WORKS OF G. C. WHIPPLE PUBLISHED BY JOHN WILEY & SONS. The Microscopy of Drinking-water. Second edition, revised. 8vo, xii+338 pages, figures in the: text and 19 full-page half-tones. Cloth, $3.50. The Value of Pure Water. Large i2mo, viii+ 84 pages. Cloth, $1.00, Typhoid Fever Its Causation, Transmission and Prevention. Introduction by WILLIAM T. SEDGWICK, Ph.D. Large 12010, xxxvi + 407 pages, 50 figures. Cloth, $3.00 net. THE MICROSCOPY OF DRINKING-WATER. BY GEORGE CHANDLER WHIPPED, Professor of Sanitary Engineering, Harvard University. SECOND EDITION, REVISED. SECOND THOUSAND. A >' : i'V*v%: h NEW YORK: JOHN WILEY & SONS. LONDON: CHAPMAN & HALL, LIMITED. 1911 Copyright, 1899, 1905, BY GEORGE CHANDLER WHIPPL SfOLOfir LIEMARY THE SCIENTIFIC PRF3S MMCRT DRUMMOND AND COMPANT BROOKLVN, N. V. DEDICATED TO MY FATHER, Josepb Ik. Mbipple, 891712 PREFACE. THIS book has a twofold purpose. It is intended primarily to serve as a guide to the water-analyst and the water-works engineer, describing the methods of micro- scopical examination, assisting in the identification of the common microscopic organisms found in drinking-water and interpreting the results in the light of environmental studies. Its second purpose is to stimulate a greater interest in the study of microscopic aquatic life and general limnology from the practical and economic standpoint. The work is elementary in character. Principles are stated and briefly illustrated, but no attempt is made to present even a summary of the great mass of data that has accumulated upon the subject during the last decade. The illustrations have been drawn largely from biological researches made at the laboratory of the Boston Water Works and from the reports of the Massachusetts State Board of Health. In considering them one should remember that the environ- mental conditions of the Massachusetts water-supplies are not universal, and that every water-supply must be studied from the standpoint of its own surroundings. So far as the micro- scopic organisms are concerned, however, the troubles that vi PREFA CE. they have caused in Massachusetts may be considered as typical of those experienced elsewhere. The descriptions of the organisms in Part II are necessarily brief and limited in number. The organisms chosen for description are those that are most common in the water- supplies of New England, and those that best illustrate the most important groups of microscopic animals and plants. In many cases whole families and even orders have been omitted, and some readers will doubtless look in vain for organisms that to them seem important. The omissions have been made advisedly and with the purpose of bringing the field of microscopic aquatic life within the scope of a practical and elementary survey. For the same reason the descriptions stop at the genus and no attempt has been made to describe species and varieties. Notwithstanding this it is believed that the illustrations and descriptions are complete enough to enable the general reader to obtain a true conception of the nature of the microscopic life in drinking-water and to appre- ciate its practical importance. To the student they must serve as a skeleton outline upon which to base more detailed study. The illustrations, for the greater part, have been drawn from living specimens or from photo-micrographs of living specimens, but some of them have been reproduced from published works of standard authority. Among these may be mentioned: Pelletan and Wolle on the Diatomaceae; Woll, Rabenhorst, and Cooke on the Chlorophyceae and Cyanophyceae ; Zopf on the Fungi; Leidy, Biitschli, and Kent on the Protozoa; Hudson and Goss on the Rotifera; Baird and Herrick on the Crustacea; Lankester on the Bryo- zoa; Potts on the Spongidae; and Griffith and Henry on miscellaneous organisms. PREFACE. vil This book has been prepared during the leisure moments of a busy year. Its completion has been made possible by the kind assistance of my present and former associates in the laboratories of the Boston and Brooklyn water-supply departments and of other esteemed friends, to all of whom I tender my sincere thanks. I desire also to acknowledge the valuable assistance of my wife, Mary R. Whipple, in revising the manuscript and correcting the proof. To many others I am indebted indirectly, and among them I cannot refrain from mentioning the names of Prof. Wm. T. Sedgwick of the Massachusetts Institute of Technology; Mr. Geo. W. Rafter, C.E., of Rochester, N. Y. ; and Mr. Desmond FitzGerald, C.E., formerly Superintendent of the Boston Water Works and now Engineer of the Sudbury Department of the Metro- politan Water Works. To Prof. Sedgwick and Mr. Rafter water-analysts are indebted for the most satisfactory practical method of microscopical examination of drinking-water yet devised, and Mr. FitzGerald will be remembered not only as an eminent engineer but as the founder and patron of the first municipal laboratory for biological water-analysis in this country. GEORGE CHANDLER WHIPPLE. NEW YORK, January, 1899. PREFACE TO THE SECOND EDITION. THE author has been much gratified to note the influence which the first edition of the " Microscopy of Drinking-water" has had in stimulating the study of the microscopic organisms from practical standpoints. The methods of examination there set forth appear to have stood the test of experience. They have recently received the official endorsement of the Committee on Standard Methods of Water Analysis of the Laboratory Section of the American Public Health Association. Results obtained by them have proved of great value in problems concerning the quality of water supplies, and in many instances they have been presented as testimony in court cases. No change of methods is here suggested. Since the publication of the first edition new applications of the methods of microscopical examination have been made. Processes for treating water supplies deleteriously affected with microscopic organisms have been studied with considerable care. Perhaps the most important of these has been the use of copper sulphate as an algicide. Recent developments have brought to light but few new organisms worth mentioning by reason of their harmful effects on water supplies, but many new instances of objectionable growths of the common organisms have been placed on record, and the importance of the subject is now appre- ciated as never before. In this second edition Part I has been revised and somewhat extended, but Part II remains practically unchanged. G. C. W. CONTENTS. PART I. CHAPTER I. HISTORICAL. PAGB Early Investigators in Europe and the United States. Cloth Method. Kean's Sand Method. SedgWick's Improvements. Sedgwick-Rafter Method. Recent Improvements. Plankton Studies in Europe and America i CHAPTER II. THE OBJECT OF THE MICROSCOPICAL EXAMINATION. Sanitary Analyses. Interpretation of Analyses. Use of Microscopical Examination in Indicating Sewage Contamination in Explaining the Chemical Analyses in Explaining the Turbidity and Odor of Waters in Showing the Source of Certain Waters in Studying the Food of Fishes 8 CHAPTER III. METHODS OF MICROSCOPICAL EXAMINATION. Sedgwick-Rafter Method. The Filter. Concentration. The Cell. The Microscope. Enumeration. Sources of Error. Precision of the Method. Results of Examination. The Standard Unit. Records. The Plankton Net Method. The Plankton Pump. The Planktonokrit . . 15 CHAPTER IV. MICROSCOPIC ORGANISMS IN WATER FROM DIFFERENT SOURCES. Rain-water. Ground -water. River-\vater. Canals. Raphidomonas in the Lynn Water. Pond -water. Filtered Water 41 ix X CONTENTS. CHAPTER V. LIMNOLOGY. PAGB Physical Properties of Water. Compressibility. Density. Mobility. Thermal Stratification. Diathermancy. Temperature of Lakes. Methods of Observation. Thermophone. Seasonal Variation of Tem- perature. Periods of Circulation. Periods of Stagnation. Thermo- cline. Classification of Lakes according to Temperature. Transmis- sion of Light by Water. Color of Water. Method of Determination. Seasonal Change of Color. Bleaching of Color by Sunlight. Turbidity of Water. Methods of Determination. Transparency of Water. Absorption of Light by Water 51 CHAPTER VI. GEOGRAPHICAL DISTRIBUTION OF MICROSCOPIC ORGANISMS. Common Organisms Classified according to the Frequency of Their Occur- rence. Statistics of Their Occurrence in Massachusetts Surface-water Supplies. Relation of Each Class of Organisms to the Sanitary Chemical Analyses. Effect of Oxygen and Carbonic Acid 81 CHAPTER VII. SEASONAL DISTRIBUTION OF MICROSCOPIC ORGANISMS. Seasonal Succession of Organisms. Spring and Autumnal Growths of Diatoms. Explanation of this Seasonal Distribution. Effect of Tem- perature. Effect of Light. Heliotropism. Food-material. Stagna- tion. Seasonal Distribution of Chlorophyceae, Cyanophyceae, Schizo- phycese, Fungi, Protozoa, Rotifera, Crustacea 98- CHAPTER VIII. HORIZONTAL AND VERTICAL DISTRIBUTION OF MICROSCOPIC ORGANISMS. Littoral Organisms. Limnetic Organisms. Effect of Winds and Currents on Horizontal Distribution. Conditions Affecting Vertical Distribution. Growth above the Thermocline. Effect of the Specific Gravity of Organisms. Peculiar Vertical Distribution of Mallomonas. Protozoa. Statistics of Vertical Distribution 1091 CHAPTER IX. ODORS IN WATER-SUPPLIES. The Senses of Taste and Odor. Odors Caused by Organic Matter. Odors of Decomposition. Odors Caused by Living Organisms. Character of Odoriferous Substances. Intensity of Odors. Characteristic Odors of Different Organisms. Extent to which Water-supplies are Afflicted with Odors. Cucumber Odor Not Caused by Fresh-water Sponge. Cucum- ber Odor in Boston Water n CONTENTS. XI CHAPTER X. STORAGE OF SURFACE-WATER. PAGB Clean Watersheds. Effect of Swamps. Anabaena in Cedar Swamp. Drainage of Swamps. Self-draining Watersheds. Self-draining Reser- voirs. Stagnation of Water in Deep Reservoirs. Lake Cochituate. Removal of Organic Matter from the Sides and Bottom of Reservoirs. Blow-off at the Bottom of Deep Reservoirs. Effect of Algae and Pro- tozoa on Bacteria 134 i CHAPTER XI. STORAGE OF GROUND-WATER. Ground-water to be Stored in the Dark. Growth of Organisms in Open Reservoirs. Storage of Surface-water and Ground-water Together. Asterionella in Brooklyn Water-supply. Storage of Impure Ground- Water. Crenothrix. Storage of Filtered Water 148 CHAPTER XII. METHODS OF TREATMENT. Aeration. Decarbonation , By-passes. House Filters. Slow Sand Filtra- tion. Mechanical Filtration. Springfield Experiments. Use of Copper Sulphate 153 CHAPTER XIII. GROWTH OF ORGANISMS IN WATER-PIPES. Effect of Pipes upon the Biology of Water. Temperature. Microscopic Organisms. Amorphous Matter. Bacteria. Effect of Water upon the Biology of Water-pipes. Hamburg. Rotterdam. Boston. Food of Organisms Dwelling in Pipes. Polyzoa. Fresh-water Sponge. Effect of Pipe-moss. Friction. Odor of Water. Paludicella in Brooklyn. . . . 160 PART II. CHAPTER XIV. CLASSIFICATION OF MICROSCOPIC ORGANISMS. Table of Classification CHAPTER XV. DIATOMACE&. Diatom Cells. Shape and Size. Markings. Cell-contents. External Secretions. Movement. Multiplication. Reproduction. Classifica- tion. Description of Genera ............................. ....... 173 xii CONTENTS. CHAPTER XVI. SCHIZOMYCETES. PAGB Schizophyceas. Schizomycetes. Characteristics. Description of Genera.. 192 CHAPTER XVII. CYANOPHYCE&. Characteristics. Description of Genera 195 CHAPTER XVIII. CHLOROPHYCE&. Algae. Chlorophyceae. Characteristics. Description of Genera 204 CHAPTER XIX. FUNGI. Characteristics. Description of Genera 221 CHAPTER XX. PROTOZOA. General Characteristics. The Protozoan Cell. Rhizopoda. Mastigo- phora. Infusoria. Description of Genera 225 CHAPTER XXI. ROT IF ERA. Characteristics. Description of Genera 248 CHAPTER XXII. CRUSTACEA. Characteristics. Description of Genera 256 CHAPTER XXIII. BRYOZOA (POLYZOA). Characteristics. Description of Genera. . . . 261 CHAPTER XXIV. SPONGID&. Characteristics. Description of Genera. 264. CONTENTS. Xlii CHAPTER XXV. MISCELLANEOUS ORGANISMS. PAGE Aquatic Plants. Aquatic Animals 267 APPENDIX A. COLLECTION OF SAMPLES 269 " B. TABLES AND FORMULAE ." 272 " C. BIBLIOGRAPHY 276 " D. GLOSSARY TO PART II 311 INDEX 315 THE MICROSCOPY OF DRINKING-WATER. PART I. CHAPTER I.. HISTORICAL/ THE study of the microscopic organisms in water dates back to the seventeenth century. With the invention of the compound microscope enthusiastic observers began to search ponds and streams and ditches for new and varied kinds of microscopic life. Among the pioneers in this field of Natural History were Hooke(i665), Leeuwenhoek (1675), Ray (1724), Hudson (1762), Miiller (1773), Dillwyn (1809), Kutzing (1834), Ehrenberg (1836), Dujardin (1841), and Stein (1849). It was not until 1850 that the study of the organisms in drinking-water was recognized as having a practical sanitary value. Dr. Hassall of London was the first to call attention to it. His method of procedure is unknown, but in all proba- bility it consisted of the examination of a few drops of the sediment collected in a deep vessel after allowing the water to stand for a longer or shorter interval. Radlkofer (1865) of Munich, and Cohn (1870), Hirt (1879) an< ^ Hulwa of Bres- lau, pursued the study and emphasized its importance, but they made no radical improvement in the method. In 1875 Dr. J. D. Macdonald of London suggested im- 2 THE MICROSCOPY OF DRINKING-WATER. provements in the sedimentation method, and made a rude attempt to obtain quantitative results by allowing the water to settle for a definite length of time, collecting the sediment on a removable glass disk or watch-glass at the bottom of a tall jar, and afterwards transferring this glass disk with its accumulated sediment to the stage of the microscope for direct examination. In 1884 Dr. H. C. Sorby of England attempted to obtain a more exact enumeration by passing a gallon of the sample through a fine sieve (200 meshes to an inch) and then washing, the collected organisms into a dish and in some way counting then. In America, ?m pott ant researches were made by Torrey, Vorce, Mills, Leeds, Potts, Nichols, Farlow, and others, but previous to 1888 the work was chiefly of a qualitative character. In 1887 the Massachusetts State Board of Health began a systematic examination of all the water-supplies of the State, and two years later the State Board of Health of Connecticut began a similar but less extensive series of examinations. In 1889 the Water Board of the City of Boston established a biological laboratory* at the Chestnut Hill Reservoir for the purpose of studying systematically the biological character of the various sources of supply. In 1893 a small laboratory was established by the Public Water Board of the City of Lynn, Mass. In 1897 Mt. Prospect Laboratory, connected with the Department of Water Supply of Brooklyn, N. Y., was equipped and put in operation. It is devoted to general water analysis, and the microscopical examination of water * For the first eight years of its existence it was conducted by the author under the general direction of Mr. Desmond FitzGerald, Super- intendent of the Western Division of the Water Works. HISTORICAL. 3 from the different sources of supply forms an important part of the routine work. After Brooklyn became a part of Greater New York, in 1898, the work of this laboratory was extended to cover all the water-supplies of the city, and branch laboratories were established on the Croton and Ridge- wood watersheds.* Similar biological work has been lately undertaken by health boards and water departments and by sanitary experts in other parts of the country. The reports of the various laboratories show that during the last fifteen years about one hundred thousand samples of water have been submitted to microscopical examination in the United States, and that this number is increasing at ti.e rate of about twelve thousand a year. The method of microscopical examination first used by the Massachusetts State Board of Health was that suggested by Mr. G. H. Parker. A piece of cotton cloth was tied firmly over the end of a glass funnel and 200 c.c. of the sam- ple were made to pass through it. The organisms were left as a deposit on the cloth. After this straining the cloth was removed and inverted over an ordinary microscopical slip. The organisms, together with a small quantity of water, were dislodged upon the slip by blowing downwards upon the cloth through a piece of glass tube. This method was useful, but it did not give accurate quantitative results. Mr. F. F. Forbes of Brookline, Mass., used a modification of the cloth method. The water was filtered as in Parker's method, but the neck of the funnel passed into a tank from which the air was exhausted by an aspirator. This hastened * From 1897 to 1904 these laboratories were under the direction of the author. 4 THE MICROSCOPY OF DRINKING-WATER. the filtration and allowed a larger amount of water to be filtered. The present method of examination was foreshadowed in the work of Mr. A. L. Kean. He filtered 100 c.c. of his samples through a small quantity of coarse sand placed at the bottom of a glass funnel and supported by a plug of wire gauze. After filtration the plug was removed and the sand with its contained organisms was washed into a watch-glass with I c.c. of water. This was stirred up to separate the organisms from the sand and a portion was transferred to a cell holding one cubic millimeter. From the number of organisms found in this cell the approximate number orig- inally present in the water could be obtained. This method has become known as the " sand method." In 1889 Prof. Wm. T. Sedgwick and Mr. Geo. W. Rafter made valuable improvements upon Kean's original idea. Prof. Sedgwick suggested the use of a cell much larger than that used by Kean, bounded by a brass rim and having an area of 1000 square millimeters ruled by a dividing engine into 1000 squares. The filtration was made as before, and the sand was washed into the cell with one or two cubic centimeters of water and distributed over the bottom. The cell was then placed under the microscope and the organisms counted in a certain number of the small squares. From this count the number of organisms present in the sample was estimated. A modification of this method was the one first used by the Connecticut State Board of Health. In the Connecticut method precipitated silica was used instead of sand for the filtering medium, and this was supported upon a pledget of absorbent cotton. Mr. Rafter's improvements consisted in the substitution of a ruled square in the ocular of the microscope for the ruling HISTORICAL. 5 upon the plate, in the separation of the sand from the organ- isms by decantation, in the use of a cell covered by a cover- glass and containing just one cubic centimeter, and in the use of a specially constructed mechanical stage. The Sedgwick- Rafter method has been modified somewhat by recent experi- menters,* but its essential character has not been changed. While sanitarians have been pursuing the study of the microscopic organisms because of their effect on the quality of water-supplies, other scientists have approached the subject from an entirely different standpoint. In the same year that the Massachusetts State Board of Health began its examination of the water-supplies of the State, Victor Hensen of the Uni- versity of Kiel, Germany, published a description of a new method of studying the minute floating organisms found in, lakes. To these organisms he gave the name " plankton, f" a collective word applied to all minute animals and plants that float free in the water and that are drifted about by waves and currents. Plants attached to the shore, and animals that possess strong powers of locomotion, are not included in the plankton, but fragments of shore plants, fish-eggs, young fish- fry, etc., are included. The term 4< plankton," however, may be said to be practically synonymous with the term, "microscopic organisms" of the sanitary biologist. * Dr. Gary N. Calkins substituted a perforated rubber stopper capped by a circle of bolting-cloth in place of the plug of wire gauze. Mr. D. D. Jackson suggested a cylindrical funnel in place of the ordinary flaring chemical funnel, and added an attachment at the lower end to control the concentration and prevent the sand from becoming dry. The author has graduated the funnels, designed a simple automatic concentrating device, and applied an aspirator to hasten the filtration. He also designed the ocu- lar micrometer and the record blank now used, and suggested the idea of a standard unit of size for estimating the organisms and amorphous matter. \ From the Greek planktos, wandering. 6 THE MICROSCOPY OF DRINKING-WATER. Hensen's method is radically different from the Sedgwick- Rafter method. The latter is strictly a laboratory process. The samples of water operated on are small; the concentra- tion of the organisms is made in the laboratory. Hensen devised a net by which the organisms could be concentrated in the field, so that only the collected material need be taken to the laboratory. Even before the publication of Hensen's paper, scientists on the Continent had become interested in the study of lakes. The early observations of Prof. F. A. Forel, of Morges, Switzer- land, on Lake Geneva were followed by the establishment of a Limnological Commission in Switzerland. Under its direction many valuable lines of physical and biological research were undertaken. This was followed in 1890 by an International Commission. From this time increased attention has been given to the biology of ponds and lakes. A biological station was established by Zacharias at Lake Plon in 1891, and a group of scientists have contributed important articles to its annual reports. Apstein at Kiel, Schroeter at Zurich, and many others have made extensive and valuable observations. Biological stations have multiplied during recent years, and the work is being extended to France, Italy, Austria, Denmark, Norway, and other countries. Similar investigations have been carried on in the United States. In 1893 Prof. J. E. Reighard, acting under the direction of the Michigan Fish Commission, made a biological study of Lake St. Clair. This was followed by an examination of Lake Michi- gan by Prof. Henry B. Ward, and by studies of the Crustacea in Lake Mendota by Prof. E. A. Birge, and in Green Lake by Prof. C. Dwight Marsh. Biological stations have been recently established by a number of western universities on or in the vicinity of the Great Lakes, and on the shores of smaller bodies of water. HISTORICAL. 7 Summer-school courses in planktology and general micro- scopic ecology are given at these stations. In 1900 an American Limnological Commission * was organized for the purpose of stimulating scientific work along the various lines of natural science involved, and of co-ordinating the work of various indi- viduals and institutions. This commission has not yet made a final report. For several years the late Prof. James I. Peck, acting under the direction of the U. S. Fish Commission, made important studies of the food of certain fishes, notably the menhaden. He used the Sedgwick- Rafter method instead of the plankton net for concentrating the microscopic organisms. In 1896 Dr. C. S. Dolley, of Philadelphia, suggested the use of the centrifugal machine for the purpose of concentrating the microscopic organisms. This "planktonokrit," as it is called, lias not been developed to completeness, but experiments by Field, Kofoid, and others showed that it is likely to prove of some value. Prof. H. B. Ward and Mr. Chas. Fordyce devised a " plank- ton pump" for collecting Crustacea and other plankton organ- isms at particular depths below the surface of a lake. In many ways this was a decided improvement over the plankton net. These special methods have more value for strictly scientific studies of the organisms than for the practical uses of the water analyst or the sanitary expert. * Consisting of Dr. E. A. Birge, Dr. H. B. Ward, Dr. Charles A. Kofoh.1 Dr. C. H. Eigenmen, and G. C. Whipple. CHAPTER II. THE OBJECT OF THE MICROSCOPICAL EXAMINATION. A COMPLETE sanitary examination of water, as conducted in modern laboratories, consists of four parts, the physical, the microscopical, the bacteriological, and the chemical. The data obtained are as follows: PHYSICAL EXAMINATION. Temperature Turbidity Color Odor, (both cold and hot). MICROSCOPICAL EXAMINATION. Number of microscopic organisms per c.c. Amount of inorganic matter, amorphous matter, etc. BACTERIOLOGICAL EXAMINATION. Number of bacteria per c.c. Presence of intestinal bac- teria or others associated with pollution. CHEMICAL EXAMINATION. Total Residue on Evaporation Loss on Ignition Fixed Solids Alkalinity Hardness Chlorine Iron Nitrogen as Albuminoid Ammonia Nitrogen as Free Ammonia Nitrogen as Nitrites Nitrogen as Nitrates - Total Organic Nitrogen (Kjeldahl Method) - Oxygen consumed Dissolved Oxygen Free Carbonic Acid, etc. (Some of these are of use only in special cases.) 8 THE OBJECT OF THE MICROSCOPICAL EXAMINATION. 9 Such an analysis is intended to show whether or not the water is of such a character that it would cause sickness if used for drinking; whether or not it contains anything that would render it distasteful or unpalatable; and whether or not it contains any ingredient that would make it unfit for laundry use or for general domestic or industrial purposes. Sanitary examinations are necessary also in studying the effect of processes of purification. Opinions regarding the function and value of sanitary water analyses have undergone a change in recent years. The numerical results of a single analysis of a sample of water, when considered by themselves, are now believed to have little intrinsic value. It has been found that the value of the analysis lies in its interpretation, and that each part of the analysis must be interpreted by comparison with all the other parts and in the light of exact knowledge of the environment of the water. The interpretation of an analysis is as much a matter of expert skill as is the making of the analysis itself. The physical, biological, and chemical examinations should be interlocking in their testimony, yet these different parts are to be given different weight in the study of different problems. For example, in the detection of pollution the chemical and bacterial examinations furnish the most infor- mation, in the study of the aesthetic qualities of a water the physical and microscopical examinations are most important, while in investigations concerning the value of a water for industrial purposes the chemical and physical examinations may alone suffice. The biological examination is concerned with the micro- organisms found in water. The term " micro-organisms," when used in its broadest and most literal significance, includes all organisms which are invisible or barely visible to the 10 THE MICROSCOPY Of DRINKING-WATER. naked eye. It is frequently used in a narrower sense, how- ever, as a synonym for bacteria. Using the word in its broad sense we may divide the micro-organisms found in water into two classes, as suggested by Prof. Sedgwick. Microscopic Organisms. MICRO-ORGANISMS. Organisms, either plants or ^ animals, invisible or barely visible to the naked eye. Not requiring special culture. Easily studied with the microscope. Microscopic in size, or slightly larger. Plants or animals. Bacteria I Orga ms ms.* Requiring special cultures. Difficultly studied with the microscope. Microscopic or sub-microscopic in size. Plants. This subdivision is convenient for the sanitarian as well as for the biologist, because the two classes of organisms affect water in different ways. With certain reservations it may be said that the bacteria make a water unsafe, the microscopic organisms make it unsavory. Microscopical Examination. The microscopical exam- ination of water may be considered in five aspects: i. As indicating sewage contamination. 2. As explaining the chemical analysis. 3. As explaining the cause of tur- bidity, odors, etc., in water. 4. As a means of identifying the source of a water (in special cases). 5. As a method of studying the food of fishes and other aquatic animals. I. The microscopical examination cannot be depended upon to determine the pathogenic qualities of a drinking- * The bacteria are not considered in this volume. The reader is referred to the numerous works on Bacteriology listed in the bibliography in Appendix C. THE OBJECT OF THE MICROSCOPICAL EXAMINATION. II water. To be sure, the germs of disease are microscopic bodies, and when artificially cultivated or when found in the tissues of the body they can be studied with microscopes of high power. But when scattered through a mass of water they cannot be detected by ordinary microscopical methods, because of their small size and because they are greatly outnumbered by the ordinary water bacteria. It is questionable whether they can be discovered even by methods of culture. Not only may water contain pathogenic bacteria without discovery, it may contain the ova or larvae of some of the endoparasites of man. It is probable that endoparasitic diseases are more common than has been generally supposed ; and while diseased pork, beef, etc., are the chief agencies of infection, it is known that water polluted by animal excrement may contain the ova or larvae of such endoparasites as Tcenia solium, Tcenia saginata, Bothriocephalus latus, Ascaris lumbri- coides, Trichocephalus dispar, and Anchylostomum duodenale. Infection of animals by the drinking of water contaminated by barnyard wastes has been several times recorded, while a microscopical examination of the water has seldom revealed the presence of the suspected ova or larvae. This is not because they are too minute to be detected, but because the quantity of water examined is necessarily too small. The microscopical examination cannot show definitely whether a water is polluted by sewage unless the pollution is excessive. It can, however, give evidence which, taken with the chemical and bacterial examinations, may establish the proof. A microscopical examination of sewage reveals few of the living organisms that are found ordinarily in water. Ciliated infusoria, such as Paramaecium and Trache- locerca; fungus forms, such as mold hyphae, Saprolegnia, JLeptomitus, Leptothrix, and Beggiatoa; and miscellaneous 12 THE MICROSCOPY OF DRINKING-WATER. objects, such as yeast-cells, starch-grains, fibres of wood and paper, fibres of muscle, epithelial cells, threads of silk, woolen, cotton and linen, insect scales, feather barbs, etc., may be observed. Most of these objects are foreign to unpolluted water, and their presence in a sample of water leads one to suspect its purity. Furthermore, there are other organisms, such as Euglena viridis, which live on decaying vegetable matter and which, though not found in sewage, are often associated with it in polluted water. Their presence in a sample is a cause of suspicion. These evidences, however, should be weighed only in connection with an environmental study and with the entire sanitary analysis. The common microscopic or- ganisms found in water are not themselves the cause of disease, nor does their presence indicate sewage pollution. 2. The chemical examination determines the amount of organic matter that a sample of water contains, but it does not determine the nature of it. As the character and condition of the organic matter is very important from the sanitary point of view, the microscopical examination gives valuable in- formation by showing not only whether the organic matter in suspension is vegetable or animal, but by determining whether it is made up of living organisms or of decomposing frag- ments. For example, the amount of albuminoid ammonia in suspension is sometimes so great that one might suspect that the water was polluted did the microscope not show that the high figure was due to a growth of some organism. Or in a series of samples from a reservoir it might be difficult to account for a sudden decrease in the nitrates or free am- monia were it not for the appearance of some microscopic organism that had appropriated the nitrogen as a part of its food. THE OBJECT OF THE MICROSCOPICAL EXAMINATION. 1 3 3. By far the most important service that the micro- scopical examination renders is that of explaining the cause of the taste and odor of a water and of its color, turbidity, and sediment. Several of the microscopic organisms give rise to objectionable odors in water and, when sufficiently abundant, have a marked influence on its color. They also make the water turbid and cause unsightly scums and sedi- ments to form. Upon all such matters related to the aesthetic qualities of a water the microscopical examination is almost the only means of obtaining reliable information. 4. The presence of certain microscopic organisms in water sometimes gives a clue to its origin. In this way the presence of surface-water in a well may be detected. In the Chicago Drainage Canal case the presence of Lake Michigan water in the St. Louis water-supply was indicated by finding in it certain diatom characteristics of the Lake Michigan water. 5. The microscopic organisms form the basis of the food- supply of fish and other aquatic animals. Sometimes the relation is a direct one; that is, the microscopic organisms are themselves eaten by fish. This was well illustrated by the late Prof. Peck. The menhaden swims with its mouth open, and is provided with a peculiar filtering apparatus by which the minute organisms are caught. It was found that the presence or absence of these fish from certain sections of the Massachusetts coast depends upon the abundance of microscopic life in the water, and also that the weight of fish of any particular length depends upon the quantity of this food material at hand. The relationship between the plankton and fish life is not always so direct. In many cases the fish feed upon Crustacea and insect larvae; the Crustacea feed upon the rotifera and protozoa; the rotifera and protozoa feed upon algae; while H THE MICROSCOPY OF DRINKING-WATER. the algae nourish themselves by the absorption of soluble in- organic substances. The interrelations between different organisms of the lower world, and between the organisms and their environ- ment are matters of intense scientific interest, and limnology and microscopical ecology are fast assuming important places in scientific literature. The physical condition of lakes, the currents, waves, temperature, and transparency of water, the chemistry of water, the life-history of organisms, and various bio-chemical and bio-physical problems are more and more attracting the attention of scientists and of water-works engineers. CHAPTER III. METHODS OF MICROSCOPICAL EXAMINATION. THE most important methods of microscopical examina- tion of water now in use are:. I. The Sedgwick-Rafter Method; 2. The Plankton Net Method; 3. The Plankton Pump Method; 4. The Planktonokrit. They differ chiefly in the manner of concentrating the organisms. I. THE SEDGWICK-RAFTER METHOD. ^ The Sedgwick-Rafter Method consists of the following processes: the filtration of a measured quantity of "the sample through a layer of sand upon which the organisms are de- tained; the separation of the organisms from the sand by washing with a small measured quantity of filtered or dis- tilled water and by decanting; the microscopical examination of a portion of the decanted fluid; the enumeration of the organisms found therein; and the calculation from this of the number of organisms in the sample of water examined. The essential parts of the apparatus are the filter, the decanta- tion-tubes, the cell, and the microscope with an ocular mi- crometer. The Filter. The sand may be supported upon a plug of rolled wire gauze at the bottom of an ordinary glass funnel 7 or 8 inches in diameter, but the cylindrical funnel shown in Fig. I is preferable. The inside diameter of this funnel at 15 i6 THE MICROSCOPY OF DRINKING-WATER. c.c, 500 450 400 350 300 250 200 150 100 the top is 2 inches; the distance from the top to the begin- ning of the slope is 9 inches; the length of the slope is about 3 inches; the length of the tube of small bore is 2^ inches, and its inside diameter is J inch. The capacity of the funnel is 500 c.c. The support for the sand consists of a perforated rubber stopper pressed tightly into the stem of the funnel and capped with a circle of fine silk bolting-cloth. The circles of bolting-cloth may be cut out with a wad-cutter. Their diameter should be a little less than that of the small end of the rubber stopper. When moist the cloth readily adheres to the stopper. The sand resting upon the platform thus prepared should have a depth of at least three fourths of an inch. The quality of the sand is important. Ordinary sand is unsatisfactory unless very thoroughly washed. Pure ground quartz is preferable. Its whiteness is a decided advantage. The necessary degree of fineness of the sand depends somewhat upon the character of the water to be filtered. A sand which will pass through a sieve having 60 meshes to an inch, but which will be retained by a sieve having 120 meshes, will be found satisfactory for most samples. Such a sand is UATED CYLIN- Described as a 60-120 sand. When very mi- DRICAL FUN- nute organisms are present a finer sand must be NEL USED IN used say a 6o~i4O sand. The sand used for THE SEDG- J WICK- RAFTER many years by the author had the following METHOD - composition: Size of sand-grains 40-60 60-80 80-100 100-120 120-140 Percentage by weight. . 20 20 38 18 4 = 100 f FIG. i. GRAD- METHODS OF MICROSCOPICAL EXAMINATION. I/ The filters may be arranged conveniently in a row against the laboratory wall as shown in Fig. 2. The filtered water FIG. 2. BATTERY OF FILTERS. SEDGWICK-RAFTER METHOD. may be collected in a sloping trough and carried to a sink, or jars may be placed under the separate funnels. A hinged covering-shelf above the filters is useful to prevent the access of dust. The sample to be filtered may be measured in a graduated cylinder or flask, or the filter-funnel itself may be graduated. The graduated filter-funnel is especially useful for field work, as it saves the necessity of carrying an additional graduate. The quantity of water that should be filtered depends upon the number of organisms and the amount of amorphous 1 8 THE MICROSCOPY OF DRINKING-WATER. matter present. An inspection of the sample will enable one to judge the proper amount. Ordinarily 1000 c.c. for a ground-water and 500 c.c, for a surface-water will be found satisfactory. In some cases 250 c.c. or even 100 c.c. of a surface-water will be found more convenient. When the water is poured into the funnel care should be taken not to disturb the sand more than is necessary, otherwise organ- isms are liable to be forced through the filter. The best plan is to make the sand compact by pouring in enough distilled water to just about fill the neck of the funnel and to pour in the measured sample before the sand has become uncovered. The filtration ordinarily takes place in about half an hour, but occasionally a sample is so rich in organisms and amorphous matter that the filter becomes clogged. It then becomes necessary to agitate the sand with a glass rod or to apply a suction to hasten the filtration. If the filters are located near running water an aspirator may be attached to the faucet and connected with the filter by a rubber tube having a glass connection that fits the bore of the rubber stopper. The use of the aspirator enables the filtration to be made in a few minutes, and not only effects a saving in time, but reduces the error caused by the organisms settling on the sloping surface of the funnel. Concentration. As a result of the filtration the organ- isms and whatever other suspended matter the sample con- tained will have been collected on the sand. When all the water has passed through and before the sand has become dry the rubber stopper is removed and the sand with its accumu- lated organisms is washed down into a wide test-tube by a measured quantity of filtered or distilled water delivered from a pipette or an automatic burette. The amount of water used for washing depends upon the number of organisms ME7^HODS OF MICROSCOPICAL EXAMINATION. collected on the sand. If 500 c.c. of the sample are filtered it is usually best to wash the sand with 5 c.c., thus concen- trating the organisms one hundred times. The amount of water filtered divided by the amount of water used in wash- ing the sand gives the " degree of concentration." The degree of concentration may vary from 10 to 500 according to the contents of the sample. Ordinarily it should be 50 or 100. By shaking the tes.t-tube the organisms will become detached from the sand-grains. If this is followed by a rapid decantation into a second test-tube most of the organisms, being lighter than the sand, will pass over with the decanted fluid, while the sand is left upon the walls of the first tube. To insure accuracy the sand should be washed a second time and the two decanted por- tions mixed together. If, for example, it is desired to concentrate a sample from 500 c.c. to 10 c.c. the sand should be washed twice with 5 c.c. and the two por- tions poured together. This will give a more accurate result than a single washing with 10 c.c. Mr. D. D. Jackson has suggested the use of an attachment at the lower end of tne funnel that automatically arrests the filtration as soon as the proper degree of concentration has been reached. This is illustrated in Fig. 3. The attachment fits over the rubber cork that supports the sand, uniting with the lower end of the neck of the filter by a ground joint. The FIG. 3. CONCEN- TRATING ATTACH MENT. SEDGWICK- RAFTER METHOD. 20 THE MICRO SCOP Y OF DRINKING- IV A TER. filtered water passes out of the open tube, and filtration stops as soon as the level of the water in the funnel has reached the elevation of the outlet-tube. This elevation is made such that the water remaining in the neck of the funnel is just sufficient to give the desired degree of concentration. It is necessary to allow for the volume of the sand and to use a definite amount of sand at each filtration. The 60-120 sandl holds about 50$ of water, and ordinarily about 2 c.c. of the sjand are used; hence an allowance of i c.c. must be made for tpe water held in the sand. Thus, if it is desired to con- centrate the organisms in 5 c.c. of water, the capacity from the bottom of the sand layer to the graduation on the stem of the funnel must be 6 c.c., i.e. 4 c.c. above the 2 c.c. of sand. After filtration the attachment is removed and a plug is inserted in the hole in the stopper to prevent loss of the concentrated fluid. The stop- per then may be removed and the sand and organisms allowed to fall into a wide test-tube, after which the pro- cess is carried on as described below. The same result has been accom- plished by the author in a simpler way. In place of the attachment with the ground-glass joint a glass tube FIG. 4. SIMPLE FORM OF CONCENTRATING ATTACH- bent twice at right angles may be in- MENT. SEDGWICK-RAFTER ser ted in the opening in the rubber METHOD. . T,. r~. e stopper as shown in Fig. 4. The fun- nel stem may be graduated and a series of bent tubes pro- vid.ed corresponding to different degrees of concentration. ^ f C.C. i - 5 - - 4 - \ \ - 3 - 1 - 2 - lee ftoUa V . of and _____ Ice. of water if ____-X METHODS OF MICROSCOPICAL EXAMINATION. 21 If the operator is watching the filtration even this form of attachment is unnecessary, as the filtration may be stopped by inserting a plug in the rubber stopper as soon as the level of the water has fallen to the desired point. This method of concentrating is to be preferred to the usual one described above in which the surface of the sand is allowed to become uncovered before the sand is washed into the test-tube. As the use of either form of attachment described above retards the rate of filtration it is better not to put on the attachment until the water has fallen almost to the desired level. If the concentrated water is allowed to stand in the funnel for any length of time some of the organisms are liable to become attached to the glass sides. To prevent error from this cause the neck of the funnel may be washed with a small measured quantity of filtered water, and this may be caught in the large test-tube and used for washing the sand a second time as described above. The Cell. The cell into which a measured portion of the concentrated fluid is placed for examination is made by cementing a rectangular brass rim to an ordinary glass slip. The internal dimensions of the cell are: length 50 mm., width 20 mm., and depth I mm. It therefore has an area of 1000 sq. mm. and a capacity of I c.c. A thick cover-glass (No. 3) having dimensions equal to those of the outside of the brass rim (55 mm. by 25 mm.) forms a roof to the cell. The con- centrated organisms in the decantation-tube are distributed uniformly through the fluid by blowing into it through a pipette, and one cubic centimeter of the fluid is then trans- ferred to the cell in such a manner as to distribute the organ- isms evenly over the entire area. This may be done by laying the cover-glass diagonally over the cell so that an opening is 22 THE MICROSCOPY OF DRINKING-WATER, left at either end, and flowing the water in at one end while the air escapes at the other (see Fig. 5). FIG. 5. COUNTING-CELL, SHOWING METHOD OF FILLING. SEDGWICK- RAFTER METHOD. The -Microscope. An expensive microscope is not needed for the numerical estimation of the common micro- scopic organisms found in water. A simple, compact stand with a J-inch objective and a i-inch ocular is sufficient. For studying the organisms in detail and for general laboratory use in the study of water a large stand, with substage condenser, iris diaphragm, mechanical stage, etc., should be provided. The list of objectives should include a 2-inch, a ^-inch, a J- or ^-inch, and a T ^-inch homogeneous immersion, or their equivalents, and there should be several oculars magnifying from 4 to 12 times. The ocular micrometer consists of a square ruled upon a thin glass disk which is placed upon the diaphragm of the ocular. The square is of such a size that with a certain com- bination of objective and ocular and with a certain tube-length METHODS OF MICROSCOPICAL EXAMINATION. 2$ of the microscope, the area covered by it on the stage is just one square millimeter. For convenience it should be sub- divided as shown in Fig. 6. The size of the largest square is one square millimeter. The size of the smallest square is FIG. 6. OCULAR MICROMETER USED IN THE SEDGWICK-RAFTER METHOD. one standard unit.* The best micrometers are made by en- graving, but a serviceable micrometer for occasional use may be made by photography. f With a J-inch objective and a No. 3 ocular the square ruled for the ocular micrometer should be 7 mm. on a side. Before using the micrometer the proper tube-length must be ascertained by comparison with a stage micrometer. Enumeration. The x:ell, filled with the concentrated fluid, is placed upon the stage of the microscope and the organisms included within the area of the ruled square are counted. It is then moved so that another portion of the comes into the field of view and another square is counted. * See page 29. f- This idea was suggested by Mr. Wallace Goold Levison, Brooklyn, N. Y. 24 THE MICROSCOPY OF DRINKING-WATER. This is continued until a sufficient number of representative squares has been examined. It is obviously impracticable to count all of the 1000 squares which compose the area of the cell. It is usually sufficient to count ten or twenty squares, but a larger number ought to be scrutinized. In counting the organisms it should be remembered that some are heavy and sink to the bottom, while others are light and rise to the top. The observer should make a practice of changing the focus of the microscope so that both the upper and lower portions of each square may be examined. From the number of organisms found in the ten or twenty squares it is an easy matter to calculate the number originally present in one cubic centimeter of the sample. If / repre- sents the mimber of organisms found in twenty squares, f will represent the number found in one square, and 5 for the organisms and 3$ for the amorphous matter. Sand Error. The sand error, due to imperfect filtration, depends upon the character of the organisms, upon the size of the sand-grains, and upon the depth of the sand. In selecting a sand two opposing conditions must be adjusted. The sand must be fine enough to form an efficient filter, and yet the grains must be large enough to settle readily in the decantation-tubes. A -inch layer of the sand described on page 16 ought not to give a sand error greater than 5$ unless the water contains minute organisms. When very minute or- ganisms are present in large numbers the error from incomplete filtration may be as great as 25$ or even 50$. The effect of the size of the sand-grains on the sand error is well illustrated by the following table compiled from experiments by Calkins on the filtration of water containing yeast-cells and starch-grains: Percentage Sand Error. Size of Sand. Yeast-cells. Starch-grams. 40-60 21.6 4.4 60-80 8.7 7 ..3 80-100 5.3 7.4 100-120 3.3 1.2 * By the author. METHODS OF MICROSCOPICAL EXAMINATION. 2? Most of the organisms that pass through the sand do so 'during the early part of the filtration, belore the sand has become compacted. If, before the sample is pouted into the funnel, the sand is compacted by passing through it some distilled water, using the aspirator to increase the pressure, the sand error will be reduced considerably. Errors of Disintegration. Many of the microscopic organisms are extremely delicate. They are very susceptible to changed conditions of temperature, pressure, and light. As soon as a sample of water has been collected in a bottle some of the organisms begin to disintegrate; and if the sam- ple stands long before examination and if it is submitted to the joltings of a long trip by express, some of the organisms will break up and become unrecognizable. The process of filtration helps to disintegrate them by bringing them in violent contact with the surface of the sand, but the method of concentrating the sample by arresting the filtration as described above reduces this error to a considerable extent by keeping the sand from becoming dry and by preventing many of the organisms from even reaching the surface of the ^and. The errors due to disintegration during transit and -before examination can be avoided only by making the exami- nation at the time of collection. This is often necessary, particularly when one is searching for such delicate organisms -as Uroglena. The errors of disintegration during filtration cannot be entirely avoided, but if the examination of the concentrated fluid is supplemented by a direct examination cf the water gross mistakes may be prevented. Uroglena, Dinobryon, etc., may be detected in the sample with the naked eye after a little practice. They may be taken up with a pipette and transferred to the stage of the micro- .scope. This direct examination is important and ought 28 THE MICROSCOP Y OF DRINKING- WA TER. always to be made, but its value is qualitative and not quantitative. Decantation Error. The decantation error depends to a great extent upon care in manipulation. When the attempt is made to separate the organisms from the sand by agitating with distilled water in one test-tube and decanting into a second tube, some of the organisms remain behind attached to the sand-grains, and, what is quite as important, some of the water used in washing remains behind. The two errors act in opposition. If the sand retains a larger percentage of organisms than of water, the figures in the result will be too low; if it retains a larger percentage of water than of organisms, the concentration will be too great and the figures in the result will be too high. With the frac- tional method of washing the sand and with due care in de- canting the decantation error ought not to exceed 5 per cent. Errors in the Cell. The errors due to the unequal distri- bution of the organisms over the area of the cell are extremely variable and cannot be well stated in figures. If the concen- trated fluid is evenly mixed and well distributed over the cell, if the count is made just as soon as the material in the cell has settled, and if a large number of squares are counted, the error will be reduced to a minimum. If a sample happens to- contain such motile organisms as Trachelomonas they may collect at the edges of the cell in search of air, or if the cell stands in front of a window for any length of time organisms sensitive to light may migrate from one side of the cell to the other. Precision of the Sedgwick-Rafter Method. Examina- tion of hundreds of samples has shown that the results are usually precise within io#, i.e. two examinations of the same sample seldom differ by more than that amount. The METHODS OF MICROSCOPICAL EXAMINATION. 