is usually undesirable 
 in its results. Most of the Caucasian*-Hawaiians 
 seem to blend the least desirable traits of both 
 parents, and intermarriages of North European and 
 American stocks with dark-skinned races are con- 
 sidered biologically wasteful. 
 
 Similarly Lundborg (1920), from a study of Swedish 
 conditions, concludes that the crossing of races 
 degenerates the constitution and increases degrada- 
 tion. He finds such crossing much more common in 
 the poorer and lower classes, while the middle classes 
 are more homogeneous. In the lower classes are 
 more frequently found individuals with other race 
 characters — e.g., darker hair and eyes. Mjoen (1922) 
 has examined the results of crosses in Norway between 
 the Nordics and the Mongoloid Laplanders . He found 
 the first generation to be taller and heavier than the 
 tall Nordic parent (owing to heterosis), but that this 
 increase in size is lost in later generations. Also, 
 frequently in crosses between Lapps and Norwegians, 
 especially when Alpine blood was also present, a 
 mentally unstable type is produced, the lack of 
 balance being shown by stealing, lying, and drinking. 
 A similar unbalanced type frequently arises from 
 crosses between American Indians and French or 
 English. The writer concludes that as regards these 
 matings, the pure races have the advantage in every 
 way. For example, the incidence of tuberculosis is 
 the lowest (i-i to 1-5) where the Nordic race is 
 comparatively pure, and highest (3-6 to 4) in the 
 region where there is the largest race mixture. 
 
 As regards world eugenics, then, it would appear 
 
 * This loosely used term is meant to include Europeans and 
 Americans belonging to the " white " race. 
 
232 HEREDITY AND EUGENICS 
 
 that intermixture of unrelated races is from ever}* 
 point of view undesirable, at least as regards race 
 combinations involving one primitive and one ad- 
 vanced race. It is possible that crosses between an 
 advanced and a native race mav be advantageous 
 as leading to progress in certain tropical regions 
 where the white man cannot survive, although the 
 results of such interbreeding in various tropical 
 countries do not lead to a very hopeful outlook. But 
 the melting-pot conception is being discredited b}' 
 eugenic writers in the United States, where inter- 
 crossing has been taking place on a great scale. It 
 ma}'- now be recognised that while interbreeding of 
 related races or strains gives increased vigour, at least 
 in the F^ generation, crosses on a large scale between 
 more distant races which have for ages been separately 
 evolving create unnecessary problems, and are, for 
 the most part, wholly undesirable in their results. 
 The more advanced race is diluted and degraded by 
 such intermixture, and primitive mental and moral 
 characters are placed on a level with the more highly 
 evolved. Moreover, Goddard (191 7), in discussing 
 mental tests for immigrants into the United States, 
 states that the average steerage passenger is of low- 
 grade intelligence, perhaps even feeble-minded. He 
 examined six small groups arriving at Ellis Island, 
 by means of the Binet scale tests, and found that 
 only 2 in 148 scored as high as twelve years, which is 
 regarded as the line between feeble-minded and 
 normal. These people included Italians, Russians, 
 Jews, and Hungarians. His conclusion is that there 
 is a high percentage of feeble-minded among the 
 present immigrants. 
 
 Even after a thousand years of intermarriage, 
 separate racial traits may still be traceable in the 
 modern Englishman. The blend is only a blend 
 when considered en masse. Alternative inheri- 
 
SOCIAL AND WORLD ASPECTS 233 
 
 tance, and more or less complete segregation, still 
 appear as regards single characters. The various 
 types of modern Italian, viewed in the light of their 
 history, appear to show the same thing. Although 
 innumerable racial unions have taken place in the 
 histor}^ of mankind, yet the elements distinguish- 
 ing the original races appear, for the most part, 
 to retain their separate identity and independent 
 transmission in inheritance. The resulting race con- 
 sidered as a population will be a blend of the original 
 races, yet, for a long period at least, the elemental 
 differences continue to be separately inherited. 
 Whether, ultimatel}^ a real blend occurs is uncertain, 
 but if it ever does this mav be onlv after a thousand 
 years or so of interbreeding within the hybrid race. 
 In any case the racial elements of the more primitive 
 stock will dilute and weaken the better elements of 
 the more progressive stock, with a retarding or 
 degrading effect on the progressive stock as a whole. 
 It is, therefore, clear that miscegenation between, for 
 example, the white races and African races — which for 
 ages have been undergoing separate evolution which 
 must have been at ver}' different rates, assuming that 
 both are descendants from the same original stock — 
 is wholly undesirable from a eugenic or any other 
 reasonable point of view. 
 
 Yet it cannot be gainsaid that the negro in the 
 United States, through interbreeding chiefly with the 
 lowest strata of whites, is already producing a visible 
 effect on the colour and features, and surely also on 
 the mentalit}' of those elements. Unless this process 
 is checked, the ultimate result would appear inevitably 
 to be a gradual incorporation of these more primitive 
 elements in the whole population. The brain of the 
 average negro weighs 3 or 4 ounces less than that of 
 the average white man, but this in itself does not 
 necessarily prove a lower intelligence, because it is 
 
234 HEREDITY AND EUGENICS 
 
 well known that men of exceptional abilit}^ frequentl}^ 
 have small brains. Ferguson (1921), in a sane dis- 
 cussion of the mental status of the American negro, 
 concludes that psychological study of the negro in- 
 dicates that he will never be the mental equal of the 
 white man. Comparison of school children in the 
 elementar}^ grades shows that onl}' 20 or 25 per cent, 
 of negro children equal or exceed the average score 
 of white children. But the term " negro " in these 
 and other American statistics includes every grade of 
 mulatto, and the latter ma}^, of course, inherit the 
 ability of their white ancestor. If only pure negroes 
 were considered, their average mental ability would 
 probably be much lower. The United States census 
 of 1 910 show^ed that mulattoes constituted ap- 
 proximately one-fifth of the coloured population, 
 a fraction which continues to increase and is now 
 probably one -fourth. Mental tests of coloured 
 children in schools show that, on the average, lighter 
 skin goes with higher intelligence. 
 
 The American army intelligence tests showed a still 
 more marked difference between whites and blacks. 
 Only one-third of the negroes were sufficiently literate 
 to read a newspaper or write a letter, while three- 
 fourths of the whites passed this test. The result 
 was probably partly due to a difference in educa- 
 tional opportunities, but the Binet tests, which 
 measure ability apart from education, showed that 
 only 20 to 25 per cent, of the " negro " recruits 
 equalled or exceeded the average white recruit. 
 Moreover, the percentage of mulattoes among the 
 literates was about twice as great as among the 
 illiterates, and when the illiterates were removed 
 from a " negro " company its complexion was thereby 
 notably lightened. While the negro's mental status 
 is thus undoubtedly more primitive than that of the 
 white man, yet there is apparently no evidence for the 
 
SOCIAL AND WORLD ASPECTS 235 
 
 doctrine that his mental growth ceases at adolescence. 
 Many writers regard the negro as a case, not of 
 arrested mental development which might be over- 
 come by educational effort (although the utmost effort 
 in education does not prevent the arrest in mental 
 development of the feebleminded), but of a primitive 
 mentality with less control of the impulses and 
 emotions and less ability to deal with the abstract 
 or symbolic. The wisdom of Booker T. Washington's 
 programme of manual education for the negro as 
 most appropriate to his mental status is clearly shown. 
 As far as the muscular and nervous systems and the 
 sense organs are concerned, there is apparent^ no 
 great difference between negroes and whites, but that 
 physical differences exist is shown by the data in the 
 following paragraph. 
 
 Love and Davenport (191 9), from an analysis of the 
 sick reports of American troops in camp in the 
 United States during the war, find some notable 
 differences between white and coloured troops. That 
 negroes are relatively lacking in resistance to tuber- 
 culosis and pneumonia is shown by the fact that the 
 rate for tuberculosis was over twice as high among 
 coloured troops, while for pneumonia it was two or 
 three times as high. The rate for venereal disease 
 is three or four times higher in coloured troops, 
 epilepsy, hysteria, neuralgia, and haemorrhoids are 
 about twice as frequent, addiction to drugs is more 
 common, while skin diseases are less common than in 
 white troops. That not only the skin but also the 
 lining of the mouth and naso-pharynx is more re- 
 sistant,* is shown by the lesser frequency of diphtheria, 
 scarlet fever, German measles, and influenza. The 
 nervous system of the negroes also showed less 
 liability to neurasthenia and alcoholism, eye and 
 
 * It seems more probable that the greater incidence of respira- 
 tory diseases among negroes is due to their wide flaring nostrils. 
 
236 HEREDITY AND EUGENICS 
 
 ear defects were about half as common as in whites, 
 and there were fewer cases of metabohc disturbance, 
 such as diabetes and urinary calcuh. It thus appears 
 that the negro is a better animal as far as e3'es and 
 ears are concerned, has a more protective skin and 
 a less easily deranged metabolism, but is less resistant 
 to diseases of the lungs and pleura and to some of the 
 general diseases. 
 
 Discussing the results of the mingling of races in 
 the United States through immigration, Davenport 
 (191 7) states that nearly two-thirds of the 9,000,000 
 population of New York State are foreign born, or of 
 foreign or mixed parentage. Nearly all the European 
 countries are represented, most of them b}' many 
 thousands, and intermingling of races in the country 
 at large is taking place on a scale never before ap- 
 proached in the histor}- of man. The irregular 
 dentition which makes orthodontia a recognised 
 branch of dentistry may be a result of disharmonies 
 between teeth and jaws in the various crossed races, 
 a condition in marked contrast with the regular 
 dentition of native races, though such conditions may 
 also arise from malnutrition. Davenport concludes 
 that miscegenation commonly results in disharmony 
 of physical, mental, and temperamental qualities, 
 often leading to disharmon}' with the environment 
 and consequent unhappiness. A hybridised people 
 will tend to be restless, dissatisfied, and ineffective; 
 the high death-rate in middle life ma}'^ be due to bodil}' 
 maladjustments, and much of the crime and insanity 
 to the inheritance of badh' adjusted mental and 
 temperamental differences. It is probable that in 
 such a very heterogeneous mixture, in which there 
 has been, until recently, little selection or often even 
 negative selection of the original immigrant elements, 
 the disadvantages and disharmonies more than offset 
 any advantages that may accrue from crossing. To 
 
SOCIAL AND WORLD ASPECTS 237 
 
 look for a higher racial type from the indiscriminate 
 blending of such elements appears to be the height 
 of folly. 
 
 All general problems of race and movements of 
 population are closely connected with questions of 
 birth- and death-rates. In an able analysis of the 
 causes of death in man from an evolutionary and 
 embryological point of view, Pearl (1920) has shown, 
 from statistics of the United States, England, and 
 South Brazil, that man's greatest enemy is his own 
 endoderm. In the two former countries about 
 57 per cent, of all deaths which are biologically 
 classifiable result from breakdown and failure to 
 function of organs derived from the endoderm in their 
 embryological development. Only 8 to 13 per cent, 
 of deaths result from breakdown of ectodermal 
 organs, the remaining 30 to 35 per cent, being ascribed 
 to organs of mesodermal origin. The endoderm has 
 been least differentiated in evolution, and hence is 
 least adapted to resist the vicissitudes of environment. 
 Sanitary and public health measures are largely 
 directed to softening the asperities of the environment, 
 so that the relatively inefticient and primitive endo- 
 derm can cope with it. Organologically considered, 
 the respiratory and alimentary systems are most 
 largely responsible for human deaths. Then follow 
 in order the circulatorv and nervous svstems, the 
 kidneys, sex organs, skeletal and muscular S3'stem, 
 the skin, and finalty the endocrinal system or glands 
 of internal secretion. Differences in the efficiency, 
 structure, and functioning or tendency to disease in 
 all of these groups of organs no doubt exist and are 
 inherited. In this way the factor of heredity directly 
 affects the death-rate in families, and is often an 
 important element in determining the age at which 
 death will take place. 
 
 It is now well known from the statistical records of 
 
238 HEREDITY AND EUGENICS 
 
 civilised countries that birth-rates and death-rates 
 usually rise and fall together. A very good discussion 
 of the subject is by Dean Inge ( 1 9 1 9) . Notwithstand- 
 ing the numerous factors which have been ascribed 
 as causes of the waxing and weaning of birth-rates, 
 populations, and civilisations, we are still largely 
 in the dark as to the fundamental biological signi- 
 ficance of these fluctuations. Did the ancient civilisa- 
 tions fail to maintain themselves on account of 
 climatic changes, soil sterility, malaria, infanticide, 
 losses in war, inbreeding, natural sterility, or racial 
 ennui and hopelessness of outlook ? All of these 
 causes may have been operative in particular cases, 
 but none of them appear to be adequate to account 
 for the submergence of, for example, the classic 
 civilisations of antiquity. We see the sweep of 
 biological wave on wave of population, but the 
 nature of the operative forces which produce these 
 tides is too complex for analysis with our present 
 knowledge. 
 
 A recent wTiter (Nilsson, 1921) discusses the down- 
 fall of Greece and Rome from a racial and biological 
 point of view. He points out that both countries 
 apparently took their origin b}^ the establishment of 
 races by isolation and inbreeding after a mixture or 
 invasion of races had taken place. There was a 
 great diversity of races in the Roman Empire, and 
 Roman rule tended to mix them up. Previously 
 isolation and inbreeding had kept them relatively 
 fixed and developed them as relatively pure races. 
 Under the shelter of Roman peace and Roman 
 administration they mingled, and the result was 
 unlimited hybridising of types, destroying the many 
 fixed types which had existed, and giving rise to 
 instability of disposition and of culture. This blend- 
 ing of man}^ races is regarded as the most destructive 
 agency in the downfall of Rome. This would furnish 
 
SOCIAL AND WORLD ASPECTS 239 
 
 an unhapp}^ outlook for the results of the hetero- 
 geneous intermixture which is going on in America 
 on a scale never before equalled. Yet we can scarcely 
 believe this is the whole story. German and Gallic 
 tribes shifted and invaded their neighbours' territories 
 in great numbers even before the advent of Caesar. 
 The immediate cause of some at least of these move- 
 ments was a flood or unfavourable harvest season, 
 which destroyed their narrow margin of food reserves 
 and made it necessary for large numbers to seek their 
 subsistence in more hospitable conditions. This 
 appears to have been particularly true of some of the 
 early Scandinavian tribes. An increasing population 
 in relation to local climatic conditions and food- 
 supply must then often have been the impelhng 
 power. Nevertheless, relative stability of tribal 
 relations was maintained, and indiscriminate mingling 
 of unrelated races only began under Roman rule. 
 
 It is also arguable that all the historic civilisations 
 have been correlated with the presence of a race of 
 superior courage and initiative dominating the 
 activities of an inferior race. Their civilisation died 
 out when the ruling race failed to maintain its numbers, 
 either through miscegenation or from a variety of 
 other causes. 
 
 Since about 1876 the birth-rate in various 
 European countries has steadily declined, falling 
 from 36 per 1,000 in England and Wales to about 
 24 before the war. Similarly in Germany the rate 
 fell, with fluctuations, from nearly 41 in 1875 to 27-5 
 in 191 3. But the death-rate dropped concurrently 
 in England and Wales from 237 in 1 864 to the pre-war 
 figure of 14, and a similar decline occurred in Germany. 
 After many w^ars a rise in the birth-rate soon restores 
 the population. Statistics even show a rise in the 
 frequency of male births during and after a war. 
 Although it is difficult to understand how war con- 
 
240 HEREDITY AND EUGENICS 
 
 ditions can affect this ratio, 3^et it undoubtedly appears 
 to be the case that in some wa}^ the ratio of male to 
 female births is increased, so closely is the biological 
 status of the race amenable to economic conditions 
 like war or an epidemic. Emigration also leaves a 
 vacant space which is soon filled up by an increased 
 birth-rate, but as Carr-Saunders points out, the 
 importance of emigration in this respect has been 
 greatly overrated. 
 
 The nineteenth century was a period of rapid 
 increase in population, both in Europe and America, 
 but the birth-rate in Europe and in the Anglo-Saxon 
 population of America has been falling throughout 
 the last quarter of that century and the subsequent 
 two decades, though there may be a temporary rise 
 following the war. Of course, a permanent fall in 
 the birth-rate must ultimately take place when the 
 relatively empty countries available to the white race 
 have been filled up. The serious feature of the 
 declining birth-rate is its differential character, for 
 birth control, as practised, leads to a condition in 
 which we are breeding most largel}^ from our worst 
 stocks. Eugenists are agreed that the greatest need 
 is for some method of adjusting conditions, so as to 
 remove this menace to the future of the race. 
 
 The Problems of Population. 
 
 Problems of population have been discussed ever 
 since Malthus formulated his law that population 
 tends to increase in geometrical ratio, while the means 
 of living — food and raiment based on agriculture — 
 only increase in arithmetical ratio, thus leading to 
 human poverty, misery, and vice. The accuracy of 
 this law has often been affirmed and as often denied. 
 The fact that it led both Darwin and Wallace inde- 
 pendentl}' to the conception of natural selection 
 
SOCIAL AND WORLD ASPECTS 241 
 
 certainly stands to its credit. It does not follow, 
 however, that the law is quantitatively accurate as 
 stated, and it is in this direction that it has broken 
 down in recent 3'ears. In the meantime the law of. 
 diminishing returns has been recognised as applying 
 both to agriculture and industry. 
 
 The whole problem of population has recently been 
 discussed by Carr-Saunders (1922) in a broadminded 
 and restrained manner, and we may first give a short 
 summary of the facts and arguments he presents. He 
 points out that the fecundity of man has increased 
 in comparison with that of primitive peoples. In this 
 man agrees with cultivated plants and domesticated 
 animals generally. Civilised man creates a reserve, 
 not only for himself, but for his domesticated animals 
 and plants, which enables them to function as a more 
 prolific reproducing mechanism. This increased 
 fecundity is due to more food and better conditions 
 of life. In primitive races the number of children 
 reared in a family is usually two to four, or sometimes 
 six. Some tribes bring up only two children per 
 famil}'. Artificial abortions are frequent, and in- 
 fanticide universal. Child mortality is high, owing 
 to the hard conditions and lack of suitable food. 
 The period of lactation often lasts two years or more, 
 sometimes five or six years, or even longer. Under 
 these conditions births are fewer than in many 
 civilised families, and survivals fewer still, the popula- 
 tion tending to remain stationary in numbers over 
 long periods.* 
 
 The view of Malthus that the means of subsistence 
 can only increase in arithmetical ratio, has long been 
 disproved by statistics. On this point his argument 
 collapses, for it is seen that the arithmetical ratio 
 only holds so long as there is no advance in skill 
 
 * Darwin first directed attention to these and similar facts in 
 his Descent of Man. 
 
 16 
 
242 HEREDITY AND EUGENICS 
 
 or improvement of methods. But the history of 
 civiKsation has consisted in just such advances, which 
 lead in each case to a corresponding increase in yield 
 for a given amount of labour. The law of diminishing 
 returns, however, limits this 3^ield, both in agriculture 
 and in industry. This leads Carr-Saunders to the 
 important conception of an optimum number, which 
 he states in the following words (p. 200): " Since the 
 laws in general are applicable to all, there will be, 
 taking into account on the one hand the known arts 
 of production, and on the other hand the habits and 
 so on of the people at any one time in an}' given area, 
 a certain density- of population which will be the most 
 desirable from the point of view of return per head of 
 population. There will, in fact, under any circum- 
 stances always be an optimum number." If the 
 population is either above or below that number, 
 the return per head will be less. For an}' country 
 there is, then, an optimum population corresponding 
 to its agricultural and climatic conditions and in- 
 dustrial development. Increase in skill brings an 
 increasingly dense population and a larger income 
 per head, and so long as skill increases the optimum 
 density of population will go on increasing. To 
 Malthus the problem was one of the relative rate of 
 increase of population and food production. With 
 the conception of an optimum, it is one of densit}' of 
 population and the productiveness of industry. 
 