29 accuracy, however, depends greatly upon the character of the organisms in the water examined. Results of Examination Standard Unit. The micro- scopical examination of most samples of surface-water will show that the concentrated fluid contains minute organisms of various kinds, fragments of larger animals and plants, masses of a grayish or brownish flocculent material, and fine particles of inorganic matter. The inorganic or mineral matter is usually not considered in the Sedgwick-Rafter method; more information can be obtained by a direct examination of the sediment and by chemical analysis. The brownish flocculent material has been called "amorphous matter" because of its formless nature, and " zoogloea " because of its supposed bacterial origin. The term zoogloea has a definite meaning in bacteriology and is applied to a mass of bacteria held together by a more or less transparent gluti- nous substance. It is not strictly appropriate as applied to the brownish flocculent matter, which is not so much a collection of bacteria as the product of bacterial action. The word phytoglcea might be used in its place, but the term "amor- phous matter" is a broader term and quite as appropriate. The amorphous matter, then, includes all the irregular masses of unidentifiable organic matter. It does not include vege- table fibres, vegetable tissue, etc., nor does it include mineral matter except as this is intimately mixed with the flocculent material. The amorphous matter occurs in a finely divided state or in lumps of varying size. In order to correctly estimate its amount it is necessary to have some unit of size. A unit of volume is impracticable because of the great labor involved in determining the dimensions of the masses observed, but a unit of area approaches closely to what is desired. Such a unit was suggested by the author in 1889, 30 THE MICROSCOPY OF DRINKING-WATER. and has come into use under the name of "standard unit." The standard unit is represented by the area of a square 2O microns* on a side, i.e. by 400 square microns. The ocular micrometer shown in Fig. 6 was subdivided to correspond to this unit. The square, which covers one square millimeter on the stage of the microscope, is divided into four equal squares. Each of these quarters is subdivided into 25 smaller squares, and each of these squares contains 25 standard units. The eye will readily divide the side of a small square into fifths, and this division is the side of the standard unit square. If desired, one of the small squares may be further subdivided into squares the actual size of the standard unit as shown in the figure. This can be done on the micrometers made by photography, but not conveniently on those engraved. The microscopic organisms vary in size and in their mode of occurrence. Some are found as separate individuals, some are joined together into filaments, or into masses or colonies; some are one-celled, some are many-celled ; some are extremely simple, some are complex; some are scarcely larger than the bacteria, some are easily visible to the naked eye. It is difficult to establish a satisfactory system for counting these varied forms. If an individual count is adopted one has to decide what shall be the unit, whether a cell, or a filament, or a colony, or a mass. Practice has varied in this matter. The best system of counting by individuals is that used by the Massachusetts State Board of Health. All diatoms, desmids, rhizopods, Crustacea, the unicellular algae, and nearly all rotifera and infusoria are counted as individuals; the filamen- tous algae are counted as filaments; the social forms of infusoria and rotifera are counted as colonies; and many of the algae that occur as irregular thalli are counted as masses, * One micron = .001 millimeter. METHODS OF MICROSCOPICAL EXAMINATION. 31 This system, which, for convenience, we may call the "in- dividual counting system," does not always give satisfactory results. In the Boston water-supply it was found often that a sample which a simple inspection showed to be heavily laden with algae and which was offensive both in appearance and in odor gave a low figure in the count, while a sample that was clear and agreeable to the taste gave a very high figure. This was due largely to the great difference in the size of the organisms. A great mass of Clathrocystis was given no more weight in the result than a tiny Cyclotella. Each counted one, though the former sometimes contained a thousand times as much organic matter as the latter. In order to make the figures representing the total number of organisms bear some close relation to the actual character of the water as shown by the physical and chemical analyses, it was suggested that the standard unit already in use for the amorphous matter might be applied to the organisms as well. This "standard unit method " was adopted at the Boston Water Works, and has been used extensively elsewhere. The unit system does not involve much extra labor in the counting. Many organisms are so constant in size that they may be counted individually and then reduced to standard units by multiplying by a constant factor. Filamentous forms of constant width may be measured in length and then reduced to units. Irregular masses and variable colonies may be estimated directly in units. In practice it has been found desirable to modify the unit somewhat in cases where organ isms are especially thick or thin in order that the results may approximate a volumetric determination as nearly as possible. It is not always that the unit system gives better results than the counting system. Sometimes it is advisable to state the results both in number of individuals and in standard units. THE MICROSCOPY OF DRINKING-WATER. MICROSCOPICAL EXAMINATION. Sample of Croton Water, New York. Date of Collection, Aug. 25, 1897; Date of Examination, Aug. 25, 1897. Concentration, 500 cc. to 10 cc. Factor, 2. i 2 3 4 5 6 7 8 9 10 IS o h Number per c.c. 1-lS pk C/J DIATOMACE^E: i 10 2 1 I 2 I 80 40 I I 12 5 i i i 3 i i 90 30 2 2 I I 12 8 i 7 I 4 i i 160 5 75 10 2 IO 10 i 8 i ii 4 2 2 2 2 I 3 40 I I 9 10 i 3<> 240 25 2 5 IO 2 I 4 ; 8 2 I 5 2 I 7 IO I 10 4 22 6 2 I I 2 I I no 5 90 2 8 i 2 19 4 4 5 4 i i 150 75 2 I 37 7 6 6 2 IOO 35 2 I 2 I ii 6 2 4 i 5 3 no 5 12 16 150 5 1 '9 42 13 10 4 28 15 3 30 4 1240 10 35 470 3 8 4 2 18 2 5 20 6 2 I I I I 24 32 300 102 38 8 4 26 2O 8 10 56 % 8 20 16 8 4 36 4 IO i Present 2 9 3 150 102 s 10 40 TOO 56 ;i 60 so 2480 20 50 040 60 16 8 4 18 8 60 40 12 4 16 20 4<> 50 10 Cyclotella Synedra Tabellaria CHLOROPHYCE^:: CYANOPHYCE.*: Clathrocystis Microcystis FUNGI AND SCHIZOMYCETES: Mold Hyphae Cladothrix PROTOZOA: Mallomonas Codonella H.OTIFBRA: Polyarthra CRUSTACEA: Cvcloos. . . OTHER ORGANISMS: 20 25 40 25 IS 40 20 3 35 20 2 7 3 6 4647 540 6 AMORPHOUS MATTER MISCELLANEOUS BODIES: METHODS OF MICROSCOPICAL EXAMINATION. 33 SCHEDULES OF CLASSIFICATIONS USED AT DIFFERENT TIMES AND IN DIFFERENT LABORATORIES. INDIVIDUAL COUNTING SYSTEM. STANDARD UNIT SYSTEM. Mass. St. Bd. of Health, barker, 1887. Boston Water Works. Whipple, i88q* Mass. St. Bd. of Health. Calkins, i8qo. Conn. St. Bd. of Health. i8qi. Brooklyn Water Dept. W hippie, 1897. Boston Water Works. Hollis, 1897. Diatomaceae Diatomaceae Diatomaceae Diatomacese Diatomaceae Diatomaceae Desmidieae Palmellaceae Zoosporeae Zygnemaceae Volvocinieae Desmidieas Chlorophyceae Algae Desmidieae Protococcoi- deae Confervaceae Chlorophyceae Chlorophyceae Cyanophyceae Cyanophyceae Cyanophyceae Cyanophyceae Cyanophyceae Cyanophyceae Schizomy- cetes Fungi Fungi Fungi Fungi and Schizomycetes Fungi Protozoa Rhizopoda Infusoria Rhizopoda Infusoria Rhizopoda Infusoria Protozoa Rhizopoda Infusoria Rotifera Rotifera Vermes Rotifera Rotifera Rotifera Entomostraca Crustacea Crustacea Crustacea Crustacea Spongiaria Nematoda Annelida Miscellaneous Miscellaneous (including Zoogloea) Ova Spores Other Organisms Miscellane- ous Total Organisms Total Organisms Total Organisms Total Organisms Amorphous Matter Amorphous Matter Amorphous Matter Miscellaneous Bodies Records. The results of analysis may be recorded on a blank similar to the one shown on page 32. The ten num- bered vertical columns correspond to ten squares counted. The two right-hand columns give the results in " Number per c.c." and in " Number of Standard Units per c.c." Either * The Standard Unit system has been used since Jan. i, 1893. 34 THE MICROSCOPY OF DRINKING-WATER. or both of these columns may be used. The names of the common organisms are given in the left-hand column, and are grouped according to the system of classification described in Part II. The table on page 33 shows the schedules of classification used by different observers. It may be found- useful in the comparison of different reports. II. PLANKTON NET METHOD. The plankton net * consists of a conical net of silk bolting- cloth (No. 20) suspended from an iron ring two feet in diameter (Fig. 7). The net has a length of three feet. At the lower end it terminates in a flat metal ring to which is attached the filtering-bucket. The latter consists of a metal frame covered on the sides with bolting-cloth, and having a slightly conical bottom. In the middle of the bottom there is an outlet-tube closed with a removable plug. The bucket is about 2\ inches in diameter. It is supported on three legs when detached from the net. The filtering-net of bolting- cloth is protected by a twine net which helps to bear the strain when the net is drawn through the water. Cords extend from the iron ring to the bucket in order to further relieve the filtering-net from strain. Above the filtering-net there is a truncated canvas cone that serves as a guard, pre- venting the entrance of mud when near the bottom and pre- venting the contents of the net from spilling over the edge. The smaller diameter of this guard is about 16 inches. It is this diameter that determines the volume of water filtered when the net is drawn through the water. The whole net is * There are several modifications of Hensen's original net. The form- used by Reighard in Lake St. Clair and here described may be considered as typical. METHODS OF MICROSCOPICAL EXAMINATION. 35 suspended by three cords attached to radiating iron arms fastened to the rope by which the apparatus is raised and lowered. FIG. 7. PLANKTON NET. (After Reighard.) The net is operated as follows: It is lowered to the bottom or to the desired depth and then' drawn to the surface, the velocity of its ascent being noted. On the way down it takes in no water except what is filtered through the gauze. On the way up it filters a column of water whose cross-section 3 THE MICROSCOPY OF DRINKING-WATER. is that of the opening of the guard net and whose height is equal to the distance through which the net was drawn. This is the theoretical amount filtered. In practice the net does not strain the whole column of water through which it passes, as a portion of the water is forced aside. There- fore in order to obtain the volume of plankton in the column traversed it is necessary to multiply the observed result by a factor or coefficient. This net-coefficient varies for each net and for different velocities of ascent through the water. It also varies with the amount of clogging. With velocities of 2 to 3 ft. per second the coefficient is about 2. It is necessary to know the coefficient for each net at different velocities and to correct the results of each haul for the par- ticular velocity used. When the net reaches the surface it is allowed to drain. A stream of water played on the outside of the net detaches the organisms from the bolting-cloth and washes them down into the bucket. The bucket is then detached from the net and its collected material is transferred to a small bottle for transportation to the laboratory. The plankton net used by Birge differs from the one just described in that it has a cover instead of a guard-net. The cover slides in a rectangular frame. It is moved by delicately adjusted weights set in action by a releasing device which is operated by messengers sent down the rope. The cover may be opened or closed at any depth at the will of the operator. This enables one to collect material from the lower strata without having it contaminated with that above it. The amount of plankton collected may be determined by four methods: (i) by estimation of the volume; (2) by determination of the weight; (3) by chemical analysis; (4) by enumeration of the organisms. METHODS OF MICROSCOPICAL EXAMINATION. 37 The volume is obtained by allowing the material to stand in alcohol in a graduated cylinder for 24 hours. At the end of that time the plankton will have settled and the volume in cubic centimeters may be read from the scale. This gives the total volume in one catch. It is customary to express results in "number of cubic centimeters of plankton under one square meter of surface " or in "number of cubic centi- meters of plankton in one cubic meter of water." The approximate weight may be determined by drying on filter-paper and weighing. The results are usually ex- pressed in grams of plankton under one square meter of surface or in one cubic meter of water. The chemical analysis of the plankton usually consists of the determination of the percentage of organic material, ash, silica, etc. The enumeration of the organisms is the most important part of the laboratory investigation. The material is evenly distributed in a definite amount of alcohol by shaking, and a portion is removed to a small trough or cell and placed under the microscope. The various organisms are then counted. Lines drawn on the bottom of the cell aid the observer in covering the entire area of the cell. As in the case of volume and weight, the results are generally expressed either in " number of organisms under one square meter of surface " or in " number of organisms per cubic meter of water." Both these methods are objectionable because so many figures are involved. They often extend to the millions and some- times to the billions. It is preferable to express the smaller organisms, such as the algae and protozoa, in "number per cubic centimeter," and the larger organisms, such as the Crustacea, rotifera, etc., in " number per liter." It is evident that the " plankton net method " involves 38 THE MICROSCOPY OF DRINKING-WATER. many sources of error. Neither the amount of water strained nor the completeness of the filtration can be definitely ascer- tained. The loss of the smaller organisms by leakage through the meshes of the silk is very great, and many of the delicate organisms are crushed upon the net. The methods of estimating the volume and weight of the plankton, moreover, are exceedingly inaccurate. The met'hod of enumerating the organisms is much to be preferred. Except in the case of comparatively large organisms, such as the Rotifera, Crus- tacea, etc., the results of the net method cannot be depended upon within 50 per cent. III. PLANKTON PUMP. The plankton pump is designed to collect the plankton from any particular depth in a lake. It consists of a sort of force-pump so arranged that a definite and measurable quantity of water is delivered at each stroke; an adjustable hose through which the water is drawn from the desired depth; and a filtering-bucket into which the water is pumped. The straining is effected by allowing the water to pass through a cylinder of fine wire gauze at the lower end of the filtering- bucket. The efficiency of the strainer is increased by cover- ing the wire gauze with fine bolting-cloth. This method has the advantage of measuring the quantity of water strained with greater accuracy than is possible in the net method, but the error from imperfect filtration is large. IV. THE PLANKTONOKRIT. The planktonokrit is a modification of the centrifugal machine. The water to be examined is placed in two funnel- METHODS OF MICROSCOPICAL EXAMINATION. 39 shaped receptacles attached to an upright shaft, with the necks of the funnels pointed outwards. The receptacles have a capacity of one liter each. The funnel portion is made of tinned copper; the stem is a glass tube that has a bore of 2^ to 5 mm. The glasses are held in place by a cover, such as is employed in mounting a water-gauge. The shaft is driven by hand or belt through a series of geared wheels, so arranged that 50 revolutions of the crank, or pulley-wheel, produce 8000 revolutions of the upright shaft. By this rapid revolu- tion of the sample the organisms are thrown outwards by centrifugal force and collect in the neck of the funnel, from which they may be removed for examination. There are certain practical objections to the forms of apparatus now constructed. It is not only difficult but dangerous to use high speeds when large quantities of water are operated on. Field has been unable to use a speed greater than 3000 revolutions per minute. This speed main- tained for four minutes, however, was sufficient to throw out -all the organisms except the Cyanophyceae. By reducing the amount of the samples and by perfecting the mechanical parts of the apparatus it seems probable that excellent results may be obtained by this method. Comparison of the methods described above will show that the Sedgwick-Rafter method and the planktonokrit are designed for use in examining samples of water in the labora- tory, while the plankton net and the plankton pump are intended for field work. The latter are most serviceable in concentrating the larger microscopic organisms such as the Rotifera and Crustacea. The Sedgwick-Rafter method is the most practical and efficient method for use in sanitary water analysis. It should not be relied upon completely, but should 40 THE MICROSCOPY OF* DRINKING-WATER. be supplemented by a direct microscopical examination of the original sample of water or by the use of the planktonokrit. It is much to be desired that all results, obtained by whatever method, should be expressed in terms of the same unit, and it is hoped that the inconvenient methods of express- ing results in "grams or cubic centimeters of plankton under one square meter of surface or in one cubic meter of water " will be abandoned by planktologists and the more exact system of counting the organisms substituted. CHAPTER IV. MICROSCOPIC ORGANISMS IN WATER FROM DIFFERENT SOURCES. IN studying the distribution of microscopic organisms it will be convenient to consider the following classes of water- supply separately: RAIN-WATER. GROUND-WATER. Springs. Wells. Infiltration-galleries. Infiltration-basins. SURFACE-WATER. Streams and Canals. Natural Lakes and Ponds. Artificial Reservoirs. FILTERED WATER. Sand Filtration. Mechanical Filtration. Rain-water. Rain-water is perhaps the purest water found in nature, yet it sometimes contains micro-organisms. For the most part they are so minute that an examination by the Sedgwick-Rafter method fails to reveal them, but larger forms are sometimes observed. The study of the organisms found in rain-water is really the study of the organisms found in the air. It is worthy of more attention than has been given to it. The presence of organisms, or their spores, in the air may be demonstrated by 41 42 THE M1CROSCOP Y OF DRINKING- WA TER. sterilizing some water rich in nitrogenous matter and expos- ing it to the air in the light. After a week or two it will contain numerous forms of microscopic organisms which must have settled into the liquid from the air or developed from spores floating in the air. Rain-water collected in a sterilized jar and allowed to stand protected from the air often develops a considerable growth of algae (usually some Protococcus form), showing that the rain has not only taken up the organisms or their spores, Ijut has absorbed sufficient food material for their growth. Samples of rain-water sometimes contain a surprisingly large .amount of nitrogenous matter, especially if collected in the vicinity of a large city and at the beginning of a storm. It has been noticed' frequently that vigorous growths of algae have appeared in ponds or reservoirs immediately after a rain-storm, the growth occurring suddenly and simultaneously throughout the whole body of water. It is possible that these sudden growths may be caused by the dried spores of the algae being lifted from the shores of the ponds and scat- tered through the air by the wind, and then washed into the water by the rain. This supposition is in harmony with the theory that in the case of certain algae sporadic development occurs only after the desiccation of the spores. Ground-water. Ground-water is water that has filtered or percolated through the ground. It comes to the surface as springs or is collected in wells or infiltration-galleries. Ground-water collected directly from the soil before it has had an opportunity to stand in pipes or be exposed to the light is almost invariably free from microscopic organisms Its passage through the soil filters them out. It usually con- tains an abundant supply of plant food, extracted from the MICROSCOPIC ORGANISMS IN WA TER. 43 organic and mineral matter of the soil and modified by bac- terial action, and when the water reaches the light this food material is seized by the micro-organisms. One will recall the luxuriant aquatic vegetation at the mouth of some spring or in some watering-trough supplied with spring-water. Organisms are occasionally met with in ground-water supplies, but, with the exception of the Schizomycetes, the number of organisms depends upon the exposure of the water to the light and air; that is, it is only as a ground-water becomes a surface-water that the microscopic organisms develop. The following table, compiled from the examinations of the Massachusetts State Board of Health, gives an idea of the organisms met with in ground-water supplies. Except in the case of springs, the figures represent the average of monthly observations extending over one or more years. Spring-waters usually contain no microscopic organisms. .Several exceptions are noted in the table, one at Westport, where 45 5 Himantidium were present, and one at Millis, where the water contained 180 Chlamydomonas per cc. That these were accidental is shown by the fact that in 1893 five exami- nations of the Aqua Rex Spring showed an entire absence of organisms. Well-waters also are ordinarily free from organisms, but in some cases Crenothrix grows abundantly in the tubes of driven wells. This is particularly true if the water is rich in iron and organic matter and deficient in oxygen. Wells driven in swamps are often thus affected. The tubular wells at Provincetown are an example, Crenothrix is sometimes found there as abundant as 20000 per c.c. The water con- tains more than 0.125 parts of albuminoid ammonia per mil- lion, and the iron varies from i.oo to 5.00 parts per million. Many similar cases might be cited. Leptothrix and Spiro- >chaete forms are also observed in well-waters rich in iron. 44 THE MICROSCOP Y OF DRINKING- WA TER. MICROSCOPIC ORGANISMS IN GROUND-WATERS. (NUMBER PER c.c.) i g s 2 eu. -J- 1 s s CJ en s be c a 3 "o ^a 10 tx Total Organisms. ro co w i rt MOOOOOOOOO OOOOOOOOOO OOOOOOOMOO , *- 2.S OOOOOOMOOO OOOunOOWOO Gt <*VO O O M O OQ t* kl a a -"-aa. It OOOOOOOOOO 0000 u 00000 OOOOOOOOOO 1 Sty SWS5" - A W mOOOOOOOOO OOOOiiOOOOO OMOOOOO-^OO Chloro- phyceae oooooooooo OOOOONOOOO o-*-ooooo>-o Diato- maceae. .n M H u oo M j m ^. mm ^-^- oi M -* r^ -^- -^- ^t- MMP-cWHMf"WQ OOOOOOO O>oo OO oo oo oo 3>oo 00 00 00 oo 00 5^ &OO * be ^^ >' cs^ bo bi >L <; 2 1 ^'t^'^gi be ^ U " JJ ^ "u 13 "5 ^ ^ N j^ ^fe'^s'^^c c a ^'u 1 " 1 ^ .S ^^^^P^^^tirT fcC ~^s ss'Sn'ifi'tn 'bii^^'olblo^'bc'be'bec^' ^^^^rtrt^rtZ^ " JigtSjgtSSiSfcl^ T S'l'-c'l |-c-c'c3 2JfiftS5555s^ sassassssa >>gg>>^x ~s~>>^=** MICROSCOPIC ORGANISMS IN WAITER. 45 Crenothrix grows in tufts or in felt-like layers on the inner walls of the tubes. By the deposition of iron oxide in its gelatinous sheath it clogs up the tubes and strainers with iron- rust. Infiltration-galleries, or filter-galleries, are practically elongated wells located near some stream or pond. They are similar to wells in regard to the presence of micro-organisms. Few organisms other than Crenothrix are found. Infiltration-basins, or filter-basins, are infiltration-galleries open to the light. The water in them is sometimes affected with algae-growths. The infiltration-basin at Taunton, Mass., for example, has given trouble from this cause. In October 1894 there were more than 1000 Asterionella per c.c. present, and they were followed by a vigorous growth of Dinobryon. Infiltration-basins are practically open reservoirs for the stor- age of ground-water a subject to be treated in another chapter. Surface-water. The term " surface-water" includes all collections of water upon the surface of the earth, i.e., lakes, ponds, rivers, pools, ditches, etc. The following table shows that surface-waters contain many more microscopic organisms than ground-waters, and that standing water contains more organisms than running water. Samples from rivers, unless collected near the shore, seldom contain many organisms, and water-supplies drawn from rivers and subjected to limited storage are not often troubled with animal or vegetable growths. This may be true even where the banks of the stream are covered with aquatic vegetation. The organisms found in streams are largely sedentary forms. Their food-supply is brought to them by the water continually passing. In quiet waters there are found free-swimming forms that must go in search of their 46 MICROSCOPY OF DRINKING- WA TEX. Zooglrea (Units). t^vo VO M ^J-oO O O 00 00 00-V *** ^|f9l || M ovo loooo^t^iotx vo in o O - m\o oo ci ^2^222^ t - vorON &% M oo^ N^ N , Cl IN M M m 1-1 H- , rt . | .QQ.0. Q, CXCXQi^&iO* o. d ex *. 5.S fx t^ IH VO COVO M M M VO MOJOO.M R 6^ 11 a a a a a a a. * tuo c 3 u. MCO ^ 6 H S| O,M >w - c - ^ ^ c ^ S^ c 'S'c- Mw -' 1 'w Il||-lss, Is|S|s-3i-sl c/5 S t-TCQ c/3 U ^ H J S ->3C EL, i>TC i-J C/5 i-5O 1 1 IP 1 K ^ > _.ti ^ 1 < 'c i-J .b j'o ^ _ i Iljijlliil -=3>>>g=S^ -=5;>5ggSx -s5S>>?=2x MICROSCOPIC ORGANISMS IN WATER. 47 food. It is difficult to draw a sharp line between these two classes of organisms. Some are free-swimming at will or during a part of their life-history, and some free-swimming organisms are always found associated with sedentary forms. On most rivers there are some quiet pools where free-swim- ming forms may develop. In a sample of river-water, then, one is likely to find sedentary forms which have become detached, organisms which have developed in the quiet places or in tributary ponds, and spores or intermediate forms in the life- history of sedentary organisms. In streams draining large ponds or lakes the water naturally has the character of the pond- or lake-water, and organisms may be abundant. The number of microscopic organisms found in rivers is subject to great fluctuations. If the water is rich in food- material, littoral growths often develop with rapidity, while a heavy rain that increases the current of the water and the amount of scouring material that it carries may suddenly wash away the entire growth. With such conditions the number of organisms collected in a sample may be above the normal. At other times a rain may diminish the number of organisms in a sample by dilution. But the fluctuations are due chiefly to changes that take place in the growths in tributary ponds or swamps, and to the fact that rains may cause these ponds to overflow. The table shows that the Diatomaceae are the organisms found most constantly in rivers. Navicula, Cocconema, Gomphonema and other attached forms are common, but their numbers are small compared to those found in standing water. Some of the Chlorophyceae, particularly Conferva, Spirogyra, Draparnaldia and other filamentous forms, are often observed. The Cyanophyceae, except the Oscillarieae, seldom occur. Stony Brook, in the table, represents a stream 48 THE MICROSCOP Y OF DRINKING- WA TER. affected by tributary ponds where Cyanophyceae abound. Crenothrix is quite often found in river-water. Anthophysa is often mistaken for it, and this may account in part for the high figures in the table. Animal forms are not common in rivers unless the water is polluted. Rotifera and Crustacea are seldom seen, but Protozoa are sometimes observed. In the slow-running water of canals and ditches organ- isms sometimes develop in large numbers, but the conditions are not often such as to cause trouble in public water-sup- plies. The following instance, however, is worth noting: On Sunday, July 12, 1896, it was observed by some of the residents living in the western part of the city of Lynn, Mass., that the water drawn from the service-taps had a green color. A glass of it showed a heavy green sediment when allowed to stand even for a few minutes. On the following day it became worse, and when the water was used for washing in the laundry it was found to leave green stains on the clothes. These acted like grass- stains. Investigation showed that the stains were caused by Raphidomonas, and that these organisms were abundant in the city water. Examination of the four storage-reservoirs showed that they were not present there in sufficient numbers to account for the trouble. The water from one of the supply-reservoirs, Walden Pond, reaches the pumping-station by means of an open canal, tunnel, and pipe-line. It was in this open canal that the Raphidomonas were found. The sides of the canal were thickly covered with filamentous algae, chiefly Cladophora. The water in the canal had a dark green color. When a bottle of it was held to the light it was almost opaque and was seen to be densely crowded with moving green organisms. As many as 2000 per c.c. were present. Evidently the organisms had developed among the MICROSCOPIC ORGANISMS IN WA TER. 49 algae in the canal and had gradually scattered themselves out into the water from Walden Pond as it passed through the canal on its way to the city. The trouble was remedied by emptying the canal through the wasteways and cleaning the slopes to prevent later development. This is the only case on record where Raphidomonas has caused trouble, though the organism is often found in sur- face-water supplies. Quiescent Waters. All quiescent surface-waters are liable to contain microscopic organisms in considerable num- bers. The water that is entirely free from them is very rare. It is scarcely possible to collect a sample of stagnant water at any season of the year without obtaining one or more forms of microscopic life. The extent and character of the growths vary greatly in different ponds and at different seasons. As it is in ponds and lakes and reservoirs that the micro- scopic organisms cause the most trouble, it is these bodies of water that chiefly interest us. Before considering the organ- isms in this class of water-supplies it is important to know something about the physical conditions of water in ponds and lakes. These are discussed in the following chapter. In passing, one should observe from the table that all classes of organisms, except perhaps the Schizophyceae, are much more abundant in natural ponds and in reservoirs than in rivers. Filtered Water. Water which has been filtered either by the method of slow sand filtration or by mechanical filtration seldom contains many microscopic organisms. In the case of slew sand filtration their presence in the filtered water generally indicates that the filtration is imperfect. In the case of mechanical filtra- tion, however, microscopic organisms sometimes do appear in the effluent, although nearly always in small numbers. This is apparently due in part to the use of coarser sand and a higher 50 THE MICROSCOPY OP DRINKING-WATER. rate of filtration and in part to the fact that the organisms be- come attached to the sand grains near the surface and that some of these sand grains are carried to the bottom of the tank during the process of washing, where the organisms become dislodged from them. The presence of a few microscopic organisms in the effluent of a mechanical filter, therefore, does not necessarily indicate imperfect filtration. Occasionally growths of Crenothrix and allied species occur in the under-drains of sand filters. They usually appear where the conditions are such that the water is deprived of part of its oxygen, or where, through leakage, ground-water containing iron and carbonic acid in solution becomes mixed with the filtered water. Growths of microscopic organisms often occur in filtered water when exposed in open reservoirs to the sunlight, as described in Chapter XI. Under these conditions the water is practically a ground-water. CHAPTER V. LIMNOLOGY. LIMNOLOGY is that branch of science that treats of lakes and ponds, their geology, their geography, their physics, their chemistry, their biology, and the relations of these to each other. This subject has taken shape only within the past fifteen years, but already many valuable publications have appeared. In this chapter it is possible to consider only such limno- logical studies as are closely related to the microscopic organ- isms. The most important of these are: the temperature of the water, the amount of light received and transmitted by the water, and the food material of the organisms found in the water. The location of lakes, their shape, size, and depth, the source of their supply, the character of the water^ shed, the meteorology of the region, all have their effect upon the organisms living in the water, but they can be con- sidered only incidentally. Physical Properties of Water. The density of water varies with its pressure, with its temperature, and with the substances dissolved in it. Grassi gives the coefficient of compressibility of pure water as .0000503 per atmosphere at o C., and .0000456 at 25 C. Therefore if the density at the surface of a lake is unity, at a depth of 339 ft. (10 atmospheres) it will be 1.0005 ^ THE MICROSCOP Y OF DRINKING- IV A TER. at 678 ft. (20 atmospheres), i.ooi ; and at 1017 ft. (30 atmos- pheres), 1.0015. Water attains its maximum density at about 4 C. or 39.2 F. Assuming its density at 4 C. to be unity, its density at other temperatures is given in the following table. DENSITY OF WATER AT DIFFERENT TEMPERATURES. Temperature. Temperature. Density. Density. Centigrade. Fahrenheit. Centigrade. Fahrenheit. 32.0 .99987 IS. 3 65.0 .99859 1.6 1 35-0 .99996 21. 1 7O.O . 99802 4-0. 39-2 I . OOOOO 23-8 75-0 99739 4-4 40.0 .99999 26.6 80.0 . 99669 7.2 45-0 . 99992 29.4 85.0 .99591 10. 50.0 99975 32.2 90.0 .99510 12.7 55-0 .99946 35-0 95-0 .99418 15-5 60.0 .99907 37-7 IOO.O .99318 Water freezes at o C., or 32.0 F. Ice is lighter than water. It readily floats in water at o C, Water has a very high specific heat. It is a poor thermal conductor. Prof. W. H. Weber* gives its coefficient of conductivity as 0.0745. Water is extremely mobile. This property renders it subject to displacement by mechanical agencies, such as wind and currents (mechanical convection), and permits it to become stratified according to the density of its particles. The mobility of water varies somewhat with its temperature, Ibeing greater as the temperature is higher. When water is stratified with the warmer layers above the colder, the stratification is said to be ''direct." This occurs when the temperatures are above that of maximum density. When water is stratified with the colder layers above the warmer the stratification is said to be " inverse. This * Vierteljahreschrift der Zurich Nat. Ges., xxiv. 252, 1879. LIMNOLOGY. 53 occurs when the temperatures are below that of maximum density. With the temperatures above 39.2 it sometimes happens in a deep lake that a colder layer of water is found above a warmer layer. This is a paradox theoretically possi- ble, because the density of the water at any point in a lake depends upon its depth as well as its temperature. Thus, water at 45 F. has a density of .99992. If this water were at a depth of 1017 ft., where the pressure is 30 atmospheres its density would be .99992 -{- .0015 = 1.00142, i.e., more than that of water at 39.2 F. at the surface. In nature, however, such a condition of temperatures seldom exists for a long period, and practically represents a state of unstable equilibrium. A thermal paradox may be caused also by differences in the density of different strata due to substances in solution. Water has a slight power of diathermancy, i.e., it permits the penetration of radiant heat to a slight degree. Forel experimented on the diathermancy of water by comparing the readings of thermometers with blackened and with ordi- nary bulbs at a depth of I metre. He obtained the following results: Time Temperature Excess of Temperature Date. of of Water. of Black Bulb Thermom- Exposure. (Fahrenheit.) eter, in Fahr. Deg. Mar. 27, 1871 10 hours 44-4 10.8 July 25, 1873 17 " 72.0 14.0 " 26, 1873 15 " 74-3 15-3 Aug. i, 1873 12 " 75.2 7.6 THE TEMPERATURE OF LAKES AND PONDS. Methods of Observation. The observation of the tem- perature of the water at the surface of a lake is a compara- tively easy matter, but it requires an accurate thermometer a careful observer. Where the water is smooth the 54 THE MICROSCOPY OF D RrttKlNC-WATER. thermometer-bulb may be immersed just beneath the surface in an inclined position and the reading taken before removing it from the water. In taking the reading one must be careful to avoid parallax by holding the thermometer exactly at right angles to the line of sight. When the water is too rough for reading directly some of the surface-water may be dipped up and the temperature of that ascertained. Thermometers with bulb immersed in a cup are prepared for this purpose. Direct observations are much to be preferred. The observation of the temperature of the water at depths below the surface is more difficult. The simplest method of obtaining results that are in any way accurate is to enclose a weighted thermometer in a stoppered empty bottle and to lower this to the proper depth and fill it by drawing out the stopper. After allowing a sufficient time for the apparatus and thermometer to acquire the exact temperature of the water the bottle is drawn to the surface and the reading taken before the thermometer is removed from the bottle. If the bottle is of sufficient size, if it is allowed to remain down long enough, if it is drawn rapidly to the surface and the reading taken at once, the error ought not to exceed one degree Fahrenheit. This method is impracticable for lakes much deeper than 50 ft., and beyond that depth some form of deep-sea thermometer is necessary. Several forms of maximum and minimum ther- mometers and of self-setting thermometers have been devised. The Negretti and Zambra thermometers have been used extensively for obtaining the temperature of very deep water. Several forms of electrical thermometers have been suggested, but the. thermophone* is the only one that has proved of practical value. * Invented and patented by H. E. Warren and G. C. Whipple. LIMNOLOGY, 55 The thermophone (see Fig. 8) is an electrical thermom- eter of the resistance type. It is based upon the principle that the resistance of an electrical conductor changes with its temperature and that the rate of change is different for differ- FIG. 8. THERMOPHONE, PORTABLE FORM. (After Warren and Whipple.) ent metals. Two resistance-coils of metals that have different electrical temperature-coefficients, as copper and German silver, are put into adjacent arms of a Wheatstone bridge and located at the place where the temperature is desired, the two coils being joined together at one end, The other extremi- ties of the coils are connected by leading wires to the 56 THE MICROSCOPY OF DRINKING-WATER. terminals of a slide-wire which forms a part of the indicator. A third leading wire extends from the junction of the two coils to a movable contact on the slide-wire, having in its cir- cuit a telephone and a current-interrupter, the latter oper- ated by an independent battery connection. The telephone and interrupter serve as a galvanometer to detect the presence of a current. The slide-wire is wound around the periphery of a mahogany disc, above which there is another disc carry- ing a dial graduated in degrees of temperature. The movable contact which bears on the slide-wire is attached to a radial arm placed directly under the dial-hand, the two being moved together by turning an ebonite knob in the centre of the dial. This indicator is enclosed in a brass case in a box that also contains the batteries. The sensitive coils are enclosed in a brass tube of small diameter which is filled with oil, hermetically sealed, and coiled into a helix. Connections with the leading wires are made in an enlargement at one end. The leading wires are three in number and are made to form a triple cable. The temperature of the leading wires does not affect the reading of the instrument because two of them are of low resistance and are on opposite sides of the Wheatstone bridge. They neutralize each other. The third leading wire is connected with the galvanometer and does not come into the question. The readings of the instrument are independ- ent of pressure. The operation of taking a reading is as follows: The coil is lowered to the depth where the temperature is desired, the three leading wires are connected to the proper binding- posts of the indicator-box, the current from the battery is turned on, the telephone is held to the ear, and the index moved back and forth over the dial. A buzzing sound will be heard in the telephone, increasing or diminishing as LIMNOLOGY. the index is made to approach or recede from a certain sec- tion of the dial. A point may be found at which there is perfect silence in the telephone, and at this point the hand indicates the temperature of the distant coil. With thermo- phones adjusted for atmospheric range, i.e., from 15 to 115 F., readings correct to o. i F. may be made. With a smaller range greater precision may be obtained. Because of its accuracy, because of the ease with which the coil may be placed at any depth from the surface to the bottom of a lake, because of its extreme sensitiveness and rapidity of setting (one minute is sufficient), and because of its portability, the thermophone is better adapted than any other instrument for taking series of temperature observations in lakes at various depths. It has been used for that purpose at depths as great as 400 ft., and it was used by Prof. A. E. Burton in Greenland at much greater depths for obtaining temperatures in the crevasses of glaciers. Results of Observations. The temperature changes that take place in a body of water may be illustrated by a 70' 60 50 = 40 OA C / <- N 70' 60 50 40 30" / / \ ,1 f \ / B )TTC )M X (/ 1 7 Tl L* :MPERATU KE COCHr }E UA OF FE V JAN. FEB. MAR, APR. MAY JUNEJULYJAUG. SEP. OCT. NOV. DEC. FIG. 9. diagram that shows the temperatures at the surface and bottom of Lake Cochituate. The curves of Fig. 9 are based 58 THE MICROSCOPY OF DRINKING-WATER. on a seven-years series of weekly observations, but some irregularities have been omitted for the sake of simplicity. If one traces the line of surface temperatures, he will observe that during the winter the water immediately under the ice stands substantially at 32 F., though the ice itself often becomes much lower than 32 at its upper surface. As soon as the ice breaks up in the spring the temperature of the water begins to rise. This increase continues with some -fluctuations until about the first of August. Cooling then begins and continues regularly through the autumn until the lake freezes in December. If this curve of surface tempera- ture were compared with the mean temperature of the atmos- phere for the same period a striking agreement would be noticed, and it would be seen that the water temperature is the higher of the two. When the surface is frozen there is no comparison between the air and water tempera- tures. During the spring and early summer, when the water is warming, the water is but slightly warmer than the air,* but during the late summer and autumn it is about 5 warmer. The surface temperature of the water fluctuates with the air temperature during the course of the day as well as on different days. The maximum is usually obtained between 2 and 4 P.M. and the minimum between 5 and 7 A.M. The daily range is seldom greater than 5, though it may be much more. At the latitude of Boston the maximum sur- face temperature of the water of lakes during the summer is seldom above 80. f * It must be understood that it is the mean temperature of the air during 24 hours that is referred to, and not the maximum temperature during the daytime. f A surface temperature of 92 was observed by the author at Chestnut Hill Reservoir on Aug. 12, 1896, at 3 P.M., after a week of excessively hot weather, during which the maximum daily temperature remained above LIMNOLOG Y. 59 In small shallow ponds the surface temperature follows the atmospheric temperature much more closely than in large deep lakes where the water circulates to considerable depths. In the latter the surface temperature is often below that of the mean atmospheric temperature during the early part of the summer, and occasionally during the entire summer. Lake Cochituate is 60 ft. deep. The temperature at the bottom during the winter, when the surface is frozen, is not far from that of maximum density (39.2 F.). The heaviest water is at the bottom; the lightest is at the top; and the intermediate layers are arranged in the order of their density. With these conditions the water is in comparatively stable equilibrium. It is inversely stratified. It is the period of " winter stagnation." As soon as the ice has broken up in the spring the sur- face-water begins to grow warmer. Until it reaches the temperature of maximum density it grows more dense as it grows warmer, and as it becomes denser it tends to sink. Thus until the water throughout the vertical has acquired the temperature of maximum density there are conditions of unstable equilibrium caused by diurnal fluctuations of tem- perature that result in the thorough mixing of all the water in the lake These conditions, together with the mechanical effect: of the wind, usually cause a slight temporary lowering of the bottom temperature at this season. Finally the tem- 90, while the humiaity varied from 62$ to 95$. At the time of the obser- vation the air temperature was 95 arid the humidity 70$. The temperatures of the water below the surface were as follows : Surface 92.0 10 ft 76.2 i ft QI.5 15 " 74-0 2" 89.2 2O" 65.7 3 "..... 85.6 25 " 54-5 4 " 80.2 27 " 53.1 5 " 79-0 60 THE MICROSCOPY OF DRINKING-WATER. perature throughout the vertical becomes practically uniform,, and vertical currents are easily produced by slight changes in the temperature of the water at the surface and by the mechanical effect of the wind. This is the period of " spring circulation " or the " spring overturning." It lasts several weeks, but varies in duration in different years. As the season advances the surface-water becomes warmer than that at the bottom, and finally the difference becomes so great that the diurnal fluctuation of surface temperature and the effect of the wind are no longer able to keep up the circulation. Consequently the bottom temperature ceases to rise, the water becomes " directly stratified," and the lake enters upon the period of " summer stagnation." During this period, which extends from April to November, the bottom temperature remains almost con- stant, and the water below a depth of about 25 ft. remains stagnant. In the autumn the surface cools and the water becomes stirred up to greater and greater depths, until finally the " great overturning " takes place and all the water is in circulation. At this time there is a slight increase in the bottom temperature that corresponds to the temporary lowering of the temperature in the spring. Then follows the period of "autumnal circulation," during which the surface and bottom strata have substantially the same temperature. In December the lake freezes and "winter stagnation" begins. The use of the thermophone for obtaining series of tem- peratures at frequent intervals in the vertical has enabled the author to study the temperature changes in more detail, and to see how they are affected by the geography of the lake and the meteorology of the region. In a frozen lake the water in contact with the under sur- LIMNOLOG Y. 6l face of the ice stands always at 32 F. The temperature at the bottom varies with the depth and with the meteorological conditions at the time of freezing. In most lakes, and par- ticularly in deep lakes, it stands at the point of maximum density; in shallow lakes it may be lower than that; under abnormal conditions, as referred to on page 52, it may be slightly higher. During the period of winter stagnation the bottom temperature sometimes rises very slightly on account of direct heating by the sun's rays. This is because of the diathermancy of the water. The temperatures of the water between the surface and the bottom are illustrated by Fig. 10. 50 55 DIAGRAM SHOWING THE TEMPERATURE OF THE WATER IN CERTAIN FROZEN LAKES. OBSERVATIONS TAKEN WITH THE THERMOPHONE. FIG. 10. (After FitzGerald.) The cold water is usually confined to a thin layer seldom tnore than 5 or 10 ft. thick under the ice, and below that layer the temperature changes but little to the bottom. This is shown by the Lake Cochituate curve. This and the 62 THE MICROSCOPY OF DRINKING-WATER. (abnormal) change in the curve at the bottom may be explained as follows: During the period of autumnal circula- tion the temperature is uniform throughout the vertical. As the weather gets colder the temperature throughout the vertical drops. Until the temperature has reached the point of maximum density the circulation of the water through the vertical takes place by thermal convection. Below that tem- perature it takes place chiefly by wind action. If the wind is not sufficiently strong to induce complete circulation the bottom temperature ceases to fall at 39.2. Thus the bottom temperature at Lake Cochituate in December, 1894, was left at that point. Later the wind stirred the water to a depth of 45 ft., and above that depth the temperature became uniform at about 38.5. Freezing usually occurs on a cool, still night. The surface- water cools and freezes before the wind has had a chance to mix it with the warmer water below. The suddenness with which a lake freezes and the intensity of the wind at the time determine the depth of the layer of cold water, and the tem- perature of the air and the intensity of the wind previous to the time of freezing determine the temperature of the water at the bottom. The Lake Winnipesaukee curve (Fig. 10) represents the effect of a current flowing between two islands. A layer of cold water about 18 ft. thick was flowing over a quiet body of warmer water. The dividing line, at a depth of about 20 ft., was very sharply defined. The Crystal Lake curve (Fig. 10) shows abnormal conditions produced by springs at the bottom of the lake. During the summer the temperature of the water is simi- larly affected by meteorological conditions. After the ice has broken up the temperature of the water at all depths rises. Above 39.2 circulation takes place chiefly by the action of LI M NO LOG Y. 63 the wind. If there were no wind, or if the wind were not sufficient, the temperature at the bottom would not rise above 39.2. In very deep lakes this happens, but in most lakes the wind causes it to rise somewhat above that point. It con- tinues to rise as long as the difference in density between the water at the surface and at the bottom does not become too great for the wind to keep up the circulation. In Lake Cochituate this difference of density is produced by a differ- ence of about 5 in temperature. When stagnation has once begun the temperature at the bottom changes very little dur- ing the summer. It sometimes rises slightly on account of direct heating, as it does in the winter. If warm weather occurs early and suddenly in the spring the required dif- ference of temperature between the upper and lower lay- ers is soon obtained, and consequently the temperature at the bottom through the summer remains low. But if the season advances slowly the bottom temperature will become fixed at a higher point. In Lake Cochituate the bottom temperature varies in different years from 42 to 45- The temperatures of the water between the surface and bottom during the summer may be illustrated by the two typical curves in Fig. i r. Previous to May 13, 1895, the season had progressed gradually. On that day the atmos- pheric temperature rose to 90 and there was little wind. These conditions produced a uniform curve. Then followed several days of cold, windy weather. The surface tempera- ture fell and the water became stirred to a depth of about 17 ft. Below 20 ft., however, there was little change. These conditions usually continue through the summer, the upper layers becoming warmed and stratified, or cooled and mixed, the lower layers remaining stagnant. Between these t>4 THE MICROSCOPY OF DRINKING-WATER. upper and lower layers there is a thin layer where the tem- perature changes rapidly, sometimes 10 in one vertical foot. This region is sometimes called the thermocline* Its position and temperature gradient vary according to the depth of the lake, the intensity of the wind, and the temperature of the water above and below. The upper boundary of the thermo- cline is sometimes very sharp particularly in the autumn; the lower boundary is less distinct. In the fall the position FIG. ir. of the thermocline drops towards the bottom as circulation extends to greater and greater depths. These seasonal changes of temperature are modified some- what in very deep and in very shallow lakes and in lakes situated in extremely hot or cold climates, and these modifi- cations may be used as a basis for classification. Classification of Lakes According to Temperature. JLakes may be divided into three types, according to their surface temperatures, and into three orders, according to their bottom temperatures. The resulting nine classes are shown in Fig. 12. On these diagrams the boundaries of the shaded areas represent the limits of the temperature fluctuations at different depths. The horizontal scale represents tem- peratures in Fahrenheit degrees increasing towards the right, * Suggested by Dr. E. A. Birge. LIMNOLOG y. and the vertical scale represents depth. The three types of lakes are designated as polar, temperate, and tropical. In lakes of the polar type the surface temperature is never above that of maximum density; in lakes of the tropical type it is never below that point; in lakes of the temperate type it is POLAR TYPE TEMPERATE TYPE TROPICAL TYPE 1 1 FIRST ORDER POLAR TYPE 1 SECOND ORDER POLAR TYPE FIRST ORDER TEMPERATE TYPE FIRST ORDER TROPICAL TYPE SECOND ORDER TEMPERATE TYPE SECOND ORDER TROPICAL TYPE THIRD ORDER THIRD ORDER THIRD ORDER FIG. 12. CLASSIFICATION OF LAKES ACCORDING TO TEMPERATURE. sometimes below and sometimes above it. This division into types corresponds somewhat closely with geographical loca- tion. The three orders of lakes may be defined as follows: lakes of the first order have bottom temperatures which are prac- tically constant at or very near the point of maximum density; lakes of the second order have bottom temperatures which undergo annual fluctuations, but which are never very far from the point of maximum density; lakes of the third order have bottom temperatures which are seldom very far from the surface temperatures. The division into orders corresponds 66 THE MICROSCOPY OF DRINKING-WATER. in a general way to the character of the lakes; i.e., their size r contour, depth, surrounding topography, etc. The temperature changes which take place in the nine classes of lakes according to this system of classification are exhibited in another manner in Fig. 13. These diagrams show by curves the surface and bottom temperatures for each season of the year, the dates being plotted as abscissae, and the temperatures as ordinates. The shaded areas show the difference between the surface and bottom temperatures,. POLAR TYPE TEMPERATE TYPE TROPICAL TYPE 39.2 32.0 ^^^^^ POLAR TYPE FIRST ORDER TEMPERATE TYPE 39.2 32.0 FIRST ORDER TROPICAL TYPE SECOND ORDER POLAR TYPE SECOND ORDER TEMPERATE TYPE SECOND ORDER TROPICAL TYPE THIRD ORDER THIRD ORDER THIRD ORDER FIG. 13. CLASSIFICATION OF LAKES ACCORDING TO TEMPERATURE. the wider the shaded area the greater being the differ- ence. A study of these diagrams brings out some interesting facts concerning the phenomena of circulation and stagnation. In Fig. 12 it will be seen that the circulation periods occur LIMNOLOGY. 7 when the curve showing the temperatures at various depths becomes a vertical line; that is, when the water all has the same temperature. The stagnation periods are shown by the line being curved, the top to the right when the warmer layers are above the colder, and to the left when the colder layers are above the warmer. In Fig. 13 the circulation periods are indicated by the surface and bottom temperature curves coinciding, and the stagnation periods by these lines being apart. The distance between the lines indicates, to a certain extent, the difference in density between the top and bottom layers, and we see that the farther apart the lines become the less likelihood there is that the water will be stirred up by the wind. In lakes of the polar type there is but one opportunity for vertical circulation (except in the third order); namely, in the summer season, when the water approaches the temperature of maximum density. In a lake of the first order, that is, in one where the bottom temperature remains constantly at 39.2, the circulation period would be very short indeed, if not lacking altogether. In a lake of the second order circula- tion might and probably would continue for a longer period. In a lake of the third order the water would be in circulation nearly all the time except when frozen. The minimum tem- perature limit indicated for this order, i.e., 32 at all depths, would be possible only in very shallow bodies of water, and would simply indicate that all the water was frozen The temperature of the ice would probably be below 32 at the surface. It is probable that very few polar lakes exist. In lakes of the tropical type there is likewise but one period of circulation each year (except in the third order). This would occur not in summer, but in winter. In the first 68 THE MICROSCOPY OF DRINKING-WATER. order this circulation period would be brief or entirely want- ing; in the second it would be of longer duration; in the third order the water would be liable to be in circulation the greater part of the year. Tropical lakes are quite numerous, but observations are lacking to place them in their proper order. Most of the lakes of the United States belong to the tem- perate type. In this type there are two periods of circulation and two periods of stagnation (except in the third order), as we have seen illustrated in the case of Lake Cochituate. In lakes of the first order the circulation periods would be very short or entirely wanting; in the second order the circulation periods would be of longer duration ; in the third order the water would be in circulation throughout the year when the surface was not frozen. The above facts may be recapit- ulated in tabular form as follows: CIRCULATION PERIODS. Polar Type. Temperate Type. Tropical Type. First Order. One circulation period possible, in summer, but generally none. Two circulation periods possible, in spring and fall, but gener- ally none. One circulation period possible, in winter, but generally none. Second Order. One circulation period, in sum- mer. Two circulation periods, in spring and autumn. One circulation period, in win- ter. Third Order. Circulation at all seasons, except when surface is frozen. Circulation at all seasons, except when surface is frozen. Circulation at all seasons. Speaking in very general terms, one may say that lakes of the first order have no circulation, lakes of the third order have no stagnation (except in winter); and lakes of the second order have Both circulation and stagnation. LIMNOLOGY. 69 In view of the comparatively few series of observations of the temperature of our lakes, the author refrains from making any classification of the lakes of the United States, but the results thus far obtained seem to indicate that the first order will include only those lakes more than about two hundred feet in depth, such, for instance, as the Great Lakes, Lake Champlain, etc. ; the second order will include those with depths less than about two hundred feet, but greater than about twenty-five feet; and the third order will include those with depths less than twenty-five feet. These boundaries are only approximate, and it should be remembered that depth is not the only factor which influences the bottom tem- perature. Stagnation is sometimes observed in small artificial reser- voirs even when the depth is less than twenty feet. It is usually of short duration. TRANSMISSION OF LIGHT BY WATER. The amount of light received by the micro-organisms in a lake depends upon the intensity of the light at the surface of the water and upon the extent to which the light is trans- mitted by the water. The transmission of light by water varies chiefly with the amount of dissolved and suspended matter that it contains. The former affects its coefficient of absorption; the latter acts as a screen to shut out the light. In studying the penetration of light into a body of water it is necessary to take account of its color and its turbidity. Color of Water. Some surface-waters are colorless, but in most ponds and lakes the water has a more or less pro- nounced brownish color. This may be so slight as to be hardly preceptible, or it may be as dark as that of weak tea. It is darkest in water draining from swamps, and the color of i 70 THE MICROSCOPY OF DRINKING-WATER. the water in any pond or stream bears a close relation to the amount of swamp-land upon the tributary watershed. The color is due to dissolved substances of vegetable origin extracted from leaves, peaty matter, etc. It is quite as harmless as tea. The exact chemical nature of the color- ing matter is not known. It is complex in composition. Tannins, glucosides, and their derivatives are doubtless present. The color of a water usually bears a close relation to the albuminoid ammonia present. Carbon, however, is the important element in its composition. The color of a water varies very closely with the "oxygen consumed." Iron is usually present, and its amount varies with the depth of the color. In some waters iron alone imparts a high color, but in peaty waters it plays a subsidiary part. The color of a water is usually stated in figures based on comparisons made with some arbitrary standard, the figures increasing with the depth of the color. The Platinum-Cobalt Standard, the Natural Water Standard, and the Nessler Standard are those most commonly used. The first is the generally accepted standard. Comparisons of the water with the standard may be made in tall glass tubes or in a colorim- eter such as that used at the Boston Water Works * For field-work a color comparator, by which the color of the water is compared with disks of colored glass, is very use- ful. The water is placed in a metallic tube with glass ends and its color compared with a second tube containing distilled water and with one end covered with one or more of the glass disks. This apparatus, devised for the United States Geolog- ical Survey by Mr. Allan Hazen and the author, is illustrated in Fig. 14. * See FitzGerald and Foss, "On the Color of Water." Jour. Frank. Inst., Dec. 1894. LIMN O LOG Y. 01 U. S. Geological Survey Apparatus for Measuring the Color of Water. 100- 110 120- m U. S. Geological Survey Turbidity Rod. FIG. 14. 72 THE MICROSCOPY OF DRINKING-WATER. The amount of color in the water collected from a water- shed has a seasonal variation. This may be illustrated by the color of the water in Cold Spring Brook, at the head of Basin No. 4, Boston Water Works. This brook is fed in part from several large swamps. The figures given are based on weekly observations. AVERAGE COLOR OF WATER IN COLD SPRING BROOK, 1894. Jan. Feb. Mar. Apr. May. June. July. Aug. Sept. Oct. Nov. Dec. Av. .99 .88 .96 .93 1.42 1.59 .98 .75 .60 .69 1.44 1.20 1.04 There are usually two well-defined maxima, one in May or June and one in November or December. In the winter and early spring the color of the water is low because of dilution by the melted snow. As the yield of the watershed diminishes the color increases until the water standing in the swamp areas ceases to be discharged into the stream. During the summer the water in the swamps is high-colored, but its effect is not felt in the stream until the swamps overflow in the fall. Heavy rains during the summer may cause the swamps to discharge and increase the color of the water in the reservoirs below. It has been found that in general the color of the water delivered from any watershed bears a close relation to the rainfall. In some localities this is more notice- able than in others. In Massapequa Pond of the Brooklyn water-supply the color varies greatly from week to week, and the fluctuations are almost exactly proportional to the rain- fall. In large bodies of water the seasonal fluctuations in color are less pronounced. The hue of the water in the autumn is somewhat different from that in the spring. The fresh- fallen leaves and vege- table matter give a greenish-brown color that is quite different from the reddish-brown color produced from old peat. LIMNOLOGY 73 When colored water is exposed to the light it becomes bleached. An elaborate series of experiments made at the Bos- ton Water Works by exposing bottles of high-colored water to direct sunlight for known periods showed that during 100 hours of bright sunlight the color was reduced about 20$, and that with sufficient exposure all the color might be removed. The bleaching action was found to be independent of tem- perature. Sedimentation had but little influence on it. It was dependent entirely upon the amount of sunlight. The percentage reduction was independent of the original color of the water. This bleaching action takes place in reservoirs where colored water is stored. Stearns has stated that in an unused reservoir 20 ft. deep the color of the water decreased from .40 to .10 in six months. In Basin No. 4, referred to above, the average color of the water in the influent stream for the year 1894 was 1.04. For the same year the average color of the water at the lower end of the basin was .71. It should be stated that this difference is not due wholly to bleaching action. The amount of coloring-matter entering the reservoir is not shown by the figure 1.04, for the reason that the quantity of water flowing in the stream is not uniform. It is greatest in the spring when the melting snows give the water a color lower than the average. Furthermore, some colorless rain-water and ground-water enters the basin. There is also a loss of high-colored water at the wasteway at a season when the color of the water is above the average. It is a difficult matter to ascertain just the amount of bleaching action that takes place in a reservoir through which water is constantly flowing. Experiments (by the author) made by exposing bottles of colored water at various depths in reservoirs have shown that 74 THE MICROSCOPY OF DRINKING-WATER. the bleaching action that takes place at the surface of a reservoir is considerable, sometimes 50$ in a month, It -decreases rapidly with increasing depth, and the rapidity with which it decreases below the surface depends upon the color of the water in the reservoir, as the table on the following page will show. From these and many similar experiments it has been found possible to calculate the extent of the bleaching action that takes place in any reservoir. The results agree closely with the observed color-readings of the water in the reservoir. The experiments also bear directly upon the point under discussion, namely, the penetration of light into the water of a reservoir. EXPERIMENTS TO DETERMINE THE AMOUNT OF BLEACHING ACTION AT DIFFERENT DEPTHS. Expt. No. i. Expi. No. 2. Rxpt. No 3. Color of water in reservoir 20 37 44 Time of exposure. Aug. 6-Sept. 4 May 5-June 4 July 2-Aug. 3 Color of water exposed 175 272 170 Percentage reduction of color: At depth of o.o ft 52$ 41$ " 0.5 " t$% 23% 2o% 11 " 1.25 " 32$ Bfo 12% " " "25 " 2i# 4% 4* " " 5.0 " 14$ 4$ 3# " " " 7-5 " 3# o# % " " " 10.0 " 1% 0% 0% < " " 15.0 " 0% 0% 0% Dark room o% o% o% Turbidity of Water. The turbidity of water is due to the presence of particles of matter in suspension, such as clay, silt, finely divided organic matter, microscopic organisms, etc. There are three principal methods used for measuring tur- bidity which give fairly comparable results. These are: i, Com- parison with silica standards; 2, Platinum- wire method; 3, Tur- LIMNOLOGY. 75 bidimeter method. In all cases the results of the observations are expressed in numbers which correspond to turbidities pro- duced by equivalent amounts of finely-divided silica in parts per million. The standard of turbidity has been defined by the U. S. Geo- logical Survey as follows : " The standard of turbidity shall be a water which contains ico parts of silica per million in such a state of fineness that a bright platinum wire i millimeter in diameter can just be seen when the center of the wire is 100 millimeters below the surface of the water and the eye of the observer is 1.2 meters above the wire, the observation being made in the middle of the day, in the open air, but not in sunlight, and in a vessel so large that the sides do not shut out the light so as to influence the results. The turbidity of such water shall be 100." The most convenient method for limnological field-work is the platinum-wire method. This method requires a rod with platinum wire of a diameter of one mm. or 0.04 inches, inserted in it about one inch from the end of the rod and projecting from it at least one inch at a right angle. Near the end of the rod, at a distance of 1.2 meters (about four feet) from the platinum wire, a wire ring is placed directly above the wire, through which, with his eye directly above the ring, the observer looks in mak- ing the examination. The rod is graduated as follows: The graduation mark of 100 is placed on the rod at a distance of ico mm. from the centre of the wire. Other graduations are made according to the following table, which is based on the best obtainable data and in which the distances are intended to be such that when the water is diluted the turbidity readings will decrease in the same proportion as the percentage of the original water in the mixture. These graduations are those used to construct what is known as the U. S. Geological Survey Turbidity Rod of 1902. (See Fig. 14.) 7 6 THE MICROSCOP Y OF DRINKING- WA TER. Turbidity, Parts per Million. Vanishing Depth of Wire, mm. Turbidity, Parts per Million. Vanishing Depth of Wire, mm. Turbidity, Parts per Million. Vanishing Depth of Wire, mm. 7 I0 95 28 314 1 2O 86 8 971 30 296 130 81 9 873 35 257 140 76 10 794 40 228 150 72 ii 729 45 205 160 68.7 12 674 50 l8 7 1 80 62.4 13 627 55 171 200 57-4 14 587 60 158 250 49.1 15 55i 65 147 300 43-2 16 520 70 138 35<> 38.8 i? 493 75 130 400 35-4 18 468 80 122 500 30-9 J 9 446 85 Tl6 600 27.7 20 426 9 no 800 23-4 22 39 1 95 t5 IOOO 20.9 24 361 100 IOO 1500 17.! 26 336 no 93 200O 14-8 3OOO 12. I Procedure. Push the rod vertically down into the water as far as the wire can be seen, and then read the level of the surface of the water on the graduated scale. This will indicate the turbidity. The following precautions should be taken to insure correct results : Observations should be made in the open air, preferably in the middle of the day and not in direct sunlight. The wire should be kept bright and clean. If for any reason observations cannot be made directly under natural conditions a pail or tank may be filled with water and the observation taken in that, but in this case care should be taken that the water is thoroughly stirred before the observation is made, and no vessel should be used for this purpose unless its diameter is at least twice as great as the depth to which the wire is immersed. Waters which have a tur- bidity above 500 should be diluted with clear water, before the observations are made, but in case this is done the degree of dilution used should be stated and form a part of the report. For very clear waters the use of a black-and-white disk, as suggested beyond, will be found more satisfactory than that of the platinum wire. LTMNOLOG Y. 77 The most complete studies of the transparency of large bodies of water were those made by Forel and others in Switzerland. Three methods of experiment were employed. The first was that of the visibility of plates. This method, used by Secchi in 1865 in determining the transparency of the water in the Mediterranean Sea, consisted of lowering a white disc (20 cm. in diameter) into the water and noting the depth at which it disappeared from view, and then raising it and noting the point at which it reappeared. The mean of these two depths was called the limit of visibility. The second method, known as that of the Genevan Commission, was similar to the first, but instead of a white disc an incan- descent lamp was lowered into the water. This light when seen through the water from above presented an appearance similar to that of a street-lamp in a fog; that is, there was a bright spot surrounded by a halo of diffused light. When the light was lowered into the water the bright spot first dis- appeared from view. The depth of this point was noted as the " limit of clear vision." Finally the diffused light dis- appeared, and the depth of this point was called the " limit of diffused light." Both these methods were useful only in comparing the relative transparency of different waters or of the same water at different times. In order to get an idea of the intensity of light at different depths a photographic method. was used. Sheets of sensitized albumen paper were mounted in a frame in such a way that half of the sheet was covered with a black screen, while the other half was exposed. A series of these papers was attached to a rope and lowered into the water; they were equidistant and so supported that they assumed a horizontal position in the water. They were placed in position in the night and allowed to remain 24 78 THE MICROSCOPY OF DRINKING-WATER. hours. On the next night they were drawn up and placed in a toning-bath. A comparison of prints made at different depths enabled the observer to determine the depth at which the light ceased to affect the paper and to obtain an idea of the relative intensity of the light at different depths. To assist in this comparison an arbitrary scale was made by exposing sheets of the same paper to bright sunlight for different lengths of time. The results of the experiments are given by Forel as follows: In Lake Geneva the limit of visibility of a white disk 20 cm. in diameter was 21 m. The limit of clear vision of a 7-candle-power incandescent lamp was 40 m. ; the limit of diffused light was about 90 m. The depth at which the light ceased to affect the photographic paper was 100 m., when the paper was sensitized with chloride of silver, and about 200 m. when sensitized with iodobromide of silver. These depths were less in summer than in winter on account of the increased turbidity of the water. The transparency of the water in other lakes, as shown by the limit of visibility of a white disk,. is cited as follows: Lake Tahoe, 33 m. ; La Mer des Antilles, 50 m. ; Lac Lucal, 60 m. ; Mediterranean Sea, 42.5 m. ; Pacific Ocean, 59 m. It should be remembered that these are all comparatively clear and light-colored waters, and that in them the light penetrates to far greater detph than in turbid and colored water. For example, in Chestnut Hill Reservoir, a disc lowered into the water at a time when the color was 0.92 disappeared from view at a depth of six feet. The author's experiments have shown that the limit of visibility may be determined most accurately by using a disc about 8 inches in diameter, divided into quadrants painted LIMNOLOGY. 79 alternately black and white like the target of a level-rod, and looking vertically down upon it through a water-telescope provided with a suitable sunshade. It has been found that the limit of visibility obtained in this manner bears a close relation to the turbidity of the water as determined by a turbidimeter. It also varies with the color of the water, but the relation has not been carefully worked out. Absorption of Light by Water. The absorption of light by distilled water is said to vary with the temperature. The following coefficients are given by Wild as the result of laboratory experiments. It seems probable that the figures are too low. Temperature. Intensity of Light after passing through i dm. of Distilled Water. 24.4 C. 0.9179 17.0 0.93968 6.2 0.94769 The coefficient of absorption of light by colored water is quite unknown. The reduction of light in passing downward through a body of water is supposed to follow the law that as the depth increases arithmetically the intensity of the light decreases geometrically. For example, if the intensity of the light falling upon the surface of a pond is represented by I, and if J of the light is absorbed by the first foot of water (some colored waters absorb even more than this), then the intensity of light at the depth of I ft. will be f ; the second foot of water will absorb \ of f, and the intensity at the depth of 2 ft. will be T 9 ^; and so on. At this rate of decrease the intensity of light at a depth of 10 ft. will be only about 5$ of that at the surface. SO THE MICROSCOPY OF DRINKING-WATER. There are few accurate data extant regarding the quality of the light at different depths, but theory would lead us to infer that in passing downward from the surface to the bottom of a lake the light varies considerably in character. It is said that the red and yellow rays are most readily trans- mitted. CHAPTER VI. GEOGRAPHICAL DISTRIBUTION OF MICROSCOPIC ORGANISMS IN PONDS AND LAKES. THE microscopic organisms that are found most commonly in water-supplies taken from lakes or storage reservoirs are given in the following table,* arranged according to the usual system of classification and divided into groups according to their abundance and frequency of occurrence. The first group includes those genera which, in their season, are often found in large numbers; the second group includes those which are found but occasionally in large numbers; the third, those which often occur in small numbers; the fourth, those which are rarely observed. This division, while not wholly satisfac- tory, enables one to separate the important from the unim- portant forms. As observations multiply, the list may be extended and some genera may be changed from one group to another. The organisms printed in heavy type have given trouble in water-supplies, either by producing odors or by making the water turbid and unsuitable for laundry purposes. DIATOMACE^:. Commonly found in large numbers. Asterionella, Cyclo- tella, Melosira, Synedra, Tabellaria. Occasionally found in large numbers. Diatoma, Fragilaria, Nitzschia, Stephanodiscus. * Compiled from published biological examinations of Massachusetts water-supplies. 81 82 THE MICROSCOPY OF DRINKING- WATER. Commonly found in small numbers. Epithemia, Gom- phonema, Navicula, Stauroneis. Occasionally observed. Achnanthes, Amphiprora, Am- phora, Bacillaria, Cocconeis, Cocconema, Cymbella, Diades- mis, Encyonema, Eunotia, Grammatophora, Himantidium, Isthmia, Meridion, Odontidium, Orthosira, Pinnularia, Pleuro- sigma, Schizonema, Striatella, Surirella, Tetracyclus. CHLOROPHYCE^E. Commonly found in large numbers. Chlorococcus, Pro- tococcus, Scenedesmus. Occasionally found in large numbers. Ccelastrum, Cos- marium, Palmella, Pandorina, Polyedrium, Raphidium,, Staurastrum, Volvox. '. ' Commonly found in small numbers. Closterium, Conferva, Desmidium, Euastrum, Eudorina, Gonium, Micrasterias, Ophiocytium, Pediastrum, Sphaerozosma, Staurogenia, Tetra- spora,' Ulothrix, Xanthidium. Occasionally observed. Arthrodesmus, Bambusina, Botryo- coccus, Characium, Chaetophora, Cladophora, Dactylococcus, Dictyosphserium, Dimorphococcus, Draparnaldia, Gloeocystis, Hyalotheca, Mesocarpus, Nephrocytium, Penium, Selenas- trum, Sorastrum, Spirogyra, Stigeoclonium, Tetmemorus, Zygnema. CYANOPHYCE^:. Commonly found in large numbers. Anabsena, Clathro* cystis, Coelosphaerium, Microcystis. Occasionally found in large numbers. Aphanizomenon, Chroococcus, Oscillaria. Commonly found in small numbers. Aphanocapsa. Occasionally observed. Gloeocapsa, Lyngbya, Merismope- dia, Microcoleus, Nostoc, Rivularia, Sirosiphon, Tetrapedia., GEOGRAPHICAL DISTRIBUTION OF ORGANISMS. 83 SCHIZOMYCETES AND FUNGI. Commonly found in large numbers. Crenothrix. Occasionally found in large numbers. Cladothrix. Commonly found in small numbers. Beggiatoa, Lepto- thrix, Molds. Occasionally observed. Achlya, Leptomitus, Saprolegnia, Sarcina, Spirillum. PROTOZOA. Commonly found in large numbers. Cryptomonas, Dino- bryon, Peridinium, Synura, Uroglena. Occasionally found in large mimbers. Bursaria, Chloro- monas, Glenodinium, Mallomonas, Raphidomonas. Commonly found in small numbers. Actinophrys, Amoeba, Anthophysa, Ceratium, Cercomonas, Codonella, Epistylis, Monas, Tintinnus, Trachelomonas, Vorticella. Occasionally observed. Acineta, Arcella, Chlamydomonas, Coleps, Colpidium, Cyphodera, Difflugia, Enchelys, Euglena, Euglypha, Euplotes, Glaucoma, Halteria, Heteronema, Nas- sula, Paramaecium, Phacus, Pleuronema, Raphidodendron, Stentor, Syncrypta, Trichodina, Uvella, Zoothamnium. ROTIFERA. Commonly found in small numbers. Anuraea, Conochilus, Polyarthra, Rotifera, Synchaeta. Occasionally observed. Asplanchna, Colurus, Eosphora, Floscularia, Lacinularia, Mastigocerca, Microcodon, Mono- cerca, Monostyla, Noteus, Sacculus, Triarthra. CRUSTACEA. Commonly found in small numbers. Bosmina, Cyclops, Daphnia. Occasionally observed. Alona, Cypris, Diaptomus, Sida. 84 THE MICROSCOPY OF DRINKING-WATER. MISCELLANEOUS. Occasionally observed. Acarina, Anguillula, Batracho- spermum, Chaetonotus, Gordius, Hydra, Macrobiotus, Mey- enia, Nais, Spongilla; besides spores, ova, insect scales, pollen-grains, vegetable fibres and tissue, yeast-cells, starch- grains, etc. The above may be summarized numerically as follows: Classification. Number of Genera. Commonly found in large numbers. Occasion- ally found in large numbers. Commonly found in small numbers. Occasion- ally observed. Total. 5 3 4 i 5 o o 4 8 3 I 5 o o o 4 14 I 3 ii 5 3 o 22 21 8 5 24 12 4 IO 35 46 16 10 45 17 7 IO Fungi and Schizomycetes Total 18 21 4i 1 06 1 86 It will be observed that 186 genera have been recorded, 108 plants and 78 animals. Of these only 18 are com- monly found in large numbers, 13 plants and 5 animals. 21 more are occasionally found in large numbers, 16 plants and 5 animals. 41 genera are frequently seen in small numbers, while 106 genera, or more than one half of all are seen occasionally, some of them rarely. The most, important classes are the Diatomaceae, Chlorophyceae, Cyano- phyceae, and Protozoa, as shown by the large number of genera and by their greater abundance. Furthermore, these classes include all but one of the most troublesome genera that have been found in large numbers. 10 genera may be GEOGRAPHICAL DISTRIBUTION OF ORGANISMS. .85 said to be very troublesome because of their wide distribution, the frequency of their occurrence, and their unpleasant effects. They are Asterionella, Anabaena, Clathrocystis, Coelosphae- rium, Aphanizomenon,* Dinobryon, Peridinium, Synura, Uroglena, and Glenodinium. This list seems like a short one when one considers the annoyance that the microscopic organisms have caused in various water-supplies. The observations of sanitarians and the planktologists show that the microscopic organisms are very widely distributed in nature. They are found in all parts of the world, and under great varieties of climatic conditions. It is probable that they appeared on the earth at an early geological age. Some of them are found as fossils, notably the diatoms, which have silicious walls that are almost indestructible. In spite of the vast amount of study that has been given to the microscopic organisms we are still very far from under- standing the laws governing their distribution. Why it is that a certain genus v/ill grow vigorously in one pond and at the same time be absent from a neighboring one where the conditions apparently are as favorable, or why a form may suddenly appear in a pond where it has been never before seen, we are still unable to say with certainty. Solution of such problems involves a far-reaching knowledge of the chemical constituents and the life-history of the organisms, besides the effect of physical conditions, such as temperature, pressure, light, etc. The sciences of bio-chemistry and bio- physics are yet in their infancy. Until these have been further developed many problems connected with the micro- scopic organisms must remain unsolved. The following statistics are of some value in connection * In the reports of the Massachusetts State Board of Health this organ- ism is sometimes classed with Oscillaria. "86 THE MICROSCOPY OF DRINKING-WATER. O >SHi-i.-.ESS ESSSS>E5 > 4 1 ( OOOO++OO+O++O+O+ +OO+OOO+OOOO > ' J . : i : : J : : : : : '5 : jj :'l : \i il ! i : ! I ' 8 g * i ^x; X c *3 .- .ti.ti 8 j: J! =. GEOGRAPHICAL DISTRIBUTION OF OKGANISMS. **~'^!~! HH !~^^^!^*^^~'P > ' !""! ^ -fooooo+o+o-f 00000.00+0000000+00 [ rjHy mi ; ' s!fH ; ! H ? ! fi ; ; : :ii ; i'i=|Ly=il lIlMlillllllllllllllllllllll W aJ ' r ' W'S! C C W o o 6-< - 1 ^fj> q q q coo . < S . *i w s^ 15 E ro m +0 88 THE MICROSCOPY OF DRINKING-WATER. with this subject, as they show the relative abundance of the different classes of organisms in some of the important surface- water supplies of Massachusetts, together with some of the elements of the sanitary chemical analysis. For the purpose of this comparison 57 ponds and reser voirs were selected where monthly examinations, both chemi- cal and biological, have been carried on for a number of years by the State Hoard of Health. The results of these exami- nations were carefully studied, and the ponds (which, for convenience, we may consider to include lakes, ponds, and storage reservoirs) divided into groups as shown in the table on pages 82 and 83. The first two columns in this table give the names of the ponds and the cities which they supply. The third gives the depth of the pond, whether shallow or deep. The next four columns show the relative abundance of the four most im- portant classes of organisms; namely, the Diatomaceae, Chlorophyceae, Cyanophyceae, and Protozoa. The four groups are characterized as follows: the group to which each pond belongs is indicated by a Roman numeral. Group I. Number of organisms often as high as 1000 per c.c. Group II. Number of organisms only occasionally as high as 1000 per c.c. Group III. Number of organisms ordinarily between 100 and 500 per c.c. Group IV. Number of organisms never above 100 per c.c. These figures refer not to the numbers present in the average sample of water, but to the numbers during the season of maximum growth. The boundaries of the groups were not sharply defined, and in a number of cases it was hard to tell whether a pond should be classed in group II or GEORAPHICAL DISTRIBUTION OF ORGANISMS. III. The last five columns show the ponds divided into classes according to some of the elements of the chemical analysis; namely, color, excess of chlorine, hardness, albumi- noid ammonia (in solution), free ammonia, and nitrates In each case four classes are given, division being made accord- ing to the schedule given at the bottom of the table. If we consider the ponds with reference to the growths of organisms, we obtain from the above table the following summary: Group. Number per c.c. Number of Ponds and Reservoirs. Diato- maceae. Chloro- phyceae. Cyano- phyceae. Protozoa. I II III IV 2 4 8 1 5 II 29 12 7 10 18 22 8 7 35 7 Occasionally above 1000 per c.c Usually between 100 and 500 per c.c. . From this it appears that the Diatomaceae are the organ- isms most commonly found in large numbers. There are 24. ponds (42$ of the ponds considered) which often have these organisms as high as 1000 per c.c., while in only 6 (11$) are they always below 100 per c.c. The Chlorophyceae are not often found in great abundance, though many ponds contain them in moderate numbers. Only 5 ponds (9$) have growths of 1000 per c.c., while 29 (70$) have growths of from 100 to 500 per c.c. The Cyanophyceae are not as common as the Chlorophyceae, but where they do occur their growth is usually greater and they cause more trouble. There are 7 ponds (12 fo) that commonly have growths above 1000 per c.c., while in 22 (39$) they are never above 100 per c.c. The Protozoa are somewhat more abundant than either the Chlorophyceae or Cyanophyceae. Eight ponds (12$) often have growths. 9 THE MICROSCOP Y OF DRINKING- WA TER. above lOOO per c.c. ; 35 ponds (60$) have growths between 100 and 500 per c.c. From the table on pages 82 and 83 it also appears that 28 ponds (49$) often have high growths of one or more of these classes of organisms at some time during the year. Such growths, except in the case of certain diatoms, are nearly always noticeable and frequently are very troublesome. In 17 ponds the Diatomaceae alone reach 1000 per c.c.; in I pond the Cyanophycese alone; and in 3 ponds the Protozoa alone. One pond has heavy growths of Diatomaceae, Chloro- phyceae and Protozoa; two, of Diatomaceae, Chlorophyceae and Cyanophyceae; two, of Diatomaceae, Cyanophyceae and Protozoa. In two ponds all four classes are found in large numbers. There is but one pond where the organisms never rise above 100 per c.c. ; there are 16 where no class of organ- isms shows numbers greater than 500 per c.c. For the purpose of determining whether the depth of the pond exercises any important influence upon the growth of the organisms the following table was compiled: Depth.* Number per c.c. Number of Ponds. Diato- maceae. Chloro- phyceae. Cyano- phyceae. Protozoa. Deep. . . Deep Deep Deep Shallow.. Shallow.. Shallow.. Shallow.. 8 2 6 o 16 6 3 2 8 3 2 9 21 9 2 I 6 7 5 9 12 15 2 12 2 6 7 2 3 5 Usually between 100 and 500 per c.c Always below 100 per c.c Occasionally above 1000 per c.c Usually between 100 and 500 per c.c Always beiow 100 per c.c * Ponds of the Second Order are here called "deep ponds" ; ponds of the Third Order " shallow ponds " ; no ponds of the First Order are included. See page 63. There are 16 deep and 41 shallow ponds. Of the deep ponds 63$ at times have growths of the Diatomaceae above 1000 per c.c., while of the shallow ponds 54$ have such GEOGRAPHICAL DISTRIBUTION OF ORGANISMS. 91 growths. There are no deep ponds where the Diatomaceae are lower than 100 perc.c., while in 15$ of the shallow ponds they are lower than that figure. It thus appears that the heavy growths of the Diatomaceae are somewhat more likely to be found in the deep than in the shallow ponds. The same may be said of the Chlorophyceae, though the difference is not so marked. 31$ of the deep ponds and 27$ of the shallow ponds at times have growths as high as 1000 per c.c. The Cyanophyceae and Protozoa, on the other hand, incline toward shallower water. In the case of the former, 18$ of the deep ponds and 34$ of the shallow ponds at times have growths of 1000 per c.c., while in the case of the latter the figures are 12% and 32$ respectively In this connection it would be of interest to show statis- tically the relation that undoubtedly exists between the growths of organisms and the character of the material form- ing the bottoms of the ponds, but unfortunately the necessary data are lacking in too many cases. So far as observations have been made, it appears that muddy bottoms are very largely responsible for excessive growths of microscopic organisms. An important question, and one which is of particular interest to water analysts, is the relation between the growths of organisms and the chemical analysis of the water in which the organisms are found. Unquestionably there is such a relation, and we should very much like to be able to take up a chemical analysis and say "this water contains such and such substances in solution, and, therefore, such and such organisms may be expected to thrive well in it." In other words, we desire to know better the nature of the necessary food-supply of the microscopic organisms.* * Experiments upon this subject are now in progress. 92 THE MICROSCOP Y OF DRINKING- WA TER. The tables given on pages 89 and 90 are designed to show in a very general way the relation between the organisms in the 57 selected ponds and some of the important elements of the chemical analysis. These tables reveal several important facts: first, it is seen that the color of a water has an important influence upon the number of organisms that will be found in it. Of the 24 cases where the Diatomaceae are commonly found higher than 1000 per c.c., 12 (or 50$) occur in light-colored waters, i.e.,. water having a color lower than 0.30 on the Nessler scale, and none occur in water where the average color is above i.oo. The same fact is noticed in the case of the other organisms, but not as markedly as with the Diatomaceae. The reason for this is, doubtless, on account of the difference in specific gravity between the diatoms and the other organisms. The diatoms are heavy by reason of their siliceous cell-walls, but the other organisms are much lighter and some of them liberate gas, causing them to keep near the surface. The depth to which light penetrates in a body of water makes less difference with the growth of the Cyanophyceae, for example. than it does with the diatoms, which constantly tend to sink and which are kept near the surface chiefly by the vertical currents in the water. The "excess of chlorine" means the difference between the amount of chlorine found in a sample of water and that found in the unpolluted water of the same region. To a cer- tain extent it represents the amount of pollution which the water has received. It is important to know whether this element of the analysis bears any relation to the organisms and whether one may rightly infer that a large growth of organisms in a reservoir is any indication of the pollution of a water-supply. A study of the tables shows that only to a GEOGRAPHICAL DISTRIBUTION OF ORGANISMS. 93 A. Chemical Analysis (pans per 1,000,000). Number of Ponds and Reservoirs in which the Diatomaceac are Often above looo per c.c. Occasionally above looo per c.c. Usually be- tween too and 500 per c.c. Below too per c.c. Color o to 30 12 4 9 4 , u C rt 3 .C rt o. c _^ So 3 ptember. 1 ovember. 1-' S u g fc 3 s i , 3 1 60 88 74 49 22 9 47 Surface n 3 14 62 37S 787 "97 i6 7 s 1778 1227 266 53 621 Basin 3 15 ft. 30 ft. 18 47 i 4 13 4 6 57 260 235 768 597 1072 633 1146 1813 1487 1161 1342 253 222 34 37 543 485 Basin 4 Surface 20 ft. 78 18 74 19 IO 27 79 37 76 47 123 43 75 78 30 2Q 45 ss 40 37 22 57 40 ft. 13 18 12 21 48 38 33 21 26 25 Surface 4I 5 36 64 91 193 20.3 9i 243 186 41 3 105 Basin 6 25 ft. 28 10 4 57 42 61 46 65 iqo S6 9 58 50 ft. 4 5 21 76 5 1 39 18 47 3 214 60 16 53 A further analysis of the results at Lake Cochituate shows the vertical distribution of the different classes of organisms to be as follows: RELATIVE NUMBER OF ORGANISMS (STANDARD UNITS) PER C.C. AT THE SURFACE AND BOTTOM OF LAKE COCHIT- UATE. AVERAGE FOR THE YEAR 1895. Diato- maceae. Chloro- phyceae. Cyano- phyceae. Protozoa. Rotifera. Miscella- neous. . Total. Surface Bottom 144 160* 79 16 108 6 7 i J7 i 10 3 I 99 1 355 353 * If the dead and empty cells were excluded this figure would be much lower, t Chiefly Crcnothrix. CHAPTER IX. ODORS IN WATER-SUPPLIES. THE senses of taste and odor are distinct, but they are closely related to each other. There are some substances, like salt, that have a taste but no odor, and there are other substances, like vanilla, that have a strong odor but no taste. It is believed that the sense of taste is quite limited and that many so-called tastes are really odors, the gas or vapor given off by the substance tasted reaching the nose not only through the nostrils but through the posterior nares. Thus an odor tasted is often stronger than an odor smelled. Chemically pure water is free from both taste and odor. Water containing certain substances in solution, as sugar, salt, etc., may have a decided taste but no odor. Such taste-producing substances are met with in mineral waters or in brackish or chalybeate waters, but as a rule they are not offensive and they seldom affect large bodies of water. Most of the bad tastes observed in drinking-water are due not to in- organic but to organic substances either in solution or in sus- pension. Such substances almost invariably produce odors as well as tastes. The subject may be pursued therefore from the standpoint of odor, though in many instances the best way to observe the odor of the water is to taste it. Water taken directly from the ground and used immedi- ately is usually odorless. In certain sections of the country it has a sulphurous odor. .If it is contaminated or drawn from a swampy region it may be somewhat moldy or unpleasant. Almost all surface-waters have some odor. Many times it is too faint to be noticed by the ordinary consumer, though 117 Il8 THE MICROSCOPY OF DRINKING-WATER. it can be detected by one whose sense of smell is carefully trained. On the other hand, the water in a pond may have so strong an odor that it is offensive several hundred feet away. Between these two extremes one meets with odors that vary in intensity and in character, and that are often the source of much annoyance and complaint. It is difficult to classify the odors of surface-waters on a satisfactory basis, but they fall into three general groups: I. Odors caused by organic matter other than living organ- isms. 2. Odors caused by the decomposition of organic matter. 3. Odors caused by living organisms. I. The odors caused by organic matter other than living organisms may be included under the general term vegetable. They vary in character in different waters and at different seasons. It is difficult to find terms that will describe them exactly. It is seldom that two observers will agree as to the most appropriate descriptive adjective. To one person the odor of a water may be straw-like, to another swamp-like, to another peaty. This is due to the fact that the sense of smell in man is not well cultivated. In practice, therefore, it has become customary to use the general term vegetable instead of the terms straw-like, swamp-like, marshy, peaty, sweetish, etc. The intensity of an odor may be indicated by using the prefixes very faint, faint, distinct, decided, very strong. A better method, however, is to use numerical pre- fixes, which may be approximately defined as shown in table on p. 119. According to this method the expression " 3 f " would indicate a ' ' distinct fishy odor, " ' ' 2 v " a " faint vege- table odor," etc. The reader will understand that the above definitions are far from exact, and that the intensity of odors varying in character cannot be well compared. A faint fishy odor, for example, might often attract more attention than a distinct vegetable odor. Heating a water usually intensifies ODORS IN WATER SUPPLIES. Numerical Value. Term. Approximate Definition. None. No odor perceptible. I Very Faint. An odor that would not be ordinarily detected by the average consumer, but that could be detected in the laboratory by an ex- perienced observer. 2 Faint. An odor that the consumer might detect if his attention were called to it, but that would not otherwise attract attention. 3 Distinct. An odor that would be readily detected and that might cause the water to be regarded with disfavor. 4 Decided. An odor that would force itself upon the attention and that might make the water unpalatable. 5 Very Strong. An odor of such intensity that the water would be absolutely unfit to drink, (a term to be used only in extreme cases). its odor.* A water that has a faint odor when cold may have a distinct odor when hot. Most of the vegetable odors are caused by vegetable matter in solution. Brown-colored waters invariably have a sweetish- vegetable odor, and the intensity of the odor varies almost directly with the depth of the color. Both color and odor are due to the presence of certain glucosides, of which tannin is an example, extracted from leaves, grasses, mosses, etc. In addition to the odor, these substances have a slight astringent taste. Colorless waters containing organic matter of other origin may have vegetable odors, but they are usually less sweetish and more straw-like or peaty. Akin to the vegetable odors are the earthy odors caused by finely divided * In the laborator)" the "cold odor" is observed by shaking a partly filled bottle of the water and immediately removing the stopper and apply- ing the nose. The "hot odor "is obtained by heating a portion of the water in a tall beaker covered with a watch-glass to a point just short of boiling. When sufficiently cool the cover is slipped aside and the observa- tion made. 120 THE MICROSCOPY OF DRINKING-WATER. particles of organic matter, clay, etc. The two odors are often associated in the same sample. 2. Odors produced by the decomposition of organic matter in water are not uncommon. They are described, somewhat imperfectly, by such terms as moldy, musty, unpleasant,, disagreeable, offensive. An unpleasant odor is produced when the vegetable matter in water begins to decay. It may be said to represent the first stages of decomposition. As decomposition progresses the unpleasant odors become dis- agreeable, and then offensive. It is seldom that the decom- position of vegetable matter in water produces odors worse than "decidedly unpleasant." The disagreeable odors usually can be traced to decaying animal matter, and, as a rule, offen- sive odors are observed only in sewage or in grossly polluted water. The terms moldy and musty are more specific than the terms unpleasant, disagreeable, and offensive, but they are difficult to define. They are quite similar in character; but the musty odor is more intense and is usually applied only to sewage-polluted water. The moldy odor suggests a damp cellar, or perhaps a decaying tree-trunk in a forest. The bacteriologist will recognize this odor as similar to that given off by certain bacteria growing on nutrient gelatine. The odors of decomposition naturally are associated with the odors of the other groups, and one often finds it conven- ient to use such expressions as "distinctly vegetable and faintly moldy," i.e., "3v-f-2m," or *' decidedly fishy and disagree- able," i.e., "4f + 4d." 3. The odors of drinking-water due to the presence of living organisms are the most important because of their common occurrence, because of their offensive nature, and because they affect large bodies of water. It is only within recent years that these odors have been well understood, and even now there is much to be learned about the chemical ODORS IN WATER-SUPPLIES. 121 nature of the odoriferous substances and their relation to the life of the organisms. At one time it was supposed that it was only by decay that the organisms became offensive. It is now a well-established fact that many living organ- isms have an odor that is natural to them and that is pecul- iar to them, just as a fresh rose or an onion has a natural and peculiar odor. It has been found, also, that in most cases, and it may be true in all cases, the odor is produced by compounds analogous to the essential oils. In some cases; the oily compounds have been isolated by extraction with. ether or gasoline. Odors due to these oils have been called " odors of growth" because the oils are produced during the growth of the organisms. The oil-globules may be seen in many genera if they are examined with a sufficiently high power. They are usually most numerous in the mature forms and are often particularly abundant just before sporulation or encystment. The production of the oil represents a stor- ing-up of energy. The odors have been called " odors of disintegration," because they are most noticeable when the breaking up of the organism causes the oil-globules to be scattered through the water. It is sufficient, however, to call them the "natural odors" of the organisms, to distinguish them from the very different odors produced by their decom- position. It was stated in Chapter IV that the microscopic organ- isms are not found in ground-waters (except when stored in open reservoirs) nor in streams in sufficient abundance to cause trouble. It is in the quiescent waters of ponds and lakes and reservoirs that they develop luxuriantly, and it is to the reservoir that one should look first when investigating the cause of an odor in a public water-supply. The littoral organisms found on the sides of reservoirs. 122 THE MICROSCOPY OF DRINKING-WATER include the flowering aquatic plants, the Characeae, the filamentous algae, etc., of the vegetable kingdom and the fresh-water sponge, Bryozoa, etc., of the animal kingdom. The effect which they exert on the odor of a water is difficult to determine because they are seldom found in a reservoir where the floating microscopic organisms are absent. In many cases where a peculiar odor of a water has been charged to some of these littoral forms, subsequent investigation has made it probable that the odor was really caused by limnetic organisms that had been overlooked in the first instance. Speaking generally it may be said that in reservoirs that are large and deep the organisms attached to the shores pro- duce little or no effect on the odor of the water; and that in small shallow reservoirs where the aquatic vegetation is thick they do not impart any characteristic " natural" odor, but they may produce a sort of vegetable taste and a disagreeable odor due to decomposition. Some of the littoral aquatic plants, such as Myriophyllum and a number of the filamentous algae, possess a natural odor that is strongly " vegetable" and, at times, almost fishy; but the odor is obtained only when the plants are crushed or when fragments are broken off and scattered through the water. Under ordinary conditions of growth in a reservoir this does not happen and therefore no odor is imparted to the water except through decomposition. There are on record some apparent exceptions to the rule that the attached growths cause no odor. Hyatt * described a growth of Meridion circulare at the headwaters of the Croton River, in 1881, that was supposed to have affected the entire supply of New York City: Rafter has connected odors with * References to this and similar illustrations may be found in the bib- liography in the appendix. ODORS IN WATER-SUPPLIES. 12$ Hydrodictyon utriculatum and other Chloropbyceae: Forbes investigated a water-supply where a growth of Chara was thought to be the cause of a bad odor; and Western has stated that serious trouble was caused in Henderson, N. C., by an extensive growth of Cristatella.* All of these cases where odors in water-supplies have been attributed to certain limnetic organisms lack corroboration. The author once examined a reservoir where a mass of Melosira varians several feet thick covered the slopes to a con- siderable depth. A severe storm tore away the fragile fila- ments, and masses of Melosira passed into the distribution-pipes and caused a noticeable vegetable and oily odor in the water. In connection with the relation of the littoral organisms to odors in water-supplies some reference should be made to the " cucumber taste" that has been a frequent cause of complaint against the Boston water-supply. In 1881 the trouble was very severe. The water had a decided odor of cucumbers, which was intensified at times to a "fish-oil" odor. Heating made the odor very strong and offensive. A noted expert made an examination and concluded that the seat of the trouble was in Farm Pond, one of the sources of supply. This pond was so situated that all the water of the Sudbury system passed through it on its way to the city. Chemical analysis of the water and microscopical examination of the mud failed to reveal the cause of the odor. It was found, however, that fragments of fresh-water sponge (Spon- gilla fluviatalis) were constantly collecting on the screens and that these had the "cucumber odor." It was decided therefore that the fresh-water sponge was the cause of the odor. The conclusion was quite generally accepted and the report has been. quoted extensively. * The organism observed was probably Pectinatella and not Crista- iella. AUTHOR. 