 An optimum number, if attained in a population, 
 implies the maintenance of a standard of living. This 
 number appears to be usually approached, both among 
 primitive tribes and in civilised countries. The 
 optimum will mean greater or less density of popula- 
 tion, according to the fertility of the country in the 
 broadest sense and the skill or degree of civihsation 
 of its people. In a poor country like Patagonia, 
 inhabited by a primitive tribe, the optimum con- 
 
SOCIAL AND WORLD ASPECTS 243 
 
 ditions may be represented by the present very sparse 
 population. In a country like Belgium, where in- 
 tensive agriculture and industry can be practised by 
 an intelligent people, the present dense population 
 may still represent the optimum. It is believed that 
 many parts of India and China are over-populated, 
 and the same was true of Ireland about i 585. Under 
 these conditions the people lose their standards of 
 living, and multiply up to the limits of subsistence. 
 Such a loss of standards may result from fear, 
 oppression, repeated plagues, or similar conditions. 
 
 The author points out that the fecundity of all 
 animal species will tend to be regulated by natural 
 selection. " A limit is set to the development of 
 the strength of fecundit}" be3'ond a certain point by 
 the fact that it cannot be to the advantage of any 
 species that its fecundity should increase considerably 
 be3^ond the point which ensures the survival of the 
 species, as such an increase w^ould intensify the struggle 
 between the members of the species — this intensifica- 
 tion of the struggle not bringing any corresponding 
 advantages." Man inherited from his pre-human 
 ancestor a higher fecundit}^ than he needs. His 
 development of intellect enabled him to circumvent 
 or overcome the animals w^hich preyed on his ancestors. 
 In this way he lessened his own death-rate, but his in- 
 telligence enabled him at the same time to overcome 
 his high fecundity by infanticide and other means. 
 He thus escaped the disadvantages which would have 
 come from too high fecundity — a natural fecundity 
 w^hich would otherwise have ultimatelv been reduced 
 by selection. 
 
 That a standard of living exists among primitive 
 peoples is shown by many features of primitive life — 
 for example, by the fact that the young men are 
 made to reach a certain standard of skill and attain- 
 ment before they can marry. In the Middle Ages 
 
244 HEREDITY AND EUGENICS 
 
 and later the system of apprenticeships of the gilds 
 had similar effects. Definite laws also prevented 
 the poor, vagabonds, and Twastrels from marrying. 
 The more or less unconscious intention, as well as the 
 result of such social regulations, w^as to maintain the 
 population near the optimum by delay of marriage 
 until a certain standard was reached, and also to 
 limit reproduction on the part of those least fit in a 
 social sense. There are now no corresponding restric- 
 tions on the marriage of the wage-earning classes, 
 with the result that they soon attain their maximum 
 income and marry earlier than the professional classes, 
 whose maximum earning-power comes much later in 
 life. Maternity benefits and doles furnish a further 
 incentive to multiply. It is probable that the re- 
 sulting tendency to increase in numbers out of due 
 proportion to higher classes has the effect of lowering 
 the standard of living of the working classes, because 
 it is a phenomenon of over-population. Here we 
 see how questions of quality and quantity of popula- 
 tion are inextricabty interwoven. 
 
 Carr-Saunders considers that populations have 
 normally been stable throughout human history, and 
 that rapid increase in numbers is the exception. In 
 England, during the period 1 880-1 91 3, the average 
 income per head increased from 100 to 134 in real 
 wages. Hence there was no over-population in the 
 country, as a whole, during this period of rapid 
 growth in population. From 1840 to 1880 the birth- 
 rate remained stationary.* Then the decline set in, 
 and the birth-rate dropped gradually to about two- 
 thirds its former value. This decline is regarded as 
 a response to economic conditions, the earlier rapid 
 rate of increase having ceased to be economicalh^ 
 
 * According to Dean Inge, between 1800 and 1900 the popula- 
 tion of England increased 300 per cent., while it only increased 
 30 per cent, between 1700 and 1800. 
 
SOCIAL AND WORLD ASPECTS 245 
 
 advantageous. The decline is believed to have taken 
 place first in the higher classes, because they respond 
 more quickly to a change in economic conditions. 
 It is viewed with considerable equanimity, even as 
 regards its differential character, confined as it is 
 chiefly to the upper and middle classes, the latter, 
 through selection, including the great majority of 
 the best elements in the community. Other wTiters 
 take a much more serious view of this matter, and 
 apparently wdth good reason. It seems clear, for 
 instance, that in the United States the Anglo-Saxon 
 stock is failing to hold its own (see, for instance, 
 Holmes, 1921), and this is particularl}- true of the 
 more highl}^ trained graduates of the Universities. 
 Similarly in England the decline in the birth-rate 
 since the 'eighties has occurred chiefly in the elements 
 of the population whose inheritance is most valu- 
 able to the nation. Once a particular stock having 
 exceptional qualities is lost it is ver}- questionable 
 whether it can ever be replaced . The history of Greece 
 and Rome and other decayed nations shows that once 
 a human stock has disappeared, for whatever reason, 
 it is gone for ever. An obvious duty rests upon the 
 most highly endowed members in all ranks of society 
 to perpetuate their kind. 
 
 Before leaving the subject of quantity in popula- 
 tion, we ma}^ refer to some recent results on the 
 question of population growth. Pearl and Reed 
 (1920) have applied a logarithmic formula to the 
 growth of population in the United States since 1790, 
 and they conclude that the ultimate population of 
 that country will not exceed 197 millions — i.e., less 
 than double the present population. East (1920, 
 1 921), from a consideration of the agricultural 
 possibilities of the country, concludes that there are 
 about 800 million acres of arable land. If the popula- 
 tion limit were placed at 2-5 acres per man, which is 
 
246 HEREDITY AND EUGENICS 
 
 comparable with present conditions in France and 
 Germany, this would lead to a figure of 320 millions, 
 to which would be added 1 1 millions supported on 
 the grazing lands and forests. A total of 331 millions 
 would thus be the maximum conceivable under any- 
 thing like the present conditions of living. Long 
 before any such density of population is reached, 
 the younger countries would have ceased to be food- 
 exporting, and each country would have to be self- 
 supporting in this regard. But it is ver}^ doubtful 
 if the American population will ever reach such a 
 figure. These problems of racial movements and 
 population increase are, however, beyond our present 
 purview, and can only be touched upon here. 
 
 Population and Quality 
 
 Among primitive races natural selection and 
 differential fertility act so as to tend to preserve 
 existing types, rather than to bring about further 
 evolution. The same appears to be true of wild 
 species in nature generally. Under fixed conditions 
 they tend to remain stable, any unfavourable aberrant 
 types being cut off as they appear. But any kind of 
 change in the conditions initiates readjustments in 
 which selection may favour a different type, and 
 various processes of modification may be set in 
 motion. This must apply, at any rate, to the de- 
 velopment of adaptations, though it apparently does 
 not apply to many mutations. 
 
 As regards the history of man's peculiarly human 
 qualities, it may be the case that progress in intel- 
 lectual capacity came largely before progress in skill. 
 But this evolutionary chapter of man's intellectual 
 development remains mostly to be written. Granted 
 the striking facts of the large cranial capacity of early 
 human races and species, the reasons for this develop- 
 
SOCIAL AND WORLD ASPECTS 247 
 
 ment and the conditions under which it took place 
 remain obscure. However this transitional phase 
 from man's prehuman ancestor took place, a new era 
 began, at least as early as the Lower Palaeolithic, 
 in which tradition began to play the most impor- 
 tant role in man's subsequent development. Carr- 
 Saunders rightly emphasises the value of tradition 
 and its great importance in the evolution of civilisa- 
 tion. He concludes — and the majority of anthro- 
 pologists would apparently agree with him — that 
 '' the major part of the progress in the evolution of 
 the intellectual faculties had been accomplished far 
 back in Palaeolithic times." The artistic and cultural 
 achievements of Palaeolithic man certainly appear to 
 support this view, although the more artistic produc- 
 tions belong to the late Aurignatian and Magdalenian 
 periods of the Upper Palaeolithic. And yet we believe 
 he pushes this conception too far when he states that 
 modern races, representing the Palaeolithic culture 
 level, differ from modern Europeans in disposition 
 rather than in intellect. 
 
 It is true that observers of the children of native 
 races find that as beginners at school the}^ are 
 frequently as keen, or even keener, than the children 
 of whites. But their mental development ceases 
 early. Like the feebleminded, they show arrested 
 mental development.* In their native surroundings 
 their activities may be diverted to other matters by 
 the traditions of their fathers. This, however, can 
 hardly be said of the negroes transplanted to America 
 and living in the midst of civilised traditions, yet the 
 descendants of these negroes in the present generation 
 are shown to be inferior to white children of corre- 
 sponding age in ever}' stage of their development. 
 Evidently primitive peoples are often lacking in the 
 capacity for perseverance. Their lives frequently 
 
 * For a different view, see p. 248. 
 
248 
 
 HEREDITY AND EUGENICS 
 
 consist of periods of violent adventure and exertion in 
 war or the chase, alternating with periods of qui- 
 escence. The capacity for perseverance is one of the 
 later acquisitions of civilised man. 
 
 It is therefore difficult to follow Carr-Saunders in his 
 statement (p. 397), that " there seems to be no marked 
 difference in innate intellectual power " between 
 negroes and modern Europeans. All the evidence, 
 in fact, points to the contrar}' conclusion, but he 
 ascribes this to differences merely in disposition and 
 temperament. The same t3'pe of argument might 
 apply equall}' well to the feebleminded.* As already 
 pointed out (p. 226), the example of the Japanese, 
 who have quickly picked ujd modern science and 
 industr}', in contrast with the many primitive races 
 who are obviously incapable of doing so, is a sufficient 
 answer to the belief that the diiference involved is one 
 mereh' of temperament and not of intellectual ability. 
 This fact is sufficient to show the great gap in intel- 
 lect which exists between the Japanese and really 
 primitive peoples. 
 
 Granting, therefore, the great importance of 
 tradition in accumulating and handing on by means 
 of contact, suggestion, and language the accumulated 
 skill of civilised man, 3^et there must have been also 
 in connection with this process an increase of brain- 
 power on the part of man himself. This must have 
 taken place since Palaeolithic times, although it is not 
 clear how it came about, considered as an evolutionar}' 
 process. Concomitant with this process went on the 
 differentiation of society from its primitive beginnings, 
 in which all the units or clans were alike — the so- 
 called segmentar}^ social condition which persists in 
 
 * McDougal (192 1) refers to the fact that the negro, whether 
 living in Africa, Malaysia, the West Indies, North or South 
 America, continues to show the same fundamental ph^^sical and 
 mental qualities. 
 
SOCIAL AND WORLD ASPECTS 249 
 
 native races — to the highl}' differentiated or organic 
 condition of civilised society, in which a great variety 
 of professions and occupations exist, and men are 
 grouped according to their professions and not 
 according to their descent. Carr-Saunders points out 
 that with increasing contact between men perform- 
 ing the same functions, as populations increased in 
 density, the segmentary type of social organisation 
 necessarily gave place to the organic type, with the 
 final result that modern human society has the highly 
 differentiated and integrated structure and activities 
 of a complex organism. 
 
 Another point on which we feel it necessary to 
 differ from Carr-Saunders in his able analysis of the 
 part tradition has played in the mental evolution of 
 man is with regard to the differences between classes 
 in the same society. He concludes that the direction 
 and degree in which the intellect works is very largel}^ 
 determined by tradition, and that profound differences 
 in tradition between the classes of modern society 
 account for most of the mental differences manifested. 
 Here, again, we believe he la3^s too much stress 
 on tradition. A ver}' considerable proportion of 
 exceptional men break entirel}^ with tradition in 
 choosing their life work. The author admits that 
 the children of the professional classes are on the 
 average two years in advance of the children of 
 unskilled labourers, and hence show superior intel- 
 ligence. Similarly, McDougal (1921) quotes results 
 of observations on school-children in Pittsburg, 
 indicating a marked association between economic 
 status of the parents and school advancement or 
 intelligence of the children. Yet Carr-Saunders con- 
 cludes that there are only slight differences in intel- 
 lectual capacity between the classes. McDougal, on 
 the contrary, emphasises the dangers associated with 
 the differential birth-rate which has grown up during 
 
250 HEREDITY AND EUGENICS 
 
 the last half-century, and points out that the longer 
 the social ladder has been at work passing up the 
 exceptional members of the lower strata of society 
 to the higher, the greater will become the innate 
 germinal differences between classes. When this 
 condition is accompanied by a failure of the higher 
 strata to reproduce themselves, then it is obvious that 
 the germinal reserves of abilit}^ in the lower classes 
 are being gradually depleted and exhausted. This 
 can only mean a permanent loss of power and ability 
 to the race in which it occurs. Already McDougal 
 sees clear indications of this exhaustion in the 
 decreasing numbers who are passing up the ladder 
 during the present generation. Britain seems to have 
 gone further in this direction than any other country 
 in the depletion of its stocks showing leadership and 
 ability, although it is not clear that the United States, 
 with its great numbers of low-class immigrants 
 replacing the Anglo-Saxon stock in various parts of 
 the countr}^, is in any better case. These people 
 may absorb the tradition of their predecessors in a 
 generation or two, but it is certain that they cannot 
 absorb their germinal qualities, nor alter those which 
 are already present in their own germ plasm. 
 
 The problems envisaged in the last few paragraphs 
 have been so much written about in recent vears 
 that we do not propose to discuss them further here. 
 They remain at the heart of all questions of racial 
 improvement through eugenic ideals. The problem 
 of formulating laws which would foster an increase 
 in the more efficient and desirable members in each 
 stratum of society would seem almost to surpass the 
 wit of man, and so far as w^e know, it has not 3^et 
 been successfully accomplished in any community. 
 The task appears all the more appalling when it is 
 remembered how frequently Parliamentary laws have 
 an economic effect quite different from that antici- 
 
SOCIAL AND WORLD ASPECTS 251 
 
 pated or intended. Probably an intelligent and en- 
 lightened public opinion is more efficacious than any 
 laws that could be devised. And a large element of 
 that enlightenment will consist in an understanding 
 of the nature, the laws, and the ubiquity of heredity. 
 However, an obvious negative measure which can 
 be carried into effect is the prevention of reproduction 
 on the part of undesirables, such as the feebleminded. 
 Such measures are necessary, not so much for the 
 improvement of the race, as for arresting its rapid 
 deterioration through the multiphcation of the unfit. 
 
 nOPEKTT UBKART 
 
LIST OF GENERAL WORKS BEARING 
 
 ON EUGENICS 
 
 Babcock, E. B., and Clausen, R. E. Genetics in Relation to 
 Agriculture. 1918. London and New York: Hill Publishing 
 Co. Pp. 675, figs. 239, pis. 4. 
 
 Bateson, W. Mendel's Principles of Heredity. 1913. Cam- 
 bridge Press. Pp. 413, figs. 39. 
 
 Carr-Saunders, a. M. The Population Problem. 1922. Oxford 
 Press. Pp. 516. 
 
 Castle, W. E. Genetics and Eugenics. 1916. Harvard Univer- 
 sity Press. Pp. 357, figs. 135. 
 
 Davenport, C. B. Heredity in Relation to Eugenics. London: 
 Williams and Norgate. Pp. 298. 
 
 Doncaster, L. An Introduction to the Study of Cytology. 1920. 
 Cambridge Press. Pp. 280, figs. 31, pis. 24. 
 
 Galton, F. Hereditary Genius. 1869. London: Macmillan. 
 Second Edition, reprint, 1914. Pp. 390. 
 Inquiries into Human Faculty and its Development. 1883. 
 
 London: Macmillan. Pp. 387, pis. 5. 
 Natural Inheritance. 1889. London: Macmillan. Pp.259. 
 
 Gates, R. Ruggles. The Mutation Factor in Evolution. 1915. 
 London: Macmillan. Pp. 353, figs. 114. 
 
 Goddart, H. H. Feeblemindedness, Its Causes and Conse- 
 quences. 1914. New York: Macmillan. Pp. 599. 
 
 GuYER, M. F. Being Well-Born. 1916. Indianapolis: Bobbs- 
 Merrill Co. Pp. 374, figs. 39. 
 
 Inge, W. R. Outspoken Essays. 1919. London: Longmans. 
 Pp. 281. 
 
 McDougal, Wm. Psychology, the Study of Behaviour. 191 9. 
 
 London: Williams and Norgate. Pp. 254. 
 An Introduction to Social Psychology. 1919. London: 
 
 Methuen. Fourteenth Edition. Pp. 459. 
 National Welfare and National Decay. 1921. London: 
 
 Methuen. Pp. 214. 
 
 252 - 
 
LIST OF GENERAL WORKS 253 
 
 Morgan, T. H. The Physical Basis of Heredity. 1919. Phila- 
 delphia and London: Lippincott. Pp. 305, figs. 117. 
 
 Pearson, Karl, and Collaborators. Treasury of Human In- 
 heritance. 
 
 Plate, L. Tererbungslehre, mit besonderer Beriicksichtigung des 
 Menschen, fiir Studierende, Arzte und Ziichter. 191 3. 
 Leipzig: W. Engelmann. Pp. 519, figs. 179, pis. 3. 
 
 PoPENOE, Paul, and R. H. Johnson. Applied Eugenics. 1920. 
 New York: Macmillan. Pp. 459, figs. 46. 
 
 PUNNETT, R. C. Mendelism. 1919. Fifth Edition. London: 
 Macmillan. Pp. 219, figs. 52, pis. 7. 
 
 Shand, a. F. The Foundations of Character, being a Study of 
 the Tendencies of the Emotions and Sentiments. 1920, 
 London: Macmillan. Pp. 578. 
 
 Tansley, a. G. The New Psychology and its Relation to Life. 
 1920. London: Geo. Allen and Unwin. Pp. 283, figs. 10. 
 
 Watson, J. B. Behaviour: An Introduction to Comparative 
 Psycholog3^ 1914- New York: Henry Holt and Co 
 Pp. 439, figs. 70. 
 Psychology from the Standpoint of a Behaviourist. 1919. 
 Pp. 429, figs. 66. 
 
 Wilson, E. B. The Cell in Development and Inheritance. 1906. 
 London and New York: Macmillan. Pp. 483, figs. 194. 
 
BIBLIOGRAPHY OF PAPERS CITED 
 
 IN THE TEXT 
 
 Adkinson, June. The Behaviour of Bronchial Asthma as an 
 Inherited Character. Genetics, 1920, v. 363-418, figs. 39. 
 
 Albert, Henry. The Inheritance of SyndactyUsm, Science, 
 
 1915, N. S. 41, 951. 
 Anonymous. Hand and Foot Prints. Journ. Hered., 1916, vii. 
 511-523, figs. 12-19. 
 Brigham Young. An Illustration of Prepotency. Journ. 
 Hered., 1916, vii. 51-54, pi. i, figs. 2. 
 Arey, Leslie B. On Monozygotic Human Twins. Anat. Record, 
 
 1921, xxi. 44. 
 Atwood, Edith S., and Pond, Clara P. A Polydactylous 
 
 Family, Journ. Hered., 191 7, viii. 96, fig. i. 
 AuLD, R. C. Some Cases of Solid-Hoofed Hogs and Two-Toed 
 
 Horses. Amer. Nat., 1889, xxiii. 447-449, fig. i. 
 Baker, Henry. A Supplement to the Account of a Distempered 
 Skin, published in the 424th number of the Philosophical 
 Transactions. Phil. Trans., 1755, xlix. 21-24, fig. i. 
 Ballowitz, E. Ober hyperdaktyle Familien und die Vererbung 
 der Vielfingerigkeit des Menschen. Arch. f. Rass. u. Gesells. 
 Biol, 1904, i. 347-365, figs. II. 
 Banta, a. M. Sex and Sex Intergrades in Cladocera. Proc. Nat. 
 
 Acad. Sci., 1918, iv. 373-379. 
 Barker, Lewellys F. The Relation of the Endocrine Glands 
 
 to Heredity and Development. Science, 1922, Iv. 685-690. 
 Bateson, W. Materials for the Study of Variation. 1894. 
 London: Macmillan. Pp. 598. 
 Presidential Address : Report British Association, Australian 
 Meeting. 1915. Pp. 38. 
 Bean, R. B. Heredity of Hair Form among Filipinos. Amer. 
 Nat., 1908, xlv. 524-536. 
 The Racial Anatomy of the PhiUppine Islanders. 19 10. 
 Philadelphia: Lippincott. Pp. 236, figs. 26. 
 Beeley, a. L. Left-Handedness. Am. Journ. Phys. Anthrop., 
 1920, ii. 389-400. 
 
 254 
 
BIBLIOGRAPHY OF PAPERS CITED 255 
 
 Bergman, Emanuel. A Family with Hereditary (Genotypical) 
 Tremor. Hereditas, 1920, i. 98-106. 
 
 Berman, Louis. The Glands Regulating Personality. 1921. 
 New York: Macmillan. Pp. 300. 
 
 Bernstein, Chas. Microcephalic People, sometimes called " Pin 
 Heads." Journ. Hered., 1922, xiii. 30-39, figs. 4. 
 
 Blacker, G. F., and Lawrence, T. W. P. A Case of True Uni- 
 lateral Hermaphroditism with Ovotestis occurring in Man, 
 with a Summary and Criticism of the Recorded Cases of 
 True Hermaphroditism. Trans. Obstet. Soc. Lond., 1897, 
 xxxviii. 265-317, pis. 4. 
 
 Boas, Helene, M. Inheritance of Eye Colour in Man. Amer. 
 
 Journ. Phys. Anthrop., 1919, ii. 15-20. 
 Boas, J. E. V. Zur Beurteilung der Polydaktylie des Pferdes. 
 
 Zool. Jahrh. [Anat.], 1917, xl. 49-104, pi. i, figs. 51. 
 Bonavia, E. Studies in the Evolution of Animals. 1895. 
 
 London: Constable. Pp. 362, figs. 128. 
 Bond, C. J. On Heterochromidia Iridis in Man and x\nimals 
 from the Genetic Point of View. Journ. Genetics, 191 2, 
 ii. 99-129, pis. 4, figs. 7. 
 On Certain Factors concerned in the Production of Eye 
 
 Colour in Birds. Journ. Genetics, 1919, ix. 69-81. 
 On the Left-Sided Incidence of the Supernumerary Digit in 
 Heterodactylous Fowls. Journ. Genetics, 1920, x. 87-91. 
 
 BoNNEViE, K. Polydaktyli i norske bygdeslegter. Norsk Mag. 
 /. Ldgev., 1919a, No. 6, pp. 32. 
 Om twillingsfodslers arvelighet. Undersokelse over en norsk 
 bygdeslegt. Norsk. Mag. f. Ldgev., 1919&, No. 8, pp. 22. 
 BoTTOMLEY, W. B. Somc Effects of Organic Growth-Promoting 
 Substances (Auximones) on the Growth of Lemna minor in 
 Mineral Culture Solutions. Proc. Roy. Soc, igij, 89B, 
 481-507, pis. 2, figs. 7. 
 
 BowDiTCH, H. Red-green Colour-Blindness in Three Allied 
 
 Families. Journ. Hered., 1922. xiii. 139-142, fig. i. 
 Bridges, C. B. Triploid Intersexes in Drosophila melanogaster. 
 Science, 192 1, liv. 252-254. 
 
 Briggs, H. H. Hereditary Congenital Ptosis with Report of 
 Sixty-four Cases conforming to the Mendelian Rule of Domin- 
 ance. Trans. Amer. Ophthalmol. Soc, 191 8, xvi. 255-276. 
 
 Bristol, C. L. Otter Sheep. Amer. Nat., 1908, xiii. 282. 
 
 Brooks, W. K Heredity and Variation: Logical and Biological. 
 
 Proc Amer. Phil. Soc, 1906, xlv. 70-76. 
 Bryant, F. A. Influence of Heredity in Stammering. Journ. 
 
 Hered., 191 7, viii. 46-7. 
 
256 HEREDITY AND EUGENICS 
 
 Buchanan, J. Arthur. The Mendelianism of Migraine. Med. 
 Rec, 1920, xcviii. 807-8. 
 
 Bulloch, W. Diabetes Insipidus. " Treas. of Human Inheri- 
 tance," 1909, Part I., pp. 1-6, pi. I. 
 
 Chronic Hereditary Trophoedema. "Treas. of Human In- 
 heritance," 1909, Part I., pp. 32-38, pis. 2. 
 
 Angioneurotic (Edema (Quincke's Disease). "Treas. of 
 Human Inheritance," 1909, Part III., pp. 38-49, pis. 2. 
 
 Hermaphroditism. "Treas. of Human Inheritance," 1909, 
 Part IV., pp. 50-61, pis. 3. 
 
 Bulloch, W., and Paul Fildes. Haemophilia. " Treas. of 
 
 Human Inheritance," 1910, Part V., pp. 169-354, pis. 17. 
 Cannon, W. B. Bodily Changes in Pain, Hunger, Fear, and 
 
 Rage. 1 91 6. New York and London: Appleton. Pp. 311, 
 
 figs. 39- 
 Carlisle, Anthony. An Account of a Family having Hands and 
 
 Feet with Supernumerary Fingers and Toes. Phil. Trans., 
 
 1814, civ. 94-101. 
 
 Castle, W. E. The Origin of a Polydactylous Race of Guinea- 
 Pigs. Carnegie Inst. Publ., 1906, No. 49, pp. 17-29. 
 Genetic Studies of Rabbits and Rats. Carnegie Inst. Publ., 
 
 1922, No. 320, pp. 55, pi. I. 
 The Y-Chromosome Type of Sex-Linked Inheritance in Man- 
 Science, 1922, Iv. 703-4. 
 
 Caton, John Dean. The Origin of a Small Race of Turkeys. 
 Amer. Nat., 1887, xxi. 350-354. 
 
 CoBURN, C. A. Heredity of Wildness and Savageness in Mice. 
 Behaviour Monographs, 1922, vol. iv. No. 5, pp. 71. 
 
 Cockayne, E. A. A Piebald Family. Biometrika, 1914, x. 197- 
 200, pis. 11-18. 
 
 Cole, L. J. Twinning in Cattle, with Special Reference to the 
 Free-martin. Science, 1916, xliii. 177. 
 Inheritance of Congenital Palsy in Guinea-Pigs. Amer. Nat., 
 1920, liv. 130-151, figs. 3. 
 
 Compton, R. H. a further Contribution to the Study of Right- 
 and Left-Handedness. Journ. Genetics, 1912, ii. 53-70, 
 
 CoNARD, H. S., and C. B. Davenport. Hereditary Fragility of 
 Bone (Fragilitas osseus. Osteopsathyrosis). Eugenics Rec. 
 Of&ce, Bull. No. 14, 1915, Cold Spring Harbour, pp. 31. 
 
 Cook, O. F. Brachysm, a Hereditary Deformit}^ in Cotton and 
 other Plants. Journ. Agr. Research, 1915, iii. 387-400, pis. 10. 
 
 Cragg, E., and H. Drinkwater. Hereditary Absence of Pha- 
 langes through Five Generations. Journ. Genetics, 191 6, 
 vi. 81-89, pl- I- 
 
BIBLIOGRAPHY OF PAPERS CITED 257 
 
 Cramer, M. Beitrage zur Kenntnis der Polydaktylie und Syndak- 
 tylie beiin Menschen und einigen Haiistieren. Nov. Ada 
 Abh. k. Leop. -Carol. Dent. Akad. Natuvf., 1910, xciii. 1-40, 
 pis. 6. 
 
 Crew, F. A. E. Sex-Reversal in Frogs and Toads. A Review of 
 the Recorded Cases of Abnormality of the Reproductive 
 System, and an Account of a Breeding Experiment. Joitrn. 
 Genetics, 192 1, xi. 141-181, figs. 34. 
 
 CuNiER, F. Observation curieuse d'une Achromatopsie heredi- 
 taire depuis cinq generations. Annates d'Oculistiques, 1839, 
 i. 417-420. 
 
 CusHiNG, Harvey. Hereditary Ankylosis of the Proximal 
 Phalangeal Joints (Symphalangism). Genetics, 1916, i. 
 90-106, figs. II. 
 
 Danforth, C. H. Some Notes on a Family with Hereditary Con- 
 genital Cataract. Amer. Joiirn. Ophthalmol., June, 1914, 
 pp. 12, fig. I. 
 
 The Inheritance of Congenital Cataract. Amer. Nat., 191 6, 
 1. 442-448. 
 
 The Developmental Relations of Brachydactyly in the 
 Domestic Fowl. Amer. Journ. Anat., 1919a, xxv. 97-115, 
 
 figs. 5- 
 Evidence that Germ Cells are Subject to Selection on the 
 
 Basis of their Genetic Potentialities. Journ. Exptl. Zool., 
 
 19196, xxviii. 385-412. 
 Resemblance and Difference in Twins. Journ. Hered., 
 
 1919c, X. 399-409, figs. 14. 
 A Comparison of the Hands of a Pair of Polydactyl Negro 
 
 Twins. Amer. Journ. Phys. Anthrop., i<^igd, ii. 147-165, 
 
 figs. 21. 
 
 Darwin, Charles. Descent of Man. 1874. Second Edition. 
 Pp. 797, figs. 78. 
 The Variation of Animals and Plants under Domestication. 
 Second Edition. 2 vols. 
 
 Davenport, C. B. Heredity of Skin Colour in Negro-White 
 Crosses. Carnegie Inst. Wash. Puhl., 1913, No. 188, pp. 
 106, pis. 4. 
 
 The Feebly-Inhibited, Nomadism and Temperament Inheri- 
 tance. Carnegie Inst. Wash. Publ., 1915, No. 236, pp. 158. 
 
 The Form of Evolutionary Theory that Modern Genetical 
 Research seems to Favour. Amer. Nat., 1916, 1. 449-465. 
 
 Heredity of Albinism. Journ. Hered., 1916a, vii. 221-223, 
 figs. 3. 
 
 17 
 
258 HEREDITY AND EUGENICS 
 
 Davenport. C. B. The Hereditary Factor in Pellagra. Arch. 
 
 Internat. Med., 19165, xviii. 4-31. 
 Inheritance of Stature. Genetics, 1917a, ii. 3i3-389» figS- i9- 
 The Effects of Race Intermingling. Pvoc. Amer. Phil. Soc, 
 
 191 76, Ivi. 364-368. 
 The Personality, Heredity, and Work of Charles Otis Whit- 
 man. Amer. Nat., 1917c, li. 5-30. 
 Hereditary Tendency to form Nerve Tumours. Proc. Nat. 
 
 Acad. Set., 1918, iv. 213-214. 
 A Strain producing Multiple Births. Journ. Hered., 191 g, 
 
 X. 382-384. 
 Naval Officers: Their Heredity and Development. Carnegie 
 
 Inst. Wash. Publ., 1919, No. 289, pp. 236. 
 Influence of the Male in the Production of Twins. Amer. 
 
 Nat., 1920a, liv. 122-129. 
 Influence of the Male on the Production of Twins. Med. 
 
 Record, 19206, March 27. 
 Heredity of Constitutional Mental Disorders. Psych. Bull., 
 
 192.0c, xvii. 300-310. 
 Research in Eugenics. Science, 1921a, liv. 391-397- 
 Comparative Social Traits of Various Races. School and 
 
 Society, 1921&, xiv. 344-346. 
 
 Davenport, G. C. and C. B. Heredity of Skin Pigment in Man. 
 Amer. Nat., 1910, xliv. 641-672, 705-731. 
 
 Dean, Bashford. Albinism, Partial Albinism and Polychro- 
 matism in Hag-Fishes. Amer. Nat., 1903, xxxvii. 295-298, 
 figs. 3- 
 
 Detlefson, J. A. A Herd of Albino Cattle. Journ. Hered., 1920, 
 xi. 378-9, figs. 2. 
 
 Detlefson, J. A., and Yapp, W. W. The Inheritance of Con- 
 genital Cataract in Cattle. Amer. Nat., 1920, liv. 277-280. 
 
 Detlefson, J. A., and Carmichael, W. J. Inheritance of Syn- 
 dactylism, Black, and Dilution in Swine. Journ. Agric. 
 Research, 1921, xx. 595-604, pi. i. 
 
 DoNCASTER, L. Note on the Inheritance of Characters in which 
 Dominance appears to be influenced by Sex. Journ. 
 Genetics, 191 1, i. 377-379- 
 On Sex-limited Inheritance in Cats, and its Bearing on the 
 Sex-limited Transmission of Certain Human Abnormalities. 
 Journ. Genetics, 1913, iii. 11-23. 
 
 DoNiTZ. Sitzungsb. d. Gesells. naturf. Freunde BerHn, 1868, 
 21-22. 
 
BIBLIOGRAPHY OF PAPERS CITED 259 
 
 Drtnkwater, H. An Account of a Brachydactylous Family. 
 
 Proc. Roy. Soc. Edin., 1908, xxviii. 35-57, figs. 11. 
 The Inheritance of " Thumb-Fingerness " in a Short- 
 Fingered Family. Mendel Journ., 191 1, pp. 20, pis. 6, 
 
 figs. 4. 
 Account of a Family showing Minor-Brachydactyly. Journ . 
 
 Genetics, 1912, ii. 21-40, figs. 15. 
 Study of a Brachydactylous Family (Minor-Brachydactyly). 
 
 Compt. Rend, ^e, Conf. Internal, de Genetique, Paris (191 1), 
 
 1913. PP- 549-62, figs. 14. 
 Minor-Brachydactyly, No. 2. Journ. Genetics, 1914, iii. 
 
 217-220, pis. 3. 
 Obligatory Bi-manual Synergia with Allocheiria in a Boy 
 
 otherwise Normal. 17th Internat. Congress Med. London 
 
 (1913), 1914, pp. 117-124. 
 A Second Brachydactylous Family. Journ. Genetics, 1915, 
 
 iv. 323-340. pis. 5. figs- 3- 
 Hereditary Abnormal Segmentation of the Index and Middle 
 
 Fingers. Journ. Anat. and Physiol., 1916, 177-186, figs. 14. 
 Inheritance of Artistic and Musical Ability. Journ. Genetics, 
 
 1916, V. 229-241. 
 
 The Modern Descendants of Dr. Peter Chamberlen. Liver- 
 pool Med.-Chir. Journ., 1916, 98-105. 
 
 Phalangeal Anarthrosis (Synostosis, Ankylosis) transmitted 
 through Fourteen Generations. Proc. Roy. Soc. Med., 
 
 1917, X. (section Pathology) pp. 60-68, figs. 4. 
 
 The Inheritance of Normal and Pathological Traits in Man. 
 The Practitioner, March, 191 7, pp. 24. Contains a good 
 list of literature references. 
 
 Dublin, Louis I. The Mortality of Foreign Race Stocks. Sci. 
 Monthly, 1922, xiv. 94-104. 
 
 DuERDEN, J. S. Some Results of Ostrich Investigations. S. 
 
 African Journ. Sci., November-December, 1918, pp. 38, 
 
 tables 10, figs. 4, pis. 4. 
 Crossing the N. African and S. African Ostrich. Journ. 
 
 Genetics, 1919, viii. 155-198, tables 10, pi. i, figs. 2. 
 Social Anthropology in South Africa : Problems of Race and 
 
 Nationality. Presidential Address, South African Assoc. 
 
 for Advancement of Science, 1921, pp. 31. 
 
 Duncan, F. N. Orthodactyly. Journ. Hered., 191 7, viii. 174-5, 
 figs. 2. 
 
 DwiGHT, Timothy. Travels in New England and New York. 
 1822. Vol. iii. New Haven. 
 
26o HEREDITY AND EUGENICS 
 
 East, E. M. Hidden Feeble-Mindedness. Journ. Hered., 191 7, 
 viii. 215-217. 
 
 Population. Set. Monthly, 1920, xi. 603-624. 
 
 The Agricultural Limits of Our Population. Set. Monthly, 
 1921, xii. 55T-557. 
 East, E. M., and Jones, D. F. Inbreeding and Outbreeding: 
 
 Their Genetical and Sociological Significance. 1919. London 
 
 and Philadelphia: Lippincott. Pp. 285, figs. 46. 
 Elderton, Ethel M. On the Inheritance of the Finger Print. 
 
 Biometrika, 1920, xiii. 57-91. 
 
 Enriques, Paolo. Ricerche sulla eredita della mosche. Rivista 
 di Biologia, 1919, i. 72-81. 
 
 EsTABROOK, A. H. The Jukes in 1915. Carnegie Inst. Wash. 
 Publ., 1916, No. 240, pp. 85. 
 
 Fackenheim, J. Uber einen Fall von hereditarer Polydaktylie 
 mit gleichzeitiger erblicher zahnanomalie. Jena Zeits. f. 
 Naturw., 1888, xxii. 343-385, figs. 7. 
 
 Farabee, W. C. Inheritance of Digital Malformations in Man. 
 Papers, Peabody Museum, Harvard Univ., 1905, iii. 65-78. 
 
 Fay, Edward A. Marriages of the Deaf in America. Volta 
 Bureau, Washington, 1898, pp. 527. 
 
 Ferguson, G. O. The Mental Status of the American Negro. 
 Sci. Monthly, 192 1, xii. 533-543. 
 
 Fischer, Eugen. Fin Fall von erblicher Haararmut und die 
 
 Art ihrer Vererbung. Arch. f. Rass. u. Gesells.-Biol., 1910, 
 
 vii. 50-56. 
 
 Die Rehebother Bastards und das Bastardierungs-problem 
 
 beim Menschen. 1913. Jena. Pp. 327, pis. 19, figs. 36. 
 
 Fisher, R. A. The Genesis of Twins. Genetics, 191 9, iv. 489- 
 499. 
 
 Flinders-Petrie, W. M. The Revolutions of Civilization. 1911. 
 London and New York: Harper Bros. Pp. 136, figs. 57. 
 
 FoLKAR, Herbert H. Nodular Opacity of the Cornea in Three 
 Generations. Trans. Ophthalmol. Soc, 1909, xix. 42-54. 
 
 Friedenthal, Hans. Das Haarkleid des Menschen. 1908. 
 Berlin: G. Fischer. Pp. 179, pis. 43. 
 
 Galton, F. Fingerprints. 1892. London : Macmillan. Pp.216. 
 
 Gates, R. Ruggles. A Litter of Hybrid Dogs. Science, 1909a, 
 
 xix. 744-747- 
 The Stature and Chromosomes of (Enothera gigas, De Vries. 
 
 Arch. f. Zellforsch., 1909&, iii. 525-552. 
 The Modification of Characters by Crossing. Amer. Nal., 
 
 1915, xhx. 562-560 
 
BIBLIOGRAPHY OF PAPERS CITED 261 
 
 Gates, R. Ruggles. Vegetative Segregation in a Hybrid Race. 
 Journ. Genetics, 191 7, vi. 237-253, pi. i. 
 Mutations and Evolution. 1921. London: Wesley and 
 Wheldon. Pp. 118. 
 
 Gilpin, J. Bernard. An Introduced Species of Nova Scotia. 
 Trans. N. S. Inst. Set., 1864, i. 60-68, 
 
 GoDDART, H. H. The Kallikak Family: A Study in the Heredity 
 of Feeblemindedness. 191 2, New York: Macmillan. 
 
 Feeblemindedness: Its Causes and Consequences. 1914. 
 New York: Macmillan. 
 
 Mental Tests and the Immigrant. Journ. Delinquency, 19 17, 
 ii. 243-278. 
 
 Goldsmith, W. M. "The Catlin Mark ": The Inheritance of an 
 Unusual Opening in the Parietal Bones, Journ. Hered., 
 1922, xiii. 69-71, figs. 5. 
 
 Goring, Chas. On the Inheritance of the Diatheses of Phthisis 
 and Insanity. 1909. London: Dulau. Pp. 28, 
 
 Gossage, a. M. The Inheritance of Certain Human Abnormali- 
 ties, Quart. Journ. Med., 1908, i. 331-347. 
 
 GowEN, John W. Identical Twins in Cattle, Biol. Bull., 1922. 
 xlii, 1-6, 
 
 GuYER, M. F., and Smith, E. A. Studies on Cytolysins — II, 
 Transmission of Induced Eye Defects. Journ. Exptl. Zool., 
 1920, xxxi. 171-223, pis. 4, figs. 7, 
 
 Haddon, a. C. The Wanderings of Peoples. 191 9. Cambridge 
 Press. Pp. 124, 
 
 Haecker, V. Die Hapsburger Unterlippe, Verh. d. Deut. Zool. 
 Gesells., 191 1, 109-113. 
 Die Familientypus der Hapsburger. Zeits. f. Abst. u. 
 
 Vererb., 1911, vi. 61-89, figs. 12. 
 Entwicklungsgeschichtliche Eigenschaftsanalyze (Phano- 
 genetik). 1918. Jena: Fischer. Pp. 344. 
 
 Hankin, E. H. The Mental Ability of the Quakers. Sci. Pro- 
 gress, 1922, xvi. 654-664. 
 
 Hanna, G. Dallas. Genital Organs of Hermaphroditic Fur Seals. 
 Amer. Nat., 1921, Iv, 473-475, 
 
 Hansen, S0'ren. Heredity in the Case of Dementia Praecox and 
 Related Diseases. Hereditas, 1922, iii. 1 14-124. 
 
 Hardy, G. H. Mendelian Proportions in a Mixed Population. 
 Science, 1908, xxviii. 49-50. 
 
 Harman, N. a Study in Heredity. Six Generations of Piebalds. 
 Trans. Ophthalmol. Soc, 1909, xxix. 25-33. 
 
262 HEREDITY AND EUGENICS 
 
 Harm AN, N. BrsHOP. Congenital Cataract: A Pedigree of Five 
 Generations. Trans. Ophthalmol. Soc, 1909, xxix. 101-108. 
 Congenital Cataract. " Treas. Human Inheritance," 1910, 
 Part IV., pp. 126-166, pis. 8. 
 
 Hawkes, Onera a. Merritt. On the Relative Lengths of the 
 First and Second Toes of the Human Foot, from the Point 
 of View of Occurrence, Anatomy, and Heredity. Joiirn. 
 Genetics, 1914, iii. 249-274, pis. 3, figs. 6. 
 
 Hayden, C. C. a Case of Twinning in Dairy Cattle. Journ. 
 Hered., 1922, xiii. 22-24, ^S^- 4- 
 
 Hoffman, H. Die Nachkommenschaft bei endogenen Psychosen. 
 192 1. Berlin: Springer. Pp. 233, figs. 43. 
 
 Holmes, S. J. The Trend of the Race. 1921. London: Constable. 
 Pp. 396. 
 
 Holmes, S. J., and Schofield, R. O. Inheritance of White 
 Forelock. Journ. Hered., 191 7, viii. 359-360, fig. i. 
 
 Hooper, J. J. A Peculiar Breed of Goats. Science, 1916, xliii. 
 
 571- 
 Hope, W. B., and French, Herbert. Persistent Hereditary 
 (Edema of the Legs with Acute Exacerbations. Milroy's 
 Disease. Quart. Journ. Med., 1908, i. 312-330, pis. 2. 
 
 HoRNE, JoBSON. Dcaf-mutism. " Treas. Human Inheritance," 
 1909, pp. 27-29, pi. i; pp. 69-72, pis. 2; pp. 124-126, pi. I. 
 
 Hover, J. M. Finding the Prepotent Sire. Journ. Hered., 1916, 
 
 vii. 173-178. 
 Howe, Freeland, Jnr. A Case of Abnormality in Cat's Paws. 
 
 Amer. Nat., 1902, xxxvi. 511-526, figs. 18. 
 
 Howe, Lucien. A Bibliography of Hereditary Eye Defects. 
 Eugenics Record Office, Bull. No. 21, 1921, pp. 45. 
 
 HuDDART, Joseph. An Account of Persons who could not Dis- 
 tinguish Colours. Phil. Trans., 1777, Ixvii. 260-265. 
 
 Humphreys, Col. David. On a New Variety in the Breeds of 
 Sheep. Phil. Trans., 1813, 88-95. 
 
 Hunter, John. Account of the Free-martin. Phil. Trans., 17791 
 Ixix. 279-293. 
 
 Hurlin, Ralph, G. A Case of Inherited Syndactyly in Man. 
 Journ. Hered., 1921, xi. 334-5, figs. 2. 
 
 Hurst, C. C. Mendelian Characters in Plants, Animals, and Man. 
 Verh. Naturf. Vereines in Bri'mn., 191 1, xlix. 1-22. 
 Mendelian Heredity in Man. Eugenics Review, 1912, pp. 25, 
 figs. 6. 
 
BIBLIOGRAPHY OF PAPERS CITED 263 
 
 Huxley, Julian S. Some Recent Advances in the Biological 
 Theory of Sex. Journ. Roy. Soc. Arts, 1922, Ixx. 206-217. 
 
 Jenks, a. E. pitted Ear-Lobes of Congenital Origin. Journ. 
 Hered., 1916, vii. 553-4, figs. 7. 
 
 Jennings, H. S. The Numerical Results of Diverse Systems of 
 Breeding. Genetics, 191 6, i. 53-89. 
 
 Jones, D. F., and Mason, S. L. Inheritance of Congenital 
 Cataract. Amer. Nat., 1916a, 1. 119-126. 
 Further Remarks on the Inheritance of Congenital Cataract. 
 Amer. Nat., 19166, 1. 751-757. 
 
 Jones, F. S., and Arnold, J. F. Staggers in Sheep in Patagonia. 
 Journ. Exp. Med., 191 7, xxvi. 805-823, pis. 4. 
 
 Jordan, D. S. The Inbred Descendants of Charlemagne: A 
 Glance at the Scientific Side of Genealogy. Sci. Monthly, 
 1921, xiii. 481-492. 
 
 Jordan, H. E. A Comparative Microscopic Study of the Melanin 
 Content of Pigmented Skins, with Special Reference to the 
 Question of Colour Inheritance among Mulattoes. Amer. 
 Nat., 191 1, xlv. 449-470, figs. 3. 
 
 Keith, Sir A. The Differentiation of Mankind into Racial Types. 
 Rept. British Assoc, Bournemouth, 1920, pp. 275-281. 
 The Evolution of Human Races in the Light of the Hormone 
 Theory. Johns Hopkins Hosp. Bull., 1922, xxxiii. 155- 
 159, 195-201. 
 Kempf, Edward J. Psychopathology. 1921. London: Henry 
 Kimpton. Pp. 762, figs. 87. 
 
 Kempton, J. H. a Brachytic Variation in Maize. Bull. No. 925, 
 1921, U.S. Dept. Agric, pp. 28, pis. 19, figs. 8. 
 
 Kennel, J. Ueber eine stummelschwanzize Hauskatze und ihre 
 Nachkommenschaft. Zool. Jahrb. {Syst.), 1901, xv. 219-242, 
 figs. 2. 
 
 Key, Wilhelmine E. Heredity and Social Fitness: A Study of 
 Differential Mating in a Pennsylvania Family. Carnegie 
 Inst. Wash. Puhl., 1920, No. 296, pp. 102. 
 
 Kindred, J. E. Inheritance of a Pit in the Skin of the Left Ear. 
 Journ. Hered., 1922, xii. 336-7, fig. i. 
 
 Koch, Mathilda L., and Riddle, Oscar. The Chemical Com- 
 position of the Brain of Normal and Ataxic (?) Pigeons. Amer. 
 Journ. Physiol., 1918, xlvii. 124-136. 
 
 Kretschner, E. Korperbau und Charakter. 1922. Berlin: 
 Springer. 
 
264 HEREDITY AND EUGENICS 
 
 KuHN, Julius. Die Stammvater unserer Hunde-Rassen. 1877. 
 Vienna. 
 
 Lane, W. C. Hereditary Nose-Bleed. Journ. Hered., 1916, vii. 
 132-134, fig. I. 
 
 Laughlix, H. H. Calculating Ancestral Influence in Man: A 
 Mathematical Measure of the Facts of Bisexual Heredity. 
 Genetics, 1920, v. 435-458. 
 
 Lawrence, T. W. P. True Hermaphroditism in the Human 
 Subject. Trans. Path. Soc. Lond., 1906, Ivii. 21-24, figs. 2. 
 
 Learmonth, J. R. The Inheritance of Specific Isoagglutinins in 
 Human Blood. Journ. Genetics, 1920, x. 141-148. 
 
 Lenz, Fritz. Cber die krankhaften Erbanlagen des Mannes und 
 die Bestimmung des Geschlechts beim Menschen. 191 2. 
 Jena: Fischer. Pp. 170, figs. 23. 
 
 Lewis, T. Hereditary Malformations of the Hands and Feet, 
 " Treas. Human Inheritance," 1909a, Part I., pp. 6-10. 
 pis. 3. 
 
 Polydactylism. " Treas. Human Inheritance," 19096, Part I., 
 
 pp. 10-14, pis. 2. 
 Brachydactylism. "Treas. Human Inheritance," 1909c, 
 
 Part I.,, pp. 14-17, pis. 3. 
 
 Lewis, T., and Embleton, D. Split-Hand and Split-Foot De- 
 formities, their Types, Origin, and Transmission. Biometrika, 
 1908, vi. 26-58, pis. 7. 
 
 LiLLiE, F. R. The Free-martin: A Study of the Action of Sex 
 Hormones in the Foetal Life of Cattle. Journ. Exptl. Zool., 
 1917, xxiii. 371-422. 
 
 Little, C. C. Some Factors influencing the Human Sex-Ratio. 
 Proc. Soc. Exptl. Biol, and Med., 1919, xvi. 127-130. 
 A Note on the Origin of Piebald Spotting in Dogs. Journ. 
 
 Hered., 1920, xi. 12-15, figs. 3. 
 Inheritance of a Predisposition to Cancer in Man. Abstracts 
 of Papers, Second Eugenics Congress, New York, 1921, 
 pp. 22. 
 
 Little, C. C, and Gibbons, M. Evidence for Sex-Linked Lethal 
 Factors in Man. Proc. Soc. Exp. Biol, and Med., 192 1, xviii. 
 111-115. 
 
 LoEB, Leo. Inheritance of Cancer in Mice. Amer. Nat., 1921, 
 Iv. 510-528. 
 
 LoiSEL, G. Les Chats anoures de I'lle de Man. Bull. Mus. 
 d'Hist. Nat., 1907, 185-192. 
 
BIBLIOGRAPHY OF PAPERS CITED 265 
 
 LoRT, Rev. Michael. An Account of a Remarkable Imperfection 
 of Sight. In a letter from J. Scott to the Rev. Mr. Whisson, 
 of Trinity College, Cambridge. Phil. Trans., 1779, Ixviii. 
 611-614. 
 
 Love, A. G., and Davenport, C. B. A Comparison of White and 
 Coloured Troops in Respect to Incidence of Disease. Proc. 
 Nat. Acad. Sci,, 1919, v. 58-67. 
 
 Love, J. K. The Origin of Sporadic Congenital Deafness. Joiirn. 
 Laryngol., Rhinol., and Otol., 1920, xxxv. 263-270. 
 
 Luce, L. H. and W. H. Three Cases of Hypospadias in which 
 the Sex was Undeterminable until Puberty. Amer. Nat., 
 1890, xxiv, 1016-1019. 
 
 LuNDBORG, H. Medizinisch-biologische Familienforschungen 
 
 innerhalb eines 2232-k6pfigen Bauerngeschlechtes in 
 
 Schweden (Provinz Blekinge). 1913. Jena: Fischer. 
 
 2 Vols. Vol. i. pp. 519 -1-220; vol. ii. 10 pis., 52 charts. 
 Svenska Folktyper. 1919. Stockholm: Hasse u. TuUbergs 
 
 Boktryckeri. 
 Arv och miljo. Befolkingspolitiska synpunkter. Det nya 
 
 Sverige, 1920, xiv. 3-12. 
 Hereditary Transmission of Genotypical Deaf-mutism. 
 
 Hereditas, 1920, i. 35-40. 
 Hybrid Types of the Human Race. Joiirn. Hered., 192 1, 
 
 xii. 274-280, figs. 4. 
 
 Lush, J. L. An Hereditary Notch in the Ears of Jersey Cattle. 
 Journ. Hered., 1922, xiii. 8-13, figs. 8. 
 
 Lynch, Clara J. Short Ears an Autosomal Mutation in the 
 House-Mouse. Amer. Nat., 1921, Iv. 421-426, fig. i. 
 
 MacBride, E. W. The Study of Heredity, Part IV. Eugenics 
 Review, January, 191 7, pp. 28, figs. 5. 
 
 MacCaughey, Vaughan. Race Mixture in Hawaii. Journ. 
 
 Hered., 1919, x. 41-47, 90-95. 
 MacDonald, James, and Sinclair, James. History of Polled 
 
 Aberdeen or Angus Cattle. 1882. Edinburgh and London: 
 
 Blackw'ood. Pp. 459, illustrated. 
 
 Machin, John. An Extract from the Minutes of the Royal 
 Society, March 16, 1731, containing an Uncommon Case of a 
 Distempered Skin. Phil. Trans., 1733, xxxvii. 299-301, 
 figs. 3. 
 
 MacKinder, D. Deficiency of Fingers transmitted through Six 
 Generations. British Med. Journ., 1857, 845-6. 
 
 Hanson, J. S. Hereditary Syndactylism and Polydactylism. 
 Journ. Genetics, 19 15, v. 51-63, pis. 6. 
 
266 HEREDITY AND EUGENICS 
 
 Martin, P, J. Case of Hereditary Ichthyosis. Med.-Chirurg. 
 Trans., 1818, ix. 52-55, pis. 2. 
 
 Martins, F. Konstitution und Vererbung in ihrer Beziehungen 
 zur Pathologie. 1914. Berlin : Springer. Pp. 258, figs. 13. 
 
 Maynard, C. D. Note on a Negro Piebald. Biometrika, 1914, 
 X. 193, pis. 10, 
 
 McDouGAL, W. Psychology, the Study of Behaviour. 1919. 
 London: Williams and Norgate. Pp. 251. 
 
 McMuLLEN, Geo., and Pearson, K. On the Inheritance of the 
 Deformity known as Split-Foot or Lobster Claw. Biometrika, 
 1913, ix. 381-390, pis. 6. 
 
 Metchnikoff, E. The Nature of Man. 1903. New York and 
 London: Putnams. Pp. 309, figs. 20. 
 
 Meulengracht, E. Der chronische hereditare haemolytische 
 
 Ikterus. 1922. Leipzig: W. Klinkhardt. 
 Miller, Newton. Heredity of White Forelock. Journ. Hered., 
 
 1915, Ixi. 165-169, figs. 4. 
 MiLROY, W. F. An Undescribed Variety of Hereditary CEdema. 
 
 New York Med. Journ., 1892, Ivi. 505-508. 
 MiVART, St. George. A Monograph of the Canidae. 1890. 
 
 London: R. H. Porter. Pp. 216, 45 coloured plates, figs. 59. 
 MjOEN, Jon Alfred. Harmonic and Unharmonic Crossings. 
 
 Eugenics Review, 1922, xiv. 35-40. 
 MoHR, Otto L. A Case of Hereditary Brachyphalangy utilized 
 
 as Evidence in Forensic Medicine, Hereditas, 192 1, ii. 290- 
 
 298, figs. 10. 
 
 MoHR, Otto, and Wriedt. Chr. A New Type of Hereditary 
 Brachyphalangy in Man. Carnegie Inst. Wash. Publ., 1919, 
 No. 295, pp. 64, pis. 7. 
 
 Nettleship, E. a History of Congenital Stationary Night- 
 Blindness in Nine Consecutive Generations. Trans. 
 Ophthalmol. Soc, 1907, xxvii. 
 A Pedigree of Congenital Night- Blindness with Myopia. 
 Trans. Ophthalmol. Soc, 1912, xxxii. 
 
 NeWxMan, H. H. Night-Blindness. Journ. Genetics, 1913, iii. 
 25-38, figs. 2. 
 
 Hereditary and Organic Symmetry in Armadillo Quadru- 
 plets. Biol. Bull., 1916, xxix. 1-32, figs. 16; xxx. 173-209, 
 figs. 19. 
 
 The Biology of Twins. 191 7. University of Chicago Press. 
 
 The Experimental Production of Twins and Double Monsters 
 in the Larvae of the Starfish Patiria miniata, together with 
 a Discussion of the Causes of Twinning in General. Journ. 
 Exper. Zool., 192 1, xxxiii. 321-352, figs. 46. 
 
BIBLIOGRAPHY OF PAPERS CITED 267 
 
 Newman, H. H., and Patterson, J. T. The Limits of Hereditary 
 Control in Armadillo Quadruplets: A Study of Blastogenic 
 Variation. Journ. MorpJi., 19 rr, xxii. 855-926, figs. 24. 
 
 NiLSSON, Martin P. The Race Problem of the Roman Empire. 
 Hereditas, 1921, ii. 370-390. 
 
 Ordahl, George. Heredity of Feeblemindedness. Training 
 School Bull., March-April, 1919, pp. 2-16. 
 
 Osborn, Dorothy. Inheritance of Baldness. Journ. Hered., 
 
 1916, vii. 347-355. figs- 9- 
 OsBORN, H. L. A Case of Polydactylism. Amer. Nat., 1900, 
 
 xxxiv. 681-2, figs. 4. 
 
 Otis, Arthur S. Heredity and Mental Defect. Journ. 
 Delinquency, May, July, 1916, pp. 87-100, 125-128. 
 
 Painter, T. S. The Y-Chromosome in Mammals. Science, 192 1, 
 liii. 503-4. 
 The Sex Chromosomes of the Monkey. Science, 1922, Ixvi. 
 286-7. figs. 4. 
 
 Patterson, J. T. Polyembryonic Development in Tatusia 
 novemcincta. Journ. Morph., 1913, xxiv. 560-662, pis. 11, 
 figs. 84. 
 
 Pearl, M. D., and Pearl, R. On the Relation of Race-Crossing 
 to the Sex Ratio. Biol. Bull., 1908, xv. 194-205. 
 
 Pearl, R. A Case of Triplet Calves, with some General Con- 
 siderations regarding Multiple Gestation in normally Uni- 
 parous Animals. Ann. Rept. Maine Agr. Expt. Sta., 1912, 
 259-282, figs 2. 
 
 Pearl, R. A Contribution towards an Analysis of the Problem 
 
 of Inbreeding. Amer. Nat., 1913, xlvii. 577-614. 
 On the Results of Inbreeding a Mendelian Population: A 
 
 Correction and Extension of Previous Conclusions. Amer. 
 
 Nat., 1914a, xlviii. 57-62. 
 Inbreeding and Relationship Coefficients. A mer. Nat., igT.\h, 
 
 xlviii. 513-523. 
 Certain Evolutionary Aspects of Human Mortality Rates. 
 
 Amer. Nat., 1920, liv. 5-44. 
 A Biological Classification of the Causes of Death. Metron, 
 
 1921, i. 92-99. 
 The Biology of Death. Sci. Monthly, 192 1. 
 
 Pearl, R., and Parshley, H. M. Data on the Sex Determination 
 in Cattle. Biol. Bull., 1913, xxiv. 205-225. 
 
 Pearl, R., and Reed, L. J. On the Rate of Growth of the Popu- 
 lation of the United States since 1790, and its Mathematical 
 Representation. Proc. Nat. Acad. Sci., 1920, vi. 275-28S. 
 
268 HEREDITY AND EUGENICS 
 
 Pearl, R. and Salaman, R. N. The Relative Time of Fertilisa- 
 tion of the Ovum and the Sex Ratio amongst Jews. Amer. 
 Anthrop., 1913, xv. 668-674. 
 
 Pearson, K. On a Generalised Theory of Alternative Inheritance, 
 
 with Special Reference to Mendel's Laws. Phil. Trans. 
 
 Roy. Soc, 1904, A. 203, 53-86. 
 On the Inheritance of the Mental and Moral Characters in 
 
 Man, and Its Comparison with the Inheritance of the 
 
 Physical Characters. Biometrika, 1904, iii. 131-190. 
 A First Study of the Statistics of Pulmonary Tuberculosis. 
 
 1907. London: Dulau. Pp. 26. 
 On Inheritance of the Deformity known as Split-Foot or 
 
 Lobster Claw. Biometrika, 1908, vi. 69-79, pis. 9. 
 Notes on the Skin Colour of the Crosses between Negro and 
 
 White. Biometrika, 1909, vi. 348-353. 
 Tuberculosis, Heredity and Environment. 191 2. London: 
 
 Dulau. Pp. 46. 
 Note on the Honduras Piebald. Biometrika, 1913, ix. 330- 
 
 331, pis. 4. 
 Life, Letters, and Labours of Sir Francis Galton. 1914. 
 
 Cambridge University Press. Pp. ix-f-246, pis. 66. 
 Inheritance of Psychical Characters. Biometrika, 1919, xii. 
 
 367-372- 
 A New White-Lock Family (Barton's Case). Biometrika, 
 192 1, xiii. 347-349, pis. 2. 
 
 Pearson, K., Nettleship, and Usher. A Monograph on Albinism 
 in Man. 191 3. Drapers' Company Research Memoirs. 
 Cambridge University Press. In 4 parts. 
 
 Pell, C. E. The Law of Births and Deaths. 1912. London: 
 Fisher Unwin. Pp. 192. 
 
 PoPENOE, Paul. Concerning Prepotency. Journ. Hered., 1916, 
 vii- 331-336, fig. I. 
 Heredity and the Mind. Journ. Hered., 1916, vii. 456-462. 
 Twins Reared Apart. Journ. Hered., 1922, xiii. 142-144, fig. i. 
 
 Priestley, Rev. Joseph. An Account of Persons who could not 
 distinguish Colours. By Mr. Joseph Huddart, in a Letter to 
 the Rev. Joseph Priestley, LL.D., F.R.S. Phil. Trans. Roy. 
 Soc. Lond., 1777, Ixvii. 260-265. 
 
 PuNNETT, R. C. Eliminating Feeblemindedness. Journ. Hered., 
 191 7, viii. 464-5, 
 
 PuNNETT, R. C, and Bailey, P. G. On Inheritance of Weight in 
 Poultry. Journ. Genetics, 1914, iv. 23-39, figs. 3, pi. i. 
 Genetic Studies in Rabbits. I. On the Inheritance of 
 Weight. Journ. Genetics, 1918, viii. 1-25, figs. 12. 
 
BIBLIOGRAPHY OF PAPERS CITED 269 
 
 Ramalay, F. Inheritance of Left-Handedness. Anier. Nat., igi^, 
 xlvii. 730-738. 
 
 Riddle, O. The Determination of Sex and Its Experimental 
 Control. Bull. Amer. Acad. Med., 1914, xv. 1-20. 
 The Control of the Sex Ratio. Journ. Wash. Acad. Set., JC)iy , 
 
 vii. 319-356- 
 
 A Demonstration of the Origin of two Pairs of Female 
 Identical Twins from Two Ova of High Storage Meta- 
 bolism. Journ. Exptl. Zool., 191 8, xxvi. 227-254. 
 
 A Case of Hereditary Ataxia (?) in Pigeons. Proc. Soc- 
 Exptl. Biol, and Med., 1918, xv. 56-7. 
 RiEDER, H. Ueber gleichzeitiges Vorkommen von Brachy- und 
 
 Hyper-phalangie an der Hand. Deutsch. Arch. Klin. Med., 
 
 1899, Ixvi. 330-348, figs. 6. 
 RiscHBiETH, H. Hare-Lip and Cleft Palate. " Treas. Human 
 
 Inheritance," 1910, Part IV., pp. 79-123, pis. 8. 
 
 RiscHBiETH, H., and Barrington, Amy. Dwarfism. " Treas. 
 
 Human Inheritance," 1912, Part. VII., pp. 355-573, pis. 35. 
 
 RiTZMAN, E. G. Mendelism of Short Ears in Sheep. Journ. 
 
 Agric. Research, 1916, vi. 797-8. 
 
 Breeding Earless Sheep. Journ. Hered., 192 1, xi. 238-240, 
 
 figs. 4. 
 
 Roberts, Elmer. Polydactylism in Cattle. Journ. Hered., 1921, 
 
 xii. 84-86, figs. 5. 
 RuDiN, Ernst. Studien iiber Vererbung und Entstehung geistiger 
 
 Storungen. I. Zur Vererbung und Neuentstehung der 
 
 Dementia Praecox. 1916. Berlin: J. Springer. Pp. 172, 
 
 figs. 66. 
 
 Salaman, R. N. Heredity and the Jew. Journ. Genetics, 191 1, 
 i. 273-292, pis. 4, figs. 6. 
 
 Sang, F. The Convolutional Pattern of the Brains of Identical 
 Twins: A Study of Hereditary Resemblance in the Furrows 
 of the Cerebral Hemispheres. Phil. Trans. Roy. Soc, 19 15, 
 B. 208, 37-61, figs. 5. 
 
 Schmidt, Jghs. The Genetic Behaviour of a Secondary Sexual 
 Character. Compt. Rend. Trav. Lab. Carlsberg, 1920, vol. 
 xiv. No. 8, pp. 12, pis. 5. 
 
 ScHGFiELD, R. Inheritance of a Bilobed Ear. Journ. Hered , 
 191 7, viii. 517-8, figs. 2. 
 Inheritance of Webbed Toes. Journ. Hered., 1922, xii. 400- 1 . 
 
 ScHRGEDER. Eutstehuug uud Vererbung von Missbildungen an 
 der Hand eines Hypodactyliestammbaumes. Monatsschr . 
 Geburtshilfe Gyndkol., 1918, xlviii. 210-222, pis. 3, figs. 7 
 (From Bot. Abstr., x. 86, 1922.) 
 
270 HEREDITY AND EUGENICS 
 
 ScHULTZ, A. H. Zygodactyly and its Inheritance. Jouvn. 
 Hered., 1922, xiii. 113-117, figs. 7. 
 
 Schuster, Edgar, and Elderton, Ethel. The Inheritance of 
 Mental Ability. Galton Laboratory Memoirs — I. 1907. 
 
 Seashore, C. E. The Inheritance of Musical Talent. Musical 
 Quarterly, 1920, vi. 586-598. 
 
 Sedgwick, William. On Sexual Limitation in Hereditary 
 Disease. Brit, and Foreign Med.-Chirurg. Review, 1861, 
 xxvii. 477-489; xxviii. 198-214. 
 On the Influence of Sex in Hereditary Disease. Brit, and 
 Foreign Med.-Chirurg. Review, 1863, xxxi. 445-478; 
 xxxii. 159-197. 
 
 Seligman, C. G. a Note on Albinism, with Special Reference to 
 its Racial Characteristics among Melanesians and Poly- 
 nesians. Lancet, September 20, 1902, figs. 4. 
 Congenital Cretinism in Calves. Trans. Path. Soc. Lond., 
 1904, Iv. 1-20, figs. 6. 
 
 Sessions, Mina A. Feebleminded in Ohio. Journ. Hered., 191 7, 
 viii. 291-298, figs. 5. 
 
 Shattock, S. G., and Seligman, C. G. An Example of True 
 Hermaphroditism in the Domestic Fowl, with Remarks on 
 the Phenomenon of Allopterotism. Trans. Path. Soc. Lond., 
 1906, Ivii. 69-109, figs. 9, pi. I. 
 
 Siemens, H. W. Einfiihrung in die allgemeine Konstitutions- und 
 Vererbungs-pathologie. 192 1. Berlin: Springer. Pp. 229, 
 figs. 80. 
 
 Simpson, Q. I., and Castle, W. E. A Family of Spotted Negroes, 
 Amer. Nat., 1913, xlvii. 50-56, figs. 4. 
 
 Spillman, W. J. History and Peculiarities of the Mule-Foot Hog. 
 
 Amer. Breeders' Mag., 1910, v. 178-182. 
 
 Stand LEY, Paul C. Albinism in the Black Bear. Science, 192 1. 
 
 liv. 74. 
 Stannus, H. S. Anomalies of Pigmentation among Natives of 
 Nyasaland. Biometrika, 191 3, ix. 333-365, pis. 10. 
 Congenital Anomalies in a Native African Race. Biometrika, 
 1914, X. 1-24, pis. 6. 
 
 Stanton, Hazel M. The Inheritance of Specific Musical Capa- 
 cities. Eugenics Record Ofiice, Bull. No. 22, 1922 (from 
 - Psych. Monographs, Princeton, xxxi. 157-204). 
 
 Stieve, H. tjber Hyperphalangie des Daumens. Anat. Anz., 
 
 1916, xlviii. 565-581, fig. I. 
 St. John, Harold. Sable Island, with a Catalogue of its Vascular 
 
 Plants. Proc. Boston Nat. Hist. Soc, 1921, xxxvi. 1-103, pis. 2. 
 
BIBLIOGRAPHY OF PAPERS CITED 271 
 
 Stockard, C. R. The Artificial Production of Cyclopean Monsters. 
 Jonrn. Exptl. Zool., 1909, vi. 
 A Probable Explanation of Polyembryony in the Armadillo. 
 Amer. Nat., 1921, Iv. 62-68. 
 
 Storer, Rev. John. The Wild White Cattle of Great Britain 
 (New Edition). 1881. London. Pp. 384, figs. 12. 
 
 Stuckey, H. p. The Slit-Eyed People. Joiirn. Hered., 191 6, 
 
 vii. 147, pi. I. 
 Sullivan, Louis R. The " Samar " United Twins. Amer. Joiirn. 
 
 Phys. Anthrop., 1919, ii. 21-24, pl- i- 
 Sumner, F. B. Heredity, Environment, and Responsibility. 
 Bull. 10, Scripps Inst, for Biol. Research, 1921, pp. 12. 
 The Organism and its Environment. Scientific Monthly, 
 March, 1922, pp. 223-233. 
 
 Sumner, F. B., and Huestis, R. R. Bilateral Asymmetry in its 
 Relation to Certain Problems of Genetics. Genetics, 1921, vi. 
 445-485. figs. 5. 
 
 Swingle, W. W. Is there a Transformation of Sex in Frogs ? 
 Amer. Nat., 1922, Ivi. 193-210, pis. 2, figs. 2. 
 
 Terman, L. M. Adventures in Stupidity — A Partial Analysis 
 of the Intellectual Inferiority of a College Student. Sci. 
 Monthly, 1922, xiv. 24-40. 
 
 Thadani, K.T. A Toothless Type of Man. Journ. Hered., ig2J, 
 xii. 87-8. 
 
 Tupper, W. W., and Bartlett, H. H. A Comparison of the 
 Wood Structure of (Enothera stenomeres and its Tetraploid 
 Mutation gigas. Genetics, 1916, i. 177-184. 
 
 Uhlenhuth, E. Experimental Production of Gigantism by 
 feeding the Anterior Lobe of Hypophysis. Journ. Genl. 
 Physiol., 1 92 1, iu. 347-365. 
 The Effect of Iodine and lodothyrin on the Larvae of Sala- 
 manders — III. The Role of the Iodine in the Specific 
 Action of the Thyroid Hormone as tested in the Meta- 
 morphosis of the Axolotl Larvae. Biol. Bull., 1922, xlii. 
 143-152. figs. 3- 
 Urquhart, a. R. Insanity. " Treas. Human Inheritance," 1909, 
 
 Part III., pp. 61-69, pis. 2. 
 Usher, C. H. Histological Examination of an Adult Human 
 Albino's Eyeball, with a Note on :\Iesoblastic Pigmentation 
 in Foetal Eyes. Biometrika, 1920, xiii. 46-56, pis. 2. 
 Von Winiwarter, H. :^tudes sur la spermatogenese humaine 
 
 Arch, de Biol., 1912, xxvii. 91-189, pis. 6-7. 
 Warren, Howard C. Numerical Effects of Natural Selection 
 acting upon Mendelian Characters. Genetics, 1917. ^^- 5^5'^ ^ -• 
 
272 HEREDITY AND EUGENICS 
 
 Wegelin, Carl. U'ber eine erbliche Missbildung des kleinen 
 Fingers. Berlin Klin. Wochenschr., 191 7, liv. No. 12; 
 Review Zeits. f. Ahst. u. Vererb., 1919, xx. 159. 
 
 Whitehouse, Herbert. A Diagnosis of Degeneracy from Con- 
 ditions revealed by a Field Study of Green Lake County 
 (Wisconsin). Journ. Amer. Law and Criminology, May, 
 1918, pp. 47-79- 
 WiEMAN, H. L. Chromosomes in Man. Amer. Journ. Anat., 
 1913, xiv. 461-471, figs. 10. 
 The Chromosomes of Human Spermatocytes. Amer. Journ 
 Anat., 1917, xxi. 1-21, pis. 4. 
 
 Wilder, H. H. Duplicate Twins and Double Monsters. Amer. 
 Journ. Anat., 1904, iii. 387-472. 
 Palm and Sole Studies. Biol. Bull., 1916, xxx. 135-172^ 
 211-252, figs. 42. 
 
 WiNDLE, C. A. Teratological Evidence as to the Heredity of 
 Acquired Conditions. Journ. Linn. Sac, Zool., 1891, 
 xxiii. 448-502. 
 A Note on Identical Malformations in Twins. Journ. Anat. 
 and Physiol., 1892, xxvi. 295-299. 
 
 WiNGE, O. On a Partial Sex-linked Inheritance of Eye Colour 
 in Man. Compt. Rend. Lab. Carlsberg, 1921, vol. xiv. No. 
 12, pp. 23. 
 
 WiTscHi, Emil. Development of Gonads and Transformation of 
 Sex in the Frog. Amer. Nat., 1921, Iv. 529-538, figs. 7. 
 
 Woods, F. A. What is there in Physiognomy ? Journ. Hered., 
 1922, xii. 301-318, figs. 7. 
 
 Wriedt, Chr. Albinisme i hester. Borket, hvitborket og gule. 
 Tidsskr. Norske Landbr., 191 8, 396-406. 
 iJber die Vererbung von Ohrenlange beim Schafe. Zeitschr. 
 
 f. Abst. u. Vererb., 1919, xx. 262-3. 
 Breeding Earless Sheep. Journ. Hered., 192 1, xii. 56. 
 
 Wright, Sewall. On the Nature of Size Factors. Genetics, 
 1918, iii. 367-374- 
 
 Wright, Sewall, and Lewis, Paul A. Factors in the Resistance 
 of Guinea-Pigs to Tuberculosis, with Special Regard to In- 
 breeding and Heredity. Amer. Nat., 192 1, Iv. 20-50. 
 
 Yearsley, Macleod. Can Acquired Deafness lead to Congenital 
 Deafness ? Journ. Laryngol., Rhinol., and Otol., 1920, xxxv. 
 270-1. 
 
 Yerkes, R. M. The Heredity of Wildness and Savageness in 
 Rats. Journ. An. Behaviour, 1913, iii. 286-296. 
 
 Zeleny, Charles. The Relative Numbers of Twins and Triplets. 
 Science, 192 1, liii. 262-3. 
 
INDEX 
 
 Aberystwith, ioi 
 
 Abietineae, polyembryony in, 179 
 
 Ability, and brain, 234 
 
 inheritance of, 145, 147, 148, 
 170, 222 
 Abnormal segmentation of fingers, 
 
 Abnormalities, inheritance of, 75, 
 76, 106, 116, 125, 127, 129, 
 142, 158, 174 
 occurrence of, 93, 204 
 Abortions in primitive races, 241 
 Absence of external ear, 133, 
 
 134 
 of patella, 136 
 
 Acanthosicyos horrida, 227 
 Achondroplasia, 34, 35, 39, 40, 
 
 126, 215 
 Acromegaly, 211, 216 
 Addison's disease, 212 
 Adkinson, June, 138 
 Adrenal capsules. See Supra- 
 renal capsules 
 Adrenalin, 217, 218, 220 
 Agriculture, 241, 242 
 Ailments of twins, 188 
 Aino of Japan, 54 
 Albert, Henry, 93 
 Albinoes, eyeballs of, 44 
 Albinism, change in hereditary 
 behaviour of, 70 
 
 frequency of, 65 
 
 in animals, 68 
 
 in cattle, 69 
 
 in guinea-pigs, 125 
 
 inheritance of, 57, 6y, no 
 
 in horses, 71 
 
 in rabbits, 125 
 Albinotics, 58, 65, 68 
 Alcohol, effect on germ cells, 92 
 Alcoholism, 142, 149, 153, 235 
 Alexander, 103 
 Alkaptonuria, no 
 Allelomorphs, multiple, 27 
 
 Alpine race, 212, 231 
 Amaurosis, 117, 120, 142, 158 
 Amblystoma, 41 
 American army intelligence tests, 
 
 234 
 Americans in crosses, 230 
 Amerindians, 10 1 
 Amphibians, hermaphrodites in, 
 
 133 
 Amphioxus, 210 
 
 Analysis of the mind, 146 
 
 Ancestral inheritance in man, 209 
 
 Ancon sheep, 40 
 
 Anencephali, 193 
 
 Angioneurotic oedema, 127 
 
 Angora hair, in guinea-pigs, 1 5 
 
 in other animals, 125 
 
 Animal behaviour, 165 
 
 Aniridia, 116, 120, 130 
 
 Anodont condition, 71 
 
 Anthropoid apes, behaviour of, 
 
 165 
 
 hormones in, 217 
 
 Antibody, 144 
 
 Antisocial behaviour, 163 
 
 Apache Indians, left-handedness 
 
 in, 72 
 
 Apes, placenta of, 1 78 
 
 Apogamy, 209 
 
 Apprenticeships, 244 
 
 Arable land in the United States, 
 
 245 
 Arabs, Polydactyly in, loi 
 
 Arboreal ancestry of man, 17S 
 
 Arctomys, 68 
 
 Arey, L. B., 199 
 
 Argentine, crosses in, 230 
 
 Aristocratic society, 221 
 
 Aristotle, 98 
 
 Arizona, 39, 65 
 
 Armadillo, scutes of, 181, 19^ 
 I young of, 176, 177, 17S, iSi, 
 
 182, 199, 200 
 
 Arrested development, 89, i 54 
 
 Arsenic, in thyroxin, 214 
 1 Artificial selection, 175 
 
 273 t8 
 
2 74 
 
 HEREDITY AND EUGENICS 
 
 Artistic ability, inheritance of, 1 70 
 
 evolution of, 247 
 Assortative mating, 139, 208 
 Astlima, inheritance of, 138, 188 
 Astigmatism, inheritance of, 116 
 Ataxia, in pigeons, 109, 167 
 Ateliosis, 34, 35, 39 
 Atrichosis, 56 
 Atwood, E. S., loi 
 Aurignatian man, 247 
 Australian aborigines, mentality 
 of, 225 
 stature of, 28 
 Austria, albinoes in, 65 
 Austrians in crosses, 230 
 Autonomic bodily functions, 166 
 Auximones, 42 
 
 B 
 
 Bach family, 1 70 
 Bailey, P. G., 31 
 Baker, Henry, 121 
 Balanced lethal factors, 209 
 Baldness, inheritance of, 25 
 Baldwin, 'ji 
 
 Ballowitz, E., loi, 103, 104 
 Banta, A. M., 132 
 Bantams, silver seabright, 31 
 Bantus, abnormalities in, 71 
 crosses with Boers, 228 
 Barfurth, 96 
 Barrington, Amy, 34 
 Bartlett, H. H., 42 
 Bateson, W., 75, 84, 95, 97, 98, 
 
 no, 113, 115, 124, 205 
 Bauhin, 131 
 Beagle voyage, 169 
 Bean, R. B., 53 
 Beans, bush varieties, 35 • 
 
 pure lines in, 221 
 Bear, albino, 69 
 Beavers, albino, 68 
 Beel^y, A. L., 72, -ji, 74 
 Behaviourism, 165 
 Belgium, population in, 243 
 Bergen, Norway, 48 
 Bergman, E., 108 
 Beri-beri, 42 
 
 Berman, Louis, 215, 218, 219 
 Bermuda, 52 
 Bernstein, C., 133 
 Bilateral asymmetry, inheritance 
 
 of, 191 
 Bimanual synergia, 136 
 Binet- Simon, tests, T46, 149, 154, 
 
 232, 234 ' 
 
 Biolobed ear, inheritance of, 135 
 Biometry, 9 
 
 Biovular twins, 191. See Twins 
 Bipinnaria larva, 179 
 
 embryology of, 177 
 Birds, eye colours in, 50, 5 1 
 Birth-rates, 205, 237, 238, 239, 
 
 240, 244 
 Blacker and Lawrence, 131 
 Blastocyst, of armadillo, 177 
 
 of deer, 178 
 Blastogenic variation, 181 
 Blazek twins, 1 79 
 Bleeders. See Haemophilia 
 Blending inheritance, 167, 213, 
 
 223 
 Blindness, hereditary. See Amau- 
 rosis 
 Blood system, peculiarities in, 137 
 Blood transfusion, 129 
 Blue eyes in Nordic race, 2 1 2 
 inheritance of, 45 
 in the tropics, 207 
 sclerotics, inheritance of, 142 
 Boas, H. M., 44 
 Boas, J. E. v., 96 
 Bodily effects of anger, 2 1 8 
 Boers, crosses of, 229 
 Bohemia, 179 
 Bokhara, sheep of, 135 
 Boleyn, Anne, loi, 102 
 Bollenbach family, 5 5 
 Bonavia, E., 93 
 Bond, C. J., 49, 50, 54, 95 
 Bonnevie, K., 96, 194 
 Borneo, 103 
 Boston, 39, 40 
 Bottomley, W. B., 42 
 Bovidffi, 224 
 Bowditch, H., 113 
 Brachycephalic skulls, 212 
 Brachycephaly, proopic, 126, 216 
 Brachydactyly, 9, 10, 11, 12, 75, 
 78, 84, 89, 104, 174, 197 
 in fowls, 92 
 Brachyphalangy, 90, 91 
 Brachysm, 35 
 Brains of twins, 186 
 
 of ataxic pigeons, 109 
 of negro, 233 
 Branchial fistula, 130 
 Brazil, 65, 237 
 Briggs, H. H., 116 
 Brightness and intelligence, i 57 
 British Columbia, Indians of, 65 
 Brittle bones, inheritance of, 75, 
 
 142 
 Bronchial asthma, inheritance of, 
 
 138, 188 
 Bronchitis, 138 
 Brooks, W. K., 7 
 
INDEX 
 
 275 
 
 Bryant, F. A., 141 
 
 Bryn, 45 
 
 Buenos Ayres, 230 
 
 Bulloch, W., IK), 114, 127, 128, 
 
 131 
 Bullosa, inheritance of, 128 
 
 Bury St. Edmunds, 61 
 
 Bush varieties of vegetables, 35 
 
 Cacogenic matings, 160 
 Caesar in Gaul, 239 
 
 personality of, 220 
 Caesar's horse, 96, 97 
 CaesarotOmy, 34 
 Calcar loop, inheritance of, 176 
 Calliphora eryihrocephala, 114 
 Cambridge, 94 
 California, 39, 146, 157, 178 
 Cancer, 123, 140, 141 
 Canidae, variation in, 125 
 Cannon, W. B., 217, 218 
 Cape Cod, 65 
 Capion, Abbe, 1 14 
 Carlisle, Anthony, 104 
 Carmichael, W. J., 98 
 Carnivora, multiple births in, 200 
 Carrel, 41 
 Carr Saunders, 225, 226, 240, 241, 
 
 242, 244, 247, 248, 249 
 Caste in society, 221 
 Castle, W. E., 28, 29, 30, 31, 32, 
 
 T,Z, 50, 63, 94. i6s 
 Cataract, 75, no, m, 116 
 Catlin, 65 
 
 Caton, Dr. John D., 39 
 Cats, on Sable Island, 37 
 
 Polydactyly in, 93 
 Cattle, albino. 69 
 
 cancer of eye in, 140 
 
 cataract in, in 
 
 cretins in, 216 
 
 interfertility in, 224 
 
 intoxication by pampas grass, 
 167 
 
 notch in ear of, 135 
 
 on Sable Island, 36, 37 
 
 Polydactyly in, 97 
 
 prognathism in, 125 
 
 sterility in, 196 
 
 twin births in, 198, 202, 203 
 Caucasians, loi, 212, 215, 231 
 Causes of death, 237 
 Celosia, fasciation in, 5 
 Cephalic index, inheritance of, 
 
 145 
 Cereals, seedlings of, 74, 175 
 
 Cerebro-spinal meningitis, 153 
 
 Character, defined, 148 
 
 and handwriting, 172 
 Chartley herd of cattle, 70 
 Cheek, one bigger, inherited, i 3O 
 Child, 4 
 Children of native races, 241, 243, 
 
 247 
 Chillingham cattle, 70 
 China, over-population in, 243 
 Chinese, hair of, 53 
 
 in crosses, 230 
 
 Polydactyly in, loi 
 
 ponies, 35, 126 
 
 race, 215 
 Chipmunks, albino, 68 
 Chiriguan Indians, 30 
 Choice of ideals, 148 
 Chorea, chronic, 156 
 Chorion, 199 
 
 fusion in cattle, 201, 202 
 Chromosomes, accessory, 20 
 
 and phylogeny, 21 
 
 explained, 13, 14, 15 
 
 in heredity, 16, 24 
 
 in man, 20, 22, 209, 210 
 
 of wheat, 22 
 
 sex, 19, 20 
 Civilization, causes of downfall, 
 238, 239 
 
 measure of, 205 
 Cladocera, sex intergrades in, 132 
 Clasping the hands, 74 
 Cleft palate, 1 30 
 Cleppie Bells, yj 
 Climate and population, 242 
 Clonic spasms in guinea pigs, 
 
 167 
 Coburn, C. A., 167 
 Cockayne, E. A., 61 
 Colborn, Zerah, 104 
 Cole, L. J., 112, 167 
 Colmar, 55 
 Coloboma, inheritance of, 116, 
 
 120, 130 
 Colour-blindness, 19, 22, 24, no, 
 112, 113, 114, 115 
 
 in Europe, 1 13 
 Colour varieties of mankind, 212 
 Columba livia, 50 
 
 cenas, 50 
 Compton, R. H., 72, 74, 75 
 Conard, H. S., 75 
 Conklin, E. G., 72 
 Constricted eyelids, 109 
 Convicts, British, 140 
 Cook, O. F., 35 
 Cornea, degeneration of, 116 
 
 nodular opacity of, 116 
 Corns, 5 
 
2^6 
 
 HEREDITY AND EUGENICS 
 
 Corpora lutea, 177, 178, 196, 200 
 
 quadrigemina, 211 
 Correlation-coefficients, 28, 30, 32, 
 
 139, 140, 145, 146, 185, 209 
 Cortez, 65 
 
 Cotton, short internodes in, 35 
 Cragg, E., 90 
 
 Cranial capacity of early man, 246 
 Cretin, babies, 216 
 
 cattle, 216, 217 
 Crew, F . A . E . , sex of frogs, 132 
 Criminals and inheritance, 163 
 
 classification of, 184 
 
 feebleminded, 149 
 Crooked little finger, 193 
 Cross-bred races, 222, 229 
 Crossing, and evolution, 223 
 
 between races, 221, 225, 226, 
 227, 228, 229, 232, 233, 236 
 Cuba, 99 
 Cumberland, 113 
 Cunier, F., 118 
 Cunningham, J. D., 72 
 Curled hair, 53, 126, 127 
 Cushing, Harvey, 88, 89 
 Cuvier, 1 14 
 Cyclopia, 4, 193 
 Cytolysin, 144 
 
 D 
 
 Dachshund, 40, 126, 215 
 
 Daltonism, 112 
 
 Dampier, 65 
 
 Danforth, C. H., 92, iii, 180 
 
 Darien, 65 
 
 Darwin, C, 3, 54, 60, 99, 102, 129, 
 148, 149, 168, 169, 170, 
 193, 205, 220, 240, 241 
 Erasmus, 168 
 
 Daughters of Brigham Young, 143 
 
 Davenport, C. B., 27, 28, 29, 30, 
 35, 39, 41, 43, 52. 53, 58. 75, 
 95, 122, 123, 125, 141, 153, 157, 
 158, 162, 163, 194, 195, 196, 197, 
 200, 222, 235, 236 
 
 Deafness, 120 
 
 Deaf-mutism, inheritance of, 106, 
 107 
 
 Dean, Bashford, 68 
 
 Death, causes of, 237 
 rates, 237, 238, 243 
 
 Decay of teeth, 124 
 
 Decline in birth-rate, 244, 245 
 
 Deer, blastocyst of, 177, 178 
 
 Defectives, marriage of, 161 
 
 Deformities, origin of, 71 
 
 Dementia praecox, 156, 158 
 
 Democratic Societ^^ 221 
 
 Denmark, eye colour in, 45 
 
 Departement d'Isere, 104 
 Descent oj Man, 102, 241 
 Detlefson, J. A., 69, 98, iii 
 Development of the human mind , 
 
 225 
 Dexter Kerry cattle, 216 
 Diabetes insipidus, 128, 236 
 Differences between classes, 249 
 Differential birth-rate, 240, 249 
 Differentiation of tribes, 226, 227 
 Digital abnormalities, 76 
 Diploid chromosome numbers, 21 
 Disharmonies, physical, 222, 236 
 Dislocation of the lens of the eye, 
 
 130 
 Disposition in twins, 180, 189 
 Dizygotic twins, 192, 202 
 Dogs, coat colour in, 67, 69 
 
 eye colour in, 49 
 
 length of tail in, 68 
 
 pariah, 41 
 
 on Sable Island, ij 
 
 Polydactyly in, 93 
 
 prosopia in, 126, 215 
 
 turnspit, 41 
 
 variations in, 125 
 Dolichocephalic skulls, 212 
 Dominance, 24 
 
 variable, 55 
 Dominant factors, 174 
 Donitz, 125 
 
 Double monsters, 179, 181, 199 
 Double-yolked eggs, 203 
 Drawings of animals, 155 
 Drinkwater, H., 80, 81, 82, 83, 85, 
 
 86, 88, 90, 136, 170 
 Drosophila, 17, 20, 25, 48, 90, 100, 
 
 114, 132, 140, 196, 224 
 Ductless glands. See Endocrine 
 
 glands 
 Duerden, J. S., 25 
 Dugdale, 160 
 Duke Ernst the Iron, 124 
 Duncan, F. N., 89 
 Duplicate twins, 181, 182, 184, 
 
 186, 188 
 Dwarfness, inheritance of, 7 
 Dwarfs, human, 34, 35, 43, 44, 65, 
 212, 215, 216 
 
 trees, 36 
 
 varieties, 36 
 Dwight, Timothy, 40 
 Dynamometer and will power, i 55 
 
 Ear, bilobed, 135 
 
 conformation of, 25, 26 
 lobe fissure, 26 
 
INDEX 
 
 277 
 
 Ear, lobe, pitted, 135 
 notch in cattle, 135 
 pit, inherited, 136 
 Earl of Shrewsbury, 87 
 Early man, cave drawings of, 155 
 Ears of negroes, 236 
 
 small, in house mouse, 134 
 East, 159, ^45 
 East and Jones, 20 
 Edentates, 178 
 Edentulism, 130 
 Edwards family, 160 
 Eifect of body on mind, 166 
 Effects of adrenalin, 218 
 Elderton, Ethel M., 146, 184 
 Elimination of characters, 208, -209 
 
 of feeblemindedness, 169 
 Ellis Island, 232 
 Embleton, D., 76, ']'] 
 Embryonic budding, 176, 177, 178 
 
 191' 199 
 
 Emigration, effect of, 240 
 
 Endocrine glands, 153, 178, 210, 
 
 211, 213, 217, 218, 228 
 
 and personality, 219, 220 
 
 and physiognomy, 64, 
 
 142, 217 
 and temperament, 142 
 Endoderm and death, 237 
 England, 237 
 
 deaf mutes in, 107 
 population of, 244 
 and Wales, birth-rate of, 239 
 English in crosses, 228, 230, 231, 
 
 232 
 Enriques, Paolo, 114 
 Environment, 4, 5, 6, 145, 146, 
 190, 227 
 effect on character, 145 
 on wild horses, 38 
 Epidermolysis bullosa, 127 
 Epilepsy, 154, 155, 163, 164, 220, 
 
 235 
 and feeblemindedness, 158 
 
 Epiphyses in brachydactyly, 81 
 
 Epitarsus, 116 
 
 Eskimo, stature of, 28, 43 
 
 Estabrook, A. H., 149, 160 
 
 Eugenic action, 173 
 
 matings, 160 
 Eugenics, aims of, 204 
 Eunuchoid races, 2 1 5 
 Evening primroses, 206 
 Evolution and crossing, 223, 233 
 
 and isolation, 224 
 
 in man, 225, 226, 246, 248 
 
 of civilization, 247 
 
 of mentality, 152 
 Exogamy, 227 
 
 Expression in twins, 187 
 
 Eye colour, inheritance of, 25, 27, 
 
 44. 5S. H5. 187. 207, 
 229 
 primitive, 64 
 defects, 1 16, 130 
 Eyelids, constricted, un) 
 Eyes, absence of, 120 
 of negroes, 236 
 
 Facial types, 219, 224 
 Fackenheim, J., 97 
 Factors, dominant, 174 
 
 growth, 28, 7,1 
 
 inhibiting, 35 
 
 lethal, 90, 114, 140. 174, i(j6, 
 197, 209 
 
 multiple, 27, 33, 34, 39 
 Farabee, W. C, 78, 82 
 Farmer, J. B., 20 
 Fasciation of stems, 5 
 Fay, Edward A., 107 
 Fear and bodily changes, 2 1 7 
 Fecundity of man, 241, 243 
 Feeblemindedness and Paheo- 
 lithic man, 225 
 
 arrested development in, 235, 
 247 
 
 inheritance of, 17, 147, 149, 
 150, 154, 156, 157, i:;S, 161, 
 166 
 
 in pigeons, 167 
 
 in relation to insanity, 155 
 Feebleminded in United States, 
 152, 158, 159, 160, 232 
 
 reproduction in, 251 
 Femur, length in deer mouse, i^^ 
 Feral animals, 36, 38 
 Ferguson, G. O., 234 
 Fertilised eggs in hybrids, 16 
 Fildes, Paul, no, 114 
 Filipinos, hair of, 53, 54 
 Finger prints, 175, 176, 180, 1S2, 
 
 183 
 types of, 175, 184 
 Fischer, Eugen, 55, 56, 229 
 Fisher, R. A., 108 
 Fishes, cyclopean, 4 
 
 eggs of, 177 
 
 hermaphroditic, 133 
 Flexure of finger joint, 193 
 Flinders- Petrie, 221 
 Flower-size, inheritance of, ^3 
 Folker, H. H., 116 
 Formula for growth of population, 
 
 245 
 Formulae for ancestral influence, 
 
 210 
 
2/8 
 
 HEREDITY AND EUGENICS 
 
 Formulge for systems of breeding, 
 208 
 
 Fowls, brachydactyly in, 92 
 eye colour in, 50, 51 
 hermaphroditism in, 132 
 Polydactyly in, 93, 95, 97 
 
 Foxes on Sable Island, n 
 prognathism in, 1 2 5 
 
 France, 246 
 
 Frederick Wilhelm of Prussia, 43 
 
 Free-martins, 198, 200, 202 
 
 French in crosses, 231 
 
 Frequency of twins, 194 
 
 Freud, 165 
 
 Friedenthal, Hans, 54 
 
 Frobelius, 1 30 
 
 Frogs, change of sex in, 132 
 
 ■Functional inheritance, 144 
 
 Fusion of races, 223 
 
 Gaits in twins, 190 
 
 Gallic tribes, 239 
 
 Galton, Sir Francis, 2, 27, 149, 
 
 175, 184, 187, 188, 193, 209 
 Gamboge's Raleigh, 135 
 Garden peas, heredity in, 8 
 Gastropods, reversed symmetry 
 
 in, 72 
 Gastrula of armadillo, 177 
 Genius and ability, 222 
 
 and insanity, 155, 156 
 Georgia, 109 
 Germans in crosses, 230 
 German tribes, 239 
 Germany, 65, 137, 160, 246 
 
 birth-rate of, 239 
 Germ cells, 14 
 Germinal change, 5, 13 
 Germ plasm, 144, 156, 159, 209, 
 210, 217, 250 
 
 recessive characters in, 1 9 
 Gigantism, 41, 42, 43, loi, 212 
 Gilpin, J.B., 36, ^7^, Z^ 
 Glaucoma, 116 
 Gluteal prominences, 1 30 
 Goats and goitre, 215 
 
 breed in Kentucky, 166 
 
 on Sable Island, 37 
 Goddart, 149, 150, 152, 153, 155, 
 
 232 
 Goitre, 215 
 
 Goldsmith, W. M., 133 
 Gorilla and pituitary, 217 
 Goring, Chas., 139, 140 
 Gossage, A. M., 127 
 Gowen, John W., 202 
 Gower's disease, sex-linked, no 
 
 I Greece, downfall of, 238, 245 
 Greek race, 205 
 
 in crosses, 230 
 Grey hair, inheritance of, 25, 53 
 Growth curves, 32 
 
 of population, 245 
 
 hormones, 41 
 Guinea-pigs, coat colour in, 48, 
 
 125 
 eye colour in, 50 
 palsy in, 167 
 Polydactyly in, 93, 94 
 I resistance to tuberculosis in, 
 
 140 
 Guyer, M. F., 20, 154 
 Guyer and Smith, 144 
 Gynandromorphs, human, 131 
 
 H 
 
 Haddon, A. C, 223 
 Haecker, V., 124, 125 
 Haemophilia, no, 114 
 Haemorrhoids in negro troops, 
 
 235 
 Hag-fisher, albino, 68 
 
 Hair, absence of, 55 
 
 characters, 53, 54, 55, 214, 
 217 
 
 colour, 224 
 
 inheritance of, 25, 51, 53, 
 145, 187, 190, 229 
 
 distribution of, 54 
 Hairiness, 126 
 Hairy face, 55 
 Hallam, Colonel, 99 
 Hamburghs, gold-pencilled. 31 
 Hancock, Thomas, n 
 Handwriting, 108, 171, 172 
 
 in twins, 187, 189, 190 
 Hanna, G. D., 133 
 Hapsburg jaw, 88, 124 
 Hardy, 164, 208 
 Hare-lip. 130 
 Harman, N., 59, no, in 
 Harrison, 92 
 
 Hawaii, racial crossing in, 230 
 Hawkes, Onera A. M., 106 
 Hayden, C. C, 198 
 Hay fever, inheritance of, 138 
 Health, inheritance of, 145 
 Hemeralopia, 115 
 Hennig, 103 
 Heptadactyly, 102 
 Herbivora, multiple births in, 200 
 Heyeditayy Genius, 149 
 Heredity, 2, 4, 6, 8, 237, 251 
 
 defined, 7 
 
 limits of, 175 
 
INDEX 
 
 279 
 
 Hermaphroditism, 130, 132, 133, 
 
 193, 201 
 Hermaphroditismus masculinus, 
 
 193 
 Heron, 151 
 
 Heterochromidia iridis, 49, 61 
 
 Heterodactyly, 95 
 
 Heterosis, 29, 205, 206, 230, 231, 
 
 232 
 Heterozygous, characters redis- 
 tributed, 173 
 defined, 10 
 dominants, 16 
 Hexadactyly, 75, 93, 95, 102, 103, 
 
 104, 105, 193 
 Hill folk, 160 
 
 Hindu Amil community, 71 
 Hipparion-toes, 96 
 Hoffman, H., 158 
 Holden, Jane, 122 
 Holmes, S. J.,6i, 150, 152, 156,245 
 Homer, 38 
 Homozygous, defined, 1 1 
 
 condition in man, 192, 206 
 Honduras piebald, 59 
 Hooper, J. J., 166 
 Hope and French, 126 
 Hormones, 30, 33,41,42,201,210, 
 
 215, 216, 217, 219, 220 
 Home, J., 107 
 Hornlessness, 126 
 Horses, albino, 71 
 
 colouf of wild, 38 
 
 dwarf, 35 
 
 eye colour of, 49 
 
 inheritance in, 99 
 
 intoxication by pampas grass, 
 
 167 
 on Sable Island, ^6, ^y 
 Polydactyly in, 93, 96, 97 
 Horstmann, Elizabeth, 103 
 Hottentots, crosses of, 229 
 food of, 227 
 stature of, 43 
 women, 130 
 Hover, J. M., 142 
 Howe, Lucien, 94, 116 
 Huddart, Joseph, 113 
 Huestis, R. R., 33 
 Humours in the blood, 219 
 Humphreys, Col. David, 40 
 Hungarian immigrants, 232 
 Hunter, John, 63, 201 
 Huntingdon's chorea, 156 
 Hunting rights of primitive man, 
 
 227 
 Hurlin, R. G., 99, loi 
 Hurst, C. C, 44, 49, 51, 71, 75, 
 149, 167, 170 
 
 Huxley, 93 
 Huxley, J., 132 
 
 Hybridization in man, 223, 238 
 Hybrid origin of races, 223 
 
 races, 228, 229 
 
 vigour, 205, 206, 230, 232 
 
 walnuts, 205 
 Hydrocele, 193 
 Hyperdactyly, 10 1 
 Hyperkinetic temperaments, 162, 
 
 164 
 Hyperpituitary face, 220 
 Hypertrichosis, 130 
 Hypodactyly, 105 
 Hypophalangy, 90 
 Hypophysis, 41 
 Hypospadias, 130, 193 
 Hypothyroidism, 215, 216 
 Hypotrichosis, 128 
 Hysteria, 163, 164, 235 
 
 Ichthyosis, 117, 118, 122, 127 
 Idiocy in Jews, 142, 158 
 Idiots, 149, 153, 156, 157, 215 
 Illinois, 97 
 
 Illness in twins, 188, 189, 190 
 Imbeciles, 149, 154, 155, 156, 157 
 Immigrants in United States, 27,2, 
 
 236 
 Inbreeding, 140, 143, 206, 207, 
 
 208. 209, 223, 238 
 India, 41, 71, 243 
 Indians, American, stature of, 28, 
 
 30,43 
 crosses of, 231 
 horses of, 38, 223 
 lefthandedness in, J2 
 tribes of, 223, 226, 227 
 white, 65 
 Industry and population, 241, 242 
 Infanticide, 71, 238, 241, 243 
 Inge, Dean, 238, 244 
 Inheritance, 2 
 
 alternative, 7, 27, 99, 147, 
 
 148,205, 223, 229, 232 
 blended, 27, 52, 232 
 functional, 144 
 in horses, 99 
 in twins, 176, 179, i8u 
 Mendelian, 9 
 mental, 145, 149, 1O4, 1O5, 
 
 166,' 168, 170, 186 
 of ability, 145, 147, 148, 149, 
 
 250 
 of abnormalities, 9, 75, 76, 
 106, 116, 125. 127, 129, 130 
 of absence of external ear, 
 
 133. 134 
 
2 8o 
 
 HEREDITY AND EUGENICS 
 
 Inheritance of absence of patella, 
 136 
 of acquired characters, 5 
 of artistic ability, 1 70 
 of athletic power, 145 
 of auricular height, 145 
 of bilateral asymmetry, 191 
 of bilobed ear, 135 
 of bimanual synergia, 136 
 of branchial fistula, 1 30 
 of bronchial asthma, 1 38 
 of calcar loop, 1 76 
 of cancer, 140 
 of cephalic index, 145 
 of character, 147 
 of cheek, one large, i ^(^ 
 of cleft palate, 130 
 of clonic spasms in guinea- 
 pigs, 167 
 of coloboma, 116, 120, 130 
 of colour-blindness, 19, 22, 24, 
 
 110,112,113 
 of constricted eyelids, 109 
 of criminality, 163 
 of curliness of hair, 145 
 of differences in endocrine 
 
 glands, 142 
 of disposition, 147 
 of dwarfing, 34 
 of edentulism, 1 30 
 of effect of cytoly sin, 144 
 of eye colour, 145 
 of fingerprints, 175, 176, 180, 
 
 182, 183, 184 
 of gait, 3, 190 
 
 of gluteal prominences, 1 30 
 of hair colour, 145 
 of handwriting, 108, 145 
 of hare-lip, 130 
 of hay fever, 138 
 of hermaphroditism, 130, 131, 
 
 132, 133 
 of hypertrichosis, 1 30 
 of hypospadias, 1 30 
 of insanity, 155, 156 
 of iso-agglutinin reactions, 
 
 129 
 of Jewish physiognomy, 142 
 of luxation of femur, 1 30 
 of mathematical ability, 147, 
 
 149 
 of mental differences, 145,146, 
 
 147.236 
 of musical ability, 147, 149 
 of mutilations, 26 
 of neurofibromatosis, 141 
 of notch in ear of cattle, 135 
 of openings in parietal bones, 
 
 U3 
 
 Inheritance of peculiarities of the 
 blood system, 137 
 of personality, 220 
 of pitted ear-lobe, 135 
 of polydactylism, 76, 92, 93, 
 94, 96, 97, loi, .102, 103, 
 126, 130, 180 
 of polymastia, 129 
 of rudimentary ear-lobes, 133, 
 
 134 
 of savageness in rats, 167 
 of scute peculiarities in the 
 
 armadillo, 181 
 of size, 26-35 
 of stammering, 141 
 of strabismus, 115, 120, 130 
 of temperament, 147, 236 
 of tendency to blush, 3 
 of timidity in rats, 167 
 of tuberculosis, 139 
 of tumours, 140 
 of twinning, 178, 194 
 of warts on the hands, 123 
 of wildness in rats, 165, 166, 
 
 167 
 particulate, 27 
 sex-linked, 19, 23, 25, 47, 61, 
 
 no, 112, 114, 115, 116, 117, 
 
 118, 120, 122, 123, 124, 
 
 154, 163 
 
 through the Y- chromosome, 
 94, loi, 1 19, 210 
 Innocuous characters, 207 
 Insanity, 154, 155, 157, 166, 18S 
 Instincts in man, 165 
 Intelhgence, 157, 171, 190, 224, 
 
 233. 234, 243, 246, 248, 249 
 Intermarriage of strains, 222 
 Intersexes, 131,. 132, 193, 201 
 Interstitial tissue of the gonads, 
 
 211, 212 
 Intoxication in animals, 92, 167 
 Introduced animals on Sable 
 
 Island, ^y 
 Iodine, in thyroxin, 214 
 
 in water, 215 
 Iowa, 99 
 Ireland, 49 
 
 deaf-mutism in, 106, 107 
 
 over-population in, 243 
 Irish in crosses, 230 
 Iso-agglutinin reactions, 129 
 Isolation and origin of differences, 
 
 224, 226, 227, 238 
 Italians, in crosses, 230, 233 
 
 immigrants, 232 
 
 stature of, 30 
 Italy, pellagra in, 122 
 
 white cattle in, 71 
 
INDEX 
 
 281 
 
 Jamaica, 52 
 Japanese, Aino, 54 
 
 and modern science, 226, 248 
 
 dwarf trees, 36 
 
 in crosses, 230, 231 
 
 race, 2 1 5 
 Jaw appendages, 126 
 Jenks, A. E., 26, 135 
 Jennings, H. S., 208 
 Jewish race, 141 
 Jews, 142, 158, 232 
 Jones and Arnold, 167 
 
 and Mason, 1 1 1 
 Jordan, H. E., 53, 71, yi 
 Joseph, Wilham, 10 1 
 Jung, 165 
 
 K 
 
 Kaleia, Gratio, 103 
 
 KalHkaks, 160 
 
 Kalmucks, ears of, 1 34 
 
 Karakul sheep, 135 
 
 Kassowitz, 34 
 
 Keith, Sir Arthur, 211, 212, 213, 
 
 214, 215, 216, 217 
 Kempf, Edward J., 165, 168, 169 
 Kempton, J. H., 35 
 Kentucky, 43, 166 
 Keratosis, 5, 75, 121, 127 
 Key, Wilhelmine, 160, 162 
 Kindred, J. E., 136 
 Klebs, 131 
 
 Koch, Mathilda L., 109 
 Kiihn, J., 125 
 
 Lactation period in primitive 
 
 races, 241 
 Lambert, Edward, 120 
 Lane, W. C, 109 
 Languages of Indian tribes, 227 
 Laplanders, 231 
 Laughlin, H. H., 209, 210 
 Law of ancestral inheritance, 209 
 
 of diminishing returns, 241, 
 242 
 
 of Malthus, 240 
 
 of Nasse, 1 10 
 Lawrence, T. W. P., 131 
 Learmonth, J. R., 129 
 Lebistes reticulatus, 94 
 Le Compte family, 1 17 
 Left - handedness, frequency of, 
 72 
 
 inheritance of, 71, 90 
 
 measurement of, 73 
 Lemna minor, 42 
 
 Length of digits in foot, 106 
 
 Lenz, Fritz, 1 10 
 
 Lepidoptera, 64 
 
 Leporata, Francesco, 43 
 
 Lepra bacillus, 123 
 
 Leprosy, 123 
 
 Lepus variabilis, 69 
 
 Lethal factors, 90, 114, 140, 174, 
 
 196, 197, 209, 217 
 Leucoderma, 66 
 Lewis, T., 76, 77, 78. 84, 93. 140 
 LiUie, F. R., 201 
 Little, C. C, 67, 230 
 Little and Gibbons, 114 
 " Lobster claw," 75, 76, 91 
 Loeb, Leo, 140, 141 
 London, 55 
 
 Lort, Rev. Michael, 112 
 Louisiana, 63, 99 
 Love, A. G., 235 
 Love, J, K., 107 
 
 Lundborg, H., 106, 108, 158, 231 
 Lush, J. L., 135 
 Luxation of the femur, 1 30 
 Lynch, Clara J., 134 
 
 M 
 
 MacBride, E. W., 144, 178 
 MacCaughey, V., 230 
 MacDonald, James, 70 
 MacDougal, Wilham, 146, 147, 
 
 168, 248, 249, 250 
 Machin, John, 120 
 Mackinder, D., 90 
 McMullen, Geo., 78 
 Magdalenian man, 247 
 Maine, 1 10 
 
 Maize, brachysm in, 35 
 Malays, 215, 248 
 Malformations, inheritance of, 1 30 
 
 in twins, 192 
 Maltese family, 93, 103 
 Malthus, 240, 241, 242 
 Mameluco, 228 
 
 Mammals, variations in, 125, 126 
 Mandan Indians, hair of, 53 
 Mandibles of deer mouse, ^^ 
 Manic depressives, 158 
 Manner in twins, 187 
 Manson, J. S., 10 1 
 Manual education for negro, 235 
 for mentally defective, 
 150 
 Marchaud, 103 
 Marriage selection, 160 
 
 control of, 162, 244 
 Martin, P. J., 122 
 Maryport, 1 1 3 
 
282 
 
 HEREDITY AND EUGENICS 
 
 Massachusetts, 36, 40, 65, 94 
 Mathematical ability, inheritance 
 of, 147, 149 
 laws of inheritance, 207 
 Measuring scale of intelligence, 
 
 149 
 Medici, de, Catherine, 44 
 Mediterranean race, 2 1 2 
 Meiosis, defined, 15 
 Melancholia, 158 
 Melanism in Lepidoptera, 64 
 Melanogenesis, 53 
 Mendel, 8, 14, 17 
 
 Mendelian, dominant, 25, 60 75, 
 76, 78, 88, 89, 90, 103, 105, 
 109, no. III, 114, 117, 124, 
 126, 127, 128, 133, 135, 136, 
 141, 156, 208 
 inheritance, 9, 14, 17, 24, 48, 
 
 52, T2, 207 
 population, 208, 209 
 recessive, 106, 107, 108, 109, 
 no. III, 115, 122, 134, 138, 
 149, 150. 158, 167, 173.208, 
 217 
 Mental capacity of modern man, 
 225 
 characters, inheritance of, 
 145, 164, 166, 168, 170, 186, 
 188, 221 
 complexes, 165 
 defects, 154, 188 
 evolution, 226 
 instability in crosses, 231 
 tests for immigrants, 232 
 of negroes, 234 
 Mentality of man, 165 
 
 of negro, 234, 235, 247, 248 
 Menzies, Sir W., 98 
 Mesenchyme, hereditary inferiority 
 
 of, 142 
 Metchnikoff, 131 
 Mexico, 65 
 Mice, cancer in, 140 
 waltzing ,167 
 wildness in, 167 
 yellow, 196 
 Microcephaly, 133 
 Microphthalmus, 116, 120, 130 
 Migraine, 163 
 Migrations, 223, 226, 239 
 Miller. N., 62 
 Milroy. W. F.. 127 
 Minnesota, 69 
 
 Minor brachydactyly, 82, 88 
 Minutiae of finger prints, 175, 176, 
 
 183 
 Mirror-image patterns. 176. 179, 
 182 
 
 Mirror- writers, 73 
 Miscarriages, 196, 198 
 Miscegenation, 222, 233, 236, 239 
 Mivart, St. George, 125 
 Mixture of races, 223, 236 
 Mjoen.J. A., 231 
 Mohr, O. L., 89, 90, 91 
 Momentary blindness, 117 
 " Mongolian," 152, 153 
 Mongoloids, features of, 214, 215 
 
 pituitary of, 212, 214 
 
 stature of, 28 
 MoniUthrix, 128 
 Monkey, chromosomes of, 2 1 
 
 Polydactyly in, 93 
 Monomaniac twins, 188 
 Monozygotic twins, 191, 192, 199, 
 
 202 
 Montezuma, 65 
 Montgomery, 20 
 Montpelier, 114 
 Moore, 20 
 
 Mores and society, 163 
 Morgan, T. H., 196 
 Morons, 149, i5o,n^2, 154, 157 
 Mott, F. W., 158 
 Mouse, Californian deer, 33 
 
 house, mutation in, 1 34 
 Mousterian man, 225 
 Mulattoes, 52, 53, 234 
 Multiple births in man, 197, 200 
 
 factors, 27, I},, 34, 39, 167 
 Musical ability, inheritance of, 147, 
 
 149, 170, 171 
 Mutations, 13, 17, 38, 41, 64, 66. 
 68, 70, 75, Tj, 85, 95, 99, 
 109, III, 125. 134, 140, 151. 
 174, 175, 207, 217 
 
 following crossing, 59, 63 
 
 parallel, 125 
 
 sex-linked, 20 
 Myoclonus-epilepsy. 108, 158 
 Myopia, 115, 1 16 
 Myxoedema, 214 
 
 N 
 
 Nam family, 160 
 
 Napoleon, personality of. 220 
 
 Nasse, law of, no 
 
 Native races, 207 
 
 Natural selection, 175. 207, 209, 
 
 211, 240, 243, 246 
 Naval officers, heredity in, 164 
 Neanderthal skull, 216 
 Negrillo Akkas, 43 
 Negroes, brain of, 233 
 
 compared with whites, 235, 
 236 
 
INDEX 
 
 283 
 
 Negroes, crosses of, 233 
 features of, 214 
 hair and skin of, 52, 54, 59, 6^ 
 lefthandedness in, 72 
 mentality of, 152, 234, 247, 
 
 248 
 pituitary in, 212 
 Polydactyly in, 93, loi 
 Negro, troops in American army, 
 225 
 twins, 180 
 Nelson, 164 
 Neolithic races, 223 
 Nervous derangements, inherit- 
 ance of, 166, 167 
 system, differences inherited, 
 210, 220 
 of negroes, 235 
 Nettleship, E., 57, 61, no, 114, 
 
 116 
 Neuralgia, 235 
 Neurasthenia, 218, 220, 235 
 Neurofibromatosis, 141 
 Neurotic stocks, 156 
 Newman, H. H., 115, 119,176, 
 
 177, 178, 181, 199 
 New York, foreign born in, 236 
 
 sex-ratios in, 230 
 Nichols, 202 
 Nietzsche, 220 
 Night-blindness, 68, 75, 114, 115, 
 
 116, 189 
 Nilsson, M. P., 238 
 Nineveh, sculptures of, ^y 
 Nomadism, 162, 163 
 Nordic race, 141, 212, 231 
 Norfolk Islanders, 228 
 North Carolina, 43, 115 
 Norway, 90, 134, 141, 104 
 albinoes in, 65 
 deaf-mutes in, 106 
 eye colour in, 45, 48 
 Polydactyly in, 96 
 racial crossing in, 231 
 Nose-bleed, hereditary, 109 
 Notch in ear of cattle, 135, 203 
 Nougaret, Jean, 115 
 Nucleus, in mitosis, 13 
 Nyassaland, 59, 71 
 Nyctalopia, 117 
 Nystagmus, 1 16 
 
 O 
 
 Oats, bush varieties of, 35 
 Occipital meningocele, 193 
 Ocular defects in twins, 190 
 CEdema, angioneurotic, 127 
 
 persistent hereditary, 126, 
 127 
 
 GLnothera gi^as, 21 
 
 Lamarckiana, 21 
 
 bud colours in, 58 
 
 chromosome numbers in, 21 
 
 flower-size in, t^t^ 
 
 self-pollination in, 206 
 Ohio, 158, 197, 198 
 Openings in parietal bones, 133 
 Ophthalmia in twins, 188 
 Optic nerve, atrophy of, 116 
 Optimum density of population, 
 
 242, 243 
 Orang and thyroid, 2 1 7 
 Ordahl, G., 157 
 Organic social condition, 249 
 Organism, relation to environ- 
 ment, 6 
 
 development of, 14 
 Osborn, Dorothy, 25 
 Osteopsathyrosis, 75 
 Ostrich hybrids, 26 
 Otis, Arthur S., 157 
 Otosclerosis, 107 
 Ottawa, 39 
 
 Over-population, 243, 244 
 Oxford class lists, 146 
 
 Pain and bodily changes, 2 1 7 
 Painter, T. S., 21 
 Palaeolithic man, 151, 
 
 mental states of, 225, 
 226, 247, 248 
 races, 223, 225 
 Palm and sole patterns, 176 
 Palsy in guinea-pigs, 167 
 Pancreas, 2 1 1 
 Parathyroid glands, 2 1 i 
 Pariah dogs, 41 
 
 Parietal bones, conformation of 
 left, 193 
 openings in, 133 
 Parthenogenctic larvae, 178 
 Parthenon, 38 
 Patagonia, 38 
 
 population in, 242 
 Patella, absence of, 1 36 
 Patiria, 178 
 
 Patterson, J.T., 176, 177, 181, 199 
 Pearl, Raymond, 92, 198, 208, 
 
 229, 230, 237. 245 
 Pearson, Karl, 34, 35, 44, 52, 57, 
 
 58, 59, 60, 61, 64, 65, 66, 68. 77, 
 
 78, 139, 145, 146, 151, 153, 157. 
 
 171, 208, 209 
 Peas, bush varieties of, 35 
 Peculiarities of blood system, 137 
 Pekinese dogs, 69 
 
2 84 
 
 HEREDITY AND EUGENICS 
 
 Pellagra, 122, 123 
 
 Pelvic bones, length in deer mouse, 
 
 33 
 Pennsylvania, 79, 160, 161 
 Percy, Harry (Hotspur), 62 
 Peromyscus maniculatns, ^,3 
 Personality, 219, 221 
 Pfitzner, 10 1 
 Phaseolus vulgaris, 206 
 Phlegmatic temperaments, 162 
 Philippines, 180 
 Phocomelia, 193 
 Phrenology, 220 
 
 Piebaldism, 2>^, 50, 59, 61, 66, 6y 
 Pigeons, ataxia in, 109, 167 
 
 eye colour in, 50, 51 . 
 
 Polydactyly in, 95 
 
 twins in, 203 
 
 sex-ratio in crosses, 230 
 Pigs, abnormal race of, 99 
 
 corpora lutea in, 196 
 
 on Sable Island, 36, T)J 
 
 Polydactyly in, 97 
 
 syndactyly in, 98 
 Pima Indians, 72 
 Pineal gland, 142, 211 
 Pinus, polyembryony in, 179 
 Pitcairn Island, 228 
 Pit in skin, inheritance of, 1 36 
 Pitted ear-lobes, inheritance of, 
 
 135 
 Pittsburg school-children, 249 
 
 Pituitary and personality, 219 
 
 and size, 32, 35, 41, 43, 142, 
 211, 212 
 
 in gorilla, 217 
 Pituitocentric personalities, 220 
 Pityriasis versicolor, 123 
 Plane-tree in London, 205 
 Plate, 106 
 Pliny, 10 1 
 
 Pneumonia in negro troops, 235 
 Poa argent ina, 167 
 Pollen grains of rice, 1 5 
 Polydactjdy, 76, 92, 93, 94, 96, 97, 
 
 loi, 102, 103, 126, 130, 180 
 Polyembryony, in armadillo, 176, 
 177,178 
 
 in pines, 179 
 Polymastia, 102, 129 
 Polynesians, 43, 228 
 Polyuria, 128 
 Pond, Clara P., 10 1 
 Ponies, Chinese, 35, 126 
 
 Sable Island, 36 
 
 Shetland, 35, 36 
 Pontianak, Sultan of, 103 
 Poole, 65 
 Popenoe, Paul, 143, 164, 190 
 
 Population, 239, 240, 241, 244', 
 
 245, 246 
 " Porcupine man," 120 
 Porokeratosis, 128 
 Portuguese in crosses, 228, 23U 
 Poultry, Polydactyly in, 95 
 
 weight in, 31 
 Prepotency, 142, 143 
 Pribiloff Islands, 133 
 Priestley, Rev. Joseph, 1 1 3 
 Primitive culture, 225 
 
 man, 226, 227, 241, 243, 248 
 Primula, self sterility in, 224 
 Prognathism, 124, 125 
 Protozoa, 41 
 
 behaviour in, 165 
 Prussia, 199 
 
 Psychical characteristics, 146 
 Psychoanalysis, 166, 168, 170 
 Psychological analysis of the 
 
 mind, 147, 164 
 Psychology, 165, 168 
 Psychopathology, 165, 168 
 Pterygium, 116 
 Ptosis, 116 
 
 Puberty and stature, 4 1 
 Punnett, R. C, 9, 31, 159 
 Pure lines, 221 
 Pygopagous twins, 179 
 
 Q 
 
 Quadruplets in armadillo, 176, 
 181, 182 
 in man, 197, 200 
 Quantitative characters, 9, 213 
 Quantity in population, 245 
 Queen Charlotte Islands, Indians 
 of, 65 
 
 R 
 
 Rabbits, colour in, 48, 125 
 corpora lutea of, 1 96 
 eye colour in, 49 
 inheritance of size in, 29, 32 
 
 weight in, 31 
 injection of serum, 144 
 on Sable Island, ^7 
 Racial characters, 9 
 
 in man, 210, 211, 214, 217, 
 
 224 
 crosses, 213, 221, 224, 228, 
 229,230,231,232,233,236 
 Radiographs, 80, 85 
 Rage and bodily changes, 217 
 Raleigh, 164 
 Ramaley, F., 72 
 i Random mating, 208, 209 
 
INDEX 
 
 285 
 
 Rats, cancer in, 140 
 
 inheritance of wildness in, 
 165, 166 
 of waltzing in, 167 
 
 on Sable Island, i"] 
 Ray pattern eye colour, 49 
 Reaumur, 93, 103 
 Reduction divisions, 14, 15, 20, 24 
 Reed, L. J., 245 
 Reheboth hybrid people, 229 
 Reproductive overwork, 109 
 Reptiles, hermaphrodites in, 133 
 Resemblances, inheritance of, 24 
 
 in identical twins, 200 
 Retinitis pigmentosa, 116 
 Reversed symmetry, 72, 179 
 Rice hybrids, i 5 
 Rickets, 42 
 Riddle, O.. 109, 167 
 Ridge patterns of finger tips, 176, 
 180, 183 
 of palms and soles, 176, 
 179 
 Rieder, H., 91 
 Rischbieth, H., 34, 130 
 Ritzman, E. G., 134 
 Roberts, Elmer, 97, 98 
 Robins, albino, 68 
 Rodentia, multiple births in, 200 
 Roman rule, 238, 239 
 Rome, downfall of, 238, 245 
 Rontgen rays, 141 
 Rudimentary ear lobules, 1 34 
 Riidin, Ernst, i 58 
 Russians, immigrants, 232 
 
 in crosses, 230 
 
 Sable Island, 36, 38 
 
 wild horses on, 37 
 Salaman, R. N., 141, 142 
 Salamanders, 41, 42 
 Saltations, 126 
 Samar Island twins, 180 
 San Francisco, 39 
 Sano, F., 186 
 Santa Cruz Island, 39 
 Sarcoma, 140 
 
 Savageness, inheritance of, 167 
 Scandinavians, eye colour in, 64, 
 207 
 migrations of, 239 
 Schaefer, 218 
 Schmidt, Johs, 94 
 Schofield, R., 61, 94, 100, 135 
 Schroeder, 105 
 Schultz, A. H., 100 
 Schurmeier, 100 
 
 Schuster, E., 146 
 Schwcizcr, Marie, 103 
 Scotch in crosses, 230 
 stature of, 30, 43 
 Scotland, albinism in, 66 
 deaf-mutism in, 107 
 Scott, J., 112 
 Scurvy, 42 
 
 Scutes in armadillo, 181 
 Seals, hermaphroditism in, 133 
 Sebaceous scalp tumours, 123, 124 
 Sedgwick, William, 25, 49, 53, 66, 
 67, 76, 105, 117, 119, 120, 121, 
 122, 123, 124, 133, 134, 136, T55 
 Sedigiti, loi 
 
 Seedlings, right-handed, 74 
 Segmentary social condition, 248 
 Segregation of characters, 8, 13, 
 
 15, 213, 222, 229 
 Selection, 221, 223 
 
 against feeblemindedness, 159 
 Self-fertilisation, 208, 209 
 Self-pollination in CEnothera, 206 
 Self-sterility in plants, 224 
 Seligman, C. G., 102, 216 
 Sella turcica, 41 
 Serums, 26, 129, 144 
 Sessions, Mina A., 158 
 Sex chromosomes, 19, 132 
 in insects, 22 
 in man, 20, 22, 210 
 Sex-determination, 19, 22, 201 
 Sex-linked inheritance, 19, 20, 47, 
 61, no, 112, 114, 115, 116, 117, 
 118, 120, 122, 123. 124, 154, 
 163 
 Sex of twins, 195 
 Sex-ratio, in crosses, 229, 230 
 after war, 239 
 of twins, 202 
 Sexual selection, -jj , 207 
 Shattock, S. G., 132 
 Sheep, Ancon, 40 
 earless, 134 
 horns in, 61 
 intoxicated by pampas grass, 
 
 167 
 on Sable Island, 'S^ 
 thyroid, 214 
 twins, 194, 202 
 Shelley's face, 219 
 Shell-shock, 218 
 Shetland ponies, 35 
 Shifting of peoples, 223, 226, 239 
 Siaynanga syndaciyla, 100 
 Siamese, 2 1 q 
 Siemens, H."W., 158 
 Simpson, Q. I., 63 
 Sinclair, James, 70 
 
2 86 
 
 HEREDITY AND EUGENICS 
 
 Sinistro-dextral ratio, ^^ 
 
 Size factors, 29, 31 
 
 Size inheritance, 29, 30, 32, 34, 39 
 
 in plants, S3 
 Skiagraphs, 87, 10 1 
 Skin colour, 2, 4, 213, 224 
 
 and hormones, 212, 213, 
 
 217 
 inheritance of, 51, 52, 58, 
 
 64, 228, 229 
 of primitive man, 6^ 
 diseases in negroes, 235 
 secretions, 224 
 Slye, Maude, 140 
 Social dominance of white man, 
 
 215 
 ladder, 250 
 
 organization of early man, 
 
 226 
 
 Soudan, 43 
 
 Spanish in crosses, 230 
 
 Sparrows, albino, 68 
 
 Species, interfertility of, 224 
 
 Spermatogenesis, human, 20, 21, 
 
 22, 158 
 Spleen, enlarged, 128 
 Split hand and foot, y6, 78 
 Sports, 175 
 
 Spotting of skin, 58, 59, 63, 66, 67, 
 68,69 
 inheritance of, 69 
 Spread of culture, 227 
 Squinting. See Strabismus 
 Squirrels, albino, 68 
 Stability of savage populations, 
 
 227 
 Stammering, inheritance of, 141 
 Standard of living. 242, 243 
 Standley, Paul C, 69 
 Stannus, H. S., 58, 59, 71 
 Stanton, H. M., 171 
 Starfish, twin embryos in, 178 
 Stark, 140 
 
 State Eugenics Board, 162 
 Stature, 224 
 
 and hormones, 212, 217 
 inheritance of, 25, 27, 40, 41, 
 
 43 
 of brachydactyls, 82 
 
 of twins, 187, 189, 190 
 Sterility in free-martin, 201 
 
 in mankind, 196 
 
 interspecific, 224 
 Sternalis muscle, 193 
 Stieve, H., 92 
 Still-births, 230 
 St. John, Harold, 36 
 Stockard. C. R., 4, 176, 177 
 Stone Age, 225 
 
 Storer, Rev. John, 70 
 Strabismus, 115, 120, 130 
 Stratification of society, 221 
 Striping of flowers, 50, 58 
 Stuckey, H. P., 109 
 Stuttering, 74 
 St. Vitus' Dance, 156 
 Subpituitary face, 220 
 Suetonius, 97 
 Sulcus intertragicus, 26 
 Sullivan, L. R., 180 
 Sumner, F. B., 6, 33 
 Supernumerary, breasts, 102, 129 
 
 phalanx on thumbs, 92 
 Sweden, deaf-mutes in, 106 
 
 myoclonus epilepsy in, 108, 
 158 
 
 racial crossing in, 231 
 Swedes, stature of ,30 
 Swingle, W. W., 1 32 
 Symmetry in armadillo quad- 
 ruplets, 181 
 Syndactyly, 76 ,92, 93, 94, 98,99, 
 
 100, loi, 126 
 Syphilis, 153 
 
 Tahiti, 228 
 Taillessness, 126 
 Tallness, inheritance of, 7 
 Tamias, albino, 68 
 Tansley, A. G., 165 
 Tarpany horse, ^y 
 Tastes in twins, 189 
 Tatusia novemcincta, i jj 
 Taurae, 201 
 
 Teeth, early decay of, 124 
 Telangiectasis, multiple heredi- 
 tary, 127 
 Temperamental differences, 142, 
 
 143, 210, 248 
 Temperaments, 142, 162, 219, 236, 
 
 in animals, 165 
 Tendency to perform certain 
 
 tricks, 148 
 Tetraploid chromosome numbers, 
 
 21 
 Tetraploidy, 42 
 
 Texas, 21, 99, 115, 135, 176, 177 
 Thadani, K. T., 71 
 Thalassophilia, 164 
 Thessaly, 71 
 Thorndike, 198 
 
 Thumb joint, peculiarity in twins, 
 190 
 
 missing, 95 
 Thyroid, 142 
 
 and baldness, 25 
 
 and race, 211, 212, 213, 215 
 
INDEX 
 
 287 
 
 Thyroid, action of, 215, 216, 217 
 
 and personality, 219 
 
 and size, 32 
 
 cancer in, of rats, 140 
 
 composition of, 214 
 Thyroxin, 214, 216 
 Timidity, inheritance of, 167 
 Tissue cultures, 41 
 Titles, hereditary, 222 
 Tomatoes, bush varieties, 35 
 Toothache in twins, 188 
 Tooth anomalies, 55, 97, 102, 124, 
 
 130, 222, 236 
 Toothless families, 71 
 Tortoiseshell-coloured eyes, 49 
 Tradition, 205, 225, 226, 247, 248, 
 
 249 
 Transforrhation of sex, 131, 132 
 Tremor, hereditary, 108 
 Tribal differences, loss of, 223 
 Triplets, 197, 198, 199 
 Triploid chromosome numbers, 
 
 21 
 Trivial characters, 207 
 Troph oedema, 127 
 Tuberculosis, 123, 139 
 
 in crossed races, 231 
 
 in negroes, 235 
 Tumbling in pigeons, 167 
 Tumours from nerves, 141 
 
 in Drosophila, 140 
 
 in pituitary, 212 
 
 sebaceous, 123 
 Tupper, W, W., 42 
 Tiirdus migratorius, 68 
 Turkeys, wild, 39 
 Turnspit dog, 41 
 Twin embryos, production of, 177, 
 
 178 
 Twinning, influence of father on, 
 
 195 
 inheritance of, 194 
 Twins, 76, 146, 173, 175, 176, 178, 
 179, 180, 182-193 
 effect of separation, 1 90 
 in cattle, 198, 201, 202, 203 
 ■ in fishes, 177 
 origin of identical, 199 
 two types, 1 98 
 
 U 
 
 Uhlenhuth, E., 41 
 
 Unconscious repression, 165 
 
 Unilateral inheritance, 135, 136 
 
 Uniovular twins, 180 
 
 United States, 237, 250 
 
 Anglo-Saxons in, 245 
 arable land in, 245 
 
 United' States, births in, 200 
 
 crossingin, 230, 232,233, 
 
 236 
 feeblemindedness in, 152, 
 
 159 
 negro in, 233, 234 
 pellagra in, 122 
 population of, 245 
 
 Urquhart, A. R., 156 
 
 Usher, C. H., 44, 57, 61 
 
 Uxbridge, 91 
 
 ■ V 
 
 Variation, i , 5,6, 7 
 
 blastogenic, 181 
 
 continuity in, 27, i:;!, 17^, 
 184 
 
 discontinuity in, 27, 175 
 
 in Canidae, 125 
 
 in hybrid race, 229 
 
 in mammals, 125 
 
 in man, 21 1 
 Vegetables, bush varieties of, 35 
 
 run wild, 39 
 Venereal disease in negro troops, 
 
 235 
 Vermont, 104 
 
 Vigour from crossing, 29, 206, 223 
 
 in twins, 188 
 
 Vineland Institution, 1 50 
 
 Virginia, 89 
 
 Vitamines, 42 
 
 Voice in twins, 187, 189, 190 
 
 W 
 
 Walker, 20, 84, 88 
 Wallace, A. R., 100, 228, 240 
 Walnut hybrids, 205 
 Waltzing in mice, 167 
 Warren, H. C, 207 
 Warts on the hands, 123 
 
 inheritance of, 123 
 Washington, Booker T., 235 
 Weakening of a character by 
 
 exogamy, 104 
 Webbing. " See Syndactyly 
 Weeks, 158 
 Wegelin, Carl, 91 
 Weidenreich, 100 
 Weight in twins, 187, 189 
 Weinberg, 107, 108 
 Weismann, 144 
 West Indies, 94 
 Wheat, bush varieties of, 35 
 
 chromosomes of, 22 
 
 pure lines in, 221 
 Whisson, Rev. Mr., 112 
 Whitchurch, Sy 
 
288 
 
 HEREDITY AND EUGENICS 
 
 White cattle, 70, 71 
 
 forelock, 59, 60, 62 
 Wieman, H. L., 20 
 Wilder, H. H., 176, 179, 183 
 Wildness, inheritance of, 165, 166, 
 
 167 
 Wild horses, 37, 38 
 
 turkeys, 39 
 Wile, 10 1 
 Windle, C. A., 26, 43, 93, 129, 
 
 137, 192, 193 
 Wmge, O., 45, 46 
 Winiwarter, von, 20, 21, 22 
 Witschi, Emil, 132 
 Wolff. 10 1 
 
 Wolves, cancer in, 140 
 Woodchucks, albino, 68 
 Worcester, 40 
 
 Wriedt, Chr., 71, 89, 90, 134 
 Wyat, 102 
 
 Yapp, W. W., Ill 
 Y-chromosome, 19, 23, 94, 10 1, 
 
 1 19, 210 
 Yearsley, M., 107 
 Yellow and brown races, 225 
 Yerkes, R. M., 166, 167 
 Youatt, 99 
 Young, Brigham, 143 
 
 Zeleny, C, 199 
 Zobnomia, 168 
 Zygodactyly, 100 
 
 ftonnTY LIBURY 
 
 N. C. Slate ColUtt 
 
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ill 
 
 
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