124 THE MICROSCOPY OF DRINKING-WATER. At that time some water experts disagreed with this opin- ion. They claimed that the amount of sponge found in the pond was not sufficient to produce the odor. In the light of modern microscopical examinations we are coming to believe that the dissenters were right and that the fresh-water sponge was not the cause of the cucumber odor. The author has taken masses of Spongilla and allowed them to rot in a small quan- tity of water till the odor was unbearable. This water was then diluted with distilled water to see how large a mass of water the decayed sponge would affect. It was found that with a dilution of I to 50 ooo there was no perceptible odor. If this is true it would take a mass of sponge several feet thick over the entire bottom of Farm Pond to produce an odor as intense as that observed in 1881. Morever the odor produced by the sponge is not the ' 'cucumber odor, " although it is similar to it. There is good reason to believe that the cucumber odor observed in 1881 was due to Synura. One need not dispute the observation that the sponge that collected on the Farm Pond screens had the cucumber odor, for no doubt the sponge was covered with Synura, as it is often covered with other organisms. It is not surprising, either, that the Synura should have been overlooked in the water, because the organ- ism disintegrates readily and a comparatively small number of colonies is able to produce a considerable odor. The times of the occurrence of the odor namely, in the spring and autumn are worth noting, as they correspond with the seasons when Synura grows best and when it is most com- monly found. In February, 1892, the cucumber taste again appeared in the Boston water. This time it was definitely traced to Synura that was growing in the water just under the ice in ODORS IN WATER-SUPPLIES. 12$ Lake Cochituate. Since then it has reapppeared at intervals in other parts of the supply, notably in Basin 3 and Basin 6. It has been found that 5 or 10 colonies per c.c. are sufficient to cause a perceptible odor. The floating microscopic organisms, or the plankton, are responsible for most of those peculiar nauseating odors that are the cause of complaint in so many public water-supplies. In most, if not in all, cases the odor is due to the presence of an oily substance elaborated by the organisms during their growth. This has been proved by long-continued observa- tions and experiments, during the course of which the follow- ing facts have been noted : The odors referred to vary in character. They are difficult to describe, but they can be readily identified. Particular odors are associated with particular organisms. If an organ- ism is present in sufficient numbers its particular odor will be observed ; if it is not present in sufficient numbers its odor will not be observed. Further, the intensity of the odor varies with the number* of organisms present. If water that contains an organism which has a natural odor is filtered through paper, the odor of the filtered water f will be much fainter than before, and the filter-paper on which the organ- isms remain will have a strong odor. If the organisms are concentrated by the Sedgwick-Rafter method, the concentrate will have a decided taste and odor. If these organisms are placed in distilled water, the water will acquire the odor of the original water. Thus, the relation between particular odors and particular organisms has been well established. Indeed, in the absence of a microscopical examination, experienced * There are some exceptions to this. f In some cases the odoriferous substances from the organisms pass through the filter, and the disintegration of the organisms gives the filtered water an increased odor over the unfiltered water- 126 THE MICROSCOPY OF DRINKING-WATER. observers are often able to tell the nature of the organisms present by a simple observation of the odor. That the odors are not due to the decomposition of the organism is proved by the character of the odors themselves and by the fact that they are not accompanied necessarily by large numbers of bacteria or by the presence of free ammonia or nitrites. This is supported by the fact that, when the organisms do decay, the bacteria increase in number and the odor of the water changes in character. The natural odor is given off by some substance inside of the organism, and when this substance becomes liberated the odor is more easily detected. The odor is intensified by heat- ing, by mechanical agitation, and by change in the density of the water containing the organisms. Many of the odor-pro- ducing organisms are very delicate. Heating breaks them up and drives off the odoriferous substances. The flow of water through the pipes of a distribution system is sufficient to cause the disintegration of many forms, and it is a matter of common observation that in such cases the odor of a water at the service-taps is more pronounced than at the reservoir. If the density of a water is increased by adding to it some sub- stance, such as salt, the organisms may become distorted if not actually broken up. This causes an intensification of their odor. Increased pressure also leads to the same result. The natural odor of the organisms is due to some oily substance analogous to those substances found in higher plants and animals, and that give the odor to the peppermint and the herring. The fact was noted long ago that the addition of salt to water that was affected with certain odors developed nil oily flavor. Many of the odors caused by organisms are of a marked oily nature. The oil-globules in these organ- ODORS IN WATER-SUPPLIES. I2/ isms may be observed with the microscope. The number of oil-globules varies according to the age and condition of the organisms, and the intensity of the odor varies with the number of oil-globules present. Finally, the oily substances have been extracted from the organisms and it has been found that they possess the same odor as that observed in the water containing them. A series of experiments was made at one time to show that the amount of oil present in the organisms was sufficient to account for the odors observed in drinking-water. Some of the familiar essential oils, such as oil of peppermint, oil of clove, cod-liver oil, etc., were diluted with distilled water, and the amount of dilution at which the odor be- came unrecognizable was noted. The oil of peppermint was recognized when diluted I : 50000000; the oil of clove, I : 8000000; cod-liver oil, I : IOOOOOO; etc. The odor of kerosene oil could not be detected when diluted I : 800 ooo. The amount of oil present in water containing a known num- ber of organisms was estimated for comparison. It was found that in water containing 100 colonies of Synura per c.c. the dilution of the Synura oil was I : 25 ooo OOO; and that in a water with 50000 Asterionella per c.c. the dilution was only I : 2 ooo ooo. Thus, the production of the odor by the oil is quite within the range of possibility. An interesting fact brought out by the experiments was that the odor of the oils varied with different degrees of dilution not only in intensity but in character.* This variation of the character of the odor with its intensity is important to notice, as it accounts for the different descriptions of the same odor in a water- supply at different times and by different people. * On one occasion seven people out of ten who were asked to observe the odor of very highly diluted kerosene oil declared that it smelled like " perfumery." 128 THE MICROSCOPY OF DRINKING-WATER. The nature of the odoriferous oils or oily substances is not well known. Calkins, who isolated the odoriferous prin- ciple of Uroglena with gasoline and ether, describes it as being .similar to the essential oils. It was non-volatile at the tem- perature of boiling water. Jackson and Ellms extracted a similar substance from Anabaena with gasoline. On standing it oxidized and became resinous. It contained needle-like crystals. Experiments by the author have shown that the oils of Asterionella and Mallomonas are quite similar in char- acter. Most, if not all, of the organisms produce oil during their growth to a greater or less degree. In many cases it is quite odorless. Water is often without odor even when large num- bers of organisms are present. This is either because the organisms have not produced oil, or because the oil is odor- less. Sometimes water rich in organisms will have an oily flavor with no distinctive odor. This is true in the case of some species of Melosira. Many organisms impart a vegetable and oily taste, without a distinctive odor. This is true of Synedra pulchella and Stephanodiscus. There are, moreover, microscopic organisms that produce oils that have a distinc- tive odor, but that occur in drinking-water in such small num- bers that the odor is not detected. The organisms that have a distinctive odor and that are found in large numbers are comparatively few. Not more than twenty-five have been recorded and only about half a dozen have given serious trouble. More extended observations may lengthen this list. The distinctive odors produced by these organisms may be grouped around three general terms, aromatic, grassy, and fishy, and for convenience they may be tabulated as follows: ODORS IN WATER-SUPPLIES. I2 9 Group. Organism. Natural Odor. AROMATIC ODOR. GRASSY ODOR. FISHY ODOR. DlATOMACE^E Asterionella Cyclotella Diatoma Meridion Tabellaria PROTOZOA Cryptomonas Mallomonas CYANOPHYCE^E Anabaena Rivularia Clathrocystis Coelosphaerium Aphanizomenon CHLOROPHYCE^ Volvox Eudorina Pandorina Dictyosphaerium PROTOZOA Uroglena Synura Dinobryon Bursaria Peridinium Glenodinium Aromatic geranium- Faintly aromatic. Aromatic. -fishy. Candied violets. Aromatic violets fishy. Grassy and moldy green-corn nas- turtiums, etc. Grassy and moldy. Sweet, grassy. Grassy. Fishy. Faintly fishy. Fishy and oily. Ripe cucumbers bitter and spicy taste. Fishy, like rockweed. Irish moss salt marsh fishy. Fishy, like clam-shells. Fishy. The aromatic odors are due chiefly to the Diatomaceae. The strongest odor is that produced by Asterionella. The character of this odor changes with its intensity. When few organisms are present the water may have an undefinable aromatic odor; as they increase the odor resembles that of a rose geranium; when they are very abundant the odor becomes fishy and nauseating. The other diatoms given in the table produce the aromatic odor only when present in very large numbers. There are two Protozoa that have an aromatic odor. The odor of Cryptomonas is sweetish and resembles that of the violet. The odor of Mallomonas is similar to that of Cryptomonas, but when strong it becomes fishy. 13 THE MICROSCOPY OF DRINKING-WATER. The grassy odors are produced by the Cyanophyceae. Anabaena is the most important organism of this class. There are several species that have slightly different odors. The grassy odor is usually accompanied by a moldy odor, which is probably due to decomposition, as this organism decays rapidly. When very strong the odor of Anabaena much re- sembles raw green-corn, or even a nasturtium stem. The prevailing odor, however, is grassy, i.e. the odor of freshly cut grass. The other blue^green algae have odors that may be called grassy, but they are less distinctive than in the case of Anabaena. The fishy odors are the most disagreeable of any observed in drinking-water. That produced by Uroglena is perhaps the worst. It is quite common. Water rich in Uroglena has an odor not unlike that of cod-liver oil. The odor of Synura is almost as bad and almost as common. It resembles that of a ripe cucumber. Synura also has a distinct bitter and spicy taste. It "stays in the mouth " and is most noticeable at the back part of the tongue. Glenodinium and Peridinium both produce fishy odors. The latter somewhat resembles clam-shells. Dinobryon has a fishy odor and sug- gests sea-weed. The odor of Bursaria is like that of Irish moss. It also reminds one of a salt marsh. With certain degrees of dilution some other Protozoa have the salt-marsh odor, reminding one of the sea. Fishy odors are said to be produced by Volvox, Eudorina, and Pandorina. These Chlorophyceae are sometimes classed with the Protozoa, so that it may be said in a general way that the fishy odors are produced by microscopic organisms belonging to the animal kingdom. Some of the microscopic organisms have distinctive odors of decomposition. The Cyanophyceae when decaying give a ODORS IN WATER-SUPPLIES. 131 "pig-pen " odor. Beggiatoa and some species of Chara give the odor of sulphuretted hydrogen. All the odors given off by the decomposition of microscopic organisms are offensive. They are particularly so when the organisms contain a high percentage of nitrogen. Jackson and Ellms, in an interesting study of the decomposition of Anabaena circinnalis, found that that organism contained 9.66$ of nitrogen. They found that the "pig-pen " odor was due "to the breaking down of highly organized compounds of sulphur and phosphorus and to the presence of this high percentage of nitrogen. The gas given off during decomposition was found to have the following composition : Marsh-gas 0.8$ Carbonic acid 1.5$ Oxygen 2.9$ Nitrogen 12.4$ Hydrogen 82 .4^ 1 00. The gas that remained dissolved in the water containing the Anabaena was practically all CO 2 and represented a large per- centage of the total gas produced." Besides the odors above described, water-supplies some- times become affected with what have been called "chemical odors," such as those of carbolic acid, creosote, tar, etc. They can be traced usually to some pollution by manufactur- ing waste, though a vigorous decomposition of organic matter has been known to give an odor resembling carbolic acid. Similar odors are sometimes caused by the coating on the inside of new distribution-pipes. The extent to which water-supplies are afflicted with odors 132 THE MICROSCOPY OF DRINKING-WATER. was well shown by the investigations of the Massachusetts State Board of Health. Out of 71 water-supplies taken from ponds and reservoirs, 45, or 63$, were found to have given trouble from bad tastes or odors, and about two thirds, of these had given serious trouble. Calkins has stated that in 1404 samples from surface-water supplies in Massachusetts odors were observed as follows: Odor. Per Cent of Samples Affected. No odor to 20 Vegetable 26 Sweetish 7 Aromatic 6 Grassy 15 ;.;.. Fishy 3 Moldy 10 Disagreeable 6 Offensive 7 The intensity of these odors was not stated. Many of them probably were not strong enough to cause complaint. It must not be inferred from this that Massachusetts is more afflicted in her surface-water supplies than other sections of the country. The same troubles are observed everywhere. It is only because the Massachusetts supplies have been more carefully studied than elsewhere that attention has been drawn to them. In a previous chapter it was stated that the microscopic organisms are widely distributed both in this country and abroad. Wherever they are found in abundance they must inevitably affect the odor of the water. The question is often asked, " Are growths of organisms such as Asterionella, Synura, etc., injurious to health?" This cannot be answered authoritatively, but from the data ODORS IN WATER-SUPPLIES. 133 at hand it is believed that such organisms are not injurious, certainly not to persons in good health. The actual amount of solid matter contained in the organisms is much smaller than might be supposed. For example, it has been calculated that the weight of one Asterionella is .0000000004 gram. A growth of 100000 Asterionella per c.c. would render a water unfit to drink because of its odor, yet a tumblerful of such water would contain but eight milligrams of solid matter, and only one half of this would be organic matter. It is almost in- conceivable that such a small amount of organic matter could cause trouble unless some poisonous principle were present, and so far as is known no such substance has been found. The alleged cases of poisonous algae rest upon too uncertain evidence to be received as facts. Nevertheless there is some reason to believe that people accustomed to drinking-water free from organisms may be subjected to temporary intestinal disorders when they begin to drink water rich in microscopic organisms, just as people are affected by changing from a hard to a soft water and vice versa. It is possible that with young children and invalids such disorders may be more common than has been supposed. CHAPTER X. STORAGE OF SURFACE-WATER. To obtain a permanently safe and satisfactory surface- water supply without filtration the rainfall must be collected quickly from a clean watershed and stored in a clean reservoir. A clean watershed may be defined as one upon which there are no sources of pollution and no accumulations of decomposing organic matter. The subject of pollution is of paramount importance, but it will not be emphasized here as its discussion leads into bacteriology rather than into micros- copy. No watershed can be free from organic matter, and this must eventually decompose. The grass dies, the leaves fall, and a thin layer of decay is spread over the surface of the ground. This is repeated each season. Normally this organic matter disappears by rapid oxidation, and if the ground is sloping the rain that falls upon it runs off rapidly and absorbs comparatively little organic matter. If, however, the decaying vegetation has accumulated in thick layers, if the ground is level and becomes saturated or covered with water, decomposition takes place under different condi- tions, and the water may become highly charged with organic matter and the products of decay. The effect of swamp areas upon the color of water has been referred to. Water from a clean watershed seldom has a color higher than 30 of the Platinum Scale. The 134 STORAGE OF SURFACE-WATER. 13$ -amount of color above this figure can be generally traced to swampy land. The color of the stagnant water of swamps is sometimes very high, often 300 and sometimes as high as 500 or 700 on the Platinum Scale. From this it is easy to see that even a comparatively small percentage of swamp- land upon a watershed may have an important effect upon the color of the combined yield. A highly colored water means a water rich in organic matter. If the color is much above 50 the water has an unsightly appearance, a distinct vegetable odor, and a sweetish and somewhat astringent taste. But the pres- ence of organic matter is objectionable for another reason. It helps to furnish food-material for the microscopic organisms, and these may render the water very disagreeable. Swamps are breeding-places for many of the organisms that cause trouble in water-supplies, and numerous instances might be cited where organisms have developed in a swamp and have been washed down into a storage-reservoir, rendering the water there almost unfit for use. Cedar Swamp, at the head of the Sudbury River of the Boston water-supply, furnishes an example of this. During August, 1892, Anabaena developed abundantly in a small pond in the middle of this swamp. At one time there were .8400 filaments (about 50 ooo standard units) per c.c. A heavy rain washed the Anabaena down-stream, and on August 15 there were 2064 filaments per c.c. at the upper end of Basin 2. On August 17 the water entering the basin con- tained but 600 filaments, and a week later it contained none. The Anabaena were washed down-stream in a sort of wave. Basin 2 is a long, narrow basin. The wave of Anabaena passed through the basin, down the aqueduct, through the Chestnut Hill Reservoir, and into the service- 136 THE MICROSCOPY OF DRINKING-WATER. pipes. On August 22 Anabaena were first observed at the gate-house at the lower end of Basin 2, where there were 647 filaments per c.c., and on the following day they appeared at the terminal chamber of the conduit at Chestnut Hill Reser- voir, where there were 326 filaments per c.c. In another week they became disseminated through this reservoir and were found in the service-pipes. As the water from Basin 2 passed towards the city it became mixed with the water from other sources, so that by the time it reached the consumers the Anabaena were not sufficiently abundant to cause complaint. After the first wave of Anabaena had passed through Basin 2 the organisms began to increase through- out the basin, and the growth continued for several weeks. It was evident that the water from the swamp carried down not only the Anabaena themselves, but enough food-material to support their growth in the basin. Instances are still more common where organisms from swamps have seeded storage-reservoirs. Entering the reser- voir in comparatively small numbers, the organisms fre- quently find in the quiet water conditions favorable to their growth. Growths of some of the Flagellata may be traced directly to seeding from swamps. The draining of swamps makes a vast improvement in the quality of the water deliv- ered from a watershed. In general it should be carried out in such a way that the water falling upon the clean portions of the watershed is not obliged to pass through the swamp before entering the reservoir. This may be accomplished by a system of marginal drains or canals. The lowering of the water-table of a swamp also improves the quality of the water delivered from it. Small mill-ponds and other imperfectly cleaned ponds or pools are also frequent breeding-places of microscopic organ- S TOR A GE OF S URFA CE- IV A TER. I 3 7 isms. Again the Boston water-supply furnishes an example* A short distance above Basin 3 there were at one time several mill-ponds. These ponds were favorite habitats of Synura. These organisms were often found there in large numbers, and when the water was let down-stream through the mills or when heavy rains caused the ponds to overflow, the Synura would become numerous in Basin 3. Thus it is seen that in order to avoid the growth of trouble- some organisms the water should be delivered from a water- shed quickly, and should not be allowed to stand in shallow ponds or pools in contact with organic matter. As far as possible a watershed should be self-draining. It may be added that the storage reservoir also should be self-draining. It often happens, when the bottom of a reservoir is uneven, that water is left in small pools as the reservoir is drawn down. These pools are usually shallow and the water becomes warm and stagnant. They often become filled with rich cultures of organisms, and when they overflow the organ- isms are scattered through the reservoir. Such pools or pockets should be provided with an outlet. If this is impos- sible it may be advisable to fill them up. The author once observed a "pocket" in a reservoir that was excavated to a considerable depth for the sake of removing all the organic matter at the bottom. This pocket could not be drained, and during the summer it became the breeding-place of Synura and other Protozoa. It would have been better to have removed a portion of the organic matter and to have covered the remainder with clean material. It has been stated that water should not be allowed to stand for any length of time in contact with organic matter. It is quite as bad for water to stand over a swamp as it is for it to stand in a swamp. It may be worse, for if the water 338 THE MICROSCOPY OF DRINKING-WATER. has sufficient depth the decomposition of the organic matter at the bottom may take place in the absence of oxygen, and under these conditions some of the resulting products are more easily taken up by the water. This brings us to the consideration of the so-called " stagnation effects." Stagnation. By the term "stagnation " is meant a con- tinued state of quiescence of the lower layers of water in a lake or reservoir caused by thermal stratification, as described in Chapter V. During these periods of quiescence the water below the thermocline, i.e. the stagnant water, undergoes certain changes, the character and amount of these changes varying with the nature of the water and especially with the presence or absence of organic matter at the bottom of the reservoir. Stagnation may be studied best in ponds where there is a considerable deposit of organic matter at the bottom, and of such ponds Lake Cochituate is an excellent example. Near the efflux gate-house the lake has a depth of 60 ft. At the bottom there is a layer of organic matter of unknown thickness. The upper portion of this is due to deposition of organisms and other organic material transported by the water. The period of summer stagnation extends from April to November, and during this time the deposit of organic matter at the bottom is accumulating. The changes that take place in the water at the bottom of Lake Cochituate during the summer are shown in the fol- lowing table, where the analyses of the water at the surface and bottom are compared. The most conspicuous change is that of the color (see Fig. 18). While the water at the sur- face is bleaching under the action of the sunlight, that at the bottom grows rapidly darker until, near the close of the stagnation period, it has a decided opalescent turbidity and a STORAGE OF SURFACE-WATER. 139 <. ty) W ^ 2 u w o < 5 3 C/) ^ u P-I o S IS * e/> D W Q in u /During period of t" circulation [During period of 1 stagnation. /During period of j circulation. alfre tuonog : g ei . : o 3 G ; : : QoOb, v V PH I' 5 : " 8 ; : : rt o raonog : ^ * : : VO 00 i co : : : h monog : vo ,, o. S J i : 13 J* <= 2 ^ns : t in ro -^ T : : : s c monog : M m o> J : : s S 1 vo aDBpng I ro vo M : : : c 3 tn is monog : CO 0^ w oo O o w n M 1 5 c o aoHjjng oo' * VO O M O O 00 ON 00 -- a d> v -a raonog : ^ m o m vo O ^ ro * in O in a o aDBjjng ; , ro cT 5 in - O U"N . in w (0 V jj raojjog ; S * ? O Q 1 1 ; ; .2 pns 8, S J o w 2 * s uio^og ' 8 8 8 8 8 . : h z aoBjans g 8 8 8 8:88 Q v ' 2 oionog i ? M. CO OO 0) <| wepns ? MOM q q o * ro O O O 3 I'Sal oiojiog : ON *" \O ? I ': <'|H a , 3 ns y 3 40" ~~ -T^ ^ \ \ 80 30 JAN. FEB. MAR APR. MAYilUNEpULYUuG. SEP. OCT. NOV. DEC. FIG. 20. through the pipes of a distribution system. The nature of these changes is shown by Fig. 20, where the curves represent 160 GROWTH OF ORGANISMS IN WATER-PIPES. l6l the averages of weekly temperature observations for five years at Chestnut Hill Reservoir and at two taps, one at Park Square, 5 miles from the reservoir, and the other at Mattapan, 1 1 miles from the reservoir. During the spring and summer the water grows cooler as it passes through the pipes, and dur- ing the autumn and winter it grows warmer. The maximum temperature at Mattapan is never as high as that at Park Square, but the minimum temperature is about the same at both places, though it occurs later in the season at Mattapan. Samples taken at the same places serve to illustrate the changes that take place in the organisms of the water due to their passage through the pipes. Weekly observations for five years (1891-5) showed the following average number of organisms present: Number of Standard Units per c.c. Organisms. Amorphous Matter. Chestnut Hill Reservoir 248 222 Brookline Reservoir 215 212 Tap in Park Square 189 190 Tap in Mattapan 81 105 The greatest reduction does not occur near the reservoirs, where the pipes are large and the currents swift, but at the extremities of the distribution system, where the pipes are smaller. The observations showed that during the winter, when there are comparatively few organisms in the water, the reduction in the pipes is much less than during the summer, when organisms are more abundant. During the six months of the year, from November to April, there was a reduc- tion of 44$ in organisms and 24$ in amorphous matter in about 6 miles of pipe; while during the six months from May to October the reduction was 62$ for the organisms and 53$ for the amorphous matter. It is worth noting that 162 THE MICROSCOP Y OF DRINKING- WA TER. the reduction in organisms was greater than the reduction in amorphous matter. Not only are the microscopic organisms and amorphous matter reduced in the pipes, but the bacteria also tend to decrease. This fact has been observed in many cities. In the pipes of the Boston Water Works the decrease does not occur throughout the entire year. In the summer, when the temperature of the water is high and when the organisms in the water and those growing in the pipes are passing rapidly through stages of growth and decay, there is a considerable increase. This is shown in Fig. 21. MICROSCOPIC ORGANISMS, BACTERIA.AND AMORPHOUS MATTER IN THE BOSTON WATER PIPES. THE CURVES REPRESENT THE AVERAGES OF WEEKLY ANALYSES FOR THE YEARS 1891-5. 300 Q /^\ 300 t ^ / \ | 200 A / / \ 200 K f v/ N 1 100 \ /TAPIN M^ ^x ^/ *~\ 100 1 . \ \ / ZL_ / C x^^ o MICROSCOPIC ORGANISMS. 200 200 i / \ . ^. 100 / \ 1 ^ 100 5 1 x^ "~N \ ^ i^Q ^c "N s^^ 1 BACTERIA. /^ ' <~\ P 200 s V -*S \ 200 1 ^ \ if 100 ^ ,& / AMC ^ ^T^ . 5 r <= ^T* )RPHOUS MATTER. JAN. FEE. MAR APR MAY JUNE IULY AUG SEP. OCT NOV. DEC FIG. 21. In order to determine what organisms showed the greatest reduction in the pipes, a detailed study of the examinations GROWTH OF ORGANISMS IN WATER-PIPES. 163 above referred to was made for the years 1892 and 1893. The following were the results: PERCENTAGE REDUCTION OF MICROSCOPIC ORGANISMS IN THE DISTRIBUTION-PIPES BETWEEN PARK SQUARE AND MATTAPAN, BOSTON, MASS. Average for the years 1892 and 1893. Diatomaceae 58 per cent Chlorophyceae 57 " " Cyanophyceae 54 * ' " Protozoa 64 " " Miscellaneous 58 " " Organisms of all kinds 56 " " Questions naturally arise as to the cause and effect of this reduction of organisms in the pipes. They may be considered under the following topics: sedimentation, disintegration, decomposition, and consumption by other organisms. Most of the microscopic organisms are heavier than water. Some always settle in quiet water, and they do so in the pipes whenever the current is reduced to a certain point. Others, which in ponds usually rise to the surface on account of the gas-bubbles which they contain, will settle in the pipes when the pressure of the water has deprived them of their gas. In dead ends the organisms and particles of amorphous matter often accumulate and form deposits upon the bottom of the pipes. They also tend to deposit on up-grades. It is a matter of frequent observation that the water from the high points of a distribution system contains fewer organisms than that from the low points. The same fact has been observed in high buildings, where the difference between the water on the upper stories and that on the lower floor is often con- siderable. 164 THE MICROSCOPY OF DRINKING-WATER. Many of the common organisms are very fragile. Even a slight agitation of the water will break them up. This is particularly true of certain Protozoa, but it also happens to the siliceous cells of diatoms. The organisms found in surface-waters are accustomed to live in the light. When they enter the dark pipes they are liable to die and decompose. This is particularly true of some of the organisms that are abundant in the summer. Microscopical examination of samples from the service-taps has often revealed organisms in a decomposing condition, swarming with bacteria. This decomposition tends to reduce the numbers of organisms in the pipes. Another important consideration in the reduction of organisms is the fact that in many of the distribution systems where surface-waters are used the pipes are covered with growths of sponge, etc. These attached growths depend for their food-material upon the minute organisms found in the water. If the growths are abundant, the removal of organ- isms from the water by this means may be considerable. 2. Comparatively little has been written in this country upon the biology of aqueducts and pipes. Our attention has been called to growths of Crenothrix and of fresh-water sponge, but no attempt has been made to give an accurate account of the organisms infesting the distribution systems of our water-supplies. In Europe, however, the subject has been considered to some extent. In the city of Hamburg the minute animals inhabiting water-pipes were studied by Hartwig Petersen in 1876. Ten years later Karl Kraepelin made a more extended study. His observations were of much interest. He found an animal growth, often more than one centimeter thick, covering the entire surface of the pipes. The composition of this growth GROWTH OF ORGANISMS IN WATER-PIPES. 165 varied in different places. He gave a list of sixty different species observed. In many places the walls of the pipes were covered with fresh-water sponges, chiefly Spongilla fluviatilis and Spongilla lacustris. Mollusks were conspicuous, espe- cially the mussel, Dreyssena polymorpha. Snails were also numerous. Hundreds of " water-lice " (Asellus aquaticus) and "water-crabs" (Gammarus pulex) were found at every examination. The material known as "pipe-moss " was com- mon, and consisted largely of Cordylophora lacustris and the Bryozoa, Plumatella and Paludicella. At the time when Crenothrix was giving so much trouble at Rotterdam, Hugo de Vries made an extended study of the animals and plants found in the water-pipes of that city. His observations were confined chiefly to the pipes and canals which conveyed the unfiltered water of the river Maas to the filter-beds. In speaking of one of the canals he said: " The walls were thickly covered with living organisms up to the water-level. They formed an almost continuous coating of varying composition. There were only one or two excep- tions to this. In one place, where the water came from the pumps with great velocity, the walls were free from living organisms; and in another place, where there was almost no current, only one living form was seen. There was a sec- tion of one of the canals, where a gentle current was flowing, that was a magnificent aquarium. The walls were everywhere covered with white tufts of fresh-water sponge (Spongilla fluviatilis). Many of these tufts reached a diameter of 6 or 8 inches, but most of them were somewhat smaller. Between the sponge patches were seated countless numbers of the mussel, Dreyssena polymorpha. Individuals old and young were often seen grouped together in colonies which sometimes extended completely over the sponges. But what 1 66 THE MICROSCOPY OF DRINKING-WATER. most of all attracted attention was a luxuriant growth of the 4 horn-polyp,' Cordylophora lacustris. It covered the mussel-shells and occupied all the space between the sponges. The stalks reached a length of an inch or more. On and between the Cordylophora swarmed countless numbers of Vorticella, Acineta, and other Protozoa and Rotifera. These organisms had no lack of food-material, and the absence of light protected them from many foes which, in the light, thin out their ranks. Over all these animals Crenothrix was found growing in abundance. The shells of the mussels and the stems of the 'horn-polyps ' were coated with a thick felt-like layer of these 'iron-bacteria/ In other localities in the pipes the place of the 'horn-polyps' was occupied by the Bryozoa, or 'Moss-animalcules.' All of these branching forms were spoken of collectively by the workmen as * pipe- moss.' " In the summer of 1896, when the pipes of the Metropoli- tan Water Works were being laid in Beacon Street, Boston, near the Chestnut Hill reservoir, a i6-inch main leading from the Fisher Hill reservoir to the Brighton district was opened. This afforded an opportunity to examine the material on the inside of a pipe that had been laid ten years. Inspection showed that besides the usual coating of iron-rust, tubercles, etc., there were numerous patches of fresh-water sponge (both Spongilla and Meyenia), brownish or almost white in color, and about the size of the palm of one's hand. What was most conspicuous, however, was a sort of brown matting which covered much larger areas, and which had a thickness of about i inch. It had a very rough surface and, when dried, reminded one of a piece of coarse burlap. This proved to be an animal form belonging to the Bryozoa, known as JFredericella. As fragments of it had several times before GROWTH OF ORGANISMS IN WATER-PIPES. 1 67 been observed in the water from the service-taps, and as it had been seen growing in some small pipes connected with the filtration experiments at the Chestnut Hill reservoir, more extended observations were made in different parts of the distribution system. These brought out the fact that sponges and the Bryozoa were well established in the pipes. Many other organisms were also observed. In some places almost pure cultures of Stentor and Zoothamnium were found. At other points hosts of different organisms were seen, such as snails, mussels, Hydra, Nais, and Anguillula, Acineta, Vorticella, Arcella, Amoeba, countless numbers of ciliated infusoria, and many other forms. The growths were distinctly animal in their nature, but in many places parasitic vegetable forms, such as Achlya, Crenothrix, Leptothrix, etc., were common. The most important class of organisms found, however, was the Bryozoa, of which Fredericella and Plumatella were the chief representatives. The fact that the organisms that dwell in water-pipes depend for their food-material upon the algae, protozoa, etc., contained in the water may be easily demonstrated by experiment. Specimens of Fredericella and Plumatella were once placed in a series of jars, some of which were supplied with water rich in its microscopic contents, while others were supplied with the same water after filtration. All the jars were kept in semi-darkness at the same temperature, and were examined daily. The Fredericella and Plumatella that had been supplied with filtered water soon began to die, while those in the other jars lived as long as the experiment was continued. Some of the same Bryozoa were placed in jars furnished with water from the Newton supply,* and after * A ground-water almost free from microscopic organisms. 1 68 THE MICROSCOPY OF DRINKING-WATER. about a week they died for want of food. Dr. G. H. Parker* once made a similar experiment on fresh-water sponge, and obtained the same result. With these facts established, we may confidently affirm that fresh-water sponge, Bryozoa, and similar pipe-dwellers will be absent from water-pipes where ground-water or water that has been effectively filtered is used. One naturally asks, " What is the effect of these organ- isms growing in the pipes? " In a certain sense they tend to improve the quality of the water by reducing the number of floating microscopic organisms; but they themselves must in time decay, and any one whose nose has ever had an experi- ence with decomposing sponge will appreciate the fact that better places for these organisms may be found than the dis- tribution systems of our water-supplies. It should be stated, however, that in all probability very large quantities would be required to produce tastes or odors that would be noticed in the water. Perhaps the greatest objection to their presence is the fact that they tend to impede the flow of water in the pipes. When one considers that a coating J inch thick diminishes the area of the cross-section of a 24-inch pipe by 4#, and of a 6-inch pipe by 15$, and when one learns that these organisms often form layers even thicker than this, it will be seen that such growths are matters of no little impor- tance. Furthermore, fingers of the fresh-water sponge some- times extend several inches into the water, and the matting of the Bryozoa is always rough on account of the stiff branches that are extended in order that the organisms may secure their food. This roughness of the surface must * G. H. Parker, Experiments on Fresh-water Sponge, Special Report of the Massachusetts State Board of Health, 1890, p. 618. GROWTH OF ORGANISMS IN WATER-PIPES. 169 increase the friction of the pipe by a considerable but indefinite amount. Organisms growing on the inner walls of water-pipes tend to promote tuberculation. This takes place in the following manner : Between the organisms and the walls of the pipe there is a layer of water from which the oxygen is at times temporarily exhausted and in which carbonic acid is abundant, these conditions being brought about by the organisms. If the organisms are torn away the pipe- coating may be removed and a little spot of iron thus exposed to the action of 'the 'carbonic acid. Corrosion thus begins and iron oxide becomes deposited in crystalline form around this spot, forming what is known as a tubercle. These tubercles greatly increase the roughness of the pipe and conse- quently retard the flow of water. An interesting experience with pipe moss is on record at the Brooklyn Water Department. In November, 1897, the water in the Mt. Prospect reservoir became so filled with Asterio- nella that it was deemed advisable to shut off the reservoir and pump directly into the pipes. This action was followed by the appearance of brown fibrous masses in the tap-water. In a number of instances this fibrous matting stopped up the taps, and even large pipes were choked. The water at the same time had a distinctly moldy and unpleasant odor. The fibrous mat- ting proved to be Paludicella. It had been growing on the inner walls of the pipes, and the change of currents and the pulsations of the pump, due to the direct pumping into the pipes, had dis- lodged it. Systematic and thorough flushing of the pipes materi- ally improved the conditions. PART II. CHAPTER XIV. CLASSIFICATION OF THE MICROSCOPIC ORGANISMS. THE microscopic organisms found in drinking-water in- clude the lowest forms of life. Some of them belong to the vegetable kingdom, some belong to the animal kingdom, while others possess characteristics that pertain to both. There is in reality no sharp dividing-line between the vege- tal and the animal in the low forms of life. Nature's boundaries are always shaded on both sides. Classification of organisms into groups is necessary, but it must be borne in mind that all classifications are artificial .and subject to change. The one outlined below and used throughout this volume is believed to be the most convenient for the work at hand. A number of groups, not pertaining to the microscopical examination of drinking-water, are omitted. CLASSIFICATION OF THE MICROSCOPIC ORGANISMS. Plants. DIATOMACE^E. ALG^E (in the narrower sense). SCHIZOPHYCE.E. Chlorophycea. Schizomycetes. FUNGI. Cyanophycea. VARIOUS HIGHER PLANTS. 171 1/2 THE MICROSCOPY OF DRINKING-WATER. Animals. PROTOZOA. CRUSTACEA. Rhizopoda. Entomostraca. Mastigophora (Flagellata). BRYOZOA (POLYZOA). Infusoria (in the narrower sense). SPONGID^E. ROTIFERA. VARIOUS HIGHER ANIMALS* CHAPTER XV. DIATOMACE^E. THE Diatomaceae comprise a group of minute vegetable forms of a low order. Their exact position in the scale of life has been the subject of much controversy. The early writers considered them to belong to the animal kingdom because of the power of movement that some of them possess. Later, when they had become generally recognized as plants, they were considered as a Class or Order of the Algae. Recent cryptogamists, however, prefer to class them as an inde- pendent group, thereby recognizing the fact that they are quite different from most unicellular plants. This differ- ence lies chiefly in the possession of siliceous cell-walls upon which may be observed certain markings that are constant in size and arrangement for each species. The great beauty of these markings, together with the infinite variety in the sizes and shapes of the ceils of different species, have long made them objects of special study by microscopists. Diatom Cells. A diatom cell is constructed like a box. There is a top and a bottom, known as the upper and lower valve, on both of which markings are found. The valves are connected by membranes known as "sutural zones," " con- nective membranes," " girdles," or, when detached, as *' hoops." There are two of these membranes, one attached to each valve, and they are so arranged that one slides over 173 174 THE MICROSCOPY OF DRINKING-WATER. the other just as the rim of a box-cover fits over the sides. This arrangement may be seen in Plate I, Figs. A, B, and C, where a typical diatom, Navicula viridis, is shown in three views. A represents the valve * view of the diatom, that is, the view seen when looking directly at the valve or the top of the box. B represents the girdle* view, the view seen when looking at the connective membrane. C is a cross-section through the diatom. The upper or outer valve is indicated by a, and its connec- tive membrane by c. The girdle view shows how this connec- tive membrane of the larger valve fits over a similar one, c\ attached to the lower or smaller valve, b. These girdles have the power of sliding one upon the other so that the thickness of the diatom, i.e. the distance between the valves, is variable. The valves of the diatom shown in the figure are covered with furrows or markings, g. At the centre and at each end there are slight thickenings of the cell-wall, known as nodules. The central one is called the central nodule, d, and those at * The terms used by different writers to express these two views of a diatom are' very confusing. In the following list the terms under A repre- sent the valve view and those under B the girdle view. A B Valve view. Girdle view. Side view. Front view. Top view. Zonal view. Face valvaire. Face connective. Primary side. Secondary side. Secondary side. Primary side. Vue de profil. Vue de face. The terms "side view" and "front view" are those generally used by English and American diatomists, but the author has avoided them as not being in themselves sufficiently clear, and has preferred to use the less euphonious but more self-explanatory terms, "valve view" and "girdle view." In consulting books on diatoms the reader should be careful to note the way in which the two views are-designated. D I A TO MA CEJE. 1 7 5 the ends, terminal nodules, e, e. Between these nodules and extending along the medial line of the valve there is a sort of ridge, /, in which there is a furrow called a raphe, or raphe. Through this the living matter of the diatom probably com- municates with the outer world. The slit is supposed to be somewhat enlarged at the nodules. The raphe, the nodules, and the markings, taken in connection with the shape and size of the valves, are the most important external features of a diatom and are the first to be considered in studying them. Shape and Size. There is probably no class of unicellu- lar organisms in which the outlines vary more than in those of the diatoms. From the straight line to the circle almost all the geometrical figures may be found. Some of these may be described as circular, oval, oblong, elliptical, saddle-shaped, boat-shaped, triangular, undulate, sigmoid, linear, etc. The. variations in shape are most marked in the valve view. The girdle view, as a rule, is more or less rectangular. The valves are usually plane surfaces, with only slight curvatures or undulations. Occasionally the surface is warped as in Am- phiprora and Surirella. As a rule the two valves of a frustule are nearly parallel, but in such forms as Meridion, Gom- phonema, etc., the frustule is wedge-shaped when seen in girdle view. The most varied forms are found in salt or brackish water, and the common fresh-water forms are so simple and so characteristic that the reader will have little difficulty in assigning them their proper generic names. Some genera have the cell divided more or less completely by internal plates, called septa, when fully developed as in Rhabdonema; and vittae, when incomplete as in Gramma- tophora. Some diatoms have external expansions on the mar- gin of the valves. Surirella, for example, has thin expansions known as alae, or wings. When these alae are imperfectly THE MICROSCOPY OF DRINKING-WATER. developed they are called keels. Nitzschia for this reason is said to be carinate. These wings or keels usually extend along the border of the raphe. Certain filamentous forms, such as Melosira, have processes at the point of attachment. In others these processes are elongated into horns, or bristles. Diatoms vary in size from the minute Cyclotella, less than 10 microns* in diameter, to such large forms as Surirella and Navicula, that sometimes are one millimeter long. Some filamentous forms grow to a considerable length, often several feet. Markings. The valves of most diatoms are marked with lines or points. In many cases the lines may be resolved into series of points, pearls, beads, or striae, when a higher power of the microscope is used. The variations in the number and size of these points and their uniformity in differ- ent individuals of the same species make them convenient objects for testing the resolving power of microscopes. The variation in the number of these striae may be seen from the following table : Number of Striae per Millimeter. Longitudinal. Transverse. Epithemia ocellata, Kz 800 430 Navicula major, Kz 850 630 " viridis, Kz 2400 720 lyra 850 1000 Cymbella navicula, Ehb 1200 1500 Pleurosigma angulatum, Sm 1580 2100 Synedra pulchella, Kz 670 2150 Navicula rhomboides 1700 2700 Amphipleura pellucida, Ktz 3400 3700 to 5200 The extreme minuteness of these points, their various appearances under different conditions, and the difficulty of studying them even with microscopes of the highest magnify- ing powers, have given rise to many different theories concern- * One micro-millimeter, or micron (//), equals .001 millimeter. DIATOMACEsE. 177 ing the character of the valves. Some writers insist that the points are elevations: others claim that they are depressions. Recent students agree that the structure is more complex than was formerly considered to be the case. The following con- ception of M. J. Deby, while perhaps not correct for all cases, is a good illustration of the modern view (see Fig. 22). d \ d' C c' n n' TRICERATIUM PLEUROSIGMA FIG. 22. TRANSVERSE SECTION OF A DIATOM VALVE. (After Deby.) 4i. Upper (outer) layer. d. Inter-alveolar pillars. b. Lower (inner) layer. m. Thin part of upper layer. t. Cavities. . Bottom of alveolae. "The valves of most diatoms are composed of two layers, between which there are circular or hexagonal cavities bounded by walls of silica. The upper layer is not uniform in thickness, but is thin just above the cavities, and thicker, rising in pointed or rounded prominences, above the intersec- tion of the walls of the cavities. The upper layer is lightly silicified, and the thin portions are easily broken, making openings into the cavities. The lower layer bears varied designs the nature of which has not been well established. What authors have described as areolae, pearls, pores, orifices, granular projections, depressions, hexagons, beads, points, etc., are really one and the same thing." Cell-contents. The frustule of a diatom is somewhat analogous to the shell of a bivalve, the living matter is inside. Just inside the cell-wall there is a thin protoplasmic lining (primordial utricle). This protoplasm sends radiating streams through the cell, and it is possible that a portion of 1/8 THE MICROSCOPY OF DRINKING-WATER. it extends through the openings in the cell-wall and communi- cates with the outer world. It is this layer of protoplasm also* that secretes the silica of the cell-wall. Between the streams of protoplasm (PI. I, Fig. C) there are what appear to be empty cavities. In or on the borders of these, oil-globules may be sometimes observed. There is a nucleus, and probably a nucleolus, located near the centre of the cell. The most conspicuous portion of the cell-contents, however,, consists of colored lumps or plates, which are usually constant in appearance and position for any particular species. The brown coloring matter of these "chromatophore plates" is known as diatomin. It is a substance analogous to chloro- phyll and has been considered by some writers to be a com- pound of chlorophyll and phycoxanthin. The spectrum of diatomin is very similar to that of chlorophyll. There are two absorption-bands, one between B and C in the orange- yellow, and one between E and F in the indigo-violet. Diatomin is soluble in dilute alcohol, giving a brownish-yellow solution that is sometimes very slightly fluorescent. When dried or treated with concentrated sulphuric acid it assumes a green color. When living diatoms are exposed to the direct rays of the sun or subjected to heat for a considerable time the color of the chromatophore plates changes from brown to green. In certain species other internal features have been noted ; namely, the contractile zonal membrane, the germinative dot, double nucleus, etc., but of these there is little known. External Secretions. Living diatoms are covered with a transparent gelatinous envelope, which is probably a secre- tion from the protoplasm. In many species it is very thin and can be discerned only by the use of staining agents. In the filamentous and chain-forming species it serves to hold DIATOMACE&. the frustules together. In Tabellaria, for example, little lumps of the gelatinous substance may be seen at the corners of the frustules at the point of attachment. Some species secrete great quantities of gelatinous material and are entirely embedded in it. In a few cases it is of a firmer consistency' and forms tubes, stalks, or stipes, upon the ends of which the frustules are seated. These stalks attach themselves to stones, wood, etc., immersed in the water. Movement. Some of the diatoms exhibit the phenome- non of spontaneous movement. This has always excited interest and has been the subject of much speculation. It was the chief argument advanced by the early writers for placing the diatoms in the animal kingdom. The most peculiar movement is that of Bacillaria paradoxa, whose frus- tules slide over each other in a longitudinal direction until they are all but detached, and then stop, reverse their motion, and slide backwards in the opposite direction until they are again all but detached. This alternate motion is repeated at quite regular intervals. Some of the free species show the greatest movement, and of these Navicula is one of the most interesting. Its motion has been described as " a sudden advance in a straight line, a little hesitation, then other rectilinear nrovements, and, after a short pause, a return upon nearly the same path by similar movements." The move- ment appears to be a mechanical one. The diatoms do not turn aside to avoid obstacles, although their direction is sometimes changed by them. The rapidity of their motion has been calculated to be "400 times their own length in three minutes." Their motion shows the expenditure of con- siderable force. Objects 50 or 100 times their size are some- times pushed aside. Various hypotheses have been advanced to account for the l8o THE MICROSCOPY OF DRINKING-WATER. movement of diatoms. Naegeli suggested that it was due to endosmotic and exosmotic currents; Ehrenberg claimed that the movement was due to cilia; another writer, that it was caused by a snail-like foot outside the frustule; another, that it was due to a layer of protoplasm covering the raph. H. L. Smith, after much study, came to the conclusion " that the motion of Naviculae is due to injection and expulsion of water, and that these currents are caused by different tensions of the internal membranous sac in the two halves of the trustule." In spite of all the study that has been given to the sub- ject, we must admit that the cause of the movement of diatoms is unknown. The "cilia theory" seems the most probable, but it is doubtful if the cilia are more than mucous threads. Multiplication. Diatoms multiply by a process of halv- ing or splitting, the Greek word for which gives rise to the name diatom. The cell-division is similar to that in all plants, but in this case the process is of especial interest because of the rigid character of the cell-walls. The process begins by a division of the nucleus and iiucleolus. The protoplasm expands or increases in bulk, forcing the valves apart, the hoops sliding one out of the other. The two halves of the nucleus separate, the diatomin collects at either side, and a membrane forms, dividing the cell into two parts. Finally the two parts separate. The newly formed membrane becomes charged with silica, making a new valve, and soon after its hoop develops. This process is well illustrated by a drawing of M. J. Deby, shown on PL I, Figs. D,E, and F. Sometimes the frustules separate entirely ; sometimes they remain attached forming filaments, as in Mel- osira, bands as in Fragiiaria, or zigzag chains as in Tabellaria. DIA TO MA CEJZ. 1 8 1 The above is the usually accepted theory of cell-division. It is probably correct in many, if not in most cases. It assumes that the siliceous walls are not able to expand, and the result is that after repeated division the frustules become smaller. It is claimed that in some cases the cell-wall does expand, and therefore that the size of the frustules does not decrease after division. The generally accepted theory of cell-division assumes that a diatom frustule has two valves, one the larger and older, and the other the smaller and younger. After division two cells are formed, one equal in size to the larger valve and the other equal to the smaller one, the difference in size being twice the thickness of the hoop. This theory also assumes that both the mother- and the daughter-cell have the power of further division. From these assumptions certain laws of multiplication may be deduced. For example: If A is the parent cell, After one period of time, /, A will have produced B\ 4< two periods" " 2t, A " " " ' ', and B " " " C\ " three " " " $/, A " " " B", B li il " C", B' " " " C\ C " " " D\ and so on. From this it happens that After t we have \A + iB\ " 2t " " lA + 2B + C; and so on. The laws may be expressed mathematically as follows: 1 82 THE MICROSCOPY OF DRINKING-WATER. 1. As the number of periods of division increases in arithmetical progression the total number of frustules increases in geometrical progression. 2. The number of frustules equal in size after any period of division are represented by the terms of the binomial theorem (a -f- <)", where a and b are unity. These laws have been demonstrated experimentally, the first by the author* and the second by Miquel.f Reproduction. The continued process of multiplication results in a constant diminution in the size of the frustules. After a certain minimum limit of size has been reached or after their power of multiplication has become exhausted, a reproductive process takes place. Usually this consists of a conjugation which results in the formation of a large cell, or auxospore, capable of reproducing a frustule of large size which, by multiplication, gives. rise to a new series of frustules like the first. This theory, known as " Pfitzer's Auxospore Theory," was advanced in 1871. Count Castracane has shown that its application is not universal, and that in the case of some diatoms reproduction takes place through the forma- tion of spores, or " gonids, " which become fertilized by conjugation and, after a period of repose, attain a condition for living an independent life and reproducing in every respect the adult type of mother-cell. The author has ob- served these spore-like bodies in the cells of Asterionella. There are few reliable data to be found in regard to the reproduction of diatoms. True conjugation has been observed in comparatively few genera. It is believed that there are four methods of conjugation. First, a single frustule, self- fertilized, producing one sporange and one auxospore; second, * G. C. Whipple, "Some Observations on the Growth of Diatoms in Surface Waters." Tech. Quar., vol. vn., No. 3. Oct. 1894. fP. Miquel,.Annales de Micrographie, No. n, 1892. D I A TO MA CE&. 1 8 3 a single frustule, self-fertilized, producing two sporanges and two auxospores; third, two conjugating frustules, with un- differentiated endochrome, producing one sporange and one auxospore; fourth, two conjugating frustules, with differen- tiated endochrome, producing two sporangial cells, one of which is sometimes abortive. Good examples of conjugation may be found in Surirella splendida, Epithemia turgida, and in various species of Melosira. The sporangial frustules of JVlelosira (shown in PL III, Fig. I/) are quite common. Classification of Diatoms. Several methods of classifi- cation of diatoms have been proposed, but only two are worthy of attention, and even these must be considered as provisional. The most recent is that proposed by Pfitzer and elaborated by Petit. It is based upon two assumptions, namely, that the internal disposition of the endochrome is constant for all individuals of the same species, and that the relation between the frustule and the endochrome is fixed and common to all species of the same genus. The family Diatomaceae is divided into two sub-families, the Placochromaticeae and the Cocco- chromaticeae. The genera of the first sub-family have the endochrome arranged in plates or layers, and those of the second sub-family, in lumps or small granular masses. Secondary classification into tribes, etc., depends upon the symmetry of the valves with reference to the axes, the dis- similarity of the valves of a single frustule, the presence or absence of an intervalvular diaphragm, the raphe, nodules, etc. There is little to be said in favor of this system, but it is worthy of study as the authors have tried to do what has been long neglected, namely, to emphasize the study of the entire cell with its contents rather than to confine the atten- tion wholly to the cell-wall or frustule. 1 84 THE MICROSCOPY OF DRINKING-WATER. The most useful system of classification and the one generally recognized is that suggested by H. L. Smith. It is based almost entirely on the morphology of the frustule. This has the advantage of enabling one to classify both living and fossil forms, but it has tended to divert observers from the study of the diatom as a living cell to the study of the shell alone. According to Smith's classification the Diatomaceae are divided into three tribes characterized by the presence or absence of a raphe. An outline of this classification, together with descriptions of the genera most common in drinking- water, is given below. The names of the genera are printed in heavy type. TRIBE I. RAPHIDIE^E. Always possessing a distinct raphe on one or both valves. Central nodule generally present and conspicuous. Frustules mostly bacillar in valve view; sometimes broadly oval; with- out spines or other processes. Navicula major is the typical form. FAMILY CYMBELLE^E. Raphe mostly curved. Valves alike, more or less arcuate, cymbiform. Amphora. Frustules single, ovoidal in girdle view, the girdle often striated or longitudinally punctate. Valves extremely unsymmetrical, with a convex and concave side, with an eccentric raphe, with medial and terminal nodules. The raphe is sometimes near the convex side, sometimes near the concave side, and the medial nodule is often away from the centre. There are trans- verse striae, radiating somewhat from the medial nodule. This genus is very ornate. There are a number of species, none of them very common in water. (PI. I, Figs, i and 2 . ) Cymbella. Frustules generally single, elongated, symmetrical with respect D I A TO MA CE&. 1 8 $ to the minor axis. Valves more or less arched, with one side very convex and the other side slightly or not at all convex ; asymmetrically divided by a curved raphe ; possessing terminal and medial nodules ; marked by transverse bead-like striae, which do not extend to the raphe, but have a clear space, wider at the medial nodule than elsewhere. There are a number of common species. (PI. I, Figs. 3 and 4.) Encyonema. Frustules, when young, enclosed in a hyaline mucilaginous tube, in which they multiply by division, pushing each other forward in an alternately inverse position. Valves symmetrical with respect to the minor axis, convex on one side, straight on the other, with rounded extremities that project beyond the straight side. A straight raphe divides the valves into two unequal parts. There are medial and terminal nodules. The striae are transverse or radiating somewhat from the medial nodule. There is a clear space around the medial nodule, but elsewhere the striae approach closely to the raphe. There are several species. (PI. I, Fig. 5.) Cocconema. Frustules, when young, borne singly or in pairs on filamentous pedicels, which may be simple or branched. They form muci- laginous layers on submerged objects. Later they become free- swimming. The valves are long, large, strongly arched, convex on one side, concave on the other side save for a little inflation in the middle. The raphe is curved. There are medial and terminal nodules. The striae are rather large pearls, transverse, with very slight radiation, and not approaching the raphe closely. (PI. I, Fig. 6.) FAMILY NAVICULE^E. Valves symmetrically divided by the raph. Frustules not cuneate or cymbiform. Navicula. Frustules single, symmetrical with respect to both axes. Valves naviculoid, or boat-shaped; of various proportions, some very long and narrow, others short and wide, others ellipsoidal ; with straight or slightly curving sides ; with ends pointed or rounded. There is a straight raphe with conspicuous medial 186 THE MICROSCOPY OF DRINKING-WATER. and terminal nodules. The valves are marked with transverse furrows, that have a slight radial tendency. The frustules are rectangular in girdle view and show the nodules plainly. There is a vast number of species and varieties, many of which are very common. In some species the striae can be resolved into pearls. These are the Naviculae proper. In other species they cannot be resolved, and the valves usually have wide rounded ends. These were formerly set apart as a separate genus, Pinnularia. (PI. I, Figs. 7 and 8.) StauroneLs. Frustules similar to those of Navicula. Valves symmetrical, possessing a straight raphe, with medial and terminal nodules. The striae are pearled. There is a narrow clear space along the raphe and a wider transverse clear space at the medial nodule extending to the sides of the valve, so that the valves have the appearance of being marked with a cross. A number of species have been described, but in some instances they are very similar to Navicula. (PL I, Figs. 9 and 10.) Schizonema. Frustules quite similar to those of Navicula, and enclosed in mucilaginous tubes, as Encyonema. Raphe straight, sometimes showing a double line. Striae generally parallel, reaching to the raph6, but not to the central nodule, around which there is a clear space. More common in salt water than in fresh water. Pleurosigma. Frustules like those of Navicula, but with axis turned like a letter S. Raphe sigmoidal. Striae ornate, pearled, very fine on some species. Endochrome in two layers. (PI. I, Fig. n.) FAMILY GOMPHONEME^E. Valves cuneate ; central nodule un- equally distant from the ends. Gomphonema. Frustules borne on pedicels more or less branched. Valves wedge-shaped, with more or less undulating margins and rounded ends. A central nodule near the large end. Raphe straight, dividing the valve symmetrically. Striae pearled, transverse, radiating slightly about the nodules. The frustules seen in girdle view are wedge-shaped, with straight sides and DIA TO MA CEM. 1 8/ with central nodule visible. There are a number of species, some of which are common. (PL I, Fig. 12.) FAMILY COCCONIDE^:. Frustules with valves unlike. Valves broadly oval. Cocconeis. Frustules somewhat arched or lens -shaped ; in valve view, elliptical or discoidal. Striae have a general direction trans- verse to the axis, but the convexity of the frustules gives them the appearance of inclining towards the poles. Upper and lower valves dissimilar, possessing a medial nodule and raphe or pseudo-raphe. (PL I, Figs. 13 and 14.) TRIBE II. PSEUDO-RAPHIDIE^E. Possessing a false raphe (simple line or blank space) on one or both valves; with or without nodules. Frustules generally bacillar, sometimes oval or suborbicular, without processes, spines, or awns. Synedra Gaillonii is the typical form. FAMILY FRAGILARIE^E. Frustules adherent, forming a ribbon-like, fan-like, or zigzag filament, or attached by a gelatinous cushion or stipe. Epithemia. Frustules cymbiform, symmetrical with respect to the minor axis, with a false raphe and no nodules. Valves marked by lines and pearls approximately at right angles to the major axis, but inclined towards the end of the frustule on the convex side. The frustules in girdle view are seen to be somewhat inflated at the centre. There are several species, differing considerably in the shape of the valves. (PL I, Figs. 15 and 16.) Eunotia. Frustules elongated, symmetrical with respect to the minor axis. Occurring singly, free -swimming or attached. Valves arcuate, with the convex side undulated. Transversely striated, with two false terminal nodules and no medial line. The frustules 1 88 THE MICROSCOPY OF DRINKING-WATER. are quadrangular in girdle view. There are but few species, the most common being the E. tridentula. (PI. I, Fig. 17.) Himantidium. Sometimes included under Eunotia. The frustules differ from Eunotia by remaining attached after division, forming a band as in Fragilaria ; by having the convex side of the valve entire instead of undulate ; and by being somewhat bent in girdle view. (PI. II, Figs, i and 2.) Asterionella. Frustules long, linear, inflated at the ends. They are united by their extremities into stars or chains, as shown in the girdle view. The typical group is composed of 8 frustules sym- metrically and radially arranged. Groups of 4, 6, or 7 are common. When rapidly dividing they may assume a spiral arrangement. The valves are very finely striated, with a straight pseudo-raphe. There is one general species, the A. formosa, characterized by having the basal end of the frustules much larger than the free end, and by having on that end a larger surface in contact with the adjoining frustules. There are several varieties, advanced by some authors to the rank of species. The most common is A. formosa, var. gracillima. (PI. II, Figs. 3 to 7.) Synedra. Frustules elongated, straight or slightly curved. Valves some- what dilated at the centre and with a medial line or false raphe and occasionally false nodules. They usually have straight and almost, but not quite, parallel-sides. They are finely trans- versely striated. There are several common species. S. pulchella has lanceolate valves, with ends somewhat attenuated. In girdle view they are seen to be attached valve to valve and present the appearance of a long band or a fine-toothed comb. S. ulna has a very long rectilinear valve, with conspicuous transverse striae. There is a false raphe, with a narrow clear space. They are often free-floating. S. lanceolata has a long thin valve, swollen at the centre, but tapering to sharp points at the ends. S. radians has straight needle-like valves. They are united at the base like Asterionella, but the frustules do not lie in the same plane. (PL II, Figs. 8 to n.) D I A TO MA CEsE. 1 8 9 Fragilaria. Frustules attached side by side, forming bands as in the case of Synedra pulchella. Valves elongated, straight, with ends lanceolate or slightly rounded. In girdle view the frustules are rectangular and are in contact with each other through their entire length. Valves transversely striated, with a false raphe scarcely visible. There are several common species. (PL II, Figs. 12 and 13.) Diatoma. Frustules attached by their angles forming zigzag chains, or rarely in bands. In girdle view they are quadrangular. Valves elliptical-lanceolate, with transverse ribs, between which are fine striae. There is a longitudinal pseudo-raphe. There are two common species, D. vulgar e and D. tenue. (PI. Ill, Figs, i to 3.) Meridion. Frustules attached valve to valve, forming curved bands seen as fans, circles, or spiral bands. The frustules are wedge- shaped in girdle view, which causes the peculiar shape of the bands. Valves also wedge-shaped, with somewhat rounded ends ; furnished with transverse ribs, between which are fine striae. Pseudo-raphe indistinct. There is one principal species, M. circulare. (PI. Ill, Figs. 4 and 5.) FAMILY TABELLARIE^. Frustules with internal plates, or imperfect septa, often forming a filament. Tabellaria. Frustules square or rectangular in girdle view, attached by their corners and forming zigzag chains. In this view they are seen to be marked with longitudinal dividing plates, which extend from the ends not quite to the middle and which ter- minate in rounded points. The valves are long and thin, and are dilated at the extremities and in the middle. There are fine tranverse striae and an indistinct pseudo-raphe. The endo- chrome is usually in rounded lumps. There are two very com- mon species, T. fenestrata and T. flocculosa. (PI. Ill, Figs. 6 to 9.) 1 90 THE MICROSCOPY OF DRINKING-WATER. FAMILY SURIRELLE^E. Frustules alate or carinate ; frequently cuneate. Nitzschia. Frustules free, single, elongated, linear, slightly arched, or sigmoidal ; with a longitudinal keel and one or more rows of longitudinal points. Valves finely striated, without nodules. There are many species. (PI. Ill, Figs. 10 to 12.) Surirella. Frustules free, single, furnished with alae on each side. A transverse section of the frustule shows a double-concave outline. Valves oval or elliptical, with conspicuous transverse tubular striae, or canaliculi, between which there are sometimes very fine pearled strias. There is a wide clear space, or pseudo-raphe. The frustules are sometimes cuneate in girdle view. The valves sometimes have a warped surface. There are many common species, most of them of very large size. (PL III, Figs. 13 and 14.) TRIBE III. CRYPTO-RAPHIDIE^E. Never possessing a raphe or a false raphe. Frustules generally circular or angular, often provided with teeth, spines, or processes. Stephanodiscus Niagara is the typical form. FAMILY MELOSIRE^E. Frustules cylindrical, adhering and forming a stout filament ; valves circular, sometimes armed with spines. Melosira. Frustules with circular valves and very wide connective bands, attached valve to valve so as to form long cylindrical fila- ments. In girdle view they are usually rectangular, though sometimes with rounded ends ; at the centre there are often conspicuous constrictions. The girdles are often marked with dots. The valves are radially striated, with a clear central space. At the edge there is often a keel or row of projecting points, seen in girdle view. There are several common species. M. granulata is the most common free-floating form, and M. DIA TO MA CE&. 1 9 1 variant, the most common filamentous form. (PI. Ill, Figs. 15 to 17.) FAMILY COSCINODISCE^E. Valves circular, generally with radiating cellules, granules, or puncta ; sometimes with marginal or intra- marginal spines or distinct ribs ; without distinct processes. . Cyclotella. Frustules discoidal, single, occasionally attached valve to valve, but never forming long filaments. Valves circular, finely marked by radial striae. 'There is usually an outer ring of radial lines, inside of which there are puncta and fine dots somewhat irregularly arranged. These cannot be seen with low powers. In girdle view the frustules appear rectangular or somewhat sigmoidal, with warped valves, as in C. operculaia. They are often of very small size. (PL III, Figs. 18 and 19.) Stephanodiscus. Frustules discoidal, single. Valves circular, with curved sur- face, with fringe of minute marginal teeth. Striae fine radial. Frustules rectangular in girdle view, showing projection of middle of valve. Teeth most conspicuous in girdle view. Endochrome conspicuous, in rounded lumps. The frustules are often of considerable size. (PI. Ill, Figs. 20 and 21.) CHAPTER XVL SCHIZOMYCETES. THE Schizophyceae comprise those vegetable organisms in which the chief mode of propagation is that of cell-division. They are either destitute of chlorophyll or contain besides the chlorophyll a coloring substance known as phycocyan or phycochrome, which itself may be a modification of chloro- phyll. The cells have a somewhat firm cell-wall, but no nucleus. The Schizophyceae may be divided into two classes, the Schizomycetes and the Cyanophyceae. The latter contain chlorophyll, but the former do not. Besides the bacteria, which are not described in this work. there are but four genera belonging to the Schizomycetes that are of interest to the water-analyst. They are so imperfectly understood that no satisfactory classification has been suggested. Some authorities include them among the Fungi. iLeptothrix. Simple filaments, with indistinct or no articulation, without oscillating movement, and with no sulphur-granules. There are several indistinct species. They are usually colorless. The aquatic forms occur as interwoven masses of long slender fila- ments, the diameter of which varies from i to 3 ju. Lepto- 192 SCHIZOMYCETES. 193 thrix ochracea, observed in driven wells where the water con- tains much iron, is generally referred to the genus Crenothrix, but its relation to the typical form of Crenothrix is not under- stood. Very slender forms of Oscillaria are liable to be mis- taken for Leptothrix. (PL IV, Fig. i.) Cladothrix. Fine filaments resembling those of Leptothrix, colorless, usually indistinctly articulated, straight, undulated, or twisted. There are several stages of development, giving rise to cocci-, vibrio-, spirochsetae-, and filamentous-forms. The special characteristic of the genus is that of false branching, a turning aside of single portions of the filaments followed by subsequent ter- minal growth. There are several indistinct species. The most important is C. dichotoma, which is found in sewage and pol- luted water. (PL IV, Fig. 2.) Beggiatoa. Threads indistinctly articulated, colorless, containing numerous dark sulphur-granules. The filaments often have an active oscillating movement. They are usually short and from i to 3 yu in diameter. Sometimes abundant in sulphur springs. There are several doubtful species. The most common is B. alba. (PL IV, Fig. 3.) Crenothrix. Filaments cylindrical, transversely divided into cells, sur- rounded by a gelatinous sheath which becomes yellow or yellowish-brown through deposits of iron or manganese. Multi- plication takes place by transverse fission and occasionally by longitudinal fission. Cells also escape from the sheath at the end or side and, by division, form new filaments. Repro- duction occurs through spores formed from the cells within the sheath. There is one principal species, C. Kuhniana. It occurs in single filaments or in brownish tufts or mats, often of considerable thickness. The filaments are i ^ to 4 /* thick, and the sheath is several times the thickness of the filaments. Articulation is distinct. When the iron of the sheath is dis- solved by dilute hydrochloric acid the cells appear in side view as distinct rectangles, each one somewhat removed from its neighbor. This appearance is characteristic of Crenothrix. IQ4 THE MICROSCOPY OF DRINKING-WATER. During growth the cells sometimes push themselves forward in the sheath, leaving the empty sheath behind. The older portion of the sheath is darker colored than the growing points. Crenothrix occurs chiefly in ground- waters rich in organic matter, iron salts nnd carbonic acid and deficient in oxygen. Its growth is favored by darkness. (PI. IV, Fig. 4.) Jackson has proposed a new classification of this genus, based on the character of the sheath-deposit. C. Kuhniana, which deposits iron, he maintains ; Leptothrix ochracea, which, deposits alumina, he renames C. ochracea; and a new species,, which deposits manganese, he calls C. manganifera. CHAPTER XVII. CYANOPHYCE^E. THE plants belonging to the Cyanophyceae, or Phyco- chromophyceae, are characterized by the presence of chloro- phyll plus certain coloring substances known as cyanophyll, phycocyanine, phycoxanthine, etc., which are probably modifications of chlorophyll; by the absence of a nucleus and usually of starch-grains; and by extremely simple but imper- fectly understood methods of reproduction. The plants are one- or many-celled. By successive division of the cells they are very commonly associated in families that take the form of filaments or of spherical or irregular masses. The cell-wall is often distinct and sharply defined, but in some cases it is fused with a gelatinous mass in which the cells are embedded. This gelatinous matrix is more common in the terrestrial than in the aquatic species. The cell-con- tents are usually granular and homogeneous. The color varies considerably in different species and under different conditions. It is never a chlorophyll green, but ranges from a color approaching that to a blue-green, orange-yellow, brown, red, or violet. The coloring matter known as phycocyanine has a bluish color when viewed by transmitted light, and a reddish color when viewed by re- flected light. This phenomenon is often observed in ponds where Cyanophyceae are abundant. Looking directly at the 195 196 THE MICROSCOPY OF DRIN KING-WATER. pond the water may have a reddish-brown color, while a bottle filled with the water and held to the light may present a de- cidedly bluish-green appearance. This is particularly true when the plants have begun to decay. The phycoxanthine is said to have a yellowish color. The liberation of the gas- bubbles from some species seems to have an effect on the color of the organisms. Anabaena, for example, may have a brownish-green color in a reservoir and a very light blue- green color after it has passed through the pipes of a dis- tribution system, where the pressure has caused the gas to be expelled. The Cyanophyceae are usually separated into five or six groups, which are ranked by different writers as orders, families, or sections. The groups are here considered as families belonging to two orders. ORDER I. CYSTIPHOR^E. Unicellular plants with spherical, oblong, or cylindrical cells enclosed in a tegument and associated in families, sur- rounded by a universal tegument or immersed in a generally colorless, mucilaginous substance of varying consistency. Division takes place in one, two, or three directions, the cells after division usually remaining together forming an amor- phous thallus. It is probable that most of the forms belong- ing to this order are but intermediate stages in the life-history of plants higher in the scale of life. There is but one family. It contains about a dozen rather imperfectly defined genera. FAMILY CHROOCOCCACE^E. Thallus mucous or gelatinous, amor- phous, enclosing cells and families irregularly disposed. Chroococcus. Cells spherical, or more or less angular from compression, solitary or united in small families. Cell-membrane thin or C YA NOPH YCEJE. 1 9 7 confluent in a more or less firm jelly. Cell-contents pale bluish-green, rarely yellowish. Propagation by division in three directions. Several species are described. Most of them are terrestrial and not aquatic. The most common aquatic species are C. turgidus, the cells of which are from 10 to 25 /< in diameter, and C. cohcerens, the cells of which are from 3 to 6 fj. in diameter. (PL IV, Fig. 5.) -' Gloeocapsa. Cells spherical, single or in groups ; each cell surrounded by a vesculiform tegument and groups of cells surrounded by an additional tegument. Cell-membrane thick, lamellated, and sometimes colored. Division in three directions. Cell- contents bluish-green, brownish, or reddish. There are many ;i :i described species, based on slight distinctions and variations in size and color. Gloeocapsa found in water usually has smaller cells and a more distinct tegument than Chroococcus. Comparatively few species are aquatic. (PI. IV, Fig. 6.) Aphanocapsa. Cells spherical, with a thick, soft, colorless tegument, confluent in a homogeneous mucous stratum which is sometimes of a brownish color. Cell-contents bluish-green, brownish, etc. The cells divide alternately in three directions. There are several species. The cells vary in size from 3 to 6 //. (PI. IV, Fig. ?) Microcystis. Cells spherical, numerous, densely aggregated, enclosed in a very thin, globose mother-vesicle, forming solid families, singly or several surrounded by a universal tegument. Cell -contents aeruginous to yellowish-brown. The cells divide alternately in three directions. This genus represents a condition of frequent occurrence in the process of development of higher forms There are several indistinct species common in water. The cells vary in size from 4 to 7 fi in diameter and the colonies from 10 to 100 /*. (PI. IV, Fig. 8.) Clathrocystis. Cells very numerous, small, spherical or oval, aeruginous, em- bedded in a colorless matrix. Multiplication by division of the cells within the thallus. The thallus is at first solid, then, 198 THE MICROSCOPY OF DRINKING-WATER. becomes saccate and clathrate (perforated) ; broken fragments are irregularly lobed. There is but one species, C. ceruginosa. The cells are from 2 to 4 >u in diameter and the thailus from 25 JJL to 5 mm. This species is widely distributed. (PI. IV, Fig. 9-) Ccelosphzerium. Cells numerous, minute, globose or subglobose, geminate, quaternate, or scattered, immersed in a mucous stratum. Cell- contents aeruginous, granulose. The thailus is globose, vesic- ular, hollow, the cells being found only on the outer surface. Multiplication takes place by division of the cells on the surface and by the escape and further development of certain peri- pheral cells. There is one common species, C. Kuetzingianum. The cells are from 2 to 5 >w in diameter and the thailus from 50 to 500 ;*. (PI. IV, Fig. 10.) Merismopedia. Cells globose or oblong, seruginous or brownish, with confluent teguments. Division in two directions. The thailus is tabular, quadrate, free-swimming, the cells being arranged in groups of 4, 8, 1 6, 32, 64, 128, etc. There are several indistinct species. The diameter of the cells varies from 3 to 7 >u. (PL IV, Fig. ii.) Gloeothece. Similar to Gloeocapsa, but with oblong or cylindrical, instead of spherical cells. Terrestrial rather than aquatic. Aphanothece. Similar to Aphanocapsa, but with oblong instead of spherical cells. Tetrapedia. Cells compressed, quadrangular, equilateral, subdivided into quadrate or cuneate segments or rounded lobes, either by deep incisions or wide angular sinuses. This genus is of doubtful value. ORDER II. NEMATOGEN^E. Multicellular plants, the cells of which dividing in one direction, form filaments, often enclosed in a tubular sheath. C YA NOPH YCE^E. 1 99 The filaments (trichomes) may be either simple or branched. There are five families. FAMILY NOSTOCACE^E. Plants composed of rounded cells loosely united into filaments, or trichomes, and sometimes embedded in jelly. The filaments do not branch and never terminate in a hair- point. They sometimes forms large masses. There are three kinds of cells ordinary vegetative cells, joints, or articles ; heterocysts ; and spores. The ordinary cells are spherical, elongated, or compressed. The cell-contents are bluish -green or brownish, and are usually granular. The heterocysts are cells found at intervals in the filaments. They are spherical, elliptical, or elongated, and are usually somewhat larger than the vegetative cells. Their cell-contents are generally clear or very finely granular, and usually of a light bluish-green color. The cell-wall is sharply defined, and there are two polar lumps of gelat- inous material that cause them to adhere to the adjoining cells. The function of the heterocysts is unknown, but they are thought to be in some way connected with the process of reproduction. The spores are usually much larger than the vegetative cells. They are spherical, elliptical, or cylindrical. Their cell-contents are usually very granular and dark-colored. They seem to be more highly differentiated than the contents of the vegetative cells. The spores are heavy, and will sink in water when freed from the filaments. Multiplication takes place by division of the vegetative cells, by means of the spores, and by means of hormogons, or parts of the internal trichomes which separate from the filaments and form new plants. The character and position of the heterocysts and spores form the chief basis for the division of the Nostocacese into genera. The classification is very indefinite. Nostoc. Cells globose or elliptical ; heterocysts usually globose and somewhat larger than the vegetative cells ; spores oval and but little larger than the heterocysts. Spores and heterocysts are both intercalated in the filaments, rarely terminal. The fila- . ments are enclosed in a gelatinous envelope, and are flexuously curved and irregularly interwoven. They often form gelat- inous fronds or thalli surrounded by a firm membrane. The thalli vary in diameter and are sometimes of great size. There 200 THE MICROSCOPY OF DRINKING-WATER. are many species, both terrestrial and semi-aquatic. The species are not well defined, and many of them are inter- mediate stages in the life-history of higher forms. The true Nostoc is seldom found in drinking-water. (PL IV, Fig. 12.) Anabrena. Vegetative cells spherical, elliptical, or compressed in a quadrate form. Heterocysts much larger than the vegetative cells, subspherical, elliptical, or barrel-shaped, of a pale yel- lowish-green color, and intercalated in the filament. Spores globose or oblong-cylindrical, equal to or somewhat larger than the heterocysts, rarely smaller, never adjacent to the heterocyst. The filaments are moniliform ; are without sheaths ; are straight, curved, circinate, or intertwined ; have a bluish-green or brownish color ; and are often free-floating. There are several important but imperfectly defined species. The most common species are A . flos-aquce and A . circinalis. The vegetative cells of the former are from 5 to 7 jn in diam- eter ; those of the latter are from 8 to 1 2 /i. (PI. IV, Figs. 13 and 14.) Sphaerozyga. Vegetative cells spherical, elliptical, or transversely com- pressed ; of a bluish-green or brownish color. Heterocysts spherical or oval, intercalated, binary or solitary, only slightly larger than the vegetative cells. Spores on each side of and adjacent to the heterocysts, cylindrical, with rounded ends, considerably larger than the heterocysts. The filaments are moniliform ; are sheathless or covered with a mucilaginous coating, occasionally agglutinated in a gelatinous stratum. There are several species, terrestrial and aquatic. The genus is very similar to Anabaena. (PI. V, Fig. i.) Cylindrospermum. Vegetative cells globose, elliptical, or compressed, homo- geneous or granular. Heterocysts terminal, spherical, or oval, but little larger than the cells. Spores adjacent to the het- erocysts, oval or cylindrical, much larger than the cells. The filaments are moniliform, sheathless, and sometimes taper slightly. There are few species, and these resemble some forms of Anabaena and Sphaerozyga. (PI. V, Fig. 2.) C YA NOPH YCE^E. 2 O I Aphanizomenon. Vegetative cells cylindrical, closely connected, granular, and with little color. Heterocysts rare, intercalated, oval, but little larger in diameter than the cells. Spores very rare, intercalated, not adjacent to heterocysts, cylindrical, with rounded ends, sometimes of dark olive color. The filaments are cylindrical, slightly tapering, and densely agglutinated in fascicles, occasionally free. The fascicles are often of con- siderable size. Diameter of filaments 4 to 6 //. This genus is sometimes mistaken for Oscillaria or Anabaena. (PI. V, Fig- 3-) FAMILY OSCILLARIE^E (LYNGBY^E). Filaments without heterocysts or spores, with or without sheath, not terminating in a hair-point, single or associated in bundles enclosed in a common sheath. The division of the filaments into cylindrical cells is indistinct. Mul- tiplication is said to take place by hormogons, i.e. parts of the trichomes which separate from the rest of the filament. Oscillaria. Cells shortly cylindrical, disc-shaped in end-view, closely united into a simple, branchless, sheathless filament. The filaments are straight or somewhat curved, occasionally fascic- ulate, and have rounded ends. The color is bright bluish- green, steel-blue, etc. The filaments when in active vegetative state possess characteristic spontaneous oscillating movements. There is a large number of species, that vary in diameter from i to 50^, and have cells differing in shape and in color. There are but few free-floating forms. (PI. V, Fig. 4.) Lyngbya. Filaments enclosed singly in a sheath, branchless, but with occasional appearance of branching during multiplication, sometimes combined to form a membranaceous stratum. Cells united into short trichomes, with rounded ends, not continuous in the sheath, but separated by clear spaces. Cell-contents blue-green, granular. Sheaths pellucid, hyaline. Propagation is said to take place by hormogons and by gonidia. There are many species, terrestrial and aquatic. (PI. V, Fig. 5.) ' " 2O2 THE MICROSCOPY OF DRINKING- WATER. Microcoleus. Filaments rigid, articulate, crowded together in bundles, en- closed in a common mucous sheath, either open or closed at the apex. Sheath ample, colorless, rarely indistinct. Several species, chiefly terrestrial. (PL V, Fig. 6.) FAMILY SCYTONEME/E. Filaments with lateral ramifications (false branching) in which some of the cells change into heterocysts ; enclosed in a sheath. The cells divide transversely. The ramifica- tions are produced by the deviation of the trichome and emergence through the sheath. The branches do not have a hair-point. There are several genera. Scy tonema. Sheath enclosing a single trichome, composed of subspherical or subcylindrical cells, with scattered heterocysts. Color bluish- or yellowish-green. Ramification takes place by a fold- ing of the trichomes, followed by rupture of the sheath and the emergence of one or two portions of the folded trichome at right angles to the original filament. These branched fila- ments produce interwoven mats. Multiplication is said to take place by microgonidia. There are many species, terrestrial and aquatic. The plant is not found free-floating. (PL V, Fig. 7.) FAMILY SIROSIPHONE^E. Trichomes enclosed in an ample sheath, profusely branched. Branches are formed by longitudinal division of certain cells so as to form two sister cells, the inferior of which remains a part of the trichome, while the other, by repeated division, grows into a branch. The filaments often contain 3, 4, or more series of cells. Propagation is said to take place by means of micr-o- gonidia. Sirosiphon. Cells one-, two-, or many-seriate, in consequence of their lateral division or multiplication. The cells have a distinct membrane and the sheaths are large. The plant is never found free-floating. (PL V, Fig. 8.) FAMILY RIVULARIE^E. Filaments free or agglutinated into a definite thallus, terminating at the apex in a hair-like extremity. Heterocysts usually basal. Trichomes articulated like Oscillaria, CYANOPHYCE&. 2O3 parallel or radially disposed. Spores, when present, cylindrical, gen- erally adjacent to the basal heterocyst. Rivularia. Filaments radial, agglutinated by a firm mucilage, and forming well-defined hemispherical or bladdery forms. Heterocysts basal. No spores formed. Ramifications produced by trans- verse division of the trichomes. Color greenish to brownish. Sheaths usually distinct. Several species, terrestrial and aquatic. Occasionally found free-floating. (PI. V, Fig. 9.) CHAPTER XVIII. CHLOROPHYCE^E. THE Algae are flowerless plants of simple cellular structure, without mycelia, roots, stems, or leaves. The functions of the plants are centred in the individual cells, and only to a limited extent is there any " division of labor" among the cells. It is difficult to define the word * 'Algae," because it is used differently by different writers. In the broad sense it includes all of the thallophytes which contain chlorophyll, i.e. the Diatomaceae, Cyanophyceae, Chlorophyceae, Phaeophyceae, and Rodophyceae. This is the older meaning of the term. It is used in contradistinction to the Fungi, which contain no chlorophyll. In the narrower sense it includes only the Chlorophyceae, Phaeophyceae, and Rodophyceae. This is the later and better use of the word. The Phaeophyceae and Rodophycese are almost entirely marine forms, so that, as far as fresh-water forms are concerned, the word algae is almost synonymous with Chlorophyceae. In popular speech, how- ever, the Cyanophyceae are frequently spoken of as the "blue-green algae," and the diatoms have sometimes been called the ''brown algae." The plants belonging to the Chlorophyceae are character- ized by the presence of true chlorophyll, a nucleus, starch- grains, and often by a cell-wall made of cellulose. They are 204 CHL OROPH YCEsE. 2O 5 "*' algae " in the strictest sense of the term. They cover a great range of complexity. Some of them are minute, uni- cellular forms scarcely distinguishable from the Cyanophyceae; others resemble the Protozoa; while others are large, branch- ing, multicellular forms doubtfully included among the algae, ^ind very similar to plants much higher in the scale of life. Most of them are aquatic, but a few are terrestrial. Their color is almost always a bright chlorophyll green, but occa- sionally it is yellowish-brown or even a bright red. The Chlorophyceae increase by the ordinary processes of cell- division observed in the higher forms of plant life. The cells may separate after division, or they may remain associated in colonies or in simple or branching filaments. Reproduction takes place either asexually, i.e. without the aid of fecunda- tion, or sexually. There is but one general method of asexual reproduction, namely, the formation within the cell of spores, which become scattered and give rise to new cells. There are three general types of sexual reproduction. The simplest is the formation in the cells of zoospores, which become liberated and ultimately copulate with other zoospores. Two of these zoospores become attached by their ciliated ends, their contents become fused, and a zygospore results. After a period of rest the zygospore may develop into a new plant, or may break up into other spores. The second type of sexual reproduction is known as conjugation. Two cells come in contact, and by means of openings in the cell-walls their contents become fused. A zygospore (sometimes two) is formed, which, after a period of rest, gives rise to new plants. The highest form of sexual reproduction takes place by the formation of a rather large female oospore, which be- comes fertilized by small male cells or spermatozoids. This mode of reproduction is analogous to that observed in the 206 THE MICROSCOPY OF DRINKING-WATER. higher plants. Many of the Chlorophycese exhibit the phe- nomenon of ''alternation of generations," by which is meant the continued propagation of the plants by asexual processes with occasional intervention of the sexual processes. ORDER I. PROTOCOCCOIDE^E. Unicellular plants. Cells single or associated in families; tegument involute or naked ; no branching or terminal vege- tation. This order includes many of the free-floating green algae that are found in water. FAMILY PALMELLACE.E. Cells solitary or in families, often em- bedded in a jelly and forming an amorphous stratum. Multiplication. by cell-division. Reproduction asexual, by active gonidia. Gloeocystis. Cells globose or oblong, single or in globose families of 2-4-8 cells. Common and individual lamellose gelatinous integu- ments. Division in alternate directions. Reproduction by zoogonidia. There are several species. The size of the cells varies from 2 to 12 ju in diameter and the colonies from 10 to 100 JA. Color green, sometimes reddish. Gelatinous tegument colorless or ochraceous. Usually fixed, sometimes free-float- ing. (PI. V, Fig. 10.) Palmella. Cells globose, oval, or oblong, surrounded by a thick confluent tegument ; forming an amorphous thallus. Multiplication by alternate division of the cells in all directions. An uncertain genus. Several species, usually fixed. Size of cells varies from i to 15 /*. Thallus often large. Color generally green. (PI. V, Fig. n.) Tetraspora. Cells spherical or angular, with thick teguments confluent into a homogeneous mucous ; forming a sac-like thallus, some- times of large size. The cells divide in two directions and are seen normally in groups of four. The thalli are usually fixed, but the quartettes of cells are sometimes free-floating. CHLOROPHYCE&. 2O; Several species, all green. Cells from 3 JJL to 12 /< in diameter. (PI. V, Fig. 12.) Botryococcus. Cells generally oval, with a thin confluent tegument, densely packed, forming a botryoid, irregularly lobed thallus. One species, green, free-floating, with cells 10 JA. in diameter. (PI. VI, Fig. i.) Raphidium. Cells fusiform or cylindrical, straight or curved, pointed ends, occurring singly, in pairs, or in fascicles. Cell-membrane thin, smooth. Cell-contents green, granular, with transparent va- cuole. Division of cells in one direction. There are several species, with numerous varieties. Two species, R. polymor- phum and R. convolutum, are common free-floating forms. The latter is sometimes known by the name Selenastrum. PL VI, Fig. 2.) Dictyosphseriurti. Cells elliptical or kidney-shaped, with thick mucous invest- ment, more or less confluent, arranged in globose, hollow families. The cells are connected by delicate threads radiating from the centre of the colony and attached to the concave side of the cells. The threads branch dichotomously. Division in all directions. Two or three species. The most important species is D. reniforme. Color green, and cells 6-10 X 10-20 //. (PI. VI, Fig. 3.) TMephrocytium. Cells oblong, kidney-shaped, with ample tegument, arranged in free-swimming colonies of 2-4-8-16 cells. Two species. Green. Cells 5 x 15 to 15 X 45 V- (PL VI, Fig. 4.) Dimorphococcus. Cells in groups of four on short branches, the two intermediate contiguous cells oblique, obtuse-ovate ; the two lateral, opposite and separate from each other, lunate. In colonies with cells connected by threads radially arranged and unbranched. One free-floating species. Color green. Cells 5 to 10 /* in diam- eter. (PI. VI, Fig. 5,) FAMILY PROTOCOCCACE^E. Cells solitary or forming more or less 208 THE MICROSCOPY OF DRINKING-WATER. perfect coenobia. Propagation by asexual zoospores or by copulation of zoogonidia. In general there is no vegetative cell-division. Protococcus. Cells spherical, single or in irregular clusters. Cell-membrane thin, hyaline. Cell-contents green, sometimes reddish. There is but one species, P. vindis, with many varieties. Diameter of cells varies from 3 to 50 JJL. They are both aquatic and aerial. Some of the aquatic forms have a gelatinous tegument and are called Chlorococcus by some writers. The distinction is a difficult one to make. (PI. VI, Fig. 6.) Polyedrium. Cells single, segregate, free-swimming, compressed, 3-4-8- angled. Angles sometimes radially elongated, entire or bifid, rounded at the ends. Cell-membrane thin, even. Cell-con- tents green, granular, sometimes with oil-globules. Propaga- tion by gonidia. There are several species. One of the most common is P. longispinum. (PI. VI, Fig. 7.) Scenedesmus. Cells elliptical, oblong, or cylindrical, with equal or unequal ends, often produced into a spine-like horn ; usually laterally united, forming coenobia. Cell-contents green. Propagation by segmentation of cell-contents into brood families, set free by rupture of the maternal cell-membrane. There are several common species, S. caudatus, with several varieties, S. obtusus, and S. dimorphous. The cells are usually 2 or 3 ^ in diam- eter and from 8 to 25 jn long. (PI. VI, Fig. 8.) Hydrodictyon. Cells oblong-cylindrical, united at the ends into a reticulated, saccate ccenobium. Cell-contents green. Propagation by macrogonidia which join themselves into a ccenobium within the mother cell, and by ciliated microgonidia which copulate and form a resting-spore. One species, H. utriculatum. Aquatic and attached. (PI. VI, Fig. 9.) Ophiocytium. Cells cylindrical, elongated, curved, or circinate, one end and occasionally both ends attenuated. Cell-contents green. Propagation by zoogonidia. There are several species. The most common is O. cochleare, the cells of which are from CHL OROPH 209 5 to 8 /i in diameter and of various lengths. (PI. VI, Fig. 10.) f*ed last rum. Cells united into a plane, discoid or stellate, free-swimming ccenobium, which is continuous, or with the cells interrupted in a perforate or clathrate manner. The central cells are polygonal and entire ; those of the periphery entire, bi-lobed, with lobes sometimes pointed. Cell-contents green, granular. Propagation by macrogonidia formed within the cells, which after their escape divide, arrange themselves in a single layer, and reproduce the form of the mother plant. There are several species. The most common are P. Boryanum and P. simplex. (PI. VI, Fig. n.) Sorastrum. Cells wedge-shaped, compressed, sinuate, emarginate, or bifid at the apex ; radially disposed, forming a globose, solid, free- swimming coenobium. There is but one species, S. spinulosum. The cells are spined. They vary in size from 12 to 20 //. The coenobia vary in diameter from 25 to 75 /*. (PI. VI, Fig. 12.) Coelastrum. Cells globose, or polygonal from pressure, forming a globose, hollow ccenobium, reticulately pierced. The cells are arranged in a single layer, sometimes joined by radial gelatinous cords. Cell-contents green. Propagation by macrospores. There are several species. The most common is C. microporum, which has 8-16-32 cells, and the diameter of which varies from 40 to 100 p. (PI. VII, Fig. i.) Staurogenia. Cells oblong-oval, subquadrate, or rhomboidal, arranged in groups of 4-8-16, forming a cubical ccenobium, hollow within. Cell-contents green. Propagation by quiescent gonidia. (PI. VII, Fig. 2.) ORDER II. VOLVOCINIEiE. Unicellular plants occurring as mobile, globose, sub- globose, or flattened quadrangular ccenobia composed of 210 THE MICROSCOPY OF D R INKING WATER. bi-ciliated green cells which are more or less spherical or com- pressed. The ccenobia as a whole are motile because of the ciliated cells, and hence are free-floating. The ccenobium sometimes has an ample hyaline tegument. Cell-contents green. Propagation sexual or asexual. Asexual propaga- tion takes place by subdivision of the larger vegetative cells into new families, which separate from the mother cell when sufficiently developed. Sexual propagation takes place by means of female spore-cells, or oospores, developed from the vegetative cells, which are fertilized by antheridia devel- oped from other vegetative cells. The antheridia, after escaping from the cell in which they are formed, perforate the membrane of the oogonia, after which the oospore goes into a resting state to germinate later. This order is frequently referred by zoologists to the Protozoa. FAMILY VOLVOCACE^E. Characteristics the same as for the order, Volvox. Large coenobium, continually rotating and moving, looking like a hollow globe composed of very numerous cells (several thousand) arranged on the periphery at regular distances, con- nected by a matrical gelatin which has the appearance of a membrane in which the cells are embedded. Cells globose, bearing two cilia that extend beyond the gelatinous envelope. By the waving of these cilia the colony is kept in motion. Cell-contents green ; starch -granules and often a red pigment- spot present. With a high power the cells are seen to be con- nected to each other in a hexagonal manner by fine threads. Propagation sexual and asexual, as described under the order. The oospores and antheridia are enclosed in flask-like cells extending inward. The spermatozoids are spindle-shaped and furnished with two cilia. The resting-spores usually produce eight zoogonidia. Asexual propagation takes place by division of the larger and darker flask-like cells. These, usually eight in number, develop young volvoxes in the mother cells. They CHL OR OPH YCE^?. 2 I I are very conspicuous. The mother cell splits along well- defined lines and the young forms are set free. There is practi- cally but one species, V. globator. The ccenobia are often one millimeter in diameter. (PL VII, Fig. 3.) Eudorina, Ccenobium oval or spherical, involved in a gelatinous mucilag- inous tegument, composed of 16-32 cells arranged around the colorless sphere at equal distances. The ccenobium is often seen moving with a rolling motion. Cells globose, with two protruding cilia. Cell-contents green, sometimes with a red pigment- spot. Asexual propagation takes place by the division of the cells into 16-32 parts, each of which produces a new coenobium. Sexual propagation as described for the order. Usually four of the thirty-two cells produce antheridia, the others oogonia. The spermatozoids are pear-shaped and are bi -ciliated. There are but two species, E. elegant, and E. stagnate. The cells vary from 5 to 25 //, and the ccenobia from 25 to 150 /^, in diameter. (PI. VII, Fig. 4.) Pandorina. Coenobium globose, invested by a broad, colorless, gelatinous tegument, composed of 8 to 64 cells crowded together or aggregated in a botryoidal manner. (In this respect it differs from Eudorina. ) Cells green, globose or polygonal from com- pression, bi -ciliated, occasionally with a red pigment-spot. Sexual propagation takes place by the conjugation of zoospores produced in the cells of the coenobium, which after union give rise to resting-spores. Asexual propagation takes place by cell- division. There is but one species, P. morum. The coenobium is about 200 ju in diameter and the cells from 10 to 15 ju. (PI VII, Fig. 5.) Gonium. Ccenobium quadrangular, tabular, with rounded angles, formed from a single flat stratum of cells, girt by a broad, hyaline, plane-convex tegument. Cells 16 (4 central and 12 per- ipheral), polygonal, connected by produced angles, and fur- nished with two cilia. Cell-contents green. Asexual propaga- tion by division. Sexual propagation unknown. There is 212 THE MICROSCOPY OF DRINKING WATER. but one species, G. pec for ale. The genus is an uncertain one. (PI. VII, Fig. 6.) ORDER III. CONJUGATE. Unicellular or multicellular plants. The multicellular forms have no terminal vegetation and are destitute of true branches. The chlorophyll masses are arranged in plates, bands, or stellate masses. Starch-grains are abundant. Mul- tiplication by division in one direction. Reproduction by zygospores resulting from copulation and conjugation of two cells, or by azygospores formed without copulation. There are two families that are very different in their general char- acteristics, but that agree in their mode of reproduction. FAMILY DESMIDIE^E. The Desmidieae, or Desmids, form a large, well-defined group of unicellular algae. They are characterized by two peculiar features, by an apparent division of the cell into two symmetrical halves, and by the presence of projections from the sur- face, either inconspicuous or prolonged into spines. The cells are of various sizes and forms, often curious or ornamental, single or joined together forming a filament. The transverse constriction is sometimes deep, sometimes slight, and occasionally absent. The cell-wall is firm, almost horny. Some writers have imagined that it was slightly silic- ified. The cell is surrounded by a mucous covering and sometimes by a layer of gelatin. The cell-contents are green and granular. Starch- grains are numerous. At the ends of some of the cells there are clear spaces in which are seen granules that occasionally have a vibratory movement. Cyclosis, or a circulation of granules in the watery fluid next the cell-wall, may be observed in some species. Some species of desmids exhibit voluntary movements of the entire cell. Closterium, for example, shows certain oscillations and backward and forward gliding movements, supposed to be due to the secretion of threads of mucous. Multiplication takes place by cell-division and by conjuga- tion. In the first case the two halves of the cell stretch apart and become separated by a transverse partition ; new halves ultimately form on each of the original halves, so that two symmetrical cells CHL OROPH YCEJE. 2 I 3 result. These afterwards separate. (See PL VIII, Fig. A.) Sexual propagation by conjugation takes place as follows : Two cells approach and each sends out a tube from its centre. These tubes meet, swell hemispherically, and, by the disappearance of the separating wall, become united into a rounded zygospore with a thick tegument and sometimes with bristling projections. This zygospore, after a period of rest, loses its contents through a rent in the wall, and a new cell is formed which ultimately becomes constricted and assumes the shape of the parent cell. (See PI. VIII, Figs. B to F.) Some of the common genera are described below. The enormous number of species makes a detailed analysis impracticable. Penium. Cells straight, cylindrical or fusiform, not incised nor con- stricted in the middle ; ends rounded. Chlorophyll lamina axillary ; containing starch-granules. Cell-membrane smooth, finely granulated, or longitudinally striated. Individuals free- swimming or associated in gelatinous masses. (PI. VII, Fig. 7-) Closterium. Cells simple, elongated, lunate or crescent-shaped, entire, not constricted at the centre. Cell-wall thin, smooth or somewhat striated. The chlorophyllaceous masses are generally arranged in longitudinal laminae, interrupted in the middle by a pale transverse band. At each end there is a clear, colorless, or yellowish vacuole in which minute "dancing granules" may be seen. (PI. VII, Figs. 8 to 10.) Docidium. Cells straight, cylindrical or fusiform, elongated, constricted at the middle. The semi-cells are somewhat inflated at the base and are often separated by a suture. Ends rounded, trun- cated or divided. Transverse section circular. The chloro- phyllaceous cytioplasm has a parietal or axillary arrangement. Terminal vacuoles with ' ' dancing granules ' ' are observed in some species. (PL VII, Fig. n.) Cosmarium. Cells oblong, cylindrical, elliptical, or orbicular, with margins smooth, dentate, or crenate ; deeply constricted j ends rounded or truncate and entire ; end view oblong or oval. Chloro- 214 THE MICROSCOPY OF DRINKING-WATER. phyll masses parietal or concentrated in the centre of the semi- cells. Cell- walls smooth, punctate, warty, or rarely spinous. The zygospore is spherical, tuberculated or spinous. (PI. VII, Fig. 12, and PI. VIII, Figs. A to F.) Tetmemorus. Cells cylindrical or fusiform, slightly constricted in the middle, narrowly incised at each end, but otherwise entire. Cell-wall punctate or granulate. (PI. VII, Fig. 13.) Xanthidi'im. Oils single or geminately concatenate, inflated, very deeply constricted; semi-cells compressed, entire, spinous, protrud- ing in the centre as a rounded, truncate, or denticulate tubercle. Cell-wall firm, armed with simple or divided spines. The zygospores are globose, smooth or spinous. (PI. VIII, Figs, i and 2.) Arthrodesmus. Cells simple, compressed, deeply constricted ; semi-cells broader than long, with a single spine on each side, but otherwise smooth and entire. (PI. VIII, Fig. 3.) Euastrum. Cells oblong or elliptical, deeply constricted ; semi -cells emarginate and usually incised at their ends; sides sym- metrically sinuate or lobed, provided with circular inflated protuberances ; viewed from the vertex, elliptical. The zygo- spores are spherical, tuberculose or spinous. (PI. VIII, Fig. 4.) Micrasterias. Cells simple, lenticular, deeply constricted ; viewed from front, orbicular or broadly elliptical ; viewed from the vertex, fusi- form, with acute ends ; semi-cells three- or five-lobed ; lateral lobes entire or incised ; end lobes sinuate or emarginate and sometimes with angles bifid or produced. (PI. VIII, Fig. 5.) Staurastrum. Cells somewhat similar to those of Cosmarium in front view, but angular in end view ; angles obtuse, acute, or drawn out into horn-like processes. Cell-wall smooth, punctate or gran- ular, hairy, spinulose, or extended into arms or hair-like proc- esses. Chlorophyll masses concentrated at the centre of the CHLOROPHYCE^E. 2 I 5 semi-cells, with radiating margins. The zygospores are spined. (PI. VIII, Figs. 6 and 7.) Hyalotheca. Cells short, cylindrical, usually with a slight obtuse constric- tion in the middle ; circular in end view. The cells are closely united into long filaments, enclosed in an ample, color- less mucous sheath. The chlorophyll is concentrated in a mass which, in end view, has a radiate appearance. (PI. IX, Fig. i.) Desmidium. Cells oblong-tabulate, somewhat incised ; in end view, tri- angular or quadrangular; united intD somewhat fragile fila- ments and surrounded by a colorless mucous sheath. Chloro- phyll masses in each semi-cell concentrated and radiate to the angles. Zygospores smooth, globose or oblong. (PI. IX, Fig. 2.) Sphaerozosma. Cells bi-lobed, elliptical, or compressed, deeply incised, form- ing filaments which are almost moniliform or pinnatifid, sur- rounded by a colorless or mucous sheath. Chlorophyll mass concentrated, somewhat radiate. (PL IX, Fig. 3.) FAMILY ZYGNEMACE^E. Multicellular plants, composed of cyMn- drical cells joined into filaments and forming an articulated simple thread. Cell-wall lamellose. Chlorophyll arranged as twin stellate nuclei, as axillary laminae, or as spiral bands. Starch -grains, etc., conspicuous. Propagation by zygospores resulting from copulation, which takes place by the union of two filaments. The filaments come into proximity, the cells put out short processes^ which unite ? forming tubular passages between pairs of cells. Through these connecting tubes the cell-contents of one cell passes into and unites with the cell- contents of another. This results in the formation of a zygospore often clothed with a triple membrane. Copulation is said to be scalariform when opposite cells of two filaments unite by ladder-like tubes, geniculate when the cells become bent and unite at the angles, and lateral when the process takes place between two adjoining cells of the same filament. The family is sometimes divided into two sec- tions, the Zygnemina and Mesocarpince. In the second section the 2l6 THE MICROSCOPY OF DRINKING-WATER. spore formed is not a true zygospore. It is formed by a flowing to- gether of only a part of the cell-contents. The zygospores germinate by putting forth a single germ, which elongates by transverse division into a filament. Spirogyra. Cells cylindrical, sometimes replicate, or folded in at the ends. Chlorophyll arranged in one or several parietal spiral bands winding to the right. Copulation scalariform, sometimes lateral. Copulating cells often shorter than sterile ones and more or less swollen. Zygospores always within the wall of one of the united cells. There are very many species, differ- ing in size of cells, number and arrangement of spirals, repli- cation at the end of cells, character of the zygospore, etc- (PI. IX, Figs. 4 and 5.) Zygnema. Cells with two-axil, many-rayed chlorophyll bodies near the central cell-nucleus, containing one or more starch-granules. Copulation scalariform or lateral. Zygospore in one of the united cells. (PI. IX, Fig. 6.) Zygogonium. Like Zygnema, except that the zygospores are located in the connecting tube between the united cells. ORDER IV. SIPHONED. Unicellular plants when in the vegetative state; cells tubular or utricle-shaped, often branched. Cell-contents green, granular. Propagation by sexual fertilization, asexual zoospores, or by microgonidia. FAMILY VAUCHERIACE^E. Plants consisting of elongated, robust tubular filaments, more or less branched, growing in tufts. Chloro- phyll granules are evenly distributed on the inside walls of the cells, and starch-grains and oil-globules are conspicuous. Sexual propaga- tion takes place by means of oospores fertilized by spermatozoids. The oogonia are lateral, sessile, or borne on a simple pedicel; the antheridia usually develop on the same filament. Asexual propaga- CHL OROPH YCE^. 2 I / tion takes place by means of zoospores produced in a terminal sporangium. The zoospores are ciliated, but go through a resting period before germinating. Propagation also takes place by means of microgonidia produced in the vegetative cells. Vaucheria. The characteristics are described under the family. There are many species, aquatic and terrestrial. (PI. IX, Fig. 7.) ORDER V. CONFERVOIDE^E (NEMATOPHYCE^E). Multicellular plants consisting of simple or branched filaments forming articulated threads or membranaceous thalli. Vegetation terminal, sometimes lateral. Propagation by oospores fertilized by spermatozoids, or by copulation of zoogonidia. In many of the genera the method of propaga- tion is not well known. The order contains a great variety of forms, and various methods of classification have been adopted by different writers. There are but few genera that interest the water-analyst FAMILY CONFERVACE^E. Plants consisting of simple or branched filaments, with terminal vegetation, composed of elongated, cylindri- cal cells, rarely abbreviated or swollen. Cell-membrane sometimes lamellose. Vegetation by division in one direction. Propagation by zoospores. Conferva. Articulate threads simple ; cells cylindrical, sometimes swollen ; chlorophyll homogeneous. Vegetation by division. Propagation by zoogonidia. There are many common species, varying greatly in diameter of filaments. Many vegetative filaments of other plants are liable to be mistaken for Conferva. The characteristics of the genus are somewhat vague. (PI. IX, Fig. 8.) Cladophora. Articulate threads very much branched, the branched cells being much thinner than the primary cells. Cell-membrane thick, lamellose. Cells cylindrical, somewhat swollen. Cell- 2 I 8 THE MICROSCOP Y OF DRINKING- WA TER. contents green, containing many starch-granules. Propagation by zoogonidia, which develop in large numbers. (PI. IX, Fig. 9-) FAMILY CEDOGONIACE^E. Filaments articulated, simple or branched. Cells cylindrical, terminal cells sometimes setiform. Propagation by asexual zoospores or by oospores sexually fertilized. Plants monoecious or dioecious ; when dioecious the male plants are either dwarf, i.e. produced from short cells of the female plants, or elongated and independent. There are two genera, (Edogonium and Bulbochaete, each with many species. FAMILY ULOTRICHE^E. Filaments shortly articulate, simple, free, sometimes laterally connate in bands. Cell-membrane thick and lamellose. Cell-contents at first effused, after division transmuted into gonidia. Propagation by ciliated macrospores which do not -copulate, or by microzoospores which do or do not copulate. Ulothrix. Filaments simple, articulate. Articulations usually shorter than their diameter. Cell-membrane thin. Cell-contents green, effused or parietal, enclosing amylaceous granules. Propagation by macro- and micro-zoospores. Several common species. (PI. IX, Fig. 10.) FAMILY CH^ETOPHORACE^E. Filaments articulate, dichotomously or fasciculately branched, accumulated in tufts in a gelatinous mucus, or constituting a filamentose or foliaceous thallus. Propagation by oospores sexually fertilized, or by zoogonidia. Monoecious or dioecious. Stigeoclonium. Filaments articulate, with simple scattered branches. Branches similar to the stems, attenuated into a colorless bristle. Cell- membrane thin, hyaline. Cell -contents green, with chloro- phyll arranged in transverse bands. Propagation by oospores or zoogonidia. (PI. X, Fig. i.) Draparnaldia. Filaments articulate, much branched ; the main stem com- paratively thick, composed of large, mostly hyaline cells, with broad, transverse chlorophyll bands. Many branches and sub- CHLOROPHYCE&, 2 1 9 branches, alternate or opposite. The terminal cells ->re empty, hyaline, and often elongated into a bristle. The branch cells only are fertile. The plant is enveloped in a gelatinous covering. Propagation by resting-spores or zoogo- nidia. There are few species. (PL X, Fig. 2.) Chaetophora. Filaments articulate, with primary branches radiately disposed, and secondary branches shortly articulate, and attenuated into a bristle, the whole involved in a gelatinous mass. Propaga- tion by zoospores. (PL X, Fig. 3.) ORDER VI. CHARACE^. The Characeae are plants which occupy an intermediate position between the algae and the higher cryptogams. Each plant consists of an assemblage of long tubular cells, having a distinct central axis, with whorls of branches projecting at regular intervals at points called "nodes." The branches are sometimes spoken of as leaves, but they are quite similar to the stem. At the lower end of the stem some of the branches (rhizoids) are root-like and serve to give attachment and stability to the plant. Reproduction takes place by a peculiar sexual process. Oospheres or archegones form at the base of the branches and are fertilized by peculiar antherozoids found near them. There are two common genera, Nitella and Chara. In Nitella the stems and branches are simple and naked; the leaves are in whorls of 5 to 8 and without stipules; the leaflets are large and often many-celled; the sporocarps arise singly or in clusters in the forkings of the leaves, and each has a crown of two superimposed whorls of five cells each. In Chara the stems and lower branches are usually corticated, i.e. there is a central tube surrounded by smaller tubes, some- times spirally arranged, forming a cortex; the leaves are in 220 THE MICROSCOPY OF DRINKING-WATER. whorls of 6 to 12, and usually with one or two stipules; the leaflets are always one-celled ; the sporocarps arise from the upper side of the leaves, and each has a crown of one whorl of five cells. These plants exhibit beautifully the phenomenon of cyclosis, or circulation of protoplasm. Some species of Chara secrete calcium carbonate, and from this arises their popular name, "stone-worts." CHAPTER XIX. FUNGI. FUNGI are flowerless plants in which the special charac- teristic is the absence of chlorophyll and starch. Lacking these, they are unable to assimilate inorganic matter, and consequently live a saprophytic or a parasitic existence, that is, they live upon dead organic matter or in or upon some living host. They are essentially terrestrial plants, but some of them live a sort of semi-aquatic life. Many very different forms are included among the Fungi. On the one hand there are microscopic forms, and among them some authors include the bacteria, because they have no chlorophyll, and on the other hand there are the mush- rooms, etc., which are often of very large size. Fungi usually consist of two parts, the mycelium and the fruit. The mycelium is the vegetative portion of the plant. It is a mass of delicate, jointed, branched, colorless filaments intertwined to form a cottony or felty layer. It is the spawn of mush- rooms and the common mold or mildew seen on decaying vegetable matter. The fruit consists of certain terminal mycelium filaments erected from the general mass and bear- ing spore-cells of various kinds. It is by differences in the method of fruiting or reproduction that the different fungi are distinguished from each other. The Fungi, as a class, are of little importance in water 221 222 THE MICROSCOPY OF DRINKING-WATER. investigation. They are more often seen in sewage, and even there the number of important genera is small. For this reason a general classification of the Fungi is not given here, but simply a description of a few common genera. ORDER SACCHAROMYCETES. Saccharomyces. Cells oval or somewhat rounded, colorless, with numerous vacuoles. They do not divide by the ordinary process of cell- division, but increase by a sort of sprouting or budding. A knob-like protuberance appears at one side of the cell ; this increases in size and gradually assumes the form of the mother cell ; it then separates and itself begins to bud, or it remains attached, forming a sort of irregular beading or branching. It does not develop true mycelia. It also reproduces by means of certain large cells whose protoplasm divides and forms several spores, sometimes called ascospores. There is no sexual reproduction. The Saccharomycetes are popularly called yeasts. They are well known for the alcoholic fermentation which they produce in sugar. The S. cerevisice is the com- mon beer- yeast. Its cells average about 8 JLI in diameter. There are other species which differ in the shape and size of the cells, in the character of the spores, in the temperature and time at which sprouting takes place, in the capacity to ferment sugars, in the time required to form yeast-films in the fermenting liquid, etc. (PL X, Fig. 4. ) ORDER ASCOMYCETES. Penicillium. This is the common "blue mold." The mycelium is com- posed of very many colorless, more or less branched filaments or hyphae. The fertile hyphae are erect and septate, and branch into a series of compound branches, each of which bears simple sterigmata upon which chains of oval conidia are borne. The most common species is P. glaucum. It has a pale bluish-green color. Its erect septate hyphae are i to 2 FUNGI. 223, mm. long, bearing a minute brush-like cluster of greenish conidia 2-4 /* in diameter. (PI. X, Figs. 5 and 6.) Aspergillus. Mycelium as in Penicillium. Fertile hyphae unseptate, swollen at apex (columella), bearing simple flask-shaped sterigmata, with chains of elliptical or spherical conidia. Often small yellowish or reddish bodies (perithecia or scle- rotia) are found upon the sterile hyphae at the base of the fer- tile branches. A. repens is a common species. The color is light greenish or brownish. Fertile hyphae 2-4 mm. high, 10 j.i diam.; columella 10-30 //, head of conidia 100 JJL, conidia 5 /*.. (PL X, Fig. 7.) ORDER PHYCOMYCETES. FAMILY MUCORACEJE. riucor. Mycelium saprophytic or parasitic, richly branched, forming a felt-like layer. The hyphae are seldom divided by septa. Conidia formed in sporangia which are spherical and borne on erect hyphae. A common species is M. racemosus. Its sporangia are numerous, 20-70 yu in diameter, on the ends of long hyphae. The spores are smooth, spherical, 48 yu in diam- eter. Secondary sporangia are sometimes seen on the main fruiting-branch. The color is whitish, and later a tawny brown. There are many other species, some of which produce alcoholic fermentation in sugar. (PI. X, Fig. 8.) FAMILY SAPROLEGNIACK*:. Saprolegnia. Saprophytic or parasitic on plants or animals in water, some- times producing pathogenic conditions, as, for example, in the "salmon-disease." They are often seen on dead flies, etc. The mycelium is composed of colorless or grayish hyphae of large size attached to the substratum by root-like processes. The hyphae are not constricted, as in Leptomitus. Sexual reproduction takes place by means of fertilized oospores. Asexual reproduction takes place by zoospores produced in special club-shaped zoosporanges which are borne terminally 224 THE MICROSCOPY OF DRINKING-WATER. upon certain hyphae. The zoospores are numerous, sometimes in rows ; they are bi-ciliated and motile even within the zoosporangium. After escaping from the zoosporangium they become covered with a thin membrane which they throw off before final swarming and germination. (PL XI, Fig. i.) Achlya. Mycelium similar to that of Saprolegnia. The zoospores are non-motile when they escape from the zoosporangium. They arrange themselves in globular fashion outside the apex of the sporangium, assume a thin membrane, rest for a time, and ultimately escape, swim about, and germinate. (PI. XI, Fig. 2.) Leptomitus. Hyphae long, cylindrical, deeply constricted at intervals and at the base of the branches. Near the constriction there is usually a globular body, like an oil-globule. The grayish pro- toplasm is sometimes arranged in concentrated masses, and sometimes is uniformly distributed. The zoospores are formed in the interior of club-shaped terminal sporangia. They resem- ble those of Saprolegnia. Leptomitus is often found in masses in pipes conveying sewage or on the banks of polluted streams. (PL XI, Fig. 3.) CHAPTER XX. PROTOZOA. THE Protozoa are the lowest organisms belonging to the animal kingdom. The name Protozoa was used by the early writers to describe all minute organisms, whether animal or vegetable, but of late it has come to have a more definite meaning. It is now applied to those animal forms which are unicellular or multicellular by aggregation. Structurally the Protozoa are single cells, and where there is an aggregation of several cells each one preserves its identity. There is no differentiation, no difference in the function of the different cells. Thus, the Protozoa are definitely set off from the Metazoa or Enterozoa, which are multicellular, and which have two groups of cells, one group forming the lining to a digestive cavity and the other group forming the body-wall, which differ both in structure and in function. Most of the Protozoa are strictly unicellular. It is extremely difficult to separate the unicellular Protozoa from the unicellular Protophyta. Theoretically there is a sharp distinction between the animal and vegetable kingdoms. Definitions may be found applicable to the higher types of life, but they overlap and become confused when applied to the lowest forms. For example, the fundamental difference betwen the two kingdoms is supposed to lie in the phenome- non of nutrition. Plants can take up the carbon, oxygen, 225 226 THE MICROSCOPY OF D R INKING- WA hydrogen, and nitrogen from mineral matter dissolved in water, the nitrogen in the form of ammonia or nitrates, the carbon in the form of carbonic acid. Their food is in solution; hence they need no mouth or digestive apparatus. They absorb their nourishment through their entire surface. Animals, however, cannot take up nitrogen in a lower state than is found in the albumens, nor carbon except in combina- tion with oxygen and hydrogen in the form of fat, sugar, starch, etc. The albumens and fats are not soluble in water; consequently the food of animals must consist of more or less solid particles. Animals therefore require a mouth, digestive cavity, organs for obtaining their food, etc. As albumens, fats, etc., are found in nature only as products of plant or animal life, it follows that all animal life is dependent upon vegetable or other animal life. There are, however, certain plants that live on organic matter (insectivorous plants, pitcher- plants) and even have digestive cavities, but all their relations show that they are real plants. There are other plants that are devoid of chlorophyll (Fungi), yet no one would think of calling them animals. Then there are many unicellular or- ganisms that contain chlorophyll and have the vegetable, or holophytic, mode of nutrition, but that resemble the animal kingdom in other respects. Such, for example, are the Dino- flagellata and many of the green Flagellata. Because it is difficult to draw a sharp line between the vegetable and animal unicellular forms Haeckel proposed a new group, the Protista, lying between the two kingdoms. This group has been since known as the Phytozoa. The term is not used in this work, but the organisms have been placed in the one or the other of the two kingdoms according to the best available authority. The Protozoan Cell. The protozoan cell, or the indi- PROTOZOA 227 vidual protozoan, is a single mass of sarcode, or protoplasm, that possesses in a general way all the properties of the proto- plasm of higher animal cells. It has a certain amount of irritability and movement, it assimilates food, it grows, and reproduces its kind. It is subject to the same chemical and physical reactions that are observed in higher forms. In size it varies from the tiniest corpuscle to a mass an inch in diameter. It is irregular in form, without a definite bound- ary; or it has a cell-wall and a definite symmetrical outline. Internally the cell usually contains a solid nucleus or a nuclear substance distributed through the cell and recognized by staining. It usually contains a contractile vacuole, which may be seen to expand and contract, discharging a watery or gaseous matter through the cell. There are also permanent vacuoles of watery fluid, gastric vacuoles formed by the water taken in with the food, oil-globules, and solid particles of starch, chlorophyll, etc. Externally there may be a cor- tical substance, a denser layer of protoplasm giving definite shape to the cell that is sometimes contractile. The ex- terior protoplasm may contain such secreted products as chitin, a nitrogenous horny matter, or cellulose, a non- nitrogenous substance, forming a cell-wall, cell-cuticle, or matrix. Substances may be deposited even outside of the protoplasmic layer. If perforated they are known as shells; if closed entirely, as cysts. Cysts are usually of a horny nature and are temporary products. External secretions of calcium carbonate, silicates, etc., are sometimes present. The cell-protoplasm often exhibits certain internal flowing movements, described as the "streaming of the protoplasm." Portions of the protoplasm often extend outwards, forming processes. These are of two kinds, and the distinction be- tween them has been used as a basis of classification. Those 228 THE MICROSCOPY OF DRINKING-WATER. protozoa that have lobose, filamentous processes, known as pseudopodia, are called Myxopods; those that have motile hair-like processes, known as cilia or flagella, are called Mastigopods. The simplest Protozoa absorb solid particles of food at any point on their surface. Digestion takes place within the cell. Protozoa higher in the scale of life have a distinct oral aper- ture through which the food enters, a sort of pharyngeal passage, and an anal aperture through which undigested por- tions of food are expelled. There is no real digestive cavity. Some Protozoa exhibit a simple kind of respiration. Experi- ment has shown that they take up oxygen and give out carbonic acid. Multiplication takes place by binary division, by encystment and spore-formation, by conjugation followed by spore-formation, or by conjugation followed by increased power of division. Strictly there is no sexual reproduction, though in certain instances there are processes corresponding to it. Various classifications have been suggested for the Pro- tozoa. None are entirely satisfactory. Butschli has divided the Protozoa into four classes: the Sarcoda, Sporozoa, Masti- gophora, and Infusoria. So far as fresh-water forms are con- cerned, the Sarcoda represent the Rhizopoda as described by Leidy. The Mastigophora and Infusoria are both included by the word Infusoria as used by Kent. Btitschli's classifica- tion with some modifications is given below, so far as it relates to the forms with which the water analyst is concerned. Many families and some entire orders are omitted. CLASS RHIZOPODA. Protozoa provided with variable, retractile root-like proc- esses or pseudopodia; naked or enclosed in a carapace or PROTOZOA. 229 external skeleton that is chitinous, calcareous, or siliceous; generally one and sometimes more than one nucleus; contract- ile vacuole present or absent. There are five sub-classes -Lobosa, Reticularia, Heliozoa, Radiolaria, and Labyrinthulidea. The two latter are marine forms and therefore are omitted. The Lobosa and Reticularia are creeping animals; the Heliozoa are swimmers. SUB-CLASS LOBOSA. Rhizopoda in which the "amoeba- phase" predominates in permanence and physiological importance. Pseudopodia lobose, not filamentous, arborescent, or reticulate. A denser external layer of protoplasm usually noticed. Provided with one or more nuclei and usually with a contractile vacuole. Reproduction commonly effected by simple fission, sometimes by a kind of budding. Amoeba. A soft, colorless, granular mass of protoplasm ; possessing extensile and contractile power; devoid of investing mem- brane, but having an external thickening of protoplasm ; with variable, lobose, finger-like processes ; ingesting food by flow- ing around and engulfing it ; the absorbed food-material (diatoms, algae, etc.) is often conspicuous. There are several species that vary m size and in the character of the pseudo- podia. A common habitat is the superficial ooze of ponds or ditches. (PI. XI, Fig. 4.) Arcella. An amoeba-like organism enclosed in a chitinoid shell that is variable in shape, but more or less campanulate or dome- shaped, and that has a circular, somewhat concave base. When seen from above, it is disc -shaped, with a pale circular spot in the middle ; when seen from the side, the upper sur- face is strongly convex. The shell usually has a brown color, and is sometimes smooth and sometimes hexagonally marked. 230 THE MICROSCOPY OF DRINKING-WATER. The protoplasmic mass occupies the central portion of the shell, but pseudopodia project through an opening in the concave base. There are many species, differing in shape and in the marks, ridges, etc., on the shell. A. vulgaris is the most common. (PI. XI, Figs. 5 and 6.) Difflugia. Body enclosed in a spherical or pear-shaped membrane in which sand-grains, etc., are embedded. The lower part is sometimes prolonged as a neck, at the end of which is situated the mouth, through which finger-like pseudopodia may project. The surface of the shell is very rough and usually has a brownish or a gray color. Diatoms, etc., are frequently attached to the shell. The contained protoplasmic mass frequently has a green color, but the pseudopodia are colorless. There are several species, varying in shape and size. The diameter of DifHugia shells varies from 35 to 300 /i. (PL XI, Fig. 7-) SUB-CLASS RETICULARIA. Rhizopoda covered with a secreted shell-like membrane with agglutinated particles of lime or sand. The projected pseudopodia are not finger-like, as in the Lobosa, but thread- like and delicately and acutely branched. The external denser layer of protoplasm is not as well marked as in the Lobosa. The shell is sometimes perforated by apertures. Euglypha. Body enclosed in a hyaline, ovoid shell, composed of regular hexagonal plates of chitinoid membrane, arranged in alternat- ing longitudinal series. At the mouth the plates form a serrated margin. The upper portion of the shell is sometimes provided with spines. The protoplasm is almost entirely enclosed by the shell ; the pseudopodia are delicate and branched. There are several species. (PI. IX, Fig. 8.) Prinema. Body enclosed in a hyaline, pouch-like shell, with long axis in- clined or oblique, and with mouth subterminal. Dome PROTOZOA. 231 rounded ; mouth inverted, circular, beaded at border. Pseudo- podia as in Euglypha, but fewer in number. The two genera are quite similar, but Trinema is usually much smaller. One species. (PI. XI, Fig. 9.) SUB-CLASS HELIOZOA. Rhizopoda generally spherical in form, with numerous radial, filamentous pseudopodia, which ordinarily exhibit little change of form, though they are elastic and contractile. Protoplasm richly vacuolated. One or more nuclei and con- tractile vacuoles. Chlorophyll grains sometimes present. Skeleton products sometimes present. The Heliozoa are generally found in fresh water. They are closely related to the marine Radiolaria. Actinophrys. A spherical mass of colorless protoplasm seemingly filled with small bubbles, with numerous long, fine rays springing from all parts of the surface. Contractile vesicle large and active. The organism moves with a slow gliding motion. It feeds on smaller protozoa, algae-spores, etc. The most important species is A. sol, otherwise known as the "sun-animalcule." It is very common in swamp-water. (PI. XI, Fig. 10.) Heterophrys. Like Actinophrys in general form, but with the body enveloped with a thick stratum of protoplasm defined by a granulated or thickly villous surface and penetrated by the pseudopodal rays. CLASS MASTIGOPHORA. Protozoa bearing one or more lash-like flagella, occa- sionally supplemented by cilia, pseudopodia, etc. With an indistinct, diffuse, or definite ingestive system, and usually with one or more contractile vesicles. Multiplication takes place by fission and by sporulation of the entire body-mass, 232 7 'HE MICROSCOPY OF DRINKING-WATER. the process often being preceded by conjugation of two or more zooids. The term Flagellata is used by some writers to describe this class of Protozoa. SUB-CLASS FLAGELLATA. Nucleated cells, with a definite, corticate, external layer of protoplasm and provided with one or more vibratile flagella. Food commonly ingested through an oral aperture in the cortical protoplasm, though some genera contain chlorophyll and are sustained by nutritional processes resembling those of plants. In some genera the cuticle is developed into stalks or collar-like outgrowths. Others produce chitinous shells or masses of jelly and are connected into arborescent or spherical colonies. Food-particles, starch-gains, chromatophore and chlorophyll corpuscles, oil-globules, pigment-spots (eye-spots) are often observed in the protoplasm of the cell. The flagella of the Flagellata offer an interesting study. They are essentially different from cilia in their movement. Cilia are simply alternately bent and straightened. Flagella exhibit lashing movements to and fro and also throw them- selves into serpentine waves. There are two kinds of flagella, distinguished by their movement pulsella and tractella. The former serve to drive the organism forward in the manner of a tadpole's tail. These are never found on the Flagellata. The tractellum is carried in front of the body and draws the organism after it, as a man uses his arms in swimming. The flagella of the Flagellata are always tractella. PROTOZOA. 233 ORDER MONADINA. Small, simple Flagellata, often naked or amoeboid, usually colorless, seldom with chromatophores. With a single, large, anterior flagellum or sometimes with two additional flagella. Mouth area often wanting, never produced into a well-devel- oped pharynx. FAMILY CERCOMONADINA. Cercomonas. Animalcules free-swimming, ovate or elongate, plastic, with a single long flagellum at anterior extremity and a caudal fila- ment at the opposite extremity ; no oral aperture. There are several species. Their length varies from 10 to 25 fit. (PI. XII, Fig. i.) FAMILY HETEROMONADINA. Monas. Very minute, free-swimming animalcules, colorless, globose or ovate, plastic, with no distinct cuticle ; flagellum single, terminal ; no distinct mouth. Several species, commonly found in vegetable infusions. Their length varies from 2 to 10 JA. They move with a "swarming" motion. (PI. XII, Fig. 2.) Anthophysa. Animalcules colorless, obliquely pyriform, attached in spher- ical clusters to the extremities of slightly flexible, granular, opaque, more or less branching pedicles ; two flagella, one longer than the other ; no distinct mouth. In the common species, A. vegetans, the pedicle is dark brown and longi- tudinally striated. The detached stems somewhat resemble Crenothrix when observed with a low power. Zooids about 5 fit long; clusters 25 fit in diameter. Common in swamp- water. (PI. XII, Fig. 3.) ORDER EUGLENOIDEA. Somewhat large and highly developed monoflagellate forms, with firm, contractile, elastic cortical substance; some 234 THE MICROSCOPY OF DRINKING-WATER. forms are stiff, others are capable of annular contraction and worm-like elongation. At the base of the flagellum there is a mouth leading into a pharyngeal tube, near which is a con- tractile vacuole. Rarely with two flagella. FAMILY CCELOMONADINA. Ccelomonas. Animalcules free-swimming, monoflagellate, highly contractile and variable in form, with distinct oral aperture and a spher- oidal pharyngeal chamber; nucleus and contractile vacuole conspicuous ; no trichocysts ; with innumerable green chloro- phyll granules. Nutrition largely vegetal. One species. Length about 50 jj. (PI. XII, Fig. 4.) Raphidomonas (Gonyostomum). Animalcules free-swimming ; ovate-elongate, flexible body, widest anteriorly and tapering posteriorly, two to three times as long as wide ; two flagella, one of them trailing ; oral aperture at anterior end conducts to a conspicuous triangular or Innate pharyngeal chamber ; contractile vacuole conspicuous ; nucleus ovate ; a brownish germ -sphere posteriorly located ; many large bright green chlorophyll bodies ; numerous rod- like bodies called trichocysts ; oil-globules often present. Length 40 to 70 //. Reproduction by spores formed in the germ-sphere. One species, R. semen. The genus Trentonia, described by Dr. A. C. Stokes, is similar to Raphidomonas except that it has no trichocysts. (PL XII, Fig. 5.) FAMILY EUGLENINA. Euglena. Free-swimming animalcules, fusiform or elongate, exceedingly flexible in form ; with highly elastic cuticle terminating pos- teriorly in a tail-like prolongation ; endoplasm bright green or reddish ; flagellum flexible, issuing from an anterior notch at the bottom of which is the oral aperture and a red pigment - spot. There are several common species. E. viridis is the most common. It is often found in immense numbers in stagnant pools, forming a characteristic green or reddish scum. Length varies from 40 to 150 //. E. acus is an elongated form PROTOZOA. 235 with tapering ends. It is longer than E. viridis, but less broad. It is also less variable in form. E. deses is a very long cylin- drical form. (PI. XII, Fig. 6.) Trachelomonas. Monoflagellate animalcules, changeable in form, enclosed within a free-floating, spheroidal, indurated sheath or lorica ; flagellum protruded through an aperture in the lorica. The color of the animalcule is green, with a red pigment-spot ; the color of the lorica is generally a reddish brown. There are several species. Diameter of lorica generally about 25 /*. (PL XII, Fig. 7.) Phacus. Free-swimming animalcules; form persistent, leaf-like, with sharp-pointed, tail-like prolongation ; terminal oral aperture and tubular pharynx ; flagellum long, vibratile ; surface in- durated ; endoplasm green, with red pigment-spot ; contractile vacuole large, subspherical. Length about 50 //, but quite variable. (PL XII, Fig. 8.) ORDER ISOMASTIGODA. Small and middle-sized forms of monaxonic, rarely bilat- eral shape. Fore end with two or more flagella. Some are colored, some colorless; naked or with strong cuticle or secreting an envelope. Nutrition generally holophytic (i.e. likg a green plant). FAMILY CHRYSOMONADINA. Synura. Free-swimming animalcules, united in subspherical social clus- ters, each zooid contained in a separate membranous sheath or lorica, the posterior extremities of which are stalk-like and con- fluent; two subequal flagella, sometimes long; pigment-spots minute or absent ; two brown color-bands produced equally throughout the length of the two lateral borders ; a vacuolar space at the anterior extremity and several contractile vacuoles ; oil -globules often observed. Length of individual zooids about 35 /* ; diameter of clusters varies from 30 to 100 /A. There is 236 THE MICROSCOPY OF DRINKING-WATER. one species, . uvella, with several varieties. The colonies move with a brisk rolling motion, caused by the combined action of the flagella. Common in swamp-waters. (PL XII, Fig. 9.) Uvella. An uncertain genus. Uvella differs from Synura in the non- possession of a separate investing membrane or lorica and by the posterior location of the contractile vacuole. There are usually few zooids in the cluster. (PL XII, Fig. 10.) Syncrypta. Free-swimming animalcules, united into spherical clusters as in Synura, without lorica, but with the entire colony immersed within a gelatinous matrix, beyond the periphery of which the flagella alone project ; two subequal flagella ; brownish lateral color-bands evenly developed ; one or two pigment-spots ; contractile vacuole between the color-bands. Length of zooids about 10 yw. Diameter of colony about 50 /u, including gelatinous zooglcea. There is but one species, . volvox. It resembles Synura. It is not common. PL XII, Fig. u.) Uroglena. Animalcules forming almost colorless spheroidal colonies barely visible to the naked eye. The matrix of the colony is a trans- parent gelatinous shell filled with a watery substance. The zooids are embedded on the periphery, with their flagella extending outwards and by their vibration causing the colony to revolve. The zooids are pyriform, with anterior border rounded and truncated, tapering posteriorly and sometimes continued backwards as a contractile thread ; with two light yellowish-green pigment-bands ; one eye-spot at the base of the flagella ; two unequal flagella ; one or more contractile vacuoles ; oil-globules and a large amylaceous body often present. Length of zooids is about 6 to 12 /,/. The colonies are from 200 to 500 ^ in diameter. There are several rather indistinct species. The zooids multiply by division into twos or fours. The colonies also divide, a hollow first appearing on one side, followed by a rounding at the two poles and a sub- sequent twisting apart. The Uroglena colonies are very fra- gile. (PL XII, Figs. 12 and 13.) PROTOZOA. 237 Oinobryon. Animalcules with urn- or trumpet -shaped loricae attenuated pos- teriorly and set one into another so as to form a compound branching polythecium. The zooids are elongate-ovate, at- tached to the bottom of the loricae by transparent elastic threads ; two unequal flagella ; two brownish or greenish lateral color-bands ; a conspicuous pigment-spot ; nucleus and con- tractile vacuole sub-central. The polythecium is constructed through the successive terminal gemmation of the zooids. Length of separate loricae 1 5 to 60 ju. The polythecium may contain from 2 to 500 loricae. The usual number is bet.veen 25 and 50. Reproduction takes place by spore-formation. The spores sometimes remain attached to the polythecium, or they may become scattered. When free they are liable to be mistaken for small Cyclotella. The spores are from 8 to 20 /* in diameter. There are several species. D. sertularia is the most common. (PI. XIII, Fig. i.) Cryptomonas. Free-swimming animalcules, illoricate, but persistent in form, ovate or elongate, compressed asymmetrically ; flagella two, long, equal in length, issuing from a deep groove or furrow ; large oral aperture at the base of the flagella continued back- wards as a tubular pharynx ; two lateral bright green color- bands ; conspicuous nucleus and contractile vacuole ; oil- globules often present. Length from 40 to 60 yu. (PI. XIII, Fig. 2.) Mallomonas. Free-swimming animalcules, oval or elliptical, persistent in shape; surface covered with overlapping horny plates from which arise long hair-like setae ; under low power the surface has a crenulated appearance. One long, slender anterior flagellum ; indistinct contractile vacuole. Endoplasm vacuolar, greenish or yellowish. Length from 20 to 40 //. (PI. XIII, Fig. 30 FAMILY CHLAMYDOMONADINA. This family is often referred to the vegetable kingdom. Chlamydomonas. Animalcules ovate, with two or more flagella, one large green 23$ THE MICROSCOPY OF DRINKING-WATER. color-mass, a delicate membranous shell, usually with a pig- ment-spot and one or more contractile vacuoles. The proto- plasm divides into new individuals within the envelope. Length from 10 to 30 /*. (PI. XIII, Fig. 4.) FAMILY VOLVOCINA. Often included under Protozoa. See page SUB-CLASS CHOANOFLAGELLATA. Mastigophora provided with an upstanding collar sur- rounding the anterior pole of the cell, from which the single flagellum springs. (Omitted from this work.) SUB-CLASS DINOFLAGELLATA. Mastigophora are characterized by the presence of a longitudinal groove, marking the anterior region and the ventral surface, and from which a long flagellum projects. In every genus but one there is also a transverse groove in which lies horizontally a second flagellum, at one time mis- taken for a girdle of cilia. The animalcules are bilaterally asymmetrical. They are occasionally naked, but most genera are covered with a cuticular shell of cellulose, either entire or built of plates. The endoplasm contains chlorophyll, starch-granules, and a brown coloring matter similar to that of diatoms. The nucleus is large and branching. There is no contractile vacuole. Multiplication takes place by trans- verse binary fission. Because of the presence of the cellulose shell, chlorophyll, starch-granules, and a holophytic (vegetal) mode of nutrition the Dinoflagellata are often classed in the vegetable kingdom. Many of the Dinoflagellata are marine forms. Some are phosphorescent. PROTOZOA. 239 Peridinium. Free-swimming animalcules enclosed within a cellulose shell composed of polygonal facets. With a high power the facets exhibit a delicate reticulation. A transverse groove divides the body into two subequal parts. A second groove extends from the first towards the apical extremity. Two flagella, one in the transverse groove, the other proceeding from the junc- tion of the two grooves. Color yellowish green or brown. There are one or more pigment-spots. Length from 40 to 75 yu. There are several species. P. tabulatum is the most common. (PI. XIII, Fig. 5.) Ceratium. Free-swimming animalcules enclosed within a shell consisting of two subequal segments, one or both of which are produced into conspicuous horn-like prolongations, often covered with tooth-like processes. There is a central transverse furrow and a second groove extending from the centre of the ventral aspect towards the anterior pole. Two flagella, one of which lies in the transverse groove. The brown color is not as marked as in Peridinium. Length from 25 to 150 >u. There are several species, varying considerably in the character of the horn-like projections. (PI. XIII, Fig. 6.) Glenodinium Free-swimming animalcules covered with a smooth, cellulose shell not made up of facets, consisting of two subequal parts. There is a conspicuous transverse groove and a much less con- spicuous secondary groove. Two typical flagella. Body ovate. Color brownish. Pigment-spot sometimes present. Length about 40 to 55 yw. Glenodinium is often surrounded by a wide, irregular mass of jelly. (PI. XIII, Fig. 7.) Gymnodinium. Quite similar to Peridinium, but without a protecting shell. SUB-CLASS CYSTOFLAGELLATA. Marine forms. 240 THE MICROSCOPY OF DRINKING-WATER. CLASS INFUSORIA. In its broadest sense the word Infusoria includes all the Protozoa except the Rhizopoda and Sporozoa. As used here, following Biitschli, it includes only the Ciliata and Suctoria. SUB-CLASS CILIATA. Protozoa of relatively large size, furnished with cilia, but not with flagella. The cilia occur as a single band surround- ing the oral aperture or are dispersed over the entire body. Modification of the cilia into setae or styles is sometimes observed. There is generally a well-developed oral and anal aperture. The nucleus varies in different genera. Besides one larger, oblong nucleus a smaller one (paranucleus) is often present. One or more contractile vacuoles present. They all possess a delicate but well-defined ectoderm, elastic, but constant in form. They occur naked or enclosed in horny or siliceous shells or in gelatinous envelopes. Some genera are stalked. Multiplication takes place by transverse fission. Conjugation has been observed, but the part that it plays in the life-history is not well known. Many of the Ciliata are parasites in higher animals. The Ciliata are divided into four orders according to the character and distribution of their cilia. ORDER HYPOTRICHA. Ciliata in which the body is flattened and the locomotive cilia are confined to the ventral surface, and are often modified and enlarged to the condition of muscular appendages. Usually an adoral band of cilia, like that of Heterotricha. Dorsal surface smooth or provided with tactile hairs only. Mouth and anus conspicuous. PROTOZOA. 241 Euplotes. Animalcules free-swimming, encuirassed, elliptical or orbicular, with sharp laminate marginal edges, and usually a plane ven- tral, and convex, sometimes furrowed, dorsal surface. Peri- stome-field arcuate, extending backwards from the frontal border to or beyond the centre of the ventral surface, sometimes with a reflected and ciliate inner border. Frontal styles six or seven in number ; three or more irregularly scattered ventral styles, and five anal styles ; four isolated caudal styles along the posterior margin. Endoplast linear. Single spherical con- tractile vesicle near anal aperture. Length about 125 yw. (PL XIII, Fig. 8.) ORDER PERITRICHA. Ciliata with the cilia arranged in one anterior circlet or in two, an anterior and a posterior; the general surface of the body destitute of cilia. The Peritricha are sometimes divided into two suborders, the free-swimming forms and the attached forms. Halteria. Animalcules free-swimming, colorless, more or less globose, terminating posteriorly in a rounded point. Oral aperture terminal, eccentric, associated with a spiral or subcircular wreath of large cirrose cilia. A zone of long hair-like setae or springing-hairs developed around the equatorial region, the sudden flexure of which appendages enables the organism to progress through the water by a series of leaping movements, in addition to their ordinary swimming motions. Length 15 to 30 yu. There are several species, some of them colored green. (PL XIII, Fig. 9.) Vorticella. Animalcules ovate, spheroidal, or campanulate, attached pos- teriorly by a simple undivided, elongate and contractile, thread-like pedicle ; the pedicle enclosing an elastic, spirally disposed, muscular fibrilla, and assuming suddenly on con- traction a much-shortened and usually corkscrew-like contour. 242 THE MICROSCOPY OF DRINKING-WATER. Adoral system consisting of a spirally convolute ciliary wreath, the right limb of which descends, into the oral cleft, the left one obliquely elevated and encircling the ciliary disk. The entire adoral wreath contained within and bounded by a more or less, distinctly raised border the peristome between which and the elevated ciliary disk, on the ventral side, the widely excavated cleft or vestibulum is situated. The vestibulum is continued further into a conspicuous cleft-like pharynx, and terminates in a narrow tubular oesophagus. Anal aperture opening into the vestibulum. Contractile vesicle single, spherical, near the vestibulum. Nucleus elongate. Multipli- cation by longitudinal fission, by gemmation, and by the development of germs. There exists a very large number of species, varying considerably in size and shape. The length varies from 25 to 200 p. Vorticella are often found floating in water attached to masses of Anabsena, etc. (PI. XIII,. Fig. 10.) Zoothamnium. Animalcules structurally identical with those of Vorticella, ovate, pyriform, or globular, often dissimilar in shape and of two sizes, stationed at the extremities of a branching, highly contractile pedicle or zoodendrium. Numerous species. Epistylis. Animalcules campanulate, ovate, or pyriform, structurally sim- ilar to Vorticella, attached in numbers to a rigid, uncon- tractile, branching, tree-like pedicle or zoodendrium ; the zooids usually of similar size and shape. Numerous species. (PI. XIII, Fig. n.) ORDER HETEROTRICHA. Ciliata possessing two distinct systems of cilia, one a band or spiral or circlet of long cilia developed in the oral region, the other composed of short, fine cilia covering the entire body. The cortical layer is usually highly differentiated. Tintinnus. Animalcules ovate or pyriform, attached posteriorly by a PROTOZOA. 243 slender retractile pedicle within an indurated sheath or lorica. The shape of the lorica is generally cylindrical ; it is free- floating ; it is somewhat mucilaginous and attracts to its outer surface foreign particles, such as grains of inorganic matter, diatom-shells, etc. The peristome-field of the organism occu- pies the entire anterior border, circumscribed by a more or less complex circular or spiral wreath of long, powerful, cirrose cilia, the left limb or extremity of which is spirally involute and forms the entrance to the oral fossa. This fossa is con- tinued as a short, tubular pharynx. Anus posteriorly situated, subterminal. Cuticular cilia very fine, distributed evenly throughout, clothing both the body and the retractile pedicle. Length of lorica 80 to 150 yu. There are many species, vary- ing greatly in the size and shape of the loricae. In the fresh- water forms the lorica is generally cylindrical. Another genus, Tintinnidium, varies, from Tintinnus only in having a more mucilaginous sheath and in being permanently attached to foreign objects. (PI. XIII, Fig. 12.) Codonella. Animalcules conical or trumpet-shaped, solitary, free-swim- ming, highly contractile, inhabiting a helmet- or bell-shaped lorica, to which they are attached by their posterior extremity. The anterior region truncate or excavate, forming a circular peristome having an outer fringe of about twenty long, ten- tacle-like cilia, and an inner collar-like border, or frill, which bears an equal number of slender, lappet-like appendages. Entire cuticular surface clothed with fine, vibratile cilia. Lorica not perforated, of chitinous consistence, often of a brown color, sometimes sculptured or mixed with foreign granular substances. Length of lorica 50 to 150 JJL. Several species, mostly marine. (PI. XIV, Fig. i.) Stentor. Animalcules sedentary or free-swimming at will ; bodies highly elastic and variable in form : when swimming and contracted, clavate, pyriform, or turbinate ; when fixed and extended, trumpet-shaped, broadly expanded anteriorly, tapering off arid- attenuated towards the attached posterior extremity. Peristome 244 THE MICROSCOP Y OF DRINKING- WA TER. describing an almost complete circuit around the expanded anterior border, its left-hand extremity or limb spirally in- volute, forming a small pocket-shaped fossa conducting to the oral aperture, the right-hand limb free and usually raised con- siderably above the opposite or left-hand one. Peristomal cilia , cirrose, very large and strong; cilia of the cuticular surface very fine, distributed in even longitudinal rows, oc- casionally supplemented by scattered hair-like setae. Nucleus band-like, moniliform, or rounded. Contractile vesicle com- plex. Multiplication by oblique fission and by germs separated from the band-like endoplast. There are many species, some of large size, colorless, or greenish, bluish, brownish, etc. (PL XIV, Fig. 2.) Bursaria. Animalcules free-swimming, broadly ovate, somewhat flattened on one side, anteriorly truncate. Peristome-field pocket- '' shaped, deeply excavate, situated obliquely on the anterior half of the body, having a broad oral fossa in front, and a cleft- like lateral fissure, which extends from the left corner of the contour border to the middle of the ventral side ; no tremulous -t"* flap. Pharynx long, funicular, bent towards the left, and forming a continuation of the peristome excavation. Adoral ciliary wreath broad, much concealed, lying completely within the peristome-cleft. Cuticular cilia fine, in longitudinal rows. Anus posteriorly situated, terminal. Nucleus band-like, curved, or sinuous. Contractile vesicles distinct, usually multiple,, Few species. Length 300 to 500 yw. (PI. XIV, Fig. 3.) ORDER HOLOTRICHA. Ciliata with but one sort of cilia, these covering the body uniformly and almost completely. A variously modified extensile or undulating membrane sometimes present. Oral ~nd anal orifices usually conspicuous. Trichocysts sometimes present in the cuticular layer. Animalcules free -swimming, ovate or elongate, asymmetrical, PROTOZOA. 245* more or less flexible, but persistent in shape. Finely ciliated throughout, the cilia of the oral region not differing in size or character from those of the general surface of the body. An- oblique groove developed on the ventral surface, at the pos- terior extremity of which is situated the oral aperture. Cor- tical layer usually enclosing trichocysts. Contractile vesicles and nucleus conspicuous, the former sometimes stellate. There are several species. The most important is P. aurelia, which is often found in sewage-polluted and stagnant water. It is colorless, has a length of about 225 jw, and moves with a brisk rotatory motion. (PI. XIV, Fig. 4.) Nassula .. ?\ Animalcules ovate, cylindrical, flexible, but not polymorphic, usually highly colored rose, red, blue, yellow, etc. Oral aperture lateral. Pharynx armed with a simple horny tube or with a cylindrical fascicle of rod-like teeth. Entire surface of cuticle finely and evenly ciliate. The cortical layer sometimes containing trichocysts. There are several species, varying in color, shape, and size. Length 50 to 250 //. (PP. XIV, Fig- 5-) Coleps. Animalcules ovate, cylindrical, or barrel -shaped, persistent in shape, cuticular surface divided longitudinally and trans- versely by furrows into quadrangular facets ; these facets are smooth and indurated, the narrow furrows soft and clothed with cilia ; the anterior margin mucronate or denticulate ; the posterior extremity mucronate and provided with spines or cusps. Oral aperture apical, terminal, surrounded with cilia^ Anal aperture at posterior extremity. Color gray or light brown. The most common species is C. hirtus, which has a length of about 60 p. (PI. XIV, Fig. 6.) Enchelys. Animalcules free-swimming, elastic, and' changeable in shape, pyriform or globose. Oral aperture situated at the termination of the narrower and usually oblique truncate anterior extremity. Anal aperture at the posterior termination. Cuticular surface finely and entirely ciliate ; the cilia are longer in the region 246 THE MICROSCOPY OF DRINKING-WATER. of the mouth. Few species. Length about 25 to 50 /*. (PI. XIV, Fig. 7.). Trachelocerca. Animalcules colorless, highly elastic, and changeable in form, the anterior porlion produced as a long, flexible, narrow, neck- like process, the apical termination of which is separated by an annular constriction from the preceding part, and is perforated apically by the oral aperture. Cuticular surface evenly and finely ciliate ; a circle of larger cilia developed around the oral region. Length of extended body about 150 fit. Few species. (PL XIV, Fig. 8.) Pleuronema. Animalcules ovate, colorless. Oral aperture situated in a depressed area near the centre of the ventral surface, supple- mented by an extensile, hood-shaped, transparent membrane or velum, which is let down or retracted at will. Numerous longer vibratile cilia stationed at the entrance of the oral cavity. The general surface of the body clothed with long, stiff, hair- like setae. The cortical layer usually containing trichocysts. Length 60 to ioo//. Few species. (PI. XIV, Fig. 9.) Colpidium. Animalcules free-swimming, colorless, kidney -shaped. Entirely ciliate. Oral aperture inferior, subterminal. Pharynx sup- ported throughout its length by an undulating membrane which projects exteriorly in a tongue-like manner. Two nuclei, rounded, sub-central. Length 50 to 100 //. One species. (PI. XV, Fig. i.) SUB-CLASS SUCTORIA (TENTACULIFERA OR ACINETARIA). Protozoa with neither flagellate appendages nor cilia in their adult state, but seizing their food and effecting locomo- tion, when unattached, by means of tentacles. These are simply adhesive or tubular and provided at their distal extremity with a cup-like sucking-disk. Nucleus usually much branched. One or more contractile vesicles. Multi- plication by longitudinal or transverse fission or by external PROTOZOA. 247 or internal bud-formation. The young forms are ciliated. Most of the Suctoria are sedentary. Acineta. Animalcules solitary, ovate or elongate, secreting a protective lorica, to the sides of which they are adherent or within which they may remain freely suspended. Lorica transparent, tri- angular or urn-shaped, supported upon a rigid pedicle. Ten- tacles suctorial, capitate, distributed irregularly or in groups. There are many species. (PL XV, Fig. 2.) CHAPTER XXL ROTIFERA. THE Rotifera, or Rotatoria, comprise a well-defined group of minute multicellular animals. They are often included among the Vermes, but some of them possess characteristics that suggest the Arthropoda. Though microscopic in size, the Rotifera are quite highly organized. They have a well-defined digestive system, in- cluding a mouth, or buccal orifice; a mastax, a peculiar set of jaws for mastication; salivary glands; an oesophagus; gastric glands; a stomach; an intestine; and an anus. There is a vascular system, a muscular system, and, it is claimed, a nervous system. There is a conspicuous reproductive system, and both males and females are observed, although the males are rare. The transparency of most of the Rotifera renders these various organs subjects of easy investigation. The organisms are protected by a firm, homogeneous, structureless cuticle, often hardened by a development of chitin, forming a carapace or lorica. Some genera are further protected by an exterior casing or sheath, called an '* urceo- lus," which may be gelatinous and transparent, as in Floscu- laria, or covered with foreign particles or pellets, as in Melicerta. The Rotifera are generally bilaterally symmetrical, with a dorsal and ventral surface, with definite head region and tail 248 RO TIFERA. 249 region, broadest anteriorly and tapering posteriorly. There are three features of the Rotifera that deserve special atten- tion, partly because they are unique in the organisms of this group and partly because they are used as the basis of classi- fication. They are the ciliary wreath, the mastax, and the foot. The ciliary wreath consists of one or more circlets of cilia springing from disc-like lobes surrounding the mouth at the anterior end. By their continual lashing they present the appearance of wheels, giving to these organisms the name of "wheel-animalcules." Their function is to assist in locomo- tion, to create currents in the water by which food-particles are carried into the mouth, and to conduct this food-material through the alimentary canal. The disc-like lobe bearing the cilia is known by the names of corona, trochal disc, or velum. It takes different shapes in different rotifers. Its simplest form is an oval or circle. In more complex forms it is intricately folded, as shown on PL XVI, Figs. A to E. The ciliated wreath is often supplemented by certain projecting processes, ciliated or bearing setae or bristles. The foot, pseudopodium, or posterior extremity of a rotifer presents several different types. It may be fleshy and transversely wrinkled, or hard and jointed; it maybe non- retractile or retractile; often the jointed forms are telescopic; it may terminate in a sort of sucking-disc or in a ciliated expansion, or it may be furcate, or divided into toes, as shown on PL XVI, Figs. F to I. In some species the foot is altogether lacking. The mastax is a sort of muscular bulb forming a part of the pharynx and containing the trophi. It has an opening above from the mouth and below into the oesophagus. The trophi, or teeth, are peculiar calcareous structures. Their 250 THE MICROSCOPY OF DRINKING-WATER. function is to grind the food before it passes into the stomach, and this grinding movement may be witnessed through the transparent walls of many rotifers. The trophi consist of two toothed, hammer-like bodies, or mallei, that pound on a sort of split anvil, or incus. The malleus consists of an upper part, the head or uncus, and a lower part, the handle or manubrium. The incus also consists of two parts, a sym- metrically divided upper part, the rami, that receives the blow of the malleus, and a lower part or fulcrum. The trophi show great modifications in different genera in the shape and proportion of the various parts.* PI. XVI, Fig. J represents a typical form. These three characteristics the arrangement of the ciliary wreath, the structure of the foot, and the form of the trophi serve as the basis for dividing the Rotifera into orders and families. The following classification is that adopted by Hudson and Gosse. Only the typical and very common genera are described. * The following terms are used to describe the trophi (see PI. XVI, Figs. J to P) : Malleate. Mallei stout ; manubria and unci of nearly equal length ; unci 5- to 7-toothed ; fulcrum short. Submalleate. Mallei slender ; manubria about twice as large as the unci ; unci 3- to 5-toothed. Forcipitate. Mallei rod-like ; manubria and fulcrum long ; unci pointed or evanescent ; rami much developed and used as forceps. Incudate. Mallei evanescent ; rami highly developed into a curved forceps ; fulcrum stout. Uncinate. Unci 2-toothed ; manubria evanescent ; incus slender. Ramate. Rami subquadrate, each crossed by two or three teeth ; manubria evanescent : fulcrum rudimentary. Malleo-ramate. Mallei fastened by unci to rami ; manubria three loops soldered to the unci ; unci 3-toothed ; rami large, with many striae parallel to the teeth ; fulcrum slender. ROTIFERA. 251 ORDER RHIZOTA. Rotifera fixed when aciult; usually inhabiting a gelatinous tube excreted from the skin. Foot transversely wrinkled, not contractile within the body, ending in an adhesive suck- ing-disc or cup, without telescopic joints, never furcate. FAMILY FLOSCULARIAD/E. Corona produced longitudinally into lobes bearing the setae. Mouth central. Ciliary wreath a single half- circle above the mouth. Trophi uncinate. Floscularia. Frontal lobes short, expanded, or Wholly wanting. Setae very long and radiating, or short and cilia-like. Foot terminated by a non-retractile peduncle, ending in an adhesive disc. Inhabiting a transparent gelatinous tube into which the animal contracts when alarmed. There are several species, varying in length from 200 to 2500 //. (PL XV, Fig. 3.) FAMILY MELICERTAD^E. Corona not produced in lobes bearing setae. Mouth lateral. Ciliary wreath a marginal continuous curve bent on itself at the dorsal surface so as to encircle the corona twice, with the mouth between its upper and lower curves, and having a dorsal gap between its points of flexure. Trophi malleo-ramate. Melicerta. Corona of four lobes. Dorsal gap wide. Dorsal antennae minute. Ventral antennae obvious. Inhabiting tubes built up of pellets. Length 800 to 1500 //. Few species. M. ringens is very common on water-plants. (PI. XV, Fig. 4. ) Conochilus. Corona horseshoe-shaped, transverse ; gap in ciliary wreath ventral. Mouth on the corona, and towards its dorsal side. Dorsal antennae very minute or absent. Ventral antennae obvi- ous. Forming free-swimming clusters of several individuals, inhabiting coherent gelatinous tubes. Length 500 to 1200 //. Two species. C. volvox is very common. (PI. XV, Fig. 5.) 2$2 THE MICROSCOPY OF DRINKING-WATER. ORDER BDELLOIDA. Rotifera that swim with their ciliary wreath and creep like a leech. Foot wholly retractile within the body, telescopic, at the end almost invariably divided into three toes. FAMILY PHILODINAD^E. Corona a pair of circular lobes transversely placed. Ciliary wreath a marginal continuous curve bent on itself at the dorsal surface so as to encircle the corona twice, with mouth between its upper and lower curves, and having also two gaps, the one dorsal between its points of flexure, the other ventral in the upper curve opposite to the mouth. Trophi ramate. Rotifer. Eyes two, within the frontal column. The most common species is R. vulgaris, which has a white body, smooth, and tapering to the foot. Spurs and dorsal antennae of moderate length. Length about 500 jn. This was one of the first rotifers discovered. It gave its name to the entire class. (PL XV, Fig. 6.) ORDER PLOIMA. Rotifera that swim with their feet and (in some cases) creep with their toes. This is the largest and most important order of Rotifera. SUB-ORDER ILLORICATA. Integument flexible, not stiffened to an enclosing shell. Foot, when present, almost invariably furcate, but not trans- versely wrinkled; rarely more than feebly telescopic, and partially retractile. FAMILY MICROCODID^E. Corona obliquely transverse, flat, circular. Mouth central. Ciliary wreath a marginal continuous curve encircling the corona, and two curves of larger cilia, one on each side of the mouth. Trophi forcipitate. Foot stylate. Microcodon. Eye single, centrally placed, just below the corona. One ROTIFERA. 253 species. Length about 200 /*, of which the foot is more than half. (PL XV, Fig. 7.) FAMILY ASPLANCHNAD^E. Corona subconical, with one or two apices. Ciliary wreath single, edging the corona. Intestine and cloaca absent. Asplanchna. Corona with two apices. Trophi incudate, not enclosed within a mastax. Stomach of moderate size, spheroidal. Viviparous. Several species. Very large and transparent. (PL XV, Fig. 8.) FAMILY SYNCH^ETAD^E. Corona a transverse spheroidal segment, sometimes much flattened, with styligerous prominences. Ciliary wreath a single interrupted or continuous marginal curve encircling the corona. Mastax very large, pear-shaped. Trophi forcipitate. Foot minute, furcate. Synchaeta. Form usually that of a long cone whose apex is the foot ; front furnished with two ciliated club-shaped prominences. Ciliary wreath of interrupted curves. Foot minute, furcate. Several species. Length 150 to 300 //. (PL XVI, Fig. i.) FAMILY TRIARTHRAD^. Body furnished with skipping append- ages. Corona transverse. Ciliary wreath single, marginal. Foot absent. Polyarthra. Eye single, occipital. Mastax very large and pear-shaped. Trophi forcipitate. Provided with two clusters of six spines on the shoulders, the spines being in the form of serrated blades. Length about 125 /*. (PL XVI, Fig. 2.) Triarthra. Eyes two, frontal. Mastax of moderate size. Trophi malleo- ramate. Spines single, two lateral, one ventral. There are three species, differing chiefly in the length of the spines. In the most common species the spines are twice the length of the body. Length of body about 150 /*. (PL XVI, Fig. 3.) FAMILY HYDATINAD^E. Corona truncate, with styligerous prom- inences. Ciliary wreath two parallel curves, the one marginal fring- 254 THE MICROSCOPY OF D KIN KING- WATER. ing the corona and mouth, the other lying within the first, the stylig- erous prominences lying between the two. Trophi malleate. Foot furcate. Hydatina. Body conical, tapering towards the foot. Foot short and con- fluent with the trunk. Eye absent. This is one of the largest of the Ploima. Length about 600 ju. FAMILY NOTOMMATAD^E. Corona obliquely transverse. Ciliary wreath of interrupted curves and clusters, usually with a marginal wreath surrounding the mouth. Trophi forcipitate. Foot furcate. This family is the most typical, the most highly organized, of the Rotifera. Diglena. Body subcylindrical, but very versatile in outline, often swelling behind and tapering to the head. Eyes two, minute, situated near the edge of the front. Foot furcate. Trophi forcipitate, generally protrusile. Several species. Length 125 to 400 /(. (PL XVI, Fig. 4.) SUB-ORDER LORICATA. Integument stiffened to a wholly or partially enclosing shell; foot various. FAMILY RATTULID^E. Body cylindrical or fusiform, smooth, with- out plicae or angles ; contained in a lorica closed all around, but open at each end, often ridged. Trophi long, asymmetrical. Eye single, cervical. Mastigocerca. Body fusiform or irregularly thick, not lunate. Toe a single style, with accessory stylets at its base. Lorica often furnished * with a thin dorsal ridge. Many species. (PL XVI, Fig. 5.) FAMILY COLURID^E. Body enclosed in a lorica, usually of firm consistence, variously compressed or depressed, open at both ends, closed dorsally, usually open or wanting ventrally. Head surrounded by a chitinous arched plate or hood. Toes two, rarely one, always exDOsed. ROT IP ERA. 255 Colurus. Body subglobose, more or less compressed. Lorica of two lateral plates, open in front, gaping behind. Frontal hood in form of a non-retractile hook. Foot prominently extruded, of distinct joints, terminated by two furcate toes. Many species. FAMILY BRACHIONID^E. Lorica box-like, open at each end, gen- erally armed with anterior and posterior spines. Foot very long, flexible, uniformly wrinkled, without articulation; toes very small. Brachionus. Lorica without elevated ridges, gibbous both dorsally and ven- trally. Foot very flexible, uniformly wrinkled, without arti- culation ; toes very small. Free-swimming. Many species. (PL XVII, Fig. i.) Noteus. Lorica facetted and covered with raised points ; gibbous dor- sally, flat ventrally. Foot obscurely jointed. Toes moderately long. Eyes wanting. Length 350 jn. FAMILY ANUR^AD/E. Lorica box-like, broadly open in front, open behind only by a narrow slit. Usually armed with spines or elastic setae. Foot wholly wanting. Anuraea Lorica an oblong box, open widely in front, narrowly in rear ; dorsal surface usually tessellated. The occipital ridge always, the anal sometimes, furnished with spines. The egg after extrusion is carried attached to the lorica. Free-swimming. Length about 125 yu. (PL XVII, Figs. 2 and 3.) Notholca. Lorica ovate, truncate and six-spined in front, sometimes pro- duced behind ; of two spoon-like plates united laterally. No posterior spines. Dorsal surface marked longitudinally with al- ternate ridges and furrows. Expelled egg not usually carried. Free-swimming. Several species. (PL XVII, Fig. 4.) ORDER SCIRTOPODA. Rotifera swimming with their ciliary wreath and skipping with arthropodous limbs; foot absent. There is but one genus, Pedalion, and that is rare., CHAPTER XXII. CRUSTACEA. THE Crustacea belong to the Arthropoda that is, to that group of the Articulates that have jointed appendages. Most of the larger Crustacea are marine, but many of the smaller forms are found in fresh water. These vary in size from objects barely visible to the naked eye to bodies several centimeters in length. The most common forms are some- what less in size than the head of a pin. The fresh-water Crustacea have been sometimes divided into two groups, the Entomostraca and the Malacostraca. The Malacostraca are comparatively large forms. They include the Amphipoda, one of which is Gammarus pulex, the "water-crab"; the Isopoda, with Asellus aquaticus, or the '* water-louse" ; and the Decapoda, or ten- footed animals. The Entomostraca may be said to include most of the smaller, free-swimming Crustacea, but the word is sometimes used in a stricter and more limited sense. The bodies of the Entomostraca are more or less distinctly jointed, and are con- tained in a horny, leathery, or brittle shell, formed of one or more parts. The shell is composed of chitin impregnated with a variable amount of carbonate of lime. It is often trans- parent, and may be striated, reticulated, notched, spinous, etc. It varies in structure in different genera. It may be a 256 CRUSTACEA. 2 57 bivalve, like a mussel-shell, or folded so as to give the appear- ance of a bivalve without being really so, or segmented, like a lobster's shell. The body of the organism is segmented, and there is generally a cephalo-thorax region and an abdominal region. In some cases there are distinct head and tail regions. There are one or two pairs of antennae springing from near the head. The feet vary in number, position, and character. In some genera they are flattened and have branchiae, or breathing-plates, attached to them, enabling them to perform the function of respiration. There is one conspic- uous eye, usually black or reddish, situated in the head region. Near the mouth are two mandibles, and near them are the maxillae, or foot-jaws, armed with spines or claws arid sometimes with branchiae. There is a heart, often square, that causes the circulation of colorless blood; and well-marked digestive, muscular, nervous, and reproductive systems. The eggs of the Entomostraca may be seen in brood-cavities inside the shell or in exterior attached egg-sacs. The young often hatch in the nauplius form, and undergo several changes before arriving at the adult condition. The Entomostraca are usually divided into four orders Copepoda, Ostracoda, Cladocera, and Phyllopoda. The last three are sometimes placed as sub-orders under the order Branchiopoda. ORDER COPEPODA. Shell jointed, forming a more or less cylindrical buckler, or carapace, enclosing the head and thorax. The anterior part of the body is composed of ten segments more or less fused. The five constituting the head bear respectively a pair of jointed antennae, a pair of branched antennules, a pair of mandibles, or masticatory organs, a pair of maxillae, and a 258 THE MICROSCOPY OF DRINKING-WATER. pair of foot-jaws. The five thoracic segments bear five pairs of jointed swimming-feet, the fifth often rudimentary. There are about five abdominal segments, nearly devoid of append- ages, and continued posteriorly by two tail-like stylets. Young hatched in the nauplius state. The Copepoda move by vigorous leaps. They lead a roving, predatory life and well deserve the name of "scav- engers." Cyclops. Copepoda with head hardly distinguishable from the body. The thorax and abdomen generally distinguishable, the former having four and. the latter six segments. Two pairs of antennae, the superior large and many-jointed, the inferior smaller, fur- nished with short setae ; both superior antennas of the male have swollen joints. The antennae assist in locomotion. Two pairs of vigorous branched foot-jaws. One eye, large, single, central. Two egg-sacs. Cyclops are very prolific, as many as 30 or 40 ova being laid at a time and broods oc- curring at short intervals. The eggs may hatch after leaving the ovary. There are many species. (PI. XVII, Fig. 5.) Dlaptomus. Copepoda resembling Cyclops in their general appearance. Thorax and abdomen each five-segmented. Antennae very long, many-jointed, with setae ; the right antenna only swollen in the male. Antennules large, bifid, the two unequal branches arising from a common footstalk. Three pairs of unbranched foot -jaws. One egg-sac. The ova hatch while borne by the female. (PI. XVII, Fig. 6.) Canthocamptus Copepoda somewhat resembling Cyclops. The ten segments of the thorax and abdomen not distinguishable. The seg- ments decrease in size as they descend. At the junction of the fourth and fifth segments the body is very movable. Antennae very short. Five pairs of swimming-feet, much longer than in cyclops. One egg-sac. (PI. XVII, Fig. 7.) CRUSTACEA. 259 I ORDER OSTRACODA. Shell consisting of two valves, entirely enclosing the body; from one to three pairs of feet; no external ovary. Cypris. Body enclosed within a horny bivalve shell, oval or remform. Superior antennae seven-jointed, with long feathery filaments arising from the last three. Inferior antennae leg-like, with claws and setae at the end. Two pairs of feet. Eye single. Color greenish, brownish, or whitish. A large number of species. The shell is seldom open wide. (PL XVII, Fig. 8.) ORDER CLADOCERA. Shell consisting of two thin chitinous plates springing from the maxillary segment. The most important characteristic is the presence of several pairs of leaf-like feet provided with branchiae, or breathing-organs. There is a large single eye. Two pairs of antennae, large, branched, and adapted for. swimming. This order contains a number of common genera. Daphnia. Head produced into a prominent beak ; valves of the carapace oval, reticulated, and terminated below by a serrated spine. Superior antennae situated beneath the beak, one-jointed or as a minute tubercle with a tuft of setae. Inferior antennae large and powerful, two-branched, one branch three-jointed, the other four-jointed. Five pairs of legs. Heart a colorless organ at the back of the head. Eye spherical, with numerous lenses. Ova carried in a cavity between the back of the animal and the shell. At certain seasons " winter eggs " are produced. Daphnia move with a louse-like, skipping move- ment. They are sometimes called ' 'arborescent water-fleas. " There are numerous species. (PI. XVII, Fig. 9.) Bosmina. Head terminated in front by a sharp beak directed forwards and downwards, and from the end of which project the long, 260 THE MICROSCOPY OF DRINKING-WATER. many-jointed, curved, and cylindrical superior antennae. In- ferior antennae two-branched, one branch three-, the other four-jointed. Five pairs of legs. Shell oval, with a spine at the lower angle of the posterior border. Eye large. Eggs hatched in a brood-cavity at the back of the shell. (PI. XVII, Fig. 10.) Sida. Shell long and narrow. Head separated from the body by a depression. Posterior margin nearly straight. No spine or tooth. Antennae large, one two-jointed, one three-jointed. Six pairs of legs. (PI. XVIII, Fig. i.) Chydorus. Shell nearly spherical ; beak long and sharp, curved down- wards and forwards. Antennae short. Eye single. Color greenish or dark reddish. Moves with an unsteady rolling motion. (PL XVIII, Fig. 2.) ORDER PHYLLOPODA. Body with or without a shell. Legs 1 1 to 60 pairs; joints foliaceous or branchiform, chiefly adapted for respiration and not motion. Two or more eyes. One or two pairs of antennae, neither adapted for swimming. Branchipus. Body without a shell. Legs eleven pairs. Antennae two pairs, the inferior horn-like and with prehensile appendages in the male. Tail formed of two plates. Cephalic horns, with fan-shaped appendages at the base. Color reddish. Floats slowly on its back. (PL XVIII, Fig. 3.) CHAPTER XXIII. BRYOZOA, OR POLYZOA. THE Bryozoa, or Polyozoa, are minute animals forming moss-like or coral-like calcareous or chitinous aggregations. The colonies are called corms, polyzoaria, or ccencecia. They often attain an enormous size. In the adult stage they lead a sedentary life attached to some submerged object. The animals themselves are small, but easily visible to the naked eye. Some of them are covered with a secreted coating, or sheath, that takes the form of a narrow, brown-colored tube; others are embedded in a mass of jelly. The genera that live in the brown, horny tubes form tree-like growths that often attain considerable length. The branches are sometimes an inch long, and each one is the home of an individual polyzoon, or polypid. The branches, or hollow twigs, are separated from the main stalk by partitions, so that, to a certain extent, each polypid lives a separate existence in its own little case, though each was formed from its next lower neighbor by a process of budding. The body of the organism is a transparent membranous sac, immersed in the jelly or concealed in the brown opaque sheath. It contains a U-shaped alimentary canal, with a con- tractile oesophagus, a stomach, and an intestine; a muscular system that permits some motion within the case, and that enables the animal to protrude itself from the case and to 261 262 THE MICROSCOPY OF DRINKING-WATER. extend and contract its tentacles; mesenteries in the form of fibrous bands; an ovary; and a rudimentary nervous system. There is no heart and no blood-vessels of any kind. The most conspicuous part of the animal is the circlet of ciliated tentacles. They are mounted on a sort of platform, or disc, called a lophophore, at the forward end of the body. This lophophore, with its crown of tentacles, may be pro- truded from the end of the protective tube at the will of the animal. The tentacles themselves may be expanded, giving a beautitul bell-shaped, flower-like appearance. They are hollow and are covered with fine hair-like cilia. They are muscular and can be bent and straightened at will. By their combined action currents in the water are set up towards the mouth, situated just beneath the lophophore. Minute organ- isms are thus swept in as food. The Bryozoa increase by a process of budding which gives rise to the branched stalks. There is also a sexual reproduc- tion. Statoblasts, or winter eggs, form within the body and escape after the death of the animal. They are sometimes formed in such abundance as to form patches of scum upon the surface of a pond. The various forms of these statoblasts assist in the classification of the Bryozoa. The following are some of the important fresh-water genera. There are many marine forms. Plumatella. Zoary confervoid, brown-colored, branched, tubular, branches distinct. Lophophore crescent-shaped. Tentacles numerous, arranged in a double row. Statoblasts elliptical, with a cel- lular dark-brown annulus, but no spines. (PL XVIII, Fig. 6.) Fredericella. Zoary tubular, branched, brown-colored. Lophophore cir- cular. Tentacles about 24, arranged in a single row. Stato- blasts elliptical or subsph^rical, smooth, no spines, without a cellular annulus. (PI. XVIII, Fig. 4.) BRYOZOA. 263 Paludicella. Zoary tubular, diffusely branched, having the appearance of brown club-shaped cells joined end to end ; apertures lateral, near the broad ends of the cells. Lophophore circular. Ten- tacles sixteen, arranged in a single row. Statoblasts elliptical, without spines, with a cellular bluish-purple annulus. (PI. XVIII, Fig. 5.) Pectinatella. Zoary massive, gelatinous, fixed. Polypids protruding from orifices arranged irregularly upon the surface. Tentacles numerous. Statoblasts circular, with a single row of double hooks, not forked at the tips, as in Cristatella. Common. (PI. XVIII, Fig. 7.) Cristatella. Zoary a mass of jelly, the polypids arranged on the outside, and the tentacles extended beyond the surface. The jelly-mass is usually long and narrow and has the power of moving slowly, creeping over submerged objects. Tentacles numer- ous, pectinate upon two arms. Statoblasts circular, with two rows of double hooks having forked tips. Rare. CHAPTER XXIV. SPONGID^E. THE fresh-water sponges are not of sufficient importance in water-supplies to warrant an extended description in this work. They differ materially from the marine sponges, which snake up by far the greater part of the Spongidae. The fresh-water sponge is an agglomeration of animal cells Into a gelatinous mass, often referred to as the "sarcode." Embedded in the sarcode and supporting it are minute siliceous needles, or spicules. These skeleton spicules interlace and give the sponge-mass a certain amount of rigidity. The sponge grows as flat patches upon the sides of water-pipes and conduits and upon submerged objects in ponds and streams; or it extends outward in large masses or in finger- like processes that sometimes branch. Its color when exposed to the light is greenish or brownish, but in the dark places of a water-supply system its color is much lighter and is some- times creamy white. The sponge feeds upon the micro- scopic organisms in water, which are drawn in through an elaborate system of pores and canals. If these pores become choked up with silt and amorphous matter the organism dies. For this reason sponge-patches are more abundant upon the top and sides of a conduit than upon the, bottom. At certain seasons the fresh-water sponges contain seed- 264 SPONG2D&. 265 like bodies known under the various names of gemmules, ovaria, statoblasts, statospheres, winter-buds, etc. They are nearly spherical and are about 0.5 mm. in diameter. They have a chitinous coat that encloses a compact mass of proto- plasmic globules. In this coat there is a circular orifice, known as the foraminal aperture, through which the proto- plasm bodies make their exit at time of germination. In most species the chitinous coat is surrounded by a "crust " in which are embedded minute spicules, called the "gemmule spicules," to distinguish them from the "skeleton spicules," referred to above. There is a third kind of spicule known as the "dermal spicule" or the "flesh spicule." They lie upon the outer lining of the canals in the deeper portions of the sponge. They are smaller than the skeleton spicules and are not bound together. Dermal spicules are'' not found in all species. The skeleton spicules differ somewhat in different species. They have a length of about 250 /*. They are usually arcuate and pointed at the ends. They may be smooth or covered with spines (PI. XVIII, Figs. 9). These skeleton spicules of sponge are commonly observed in the microscopical examina- tion of surface-waters. The gemmule spicules differ in char- acter in different genera and species. Their characteristics are used therefore in classifying the fresh-water sponges. Potts has described a number of different genera of fresh- water Spongidae, among which are Spongilla, Meyenia, Heteromeyenia, Tubella, Parmula, Carterius, etc. The first two are the most important. They are sometimes given the rank of sub-families. The Spongilla is a green, branching sponge. The skele- ton spicules are smooth and fasciculated. The dermal spicules are fusiform, pointed, and entirely spined. The 266 THE MICROSCOPY OF DRINKING- WATER. gemmule spicules are cylindrical, more or less curved, and sparsely spined the spines often recurved. (PI. XVIII, Fig. 8.) The Meyenia are usually sessile and massive. The skele- ton spicules are fusiform-acerate, abruptly pointed, coarsely spined except near the extremities; spines subconical, acute. The dermal spicules are generally absent. The gemmule spicules are irregular, birotulate, vvith rotules produced. CHAPTER XXV. MISCELLANEOUS ORGANISMS. THE miscellaneous higher animals and plants that one is likely to observe in a microscopical examination of drinking- water are so varied, and they are of such little practical importance in the interpretation of an analysis, that their description here is not warranted. It is sufficient to mention the names of a few common forms. Of the Vermes the following may be noted: Anguillula, a small, colorless thread-worm like the vinegar-eel (PI. XIX, Fig. i); Gordius, the common hair-snake; Nais, an annulate worm with bristles (PI. XIX, Fig. 2); Tubifex, another bristle-bearing worm; Chaetonotus, an elongated worm-like organism with scales on its back (PI. XIX, Fig. 3). Of the Arachnida: Macrobiotus, the water-bear (PI. XIX, Fig. 4); and the Acarina, water-mites, or water-spiders (PI. XIX, Fig- 5)- Of the Hydrozoa: the Hydra, a most interesting organism from a zoological standpoint (PI. XIX, Fig. 6). Insect larvae; Corethra, or the phantom larva; scales and fragments of insects; barbs of feathers ; epithelium-cells; ova of the Entozoa, Crustacea, Rotifera, etc. Of the vegetable kingdom may be mentioned Batra- chospermum (PI. XIX, Fig. 7); fragments of Sphagnum Moss; Myriophyllum, or water-milfoil; Ceratophyllum, or 267 268 THE MICROSCOPY OF DRINKING-WATER. hornwort (Pi. XIX, Fig. 10); Lemna, or duck-weed (PI. XIX, Fig. 12); Potamogeton, or pond-weed (PL XIX, Fig. 11); Hippuris, or mare's-tail; Anacharis, or American water- weed (PL XIX, Fig. 9); Utricularia, an insectivorous plant; pollen-grains; plant-hairs; fragments of vegetable fibres and tissue; fibres of cotton, wool, silk, hemp, etc.; starch- grains, etc. For the description of all these miscellanous organisms and objects the reader is referred to more comprehensive books on zoology, botany, and general microscopy. APPENDIX A. COLLECTION OF SAMPLES. IT cannot be too strongly emphasized that samples of water for analysis must be collected with great care. When- ever possible the analyst himself should supervise the collec- tion. If he attempts to draw inferences from analyses of samples of water about the collection of which he knows nothing he does so at the risk of his reputation. The quantity of water required for a microscopical exami- nation depends upon the nature of the water. Usually one quart is sufficient, but a gallon is to be preferred and this amount is necessary when a chemical analysis also is to be made. Glass-stoppered bottles should be used, and they should be scrupulously clean. When sent by express they should be packed in covered boxes that have compartments lined with suitable packing-paper to prevent breaking. In win- ter it may be necessary to use a felt lining to prevent freezing. If collecting a sample of water from a service-tap, allow the water to run for several minutes before filling the bottle. Rinse the bottle several times before the final filling. Do not fill the bottle completely, but leave a small air-space. If collecting a sample from a stream use care not to stir up the deposit on the bottom, and do not allow floating masses of vegetable matter to enter the bottle. This may be sometimes prevented by pointing the mouth of the bottle down stream. If collecting a sample from a pond use judgment in securing a 269 270 APPENDIX A. representative sample. Do not fill the bottle in such a way that the surface-scum may enter. When collecting samples from streams or lakes note carefully the nature of the littoral growths in the vicinity. These are sometimes of value in the interpretation of an analysis. Numerous methods have been suggested for collecting samples from depths below the surface. The simplest method consists of lowering a weighted stoppered bottle to the desired depth and pulling out the stopper by means of a separate cord. When the bottle is full it may be drawn to the surface with little probability that the water will be displaced. An extra precaution to avoid admixture with the upper layers of water may be taken by using a rubber stopper fitted with a glass tube bent at right angles above the stopper and sealed at the end. With this arrangement the water is allowed to enter the bottle by breaking the glass tube by a pull from an auxili- ary cord. Or an inflated rubber ball may be put into the bottle. When the water enters, the ball will be forced up into the neck of the bottle on the inside and make an effective seal. When collecting samples from depths greater than 50 ft. it is desirable to avoid the use of the auxiliary cord. The following ap- paratus has proved very satisfactory down to depths of 400 ft. (See Fig. 23.) The frame for holding the bottle consists of a brass wire, A, attached to a weight, B, which is APPARATUS FOR COLLECTING SAMPLES OF WATER COLLECTION OF SAMPLES. made by rolling a sheet of brass so as to form the sides of a shallow pan and filling this with melted lead to the height in- dicated by the dotted line. At each side where the wire rod is attached a strip of brass extends upward, terminating in a clip, C. These brass strips have considerable spring and are- designed to hold the bottle in place, as shown in the cut. Guides, D, prevent the strips from being bent too far inward, and the uprights, A, prevent them from being bent too far outward. The bottle may be inserted easily by holding back the springs, C, and pushing it between the clips. The frame is supported by the spring, F, joined to the sinking- rope, E. A flexible cord, G, extends from the top of the spring, E, to the stopper, //", of the bottle, /. The length of this cord and the length and stiffness of the spring are so adjusted that when the apparatus is suspended in the water by the sinking-rope the cord will be just a little slack. In this condition it is lowered to the depth at which one wishes to fill the bottle. A sudden jerk given to the rope stretches the spring and produces sufficient tension on the cord, G, to pull out the stopper. As a precaution against a possible loss of the apparatus through breaking of,the spring, a safety-cord, not shown in the figure, extends through the helix connecting the sinking-rope, E, directly to the frame, J. This safety- cord, which is always somewhat slack, is also adjusted to prevent too great a stretching of the spring. With great depths it is necessary to reduce the size of the aperture through which the water enters the bottle and to close this with a suitable valve. This may be done by pass ing a piece of brass tube through a rubber stopper and closing this tube at the top with a brass plug ground to fit. Or the spring may be us.ed to break the end of a sealed glass tube inserted in the stopper. 3 APPENDIX B. TABLES AND FORMULA. WEIGHTS AND MEASURES CONVERSION TABLES. I Ib. Avoir. = 1.215 lbs. Troy or Apoth. = 7000 grains Troy = 453.6 grams. i Ib. Troy or Apoth. = .823 Ib. Avoir. = 5760 grains Troy = 373.2 grams. i oz. Avoir. .960 fluid ounce = 28.35 grams. I oz. Troy or Apoth. = 1.053 fluid ounces = 31.10 grams. i grain Troy = .0648 gram. i kilogram = 2.205 lbs. Avoir. = 2.679 lbs - Troy or Apoth. i gram = .035 oz. Avoir. = .032 oz. Troy or Apoth. = 15.432 grains Troy. I milligram = .0154 grain Troy. i Imperial gallon = 1.201 U. S. fluid gallons = 277.4 cubic inches = 4546 cubic centimeters. I U. S. fluid gallon = .833 Imperial gallon = 231 cubic inches = 3785 cubic centimeters. I U. S. fluid gallon = 8.332 lbs. Avoir. = 10.127 lbs. Troy or Apoth. i fluid ounce = 1.042 oz. Avoir. = .949 oz. Troy or Apoth. = 29.57 cubic cen- timeters. I liter = .264 U. S. fluid gallon=.22O Imperial gallon = 2i.O28 cubic inches. I liter = 33.82 fluid ounces = 2.205 lbs. Avoir. = 2.679 lbs. Troy or Apoth. i cubic centimeter = .033 fluid ounce = .035 oz. Avoir. = .032 oz. Troy or Apoth. i inch = 2.54 centimeters = 25.4 millimeters. I foot = 30.48 centimeters. I yard = 91.44 centimeters = .9144 meter. i meter = 1.0936 yards = 3.28 feet = 39.37 inches. i centimeter = .3937 inch. i millimeter = .0394 inch = .442 Paris lines. I micron (/*)=. oo i millimeter= ^ 7 inch = . 000039 inch = .ooo4 Paris line. I Paris line = .089 inch = 2.26 millimeters = 2260.6 microns. i cubic yard = .7645 cubic meter. i cubic foot = .O283 cubic meter 7.481 U. S. gallons=6.232 Imperial gallons. i cubic inch = 16.39 cubic centimeters. i cubic meter = 35.216 cubic feet = 1.308 cubic yards. I cubic centimeter = .061 cubic inch. 272 LABORATORY TABLES AND FORMULAE. 2/3 TABLE FOR TRANSFORMING MICROMILLIMETERS (MICRONS) TO INCHES. Microns. Decimals of an Inch. Fractions of an Inch. Microns. Decimals of an Inch. Fractions of an Inch. I .000039 1/25000 25 . 000984 I/IOOO 2 .000079 I/I2500 30 -OOIl8l 1/833 3 .000118 1/3333 35 .001378 I/7I4 4 .000157 1/6250 40 -001575 1/625 5 .000197 1/5000 45 .001772 1/533 6 .000236 1/4333 50 .001969 1/500 7 .000276 1/3285 60 .002362 1/416 8 .000315 1/3125 70 .002756 1/357 9 .000354 1/2777 80 .003150 1/312 10 .000394 1/2500 90 003543 1/277 15 .000591 1/1666 IOO .003937 1/250 20 .000787 1/1250 TABLE FOR TRANSFORMING CENTIGRADE TO FAHRENHEIT DEGREES OF TEMPERATURE. Centigrade. Fahrenheit. Centigrade. Fahrenheit. Centigrade. Fahrenheit. - 17-7 4.0 39-2 2 3 .8 75-0 - 15-0 5-0 4.4 40.0 25.0 77.0 12.2 IO.O 5-0 41.0 26.6 80.0 IO.O 14.0 7.2 45-0 29.4 85.0 ~ 9-4 15.0 IO.O 50.0 30.0 86.0 - 6.6 20.0 12.7 55-0 32.2 90.0 - 5-0 23.0 15-0 59o 35.0 95.o - 3-8 25-0 15.5 60.0 37-7 IOO.O i.i 3O.O 18.3 65.0 40.0 104.0 32.0 20.0 68.0 1.6 35-0 21- 1 70.0 TABLE FOR TRANSFORMING STATEMENTS OF CHEMICAL COMPOSITION. Grains per Grains per Parts per Parts per U. S. Gallon. Imp. Gallon. 100,000. 1,000,000. I grain per I grain per U. S. gallon Imperial gallon. I. 0.830 1. 2O I. I.7I 1-43 I7.I 14.3 I part per I 00,000 0.585 0.70 IO.O I part per I ooo ooo o 058 o 07 o. 10 j 2/4 APPENDIX B. TABLE* FOR TRANSFORMING COLOR - READINGS OF THE NESSLER (NATURAL WATER) SCALE TO THOSE OF THE PLATINUM-COBALT SCALE. Nessler Scale. Platinum- cobalt Scale. Nessler Scale. Platinum- cobalt Scale. Nessler Scale. Platinum- cobalt Scale. O O 70 -58 .42 . IO .06 . IO 74 .60 50 .16 . 10 .18 .80 63 56 .20 13 .20 .90 .70 .60 .22 .20 .26 99 .80 .70 .29, .26 30 .00 .81 .72 30 30 33 . IO .88 .80 .36 .40 39 13 .90 .86 .40 .42 .40 .20 95 .90 43 50 .46 .27 I.OO 2.00 50 57 50 30 1.02 .60 52 .40 I.O9 * Based upon several series of comparisons by the analysts of the Boston Water Supply Department. DIRECTIONS FOR CLEANING GLASSWARE. To clean bottles to be used for collecting samples of water. Wash with chromic acid prepared by saturating strong sul- phuric acid with potassium bichromate. Rinse thoroughly several times with distilled water. Drain and dry. To remove the gelatinous film that sometimes collects, use shot, clean gravel, or cotton waste and sand, and afterwards wash with acid. To clean cover-slips. Immerse for a few hours, or boil, in nitric acid, or in chromic acid prepared as above. Rinse in water, and store in alcohol to which a little ammonia has been added. To clean counting-cells. Wash with cold distilled water and wipe dry with a clean linen cloth free from lint. By blowing a stream of water from a wash-bottle into the corners of the cell the organisms may be prevented from becoming lodged there. LABORATORY TABLES AND FORMULA. 275 PRESERVATION OF MICROSCOPIC ORGANISMS. The microscopic organisms may be preserved in permanent mounts upon glass slips according to methods described in the various text-books on microscopical technique. For practical study it is more convenient to preserve them in mass in 2-oz. bottles. For this purpose the following killing and preservative fluids may be found useful: Kings Fluid (for preserving algae, etc.). Camphor-water* 50 grams. Distilled water 50 ' ' Glacial acetic acid. 0.50*' Copper nitrate, crystals 0.20 ' * Copper chloride, crystals 0.20 " Corrosive Acetic Acid (for killing). Saturated solution of mercuric chloride plus 10$ of acetic acid. After using, wash with water. Preserve in alcohol. Formaldehyde. For killing, use a 40$ solution, sold under the name of "Formalin." For preserving, use solutions vary- ing from 5$ to 10$, according to the organisms. Picro-sulphuric Acid ([or killing). Distilled water saturated with picric acid.. . . 100 c.c. Sulphuric acid, strong.. 2 c.c. After using, wash with 60% alcohol. Corrosive Sublimate (for killing Protozoa). To water con- taining the organisms add an equal volume of saturated cor- rosive sublimate. Decant, and add 50$ alcohol, changing this in an hour to 70$. * Made by letting a lump of camphor stand in distilled water for a few days. APPENDIX C. BIBLIOGRAPHY. THE following is a partial list of references to articles on the microscopic organisms and their relation to drinking-water, to- gether with such other references as will enable the student *o investigate the broader subjects of sanitary water-analysis and limnology. MICROSCOPY. Bausch, Edw. Manipulation of the Microscope. Rochester, N. Y. : Bausch & Lomb Optical Co. Beale, L. S. How to Work with the Microscope. 5th edition. Philadelphia: Lindsay & Blakiston, 1880. Behrens, J. W. A Guide for the Microscopical Investigation of Vegetable Substances. Translated by Rev. A. B. Hervey. Boston: S. E. Cassino, 1885. Carpenter, W. B. The Microscope and its Revelations, yth edition. Edited by Dallinger. Philadelphia: P. Blakiston, Son & Co., 1891. Davis, Geo. E. Practical Microscopy. 3d edition. Philadelphia: J. B. Lippincott Co., 1889. Davis and Mathews. The Preparation and Mounting of Microscopic Objects. New York: G. P. Putnam's Sons, 1890. Deby, Julian. A Bibliography of the Microscope and Micrographic Studies. London: D. Bogue, 1882. Frey, H. The Microscope and Microscopical Technology. New York: Wm. Wood & Co., 1880. Gage, S. H. The Microscope and Microscopical Methods. 7th edition Ithaca, N. Y.: Comstock Pub. Co. 276 BIBLIOGRAPHY. Lankester, E. Half -hours with the Microscope: A Popular Guide to the Use of the Microscope as a Means of Amusement and Instruction. 20th edition. London, 1898. Naegeli and Schwendener. The Microscope in Theory and Practice. 2d edition. London: Swan, Sonnenschein, Lowry & Co. Nave, J. Collector's Handy-book. London: W. H. Allen & Co. Pringle, Andrew. Practical Photo-micrography. New York: Scovell & Adams Co., 1890. Van Heurck, H. Le Microscope sa construction, son mainiement, et son application speciale a 1'anatomie vegetale et aux diatomees. 3d edition. Brussels, 1878. BIOLOGY, BOTANY, ZOOLOGY. Bessey, C. F. Botany (Advanced Course). New York: Henry Holt & Co., 1888. Davenport, Chas. B. Experimental Morphology. Part I. Effect of Chemical and Physical Agents upon Protoplasm. Part II. Effect of Chemical and Physical Agents upon Growth. New York: Macmillan Co. Dragendorff, G. Plant Analysis, Qualitative and Quantitative. Goebel, K. Outlines of Classification and Special Morphology of Plants. Huxley and Martin. A Course of Elementary Instruction in Practical Biology. London: Macmillan & Co., 1883. Klebs, G. Die Bedingungen d. Fortpflanzung bei einigen Algen u. Pilzen. Jena: Gustav Fischer, 1896. Mandel, John A. Hand-book for Eio-chemical Laboratory. New York: John Wiley & Sons, 1896. Parker, T. Jeffrey, and Haswell, W. A. A Text-book of Zoology. London: Macmillan & Co., 1897. Poulsen, V. A. Botanical Micro-chemistry. Translated by Wm. Trelease. Boston: Cassino & Co., 1884. Ranvier. Traite d'Histologie. Paris: Savy, 1875, 1882. Sachs, Julius. Text-book of Botany. Oxford: Clarendon Press, 1882. Schafer. Essentials of Histology. Philadelphia: Lea, 1885. Sedgwick, Wm. T., and E. B. Wilson. General Biology. New York: Henry Holt & Co., 1895. Stohr. Text -book of Histology. Translation by Schafer. Philadelphia: Blakiston, 1896. Strasburger, E. Microscopic Botany: A Manual of the Microscope in Vegetable Histology. Boston: S. E. Cassino, 1887. Taylor, J. E. 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Claparede et Lachmann. Etudes sur les Infusories. Geneve, 1858-61. Delage, Y., and E. He"rouard. Traite de Zoologie concrete. I. Laspcellule et les Protozoaires. Paris, 1897. Dujardin, F. Histoire Naturelle des Infusoires. 1841. v, 290 APPENDIX C. Ehrenberg, Chr. Fr. Die Infusionsthierchen als vollkommene Organ- ismen. 1838. Engelmann, Th. W. Zur Naturgeschichte der Infusionsthiere. Leipzig, 1862. Hertwig, R., und E. Lesser. Ueber Rhizopoden und denselben nahe stehende Organismen. Archiv. f. Mikroskopische Anatomic. Bd. X. Supple- mentheft. 1874. Killicott, D. S. Observations on Fresh-water Infusoria. Proc. Am. Soc. /Microscopy. Columbus, O., 1888. Kent, W. Saville. A Manual of the Infusoria. 3 vols. London, 1880-81. >' Lankester, E. R. Protozoa. Encyc. Brit., XIX. Leidy, J. Fresh-water Rhizopods of North America. U. S. Geol. Sur.. Washington, 1879. Perty, M. Zur kenntnis der kleinsten Lebensformen. 1852. Stein, F. Der Organismus der Infusionsthiere. 3 Bde. 1859-78. Die Infusionsthiere auf ihre Entwickelungsgeschichte untersucht. Leipzig, 1854. Stokes, A. C. A Preliminary Contribution toward a History of the Fresh- . water Infusoria of the U. S. Jour, of the Trenton Nat. His. Soc., I> Jan., 1888. Some New Infusoria. American Naturalist, Jan., 1885. ROTIFERA. Bourne, A. C. Rotifera, in Encyc. Britan., XXI, 1886. Delage, Y., et E. H&rouard. Traite de Zoologie concrete. Paris, 1897. Herrick, C. L. Notes on American Rotifera. Bull. Sci. Lab. Dennison University, 43-62. Granville, Ohio, 1885. Hudson and Gosse. The Rotifera, or Wheel-animalcules. 2 vols. London, 1886. Jennings, H. S. The Rotatoria of the Great Lakes. Bulletin of the Michigan Fish Commission, No. 3, 1894. CRUSTACEA. Baird, W. The Natural History of the British Entomostraca. London: Ray Society, 1850. Birge, E. A. Notes on the Crustacea in Chicago Water Supply, with Remarks on the Formation of the Carapace. Chic. Med. Journal and Examiner, XIV, 584-590. Chicago, 1881. BIBLIOGRAPHY. 29 1 Forbes, S. A. A Preliminary Report on the Aquatic Invertebrate Fauna of the Yellowstone National Park, Wyoming, and of the Flathead Region of Montana. Bull. U. S. Fish Com. for 1891, 209-258. Fordyce, Charles. The Cladocera of Nebraska. Studies from the Zoological Laboratory, the University of Nebraska, under the direction of Henry B. Ward, No. 42. Herrick, C. L. Microscopic Entomostraca. An. Rept. of the Geology and Nat. His. Sur. Minn., 1878, 81-123. A Final Report on the Crustacea of Minnesota, included in the orders Cladocera and Copepoda. From the Annual Report of Progress for 1883 of the Geol. and Nat. Hist. Survey of Minnesota. Juday, Chancey. The Diurnal Movement of Plankton Crustacea. Transac- tions of the Wisconsin Acad. of Sciences, Arts and Letters. Vol. XIV, Aug., 1904. - The Plankton of Winona Lake. Proc. Ind. Acad. Sciences. 1902. Marsh, C. Dwight. On the Cyclopidae and Calanidae of Lake St. Clair. Bulletin No. 5 of the Michigan Fish Commission. On the Deep-water Crustacea of Green Lake. Wis. Acad. ScL Arts and Letters, VIII, 211-213. BRYOZOA (POLYZOA). Allman, G. J. The Fresh-water Polyzoa. Fol. London: Ray Society, 1856. Braem, F. Untersuchungen iiber die Bryozoen des Siissenwassers. Bibl. Zool., VI, 1890. Die Geschlechtliche Entwickelung von Plumatella fungosa. Zoologica, XXIII. Davenport, C. B. Cristatella: The Origin and Development of the Individual in the Colony. Bull. Mus. Comp. Zool. Harvard College, XX, 1890. Hyatt, A. Observations on Polyzoa. Proc. Essex Inst., IV and V, Salem, 1866-1868. Kraepelin, K. Die deutschen Siisswasser-Bryozoa. Abh. Natur-Verein, Hamburg, X, 168. ^ Lankester, E. R. Polyzoa, in Encyc. Brit. Oka, A. Observations on Fresh-water Polyzoa. Jour. Sci. College. Tokio, Japan, IV, 1891. Stokes, A. C. The Statoblasts of our Polyzoa. The Microscope, IX, 1889. SPONGID^E. Bowerbank, J. S. Monograph of the Spongillidae. Proc. Zool. Soc. Lon don, 1863. - On the British Spongiadae. 3 vols. London: Ray Soc., 1864-1874. 2Q2 APPENDIX C. Carter, H. J. Note on Spongilla fragilis, Leidy, and on a new species of Spongilla (Mackay's) from Nova Scotia. Ann. Mag. Nat. Hist., XV, 18. On a Variety of the Fresh-water Sponge Meyenia fluviatilis. Ibidem, 453-456, 1885. Dawson, G. M. On some Canadian Species of Spongilla. Canadian Naturalist, N. S., VIII, 1-5, 1878. Goetta, A. Untersuchungen zur Entwickelungsgeschichte von Spongilla fluviatilis. Hamburg, u. Leipzig, 1886. Kellcott, D. S. The Mills Collection of Fresh-water Sponges. Bull. Buf- falo Soc. Nat. Sc., V, 99-104, 1891. Kraepelin, K. Die Fauna der Hamburger Wasserleitung. Abh. Naturw. Verein, Hamburg, XI. Maas, O. Zur Metamorphose der Spongillalarve. Zool. Anzeiger, XII, 483-487, 1889. Mackay, A. H. Fresh-water Sponges of Canada and Newfoundland. Proc. Trans. Roy. Soc. Canada, VII, p. 85-95. l88 9- Mills, H. A New Fresh-water Sponge, Heteromeyenia radiospeculata. The Microscope, 1888, 52. Notes on the Spongillidae of Buffalo. Bull. Buffalo Soc. Nat. Sci., IV, 56-60. Potts, E. Fresh-water Sponges of Fairmount Park. Proc. Acad. Nat. Sci., Philadelphia, 1880, 330, 331. On Fresh-water Sponges. Proc. Acad. Nat. Sci., Philadelphia, 1880, 356, 357. Sponges from the Neighborhood of Boston. Ibid., 1882, 69, 70. Our Fresh-water Sponges. American Naturalist, 1883, 1293-1296. On the Wide Distribution of some American Sponges. Proc. Acad. Nat. Sci., Philadelphia, 1884, 215-217. Contributions toward a Synopsis of the American Forms of Fresh- water Sponges, with Descriptions of those named by other authors and from all parts of the world. Proc. Acad. Nat. Sci., Philadelphia, 1887, p. 158-279. Biology of Fresh-water Sponges. Amer. Monthly Micr. Jour., IX, 43-46, 74-77- 1888. Fresh-water Sponges. The Microscope, 1890. Weltner, W. Spongillidenstudien. Litteratur iiber Spongilliden. Arch, f. Naturgesch, 209-244, 245-284. 1893. MICROSCOPIC ORGANISMS AND WATER SUPPLIES. Allman, Geo. Jas. On Microscopic Algae as a Cause of the Phenomenon of the Coloration of Large Masses of Water. Physiologist (England), IV, 1852. BIBLIOGRAPHY. 293 Arthur, J. C. A Supposed Poisonous Sea-weed in the Lakes of Minnesota. Science, II, 333. Attfield, D. Harvey. The Probable Destruction of Bacteria in Polluted River Water by Infusoria. Brit. Med. Jour., June 17, 1893. Babcock, H. H. On the Effect of the Reversal of the Chicago River on the Hydrant Water. Lens, I, 103, 1872. Barrows, Walter B. Plants in City Water. Rept. Bd. Water Commis- sioners, Middletown, Conn., 1885, 10, n. Beale, Lionel S. The Constituents of Sewage in the Mud of the Thames. Roy. Micr. Soc. Jour., Feb., 1884. Bennett, A. W. On Vegetable Growth as Evidence of Purity or Impur- ity of Water. St. Thomas Hospital Reports, XV (xx.). Reprint, 1892. Bentivegna, R., and A. Sclavo. Un caso d'inquinamento in una condut- tura di acqua potabile per lo sviluppo della Crenothrix, Roma, 1890. Riv. d'ig. e. san. publ. Roma, 1890. Bischoff. Bericht iiber die chemische und mikroskopischen Untersuchungen der Wasser der Tegeler Anlage. Berlin, 1879. Bokorny. Purification of Streams by Chlorophyllaceous Plants. Arch. fii- Hyg., XX, 1894; Jour Roy. Micr. Soc., Dec., 1894, 714. Boston Water Works. Annual Reports. 1892 et seq. Each report contains a summary of the work of the biological laboratory, with tables of tem- perature, color, micro-organisms, rainfall, etc. 1892. Temperature Curves for Lake Cochituate. Reference to the Standard Unit. Odor caused by Synura. 1893. Reference to Standard Unit. Note on the color of the water. Description of Synura and its effect on the water. Description of a new colorimeter. An investigation of the cause of the color of natural water. 1894. An account of stagnation phenomena in Lake Cochituate. Note on the seasonal distribution of the Diatomaceae and Infusoria. A key to the Infusoria found in the Boston water supply. The bleaching effect of sunlight on the coloring matter of water. 1895. The effect of light on the growth of diatoms. Breckenfell A. H. An Infusorian in the Water of San Francisco. Am. Mo. Micro. Jour., V, 1884. Brush, C. B. Deterioration of Water in Reservoirs and Conduits, its Causes and Modes of Prevention. Rept. Bd. of Health of New Jersey, Trenton, 1889-90, XIV, 107-110. Calkins, Gary N. On Uroglena, a genus of colony-building infusoria observed in certain water supplies of Massachusetts. 23d Ann. Rep. of Mass. St. Bd. of Health. 294 APPENDIX C. Campbell, Douglas N. Plants of the Detroit River. Bull. Torrey Bot Club, 1886. Chamberlain, C. W. Organic Impurities in Drinking Water. Ann. Rept. Conn. St. Bd. of Health, 1883. Conn, F. Ueber den Brunnenfaden (Crenothrix polyspora), mit Bemer- kungen iiber die Mikroskopische Analyse des Brunnenwassers. In Beitrage zur Biologic der Pflanzen, 1870. Conn, H. W. Report on Uroglena in Middletown, Conn., in 24th Ann. Rept. of Middletown Water Commissioners for year ending Dec. 31. 1889. Also paper by Prof. Williston. Connecticut State Board of Health Reports for 1891 et seq., contain results of monthly analyses of the water supplies of the State. 1891. Report on the Examination of Certain Connecticut Water Supplies. By S. W. Williston, H. E. Smith, Thos. G. Lee, and Chas.. J. Foote. 1894. Report on the Sanitary Condition of the New Haven Water Supply in May, 1894. Report of the Investigations of Rivers Pollution and Water Supplies. 1895. Report of the Investigations of Rivers Pollution and Water Supplies. 1896. Ditto. Description of Connecticut Public Water Supplies. (Statistics.) Celli, A., Casagrandi O. Bajardi, A. Studio Batteriologico DelPAcqua Marcia. Estratto dagli Annali d'Igiene Sperimentale, Fasc. IV, Anno, 1903. Currier, Chas. G. Self -Purification of Flowing Water and the Influence of Polluted Water in the Causation of Disease. With discussion. Trans. A. S. C. E., XXIV, Feb., 1891. Cutter, E. Suspicious Organisms in Croton Water. Med. Rec., XXI, 365-368. New York, 1882. Davis, Floyd. An Elementary Handbook of Potable Water. Boston: Silver, Burdett & Co., 1891. De Borbois, V. Sur la peste des eaux du lac Balaton. Bulletin de la Societe Hongroise de Geographic. Drown, T. M. The Odor and Color of Surface Waters. Jour. N. E. W. W. Assoc., March, 1888. - Report to Board of Health of the City of Newport, R. I., on the Con- dition of its Water Supply. Boston, 1892. Duclaux. Spontaneous Purification of River Water. Ann. Inst. Pasteur, VIII, 117, 1894. Edwards, A. Mead. Diatoms in Croton Tap Water. Quar. Jour. Micro. Sci., X, 280. JFarlow, W. G. Reports on Peculiar Condition of th'e Water Supplied to the City of Boston. Report of the >Cochituate Water Board, 1876. BIBLIOGRAPHY. 295 Farlow, W. G. Reports on Matters connected with the Boston Water Sup- ply. Bulletin of Bussey Inst, Jan., 1877. Remarks on Some Algae found in the Water Supplies of the City of Boston, 1877. On Some Impurities of Drinking Water Caused by Vegetable Growths. Supplement to ist Ann. Rept. Mass. St. Bd. of Health. Boston, 1880. Some Impurities of Drinking Water. Boston: Rand, Avery & Co., 1880. Relations of Certain Forms of Algae to Disagreeable Tastes and Odors. Science, II, 333, 1883. Field, George W. Certain Biological Problems Connected with the Proposed Charles River Dam. 1903. Appendix No. 6. Report of the Com- mittee, Charles River Dam. FitzGerald, Desmond Spongilla in Main Pipes. Trans. A. S. C. E., XV, 337. Forbes, F. F. A Study of Algae Growths in Reservoirs and Ponds. Journal of the N. E. Water Works Assoc., IV, June, 1890. -Reprinted in Fire and Water, July 19, 1890. The Relative Taste and Odor Imparted to Water by Some Algae and Infusoria. Jour, of the N. E. Water Works Assoc.,VI, June, 1891. Fteley, A. Algae in a Water Supply. Settlement to ist Ann. Rept. of Mass. St. Bd. of Health, Lunacy, and Charity, 1880. . Fuller, George W. Report on the Investigation into the Purification of the Ohio River Water at Louisville, Ky. New York: D. Van Nos- trand Co., 1898. Garrett, J. H. The Spontaneous Pollution of Reservoirs. (Odor pro- duced by Chara.) Lancet, Jan. 7, 1893. Crenothrix polyspora, var. Cheltonensis. A history of the redden- ing and contamination of a water supply and of the organism which caused it, with general remarks upon the coloration and pollution of water by other algae. Public Health, IX, 15-21. London, 1896-97. Giard, A. Sur le Crenothrix Kuhniana; la cause de Pinfection des eaux de Lille. Compt. rendu Acad. d. Sc., XCV, 247-249. Paris, 1882. Gissler, C. F. Contributions to the Fauna of the New York Croton Water.. Microscopical Observations during the years 187071. New York, 1872. Gray, W. Notes on the Proposal to Erect a Roof over the Malabar Hill Reservoir. Tr. M. and Phys. Soc. Bombay, 1882. Hassall, Arthur H. The Diatomaceae in the Water Supplied to the In- habitan ts of London : Microscopic Examination of the Water. London 1856. Hazen, Allen. The' Filtration of Public Water Supplies. New York: ' John Wiley & Sons, 1895. 296 APPENDIX C. Hill, John W. The Purification of Public Water Supplies. D. Van Nos trand, 1898. Bacteria and Other Organisms in Water. Trans. Am. Soc. Civ. Eng, XXXIII, 423-466, May, 1895. Hill, Hibbert, and J. W. Ellms. Report of the Rockville Centre Labora- tory of the Department of Health of the City of Brooklyn. 1897. Hill, W. R. The Method of Removing Organisms from the Water in the Distributing Reservoir of the City of Syracuse. N. Y. Jour, of N. E. Water Works Asso., Vol. XIV, No. 3. Hitchcock, R. Croton Water in August. Am. Mo. Micro. Jour., II, 156, 157. New York, 1881. Hollis, Frederick S. On the Distribution of Growths in Surface Water Supplies. Trans. Amer. Microscopical Soc., 23d Annual Meeting,, June, 1900. Vol. XXII. Two Growths of Chlamydomonas in Connecticut. Trans. Amer- Microscopical Soc., June, 1902. On Removing Organisms from Water. Jour, of the New England Water Works Assoc., Vol. XIV, No. 3. Horsford, E. N., and Chas. T. Jackson. Report on the Disagreeable Tastes and Odors in the Cochituate Water Supply. Ann. Rept. Coch. Water Bd., 1854. Hyatt, J. D. Sporadic Growth of Certain Diatoms and the Relation thereof to Impurities in the Water Supply of Cities. Proc. Am. Soc. Micros- copy, 197-199. 1882. Hueppe, F. Die hygienische Beurtheilung des Trinkwassers vom bio- logischen Standpunkte. Schilling's Journal fur Gasbeleuchtung und Wasserversorgung. 1887. Index Catalogue of the Library of the Surgeon-General's Office, U. S. A. Washington, 1895. Vol. XVI contains an extensive bibliography of Water and Water Supply. Continued in the Index Medicus. Jackson, D. D., and J. W. Ellms. On Odors and Tastes of Surface Waters, with special reference to Anabaena. Technology Quarterly, X, Dec., 1897. Jelliffe, Smith Ely. Preliminary Report on the Vegetable Organisms found in the Ridgewood Water Supply. Bulletin of the Torrey Botanical Club. New York, June, 1893. A Preliminary Report upon the Microscopical Organisms found in the Brooklyn Water Supply. The Brooklyn Medical Journal, Oct., 1893. A Further Contribution to the Microscopical Examination of the Brooklyn Water Supply. The Brooklyn Medical Journal, Oct., 1894. BIBLIOGRA PU Y. 297 Jelliffe, Smith Ely, and Karl M. Vogel. A Report upon Some Microscop- ical Organisms found in the New York City Water Supply New York Medical Journal, May 29, 1897. Kean, A. L., and E. 0. Jordan. A Glass of Water. A brief description of the organisms in Boston tap water. Technology Quarterly, Feb., 1889. Kellicott, S. D. Notes on Microscopic Life in the Buffalo Water Supply. Am. Jour. Micr. Pop. Science, III, 200-250. New York, 1878. Konig, Dr. J., and Emmerich, Prof. Dr. R. Die Bedeutung der Chemischen und bakteriologischen Untersuchung fur die Beurtheilung d s Wassers. Julius Springer, Berlin, 1904. Lattimore, S. A. Report on the Recent Peculiar Condition of the Hem- lock Lake Water Supply. Ann. Rept. of Ex. Bd. Rochester, N. Y., 1876-77. Le Conte, L. J. Some Facts and Conclusions bearing upon the Relations Existing between Vegetable and Animal Growths and Offensive Tastes and Odors in Certain Water Supplies. Proc. Am. Water Works Assoc., 1891. Leeds, Albert R. Report on the Results of the Chemical and Microscop- ical Examination of the Water Supply of Brooklyn, N. Y. Published by the Department of City Works, May i, 1897. Final Report of a Chemical Investigation of the Water Supply of Philadelphia. Ann. Rept. Chief Eng., 1885, 379-400. Report of the Committee on Animal and Vegetable Growths affect- ing Water Supplies. Proc. Am. Water Works Assoc., nth Ann. Meeting,. 1889. Second Rept. in Proc. i2th Ann. Meeting. Lemmermann, E. Die Algenflora der Filter des bremischen Wasserwerkes. Abhandl. d. naturw. Vereins zu Bremen, XIII. Band, 2 Heft, 1895. Lewis, W. B. Report on the Microscopical Examination of the Croton and Ridgewood Waters. 4th Ann. Rept. Metropolitan Board of Health, New York, 1869. Lewis, W. J. Microscopical Examination of Potable Waters in the State of Connecticut. Rept. Bd. Health, Conn., 1882. Macadam, Ivison. Note on the Presence of Certain Diatoms in a Town Water Supply. Proc. Roy. Phys. Soc. Edin., 483. Edinburgh, 1885. J. R. M. S., VI, ser. 2, 291. London, 1886. Mason, Wm. P. Water Supply. 3d ed. New York: John Wiley & Sons, 1902. Mass. State Board of Health. Special Reports. 1890. Special Report on Examination of Water Supplies. Examination of Water Supplies and Rivers. The Chemical Examination of Waters and the Interpretation of Analyses. Dr. T. M. Drown. 298 APPENDIX C. Mass. State Board of Health. Special Reports (Continued.) Report upon the Organisms, except the Bacteria, found in the Waters of the State. G. H. Parker. Summary of Water-Supply Statistics Rainfall, Flow of Streams, Tem- perature of Air and Water. F. P. Stearns. A Classification of the Drinking Waters of the State. Special Topics relating to the Quality of Public Water Supplies The Effect of Storage, Investigation of Deep Ponds, Special Character- istics of Cert in Surface Waters, The Natural Filtration of Water. F. P. Stearns and T. M. Drown. The Pollution and Self-Purification of Streams. F. P. Stearns. 1890. Special Report on Purification of Sewage and Water. Filtration of Sewage and Water, and Chemical Precipitation of Sewage. Hiram F. Mills. A Report of the Chemical Work of the Lawrence Experiment Station. T. M. Drown and Allen Hazen. Experiments upon the Chemical Precipitation of Sewage at the Lawrence Experiment Station. Allen Hazen. A Report of the Biological Work of the Lawrence Experiment Station. Wm. T. Sedgwick. Investigations upon Nitrification and the Nitrifying Organism. E. O. Jordan and Ellen H. Richards. 1895. Special Report upon a Metropolitan Water Supply for Boston. Improvement of the Quality of the Sudbury River Water by the Drainage of the Swamps upon the Watershed. Desmond FitzGerald. On the Amount and Character of Organic Matter in Soils and its Bearing on the Storing of Water in Reservoirs. T. M. Drown. Mass. State Board of Health. Annual Reports. The annual reports since 1890 contain reports upon the examination of water supplies and experiments on the filtration of sewage and water, besides the following papers: 1890. Suggestion as to the Selection of Sources of Water Supply. By F. P. Stearns. 1891. On the Amount of Dissolved Oxygen contained in Waters of Ponds and Reservoirs at Different Depths. T. M. Drown. The Effect of Aeration of Natural Waters. T. M. Drown. The Microscopical Examination of Water. Gary N. Calkins. The Differentiation of the Bacillus of Typhoid Fever. G. W. Fuller. 1891. On Uroglena. Gary N. Calkins. 1892. Interpretation of Water Analyses. T. M. Drown. On the Amount of Dissolved Oxygen in the Water of Ponds and Reser- voirs at Different Depths in Winter, under the Ice. T. M. Drown. BIBLIOGRAPHY. 299 Mass. State Board of Health. Annual Reports (Continued). On the Mineral Contents of Some Natural Waters in Massachusetts. T. M. Drown. A Study of odors observed in the Drinking Waters of Massachusetts. Gary N. Calkins. Seasonal Distribution of Microscopic Organisms in Surface Waters. Gary N. Calkins. Some Physical Properties of Sands and Gravels with Special Reference to their Use in Filtration. Allen Hazen. Reports on Epidemics of Typhoid Fever in Massachusetts in 1892. Wm. T. Sedgwick. 1893. On the Amount and Character of Organic Matter in Soils, and its Bearing on the Storage of Water in Reservoirs. T. M. Drown. The Filter of the Water Supply of the City of Lawrence and its Results. Hiram F. Mills. 1894. The Composition of the Water of Deep Wells. T. M. Drown. The Bacterial Contents of Certain Ground Waters. W. T. Sedgwick. Physical and Chemical Properties of Sand. H. W. Clark. Report upon an Epidemic of Typhoid Fever in Marlborough. Wm. T. Sedgwick . 1895. The Hardness of Water and Methods by which it is Determined. Ellen H. Richards. Methods Employed for the Quantitative Determination of Bacteria in Sewage and Water. G. W. Fuller and W. R. Copeland. 1896. No special papers on water or sewage analysis. 1897. No special papers on water or sewage ana'ysis. 1898. An Investigation of the Action of Water upon Lead, Tin and Zinc. H. W. Clark. The Purification of the Sewage of Cities and Towns in Massachusetts. X. H. Goodnough and W. S. Johnson. 1899. The Occurrence of Iron in Ground Waters. H. W. Clark. 1900. The Action of Water upon Metallic or Metal Lined Surface Pipes. H. W. Clark and F. B. Forbes. An Investigation in regard to the Retention of Bacteria in Ice. H. W. Clark. Studies of the Efficiency of Water Filters in removing different species of Bacteria. S. DeM. Gage. 1901. Experimental Filtration of the Water Supply of Springfield, at Ludlow. A Study of the Stability of the Effluents of Sewage Filters of Coarse Materials. H. W. Clark. 300 APPENDIX C. Mass. State Board of Health. Annual Reports Continued. Bacteriological Studies at the Lawrence Experiment Station, with special reference to the Determination of B. coli. S. DeM. Gage. 1902. On the Value of Tests for Bacteria of Specific Types as an Index of Pollution. H. W. Clark and S. DeM. Gage. Report upon the Examination of the Outlets of Sewers. 1903. Examination of Sewer Outlets and the effect of Sewage Disposal. McElroy, Samuel. Organic Life and Matter in Water. Proc. Am. Water Works Assoc. nth Annual Meeting, 1887. Mills, H. Micro-Organisms in Buffalo Water Supply and in Niagara River. Proc. Am. Soc. Micro., 1882, 165-175. Moore, G. T. Algae as a Cause of the Contamination of Drinking Water. American Journal of Pharmacy, January, 1900. Moore, George T., and Karl F. Kellerman. A Method of Destroying or Preventing the Growth of Algae and Certain Pathogenic Bacteria in Water Supplies. U. S. Dept. Agriculture, Bureau of Plant Industry, Bulletin No. 64. 1904. Copper as an Algicide and Disinfectant in Water Supplies. Bulletin No. 76, 1905. Moriez, R. L'odeur des cours d'eau au square Vauban a Lille. Rev. biol. du nord de la France, 1893-4; 55-61. Nichols, William R. Report of the Examination of Mystic Pond and its Sources of Supply. Rept. Mass. State Board of Health, II, 1871, 387-390. On the Present Condition of Certain Rivers of Massachusetts, etc. Rept. Mass. State Board of Health, V (1874), 61-152. (with W. G. Farlow and E. Burgess). On a Peculiar Condition of the Water Supplied to the City of Boston, 1875-76. Rept. Coch. Water Board, 1876. Report on Matters connected with the Boston Water Supply. Rept. Boston Water Board, I, 1877, 11-15. Circular of Information about Certain Fresh-water Algae. [Printed for private distribution.] Also, in Rept. Cambridge Water Board, 1877, 8-13. On the Condition of the Water of Springfield, Mass., during 1876 Rept. of Water Commissioners, Springfield, 1877. Report on a Peculiar Taste and Odor of the New London (Conn.) Water. Rept. New London Water Commissioners, 1880, 27-30. Tastes and Odors of Surface Waters. Jour. Assoc. of Eng. Soc., Jan., 1882. Ohio State Board of Health. Preliminary Report of an Investigation of Rivers and Deep Ground Waters of Ohio. 1897-8. BIBLIOGRAPHY. 3OI Parker, G. H. Report on the Organisms, excepting the Bacteria, found in the Waters of the State, June, 1887 July, 1889. Mass. State Board of Health. Specjal Rept. on Examination of Water Supplies. Boston, 1890. Parker, Horatio N. Some Advantages of Field Work on Surface-water Supplies. Transactions of the Amer, Microscopical Soc., June, 1900. Phipson, T. L. 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Untersuchung d. deutschen Meere zu Kiel, XII- XIV, 1-107, 1887. Methodik der Untersuchungen bei der Plankton-Expedition. Kiel u. Leipzig, 1895. Heuscher, J. Zur Naturgeschichte der Alpenseen. Jahresbericht der St. Gallischen naturf. Ges., 1888-89. Hopp^-Seyler. Ueber die Vertheilung absorbierten Gase im Wasser der Bodensees und ihre Beziehungen zu den in ihm lebenden Thieren und Pflanzen. In Schriften des Vereins f. Gesch. d. Bodensees u. s. Umge- bung, Heft 24. Imhof, O. E. Resultate meiner Studien iiber die pelagische Faune der Siisswasserbecken der Schweiz. Zeitschrift f. wissenschaftl. Zoologie r XL, 151-178, 1884. Klebahn, H. Ueber wasserbliitebildende Algen und iiber das Vorkom- men von' Gasvacuolen bei den Phycochromaceen. Forschungsber. v. Plon, IV, 189-206. Allgemeiner Charakter der Pflanzenwelt der Ploner Seen. For- schungsber. v. Plon, III, 1-17. Knudsen, Martin. De 1'influence du plankton sur les quantites d'oxygene et d'acide carbonique dissous dans 1'eau de Mer. Comptes Rendus, CXIII. Kofoid, Chas. A. On Some Important Sources of Error in the Plankton Method. Science, N. S., VI, Dec. 3, 1897. Hints on the Construction of a Tow Net. Bull. 111. State Lab. Nat. Hist., V, Art. i. Jour, of Applied Microscopy, I. The Fresh-Water Biological Stations of America. The American Naturalist, XXXII, June, 1898. Plankton Studies. Methods and Apparatus. Bull. 111. State Lab. Nat. Hist., V, 1-25, 1897. The Plankton of Echo River, Mammoth Cave. Transactions of the Amer. Micros. Soc., 22d Annual Meeting, 1899. Lankester, Ed. Ray. The Cause of the Green Color of the European Oyster. Amer. Naturalist, XX, 298. 8vo. Philadelphia, 1886. Lauterborn. Ueber Periodicitat im Auftreten und in der Fortpflanzung BIB LI OCR A PH Y. 3O/ einiger pelagischer Organismen des Rheines und seiner Altwasser. Verh. d. nat. med. Vereins zu Heidelberg, N. F., V, 1893. Lemmermann, E. Zur Algenflora des Ploner Seegebietes. 2. Beitrag. Forschungsber. v. Plon, III, 88-188, 1895. Marsh, C. Dwight. On the Limnetic Crustacea of Green Lake. Trans. Wis. Acad. of Sci., Arts, and Letters, XI, Aug., 1897. The Plankton of Fresh Water Lakes. Transactions of the Wisconsin Acad. Sci., Arts, and Letters, Vol. XIII, 1900. Peck, James I. On the Food of the Menhaden. Bull. U. S. Fish Com., XIII, 1893. The Sources of Marine Food. Bull. U. S..Fish Com., XV, 1895. Peck, James I., and N. R. Harrington. Observations on the Plankton of Puget Sound. Trans. N. Y. Acad. Sci., XVI, Feb., 1898. Reighard, J. E. A Biological Examination of Lake St. Clair. Bulletin No. 4, Michigan Fish Com., 1894. Reighard, Jacob, Prof. A Plan for the Investigation of the Biology of the Great Lakes. Transactions of the American Fisheries Society, 28th Annual Meeting, 1899, pp. 65-71. Schroter, C. Die Schwebeflora unserer Seen (Das Phytoplankton). Neu- jahrsblatt herausgegeben von der Naturforschenden Gesellschaft auf das Jahr 1897, XCIX. Schroter, C., und 0. Kirchner. Der Bodensee-Forschungen, neunter Abschnitt. Die Vegetation des Bodensses. Kommission-Verlag der Schriften des Vereins fiir Geschichte des Bodensees und seiner Umbegung von Joh. Thorn. Stettner. Lindau i. B., 1896. Schiitt. Das Pflanzenleben der Hochseen. Ergebnesse der Plankton- Expedition, 1892. Analytische Plankton-Studien, 1892. Seawell, B. L. A Method of Concentrating Plankton without Net or Filter. Trans. Amer. Microscopical Soc., June, 1902. Seligo, A. Hydrobiologische Untersuchungen, I. Schriften d. naturf. Ges. Danzig, N. F., VII, 43-89. Strodtmann, S. Die Anpassungen der Cyanophyceen an das pelagische Leben. Archiv. fiir Entwicklungsmechanik der Organismen, I, 1895. Bemerkungen iiber die Lebensverhaitnisse des Siisswasserplanktons. Forschungsber. v. Plon, III, 145-179. Planktonuntersuchungen in holsteinischen und mecklenburgischen Seen. Forschungsber. v. Plon, III, 273-287. Susta, J. Die Ernahrung des Karpfen und seiner Teichgenossen. Stettin. 252. Tanner, Z. L. On the Appliances for Collecting Pelagic Organisms, with 308 APPENDIX C. special reference to those employed by the U. S. Fish Commission. Bull. U. S. Fish Com., XIV, 1894. Ward, Henry B. Continued Biological Observations. Proc. of Nebraska Historical Soc., 2d Series, II, 1898. A Biological Examination of Lake Michigan. Bull. No. 6, Michigan Fish Com., 1896. A Plea for the Study of Limnobiology. Trans. Amer. Microscopical Soc., 22d Annual Meeting, Aug., 1899, Vol. XXI. A Comparative Study of Methods in Plankton Measurement. Trans. Amer. Microscopical Soc., 22d Annual Meeting, Aug., 1899, Vol. XXI. : A Biological Reconnoissance of some Elevated Lakes in the Sierras and the Rockies. Trans. Amer. Microscopical Soc., July, 1903, 26th Annual Meeting. Bibliography of Fresh-water Investigations during the last Five Years. Studies from the Zoological Lab. University of Nebraska, June, 1899. A Plea for the Study of Limnobiology No. 35. Studies from the Zoological Lab. University of Nebraska. A Comparative Study in Methods of Plankton Measurement No. 37. Studies from the Zoological Lab. University of Nebraska. The Fresh Water Biological Station of the World. Smithsonian Report for 1898, pp. 499~5i3> Weltner. Forschungsberichte aus der Biologischen Station zu Plon. Zeitschr. f. Fischerei u. deren Hilfswissensch., V, 1894. Wesenburg-Lund, C. Biologiske Undersoegelser over Ferskvandsorganismer. Vid. med. natur. For., 105-168. Kjobenhavn. Studier over Sokalk, Bonnemalm og Sogytje i danske Indsoer. Foredrag holdte i Dansk geologisk Forening, 12 Decbr. 1000 og 17 Januar, 1901. Sur les Aegagropila Sauteri du lac de Soro. Academic Royale des sciences et des lettres de Danemark, 1903. Sur L'Existence d'une Faune Relicte dans le lac de Fureso. Aca- demic Royale des sciences et des lettres de Danemark, extrait du Bulletin de i'annee 1902. Von dem Abhangigkeitsverhaltnis zwischen dem Bau der Plankton- organismen und spezifischen Gewicht des Siisswassers. Sonderab- druck aus dem Biologischen Centralblatt, Band XX, Nr. 18 u. 19, ausgegeben am 15 September u. i Oktober 1900. Whipple, Geo. C. A Simple Apparatus for Collecting Samples of Water au Various Depths. Science, Dec. 20, 1895. An Apparatus for Collecting Samples of Water. The Engineering Record, July 19, 1897. BIBLIOGRAPHY. 309 Zacharias, Otto. Forschungsberichte aus der biolog. Station zu Plon. Biologische Mitteilungen, I, 1893, 27-41. Beobachtungen am Plank- ton des grossen Plonersees, II, 1894, 91-137. Ueber die wechselnde Quantitat des Planktons im grossen Plonersee, III, 1895, 97-117. Ueber die horizontale und verticale Verbreitung limnetischer Organismen, III, 1895, 128-148. Quantitative Untersuchungen iiber das Limno- plankton, IV, 1896, 1-64. Ergebnisse einer bielog. Excursion an die Hochseen des Riesengebirges, IV, 1896, 65-87. Ein neues Conservierungsmittel fur gewisse Flagellaten des Planktons. Zoologischer Anzeiger, Bd. XXII, No. 579, vom Feb. 6, 1899. Ueber Pseudopodienbildung bei einem Dinoflagellaten. Biologiscbes Centralblatt, Bd. XIX, Nr. 4, February, 1899. Die Rhizopoden und Heliosoen des Siisswasserplanktons. Zoolo- gischen Anzeiger, Bd. XXII, No. 579, vom Feb., 1899. Fauna des grossen Plb'ner Sees. Forschungsber. d. biol. Station zu Plon, II, 57-64, 1894. APPENDIX D. GLOSSARY TO PART II. Adoral, relating to the mouth. Aeruginous, of the color of verdigris; blue-green. Alate, winged. Amylaceous, resembling starch. Anal, relating to the anus. Annulate, marked with rings. Antheridia, reproductive organs sup- posed to be analogous to anthers. Arcuate, bent like a knee. Articulate, composed of joints. Bacillar, rod-like. Bifid, two-cleft. Birotulate, with two recurved rounded ends. Botryoid, clustered like a bunch of grapes. Buccal, relating to the cheek. Campanulate, bell-shaped. Capitate, collected in a head. Carapace, a hard shell. Carinate, like a keel. Caudal, relating to the tail. Cervical, relating to the neck. Chitinous, horny. Ciliated, provided with cilia, or hair- like appendages. Circinate, curled round, coiled, or spirally rolled up. Cirrose, curled as a tendril. Clathrate, perforated or latticed like a window. Coccus, a minute spherical form. Ccenobium, a community of a definite number of individuals united in one body. Concatenate, linked like a chain. Connate, united congenitally. Convolute, rolled together. Cortical, relating to the external layers. Crenate, notched or scalloped. Cuneate, wedge-shaped. Cymbiform, boat-shaped. Cyst, a membranous sac without opening. Dentate, toothed. Denticulate, finely toothed. Dichotomous, dividing by pairs from top to bottom. Dioecious, the males and females represented in separate individuals. Ectoderm, the external of two ger- minal cellular layers. Emarginate, with a notch cut out of the margin at the end. Encuirassed, with an indurated dorsal shield. Encysted, enclosed in a cryst or blad- der. 3" 3 I2 APPENDIX D. Endochrome, the coloring matter of cells. Endoplast, the nucleus of a protozoan cell. Fasciculate, in bundles from a com- mon point. Filiform, long, slender, thread-like. Flagellate, provided with flagella, or lash-like appendages. Foliaceous, resembling a leaf. Forcipitate, like forceps. Funicular, like a cord or thread. Furcate, forked or divergently branched. Fusiform, tapering like a spindle. Gibbous, swollen, convex. Gonidia, propagativ bodies of small size not produced by act of fertili- zation. Heterocyst, interspersed cells of a special character differing from their neighbors. Holophytic, like a plant. Hormogons, special reproductive bodies composed of short chains of cells, parts of internal filaments. Hyaline, transparent. Hyphae, filaments of the vegetative portion of a fungus. Indurated, hardened. Intercalated, interspersed, placed be- tween others. Involute, rolled inward. Lamellated, lamellose, in layers. Lanceolate, lance-shaped, tapering at each end. Lenticular, like a lens. Lophophore, an organ bearing ten- tacles, found on the Bryozoa. Lorica, a hard protective coat. Lunate, crescent-shaped. Macrogonidia, large gonidia. Macrospores, large spores. Matrix, the birth cavity. Microgonidia, small gonidia. Mona.vonic, with but one axis. Moniliform, like a necklace, con- tracted at regular intervals. Monoecious, male and female repre- sented in one individual. Mucronate, having a small tip. Mycelium, the vegetative portion of a fungus. Naviculoid, boat-shaped. Oosphere, an ovarian sac. Oospore, spore produced in an ovarian sac. Oral, relating to the mouth. Parietal, growing near the wall- Peristome, the oral region. Pinnatifid, shaped like a feather. Pclythecium, an assemblage of many loricae. Punctate, studded with points or dots. Pyriform, pear-shaped. Reniform, kidney-shaped. Replicate, folded back. Reticulate, latticed. Retractile, capable of being drawn back. Saccate, like a bag. Sarcode, the primary vital matter of animal cells (Protoplasm). Scalariform, ladder-like. Segregate, set apart from others. Septate, separated by partitions. Setiform, in the form of a bristle. Sigmoidal, S-shaped. Sinuate, with notches or depressions. Spermatozoids, thread-like bodies, motile, and possessing fecundative power. Sporangium, sporange, a spore-case. Sporocarp, the covering or capsule enclosing a spore. Sporoderm, the covering of a spore. Statoblasts, the winter eggs, or re- productive bodies of the Bryozoa and Spongidse. Striate, covered with striae. GLOSSARY TO PART II. 3*3 Styligerous, bearing styles or prom- inences. Sub-, a prefix indicating " almost," or " nearly." Suborbicular, almost spherical. Thallus, a leaf-like expansion. Trichocyst, a rod-like body developed in the cortical layer of some pro- tozoa. Trichome, the thread or filament of filamentous algae. Turbinate, shaped like a top. Utriculate, inflated. Vacuolated, containing drops or vacuoles. Vesiculiform, bladder-like. Zoodendrum, a bill-like colony-stalk. Zoogonidia, gonidia endowed with motion. Zoospores, locomotive spores. Zygospore, a spore resulting from conjugation. INDEX. Absorption of light by water, 79 Acarina, 267 Achlya, 224 Acineta, 247 Acinetaria, 246 Actinophrys, 231 Aeration, effect on algae, 153 Algae, 204 Amorphous matter, 29 Amoeba, 229 Amphipoda, 256 Amphora, 184 Anabaena, 200 , decomposition of, 131 , in Cedar Swamp, 135 , oil isolated, 128 Anacharis, 268 Anguillula, 267 Anthophysa, 233 Anuraea, 255 Anuraeadae, 255 Aphamzomenon, 201 , growth in winter, 105 Aphanocapsa, 197 Aphanothece, 198 Arcella, 229 Aromatic odors, 128-130 Arthrodesmus, 214 Asco*n\ cetes, 222 Asellus aquaticus, 256 Aspergillus, 223 Asplanchna, 253 Asplanchnadae, 253 Asterionella, 188 , growth of, in Brooklyn, 149 , growth of, in ground-water, 148 , weight of, 133 Attachment to filter funnels, Sedg- wick -Rafter Method, 19, 20 Autumnal overtruning (autumnal circulation), 62 Bacteria, in distribution pipes, 162 Bacteria, affected by algae, 146 Bacteriological examination of water, 8 Batrachospermum, 267 Bdelloida, 252 Beggiatoa, 193 Blank, for recording results of mi- croscopical examination, 32 Bleaching of water by sunlight, 73 Bosmina, 260 Boston Water Works Laboratory, 2 Botryococcus, 207 Brachionidae, 255 Brachionus, 255 Branchipus, 259 Brooklyn Water Works Laboratory, 2 Brooklyn water-supply, growth of Asterionella, 149 , growths of Paludicella, 169 Bryozoa, 261 , growth of, in water-pipes, 166 INDEX. Bursaria, 244 Canals, organisms found in, 48 Canthocamptus, 258 Carbonic acid, 96 Cell, errors in the, 28; used in Sedg- wick-Rafter Method, 21 Centrifuge, use of, in concentrating microscopic organisms, 6, 38 Ceratium, 239 Ceratophyllum, 267 Cercomonadina, 233 Cercomonas, 233 Chaetonotus, 267 Chaetophora, 219 Chaetophoraceae, 218 Chara, 219 , odor caused by, 123 Characeae, 219 Chemical analysis of water, 8 , relation to the growth of microscopic organisms, 91-97 Chestnut Hill Reservoir, tempera- ture of, 58 Chlamydomonadina, 237 Chlamydomonas, 237 Chlorine, effect of, on the growth of microscopic organisms, 92 Chlorophyceae, 204 , seasonal distribution of, 104 Choano-flagellata, 238 Chroococcaceae, 196 Chroococcus, 196 Chydorus, 259 Chrysomonadina, 235 Ciliata, 240 Circulation periods in lakes, 68 Cladocera, 260 Cladophora, 217 Cladothrix, 193 Classification of diatoms, 183 - of lakes according to tempera- ture, 64-69 of Massachusetts Ponds and Reservoirs according to the microscopic organisms present,. 86-87 Classification of microscopic organ- isms, 171 , of microscopic organisms ac- cording to their abundance 81 Classifications of microscopic or- ganisms, schedule of, 33 Clathrocystis, 197 Cleaning glassware, directions for, 274 Clean watersheds, definition of, 134 Closterium, 213 Cocconeis, 187 Cocconema, 185 Cocconideae, 187 Codonella, 243 Coelastrum, 209 Ccelomonadina, 234 Ccelomonas, 234 Coelosphaerium, 198 Cold Spring Brook, color of, 72 Coleps, 245 Collection of samples, apparatus for, 269 Color of water, 69-73 , effect on the growth of mi- croscopic organisms, 92 Color readings, table for transform- ing, 274 Color standards, 70 Colpidium, 246 Coluridae, 254 Colurus, 255 Compressibility of water, 51 Concentrating attachment to filter- funnels, Sedgwick -Rafter Method, 19-20 Concentration of organisms by the Sedgwick -Rafter Method, 18 Conductivity, thermal, of water, 52 Conferva, 217 Confervaceae, 217 Confervoideae, 217 Conjugate, 212 INDEX. 317 Connecticut St. Bd. of Health, ex- amination of water-supplies, 2 Conochilus, 251 Copepoda, 257 Copper, use as an algicide, 157 Corethra, 267 Coscinodisceae, 191 Cosmarium, 213 Counting - cell, Sedgwick - Rafter Method, 21 Counting, methods of, by Sedgwick- Rafter Method, 30 Crenothrix, 193 , growth in distribution-pipes, 165 , growth of, in ground -waters, 43> J 5i Cristatella, 263 , odor caused by, 123 Crustacea, 256 , seasonal distribution of, 108 Cryptomonas, 237 Crypto-Raphidieae, 190 Crystal Lake, temperature of, 62 Cucumber taste, 123 Cyanophycese, 195 , seasonal distribution of, 105 Cyclops, 258 Cyclotella, 191 Cylindrospermum, 200 Cymbella, 184 Cymbelleae, 184 Cypris, 260 Cystiphorae, 196 Cystoflagellata, 239 Daphnia, 260 Decantation error, 28 Decapoda, 256 Decomposition, odors of, 120 of organisms, 131 Deep ponds, organisms in, 90 Degree of concentration, 24 Density of water, 52 Desmidieae, 212 Desmidium, 215 Diaptomus, 258 Diathermancy of water, 53 Diatoma, 189 Diatomaceae, 173 , cell of, 173 , cell -contents, 177 , classification of, 183 , external secretions, 178 , growth of, at different depths, 102 , markings, 176 , movement, 179 , multiplication of, 180 , reproduction of, 182 , seasonal distribution of, 99 , shape and size, 175 , structure of valve, 177 , succession of, 100 Dictyosphaerium, 207 Difflugia, 230 Diglena, 254 Dimorphococcus, 207 Dinobryon, 237 Dino-flagellata, 238 Disc, use of, for comparing the turbidities of water, 79 Disintegration, errors of, 27 Dissolved oxygen in Lake Cochitu- ate, 141 Distribution -pipes, diminution of microscopic organisms in, 161, 164 , growths of organisms in, 164 Docidium, 213 Dolley, Dr. C. S., method of con- centrating microscopic organisms, 7 Draparnaldia, 218 Enchelys, 245 Encyonema, 185 Endoparasites of man found in water, n Entomostraca, 256 Enumeration of organisms by the Sedgwick-Rafter Method, 23 INDEX. Epistylis, 242 Epithemia, 187 Errors in the Sedgwick -Rafter Method, 25 Euastrum, 214 Eudorina, 211 Euglena, 234 Euglenina, 234 Euglenoidea, 233 Euglypha, 230 Eunotia, 187 Euplotes, 241 Facultative limnetic organisms, 109 Filter used in -Sedgwick-Rafter Method, 15 Filters, house, 154 Filtered water, 49 Filter-basins, (infiltration basins,) growth of organisms in, 45 Filter-beds, growth of organisms on, 150 Filter-galleries, (infiltration galler- ies,) growth of organisms in, 45 Filtration, 154-157 Fishy odors, 128-130 Flagellata, 232 Flosculariadae, 251 Floscularia, 251 Forbes, F. F., method of microscop- ical examination, 3 Forel, Dr. F. A., studies of Lake Geneva, 6 Fragilaria, 189 Fredericella, 262 , growth of, in water-pipes of Boston, 167 Fungi, 221 , seasonal distribution of, 101 Funnel errors, 25 Oammarus pulex, 256 Genevan Commission, experiments on the transparency of water, 77 Geographical distribution of micro- scopic organisms, 81 Glenodinium, 239 Gloeocapsa, 197 Glceocystis, 206 Gloeothece, 198 Gomphonema, 186 Gomphonemeae, 186 Gonium, 211 Gonyostomum, 234 Gordius, 267 Grassy odors, 128-130 Ground-water, character of, 42 , organisms in, 43, 44, 45 , storage of, 148 Gymnodinium, 239 Halteria, 241 Hardness, effect of, on the growth of microscopic organisms, 95 Hassall's method of microscopical examination, i Hazen, Allen, method of comparing turbidities of water, 72 Heliotropism of diatoms, 103 Heliozoa, 231 Hensen's method of collecting mi- croscopic organisms, 5 Heteromonadina, 233 Heterophrys, 231 Heterotricha, 242 Himantidium, 188 Hippuris, 268 Holotricha, 244 Horizontal distribution of micro- scopic organisms, no Hyalotheca, 215 Hydatina, 254 Hydatinadae, 253 Hydra, 267 Hydrodictyon, 208 , odor caused by, 123 Hypotricha, 240 Illoricata, 252 INDEX. 319 Individual Counting System, 30, 31 Infusoria, 240 International Limnological Commis- sion, 6 Isomastigoda, 235 Isopoda, 256 Jackson, D. D., attachment to filter- funnels, Sedgwick-Rafter Method, J 9 , isolation of oil of Anabaena, 128 , analysis of gases of decom- position of Anabaena, 131 Kean, A. L., method of microscop- ical examination, 4 Lake Cochituate, temperature of, 57-64 Lake Winnepesaukee, temperature of, 62 Lakes, classification of, 64 Lemna, 268 Leptomitus, 224 Leptothrix, 192 Light, effect of light on the growth of diatoms, 101 , transmission of, by water, 69 Limnetic organisms, 109 Limnological Commission of Swit- zerland, 6 Limnology, definition of, 51 Littoral organisms, 105 Lobosa, 229 Loricata, 254 Lyngbya, 201 Lynn water-supply, growth of Raphidomonas, 48 Lynn Water Works Laboratory, 2 Macdonald, J. D., method of mi- croscopical examination, i Macrobiotus, 267 Malacostraca, 256 Mallomonas, 237 , peculiar case of vertical distri- bution, 114 Massachusetts ponds and reser- voirs, microscopic organisms in, 86 Massachusetts State Board of Health, examination of water-supplies, 2 Mastigophora, 231 Mastigocerca, 254 Melicertadae, 251 Melosira, 190 , odor caused by, 123 Melosireae, 190 Meridion, 189 , odor caused by, 122 i Merismopedia, 198 Meyenia, 266 Micrasterias, 214 Microcodon, 252 Microcodidae, 252 Microcoleus, 202 Microns, table for transforming, 273 Microscopical examination of water, 8 , as indicating sewage contam- ination, 10 , as explaining the chemical analysis, 12 , as explaining the cause of tur- bidity and odor of water, 13 , as a method of studying the food of fishes, 13 Microscopical examinations, number made in New England and New York, 3 Micrometer used in Sedgwick-Rafter Method, 22 Micro-organisms, effect of, dpon health, 132 , use of the term, 9 , relative number at various depths, 115-116 Microscope, outfit necessary for water analysis, 22 320 INDEX. Microcystis, 197 Monadina, 233 Monas, 233 Mt. Prospect Laboratory, 2 Mucor, 223 Myriophyllum, 267 Nais, 267 Nassula, 245 Natural odors of organisms, 121 Navicula, 185 Naviculeae, 185 Nauplius, 258 Nematogenae, 198 Nephrocytium, 207 Nitella, 219 Nitrogen, effect of, on the growth of microscopic organisms, 95 Nitzschia, 190 Nostcc, 199 Nostocaceae, 199 Noteus, 255 Notholca, 255 Notommatadae, 254 Ocular micrometer used in Sedgwick- Rafter Method, 23 Odor-producing substances in mi- croscopic organisms, 127 Odors caused by littoral organisms, 123 caused by microscopic organ- isms, 120 caused by organic matter, 118 caused by the coloring matter of water, 119 , chemical, 131 , classification of odors due to organisms, 129 in water-supplies, 117, 132 , methods of observing, 119 , natural, of organisms, 121 of growth, 121 of decomposition, 120 of disintegration, 121 Odors, terms describing their inten- sities, 119 CEdogoniaceae, 218 Oil of Anabaena, 128 of Uroglena, 128 , the cause of odors in organisms, 126 Oils, dilution at which their odor ceases to be recognized, 127 Ophiocytium, 208 Organic matter, removal from reser- voir sites, 144 Oscillaria, 177, 201 Oscillarieae, 201 Ostracoda, 260 Oxygen, dissolved in water, 137 Palmella, 206 Palmellaceae, 206 Paludicella, 263 , growth of, in Brooklyn water- pipes, 263 Pandorina, 211 Paramaecium, 244 Parker, G. H., method of microscop- ical examination, 3 Peck, Prof. James I., studies of fish- food, 7, 13 Pectinatella, 263 , odor caused by, 123 Pediastrum, 209 Pelagic organisms, 109 Penicillium, 222 Penium, 213 Peridinium, 239 Peritricha, 241 Phacus, 235 Phaeophyceae, 204 Philodinadae, 252 Phycochromophyceae, 195 Phycocyanine, 195 Phy corny cetes, 223 Phyllopoda, 259 Physical examination of water, 8 properties of water, 51 INDEX. 321 Phytoglcea, 29 Phytozoa, 226 Pinnularia, 186 Pipe-moss, 166 , effect of, on capacity of water- pipes, 1 68 Plankton, definition of, 5 Plankton Net Method, 34 Plankton pump, 7, 38 Plankton studies in America, 6 Planktonokrit, 7, 38 Pleuronema, 246 Pleurosigma, 186 Ploima, 252 Plon Biological Laboratory, 6 Plumatella, 262 Polyarthra, 253 Polyedrium, 208 Polyzoa, 261 Ponds, growth of organisms in, 136 Potamogeton, 268 Precision of the Sedgwick-Rafter Method, 28 Protococcaceae, 207 Protococcoideae, 206 Protococcus, 208 Protozoa, 225 , seasonal distribution of, 106 Protozoan cell, 226 Pseudo-raphidieae, 187 Rafter, Geo. W., improvements in the method of microscopical ex- amination, 4 Rain-water, organisms in, 41 Raphidieae, 184 Raphidium, 207 Raphidomonas, 234 in the Lynn water-supply, 48 Rattulidae, 254 Reproduction of diatoms, 182 Reticularia, 230 Rhizopoda, 229 Rhizota, 251 Rivularia, 203 Rivularieae, 202 River-water, organisms in, 45 Rodophyceae, 204 Rotifer, 252 Rotifera ( Rotate ria), 248 , seasonal distribution of, 108 Saccharomyces, 222 Sampling, errors of, 25 Sand error, 26 Sand used in Sedgwick-Rafter Method, 1 6 Sanitary water-examination, data ob- tained by, 8 Saprolegnia, 223 Sarcoda, 228 Scenedesmus, 208 Schedules of classification of micro- scopic organisms, 33 Schizonema, 186 Schizomycetes, 192 , seasonal distribution of, 106 Schizophyceae, 192 Scirtopoda, 255 Scytonema, 202 Scytonemeae, 202 Seasonal distribution of Chlorophy- ceae, 104 of Cyanophyceae, 105 of microscopic organisms, 98 Secchi, experiments on the trans- parency of water, 75 Sedgwick, Wm. T., improvements in the method of microscopical ex- amination, 4 Sedgwick-Rafter method of micro- scopical examination ; 4, 15 Seeding of reservoirs by organisms from swamps, 136 Sewage, microscopical examination of, ii Shallow ponds, organisms in, 86, 90 Sida, 259 Siphoneae, 216 Sirosiphon, 202 322 INDEX. Sirosiphoneae, 202 Smith, H. L., classification of di- atoms, 184 Soil removal, 146 Sorastrum, 209 Sorby, H. C., method of microscop- ical examination, 2 Sphagnum, 251, 267 Sphaerozosma, 215 Sphaerozyga, 199 Spirogyra, 216 Sponge, growth of, in water-pipes, 165-166 Spongidae, 264 Spongilla, 265 - , odor caused by, 123 Spring overturning (spring circula- tion), 60 Stagnant pools, growths of organ- isms in, 137 Stagnation, 59-61 , effects of, 103, 138 Statoblasts, 262 Standard Unit, 29, 31 Staurastrum, 214 Staurogenia, 209 Stauroneis, 186 Stentor, 243 Stephanodiscus, 191 Stigeoclonium, 218 Storage of ground-water, 148 Storage reservoirs, low-level gate, 147 , soil to be removed from site of, 146, 147 Storage of surface-water, 134 Stratification of water, 52 Suctoria, 246 Surface-water, organisms in, 45 , storage of, 134 Surirella, 190 Surirelleae, 190 Swamps, effect of, on water, 135 , growth of organisms in, 135 Synchaeta, 253 Synchaetadae, 253 Syncrypta, 236 Synedra, 188 Synura, 235 , odor caused by, 124 Tabellaria, 189 Tabellarieae, 189 Taste, its relation to odor, 117 Temperature of lakes and ponds, 53 - of water in distribution-pipes, 160 - of water, methods of observa- tion, 53 Tentaculifera, 246 Tetmemorus, 214 Tetrapedia, 198 Tetraspora, 206 Thermocline, 63 , its relation to the vertical dis- tribution of microscopic organisms, 114 Thermophone, 54-57 Tintinnidium, 242 Tintinnus, 242 Trachelocerca, 246 Trachelomonas, 235 Transparency of water, 77 Triarthra, 253 Triarthradse, 253 Trinema, 230 Tubifex, 267 Turbidity of water, 74-76 Ulothricheae, 218 Ulothrix, 218 Unit, Standard, 29, 31 Uroglena, 236 oil isolated, 128 Utricularia, 268 Uvella, 236 Vaucheria, 217 Vaucheriaceae, 216 Vertical distribution of microscopic organisms, in INDEX. 3 2 3 Volvocina, 238 Volvocineae, 210 Volvox, 210 Vorticella, 241 Water analysis, value of, 9 Water-pipes, growth of organisms in, 160 Weights and measures, conversion tables, 272 Wind, effect of, on horizontal dis- tribution of microscopic organ- isms, no Wind, effect of, on vertical distri- bution of microscopic organisms, "3 Xanthidium, 214 Zoogloea, 29 Zoothamnium, 242 Zygnema, 216 Zygnemaceae, 215 Zygogonium, 216 PLATE I. DIATOMACE&. PLATE I. DIATOMACEJE. Magnification 500 diameters. Fig. A. Navicula viridis, valve view. B. Navicula viridis, girdle view. ; C. Navicula viridis, transverse section. a, Outer, or older valve, b, Inner, or younger valve, c, c', Con- nective bands, or girdles, d, Central nodule- ce, Terminal nodules, f, Raphe. g, Furrows, in, Chromatophore plates. n, Nucleus, o, Oil globules. />, Cavities. , Protoplasm. Figs. D, E, F. Navicula viridis, sectional views showing multiplication by division. After Deby. a, Valve, b, Girdle, c, Protoplasm, d, Chromatophore plates, e, Central cavities, f, Nucleus and nucleolus. g, Oil globules. . i. Amphora, valve view. 2- Amphora, girdle view. 3. Cymbella, valve view. 4. Cymbella, valve view. 5. Encyonema. A, valve view. B, girdle view. 6. Cocconema. A, valve view. B, girdle view. 7. Navicula gracilis, valve view. 8. Navicula Rhyncocephara, valve view. 9. Stauroneis, valv^e view. 10. Stauroneis, girdle view. 11. Pleurosigma, valve view. 12. Gomphonema. A, valve view. B, girdle view. 13. Cocconeis, valve view. 14. Cocconeis, girdle view. 15. Epithemia, valve view. 16. Epithemia, girdle view. 17. Eunotia, valve view. PLATE I PLATE I!. DIATOMACEJE. PLATE II. DIATOMACEJE. Magnification 500 diameters. Fig. i. Himantidium, valve view. " 2. Himantidium, girdle view. " w '3. Asterionella, valve view. " 4. Asterionella, girdle view (typical form). " 5. Asterionella, girdle view, showing division of the cells. ' 6. Asterionella, girdle view, showing rapid multiplication. " 7. Asterionella. A, valve view. B, girdle view. " ^8. Synedra pulchella, valve view. ; 9. Synedra pulchella, girdle view. " 10. Synedra ulna, valve view. "' ii. Synedra ulna, girdle view. "n.2.. Fragilaria, girdle view. " 13. Fragilaria, valve view. PLATE II G.C.W.oW. PLATE III. DIATOMACE^E. PLATE III. DIATOMACE;E. Magnification 500 diameters. Fig. i. Diatoma vulgare, valve view. " 2. Diatoma vulgare, girdle view. " 3. Diatoma tenue, girdle view. " 4. Meridion circulare, valve view. : 5. Meridion circulare, girdle view. " 6> Tabellaria fenestrata, valve view. *' 7. Tabellaria fenestrata, girdle view. " 8. Tabellaria flocculosa, valve view. " 9. Tabellaria flocculosa, girdle view. e< 10. Nitzschia sigmoida, valve view. " ii. Nitzschia sigmoida, girdle view. " 12. Nitzschia longissima, girdle viev/. "' 13. Surirella, valve view. " 14. Surirella, girdle view. " 15. i^vlelosira, valve view. " 16. Melosira, girdle view. " 17. Melosira auxospore. " i8. v Cyclotella, valve view. " 19- Cyclotella, girdle view. " 20. Stephanodiscus, valve view. " 21. Stephanodiscus, girdle view. PLATE G.C.W.^vTicrocystis. "^3- Anabaena flos-aqn*^v8. Scenedesmus. *' 3. Dictyosphjerium. L ^' 9. Hydrodictyon. x 250. " 4. Nephrocytium. " 10. Ophiocytium. " 5 Dimorphococcus. I? n. Pediastrum. I " 6. Protococcus. " 12. Sorastrum. PLATE VI 12 ,3 8 10 II . G.CW.tfe/ PLATE VII. CHLOROPHYCE&. PLATE VII. Fig. i. Ccelastrum. x 500. ^Fig. 8. Closterium Dian?e. x 250. ; 2. Staurogenia. x 500. " 9. Closterium Ehrenbergii. " 3- w v / 'olvox. x 100. x 250. ' 4. Eudorina. x 250. " 10. Closterium subtile, x 250. " 5. Pandorina. x 250. " n. Docidium. x 250- *' 6. Gonium. a, top view. \S*^I2. Cosmarium. x 250. &, side view, x 500. " 13. Tetmemorus. x 250. " 7. Penium. x 250. PLATE VII 8 12 13 K > -C.yv.de/. PLATE VIII. CHLOROPHYCE^E. PLATE VIII. CHLOROPHYCE7E. Magnification 250 diameters. L Fig. A. Cosmarium, showing division. Figs. B, C, D, E, and F. Cosmarium, showing conjugation, formation of zygospore and germination of the spore. Fig. i. Xanthidium armatum. " 2. Xanthidium antilopaeum. a, front view, b, lateral view, c, end view. : 3. Arthrodesmus. a, front view- b, end view. " 4. Euastrum. a, front view, b, lateral view. 5. Micrasterias. L, " 6. Staurastrum magnum, a, front view- b, end view. " 7- Staurastrum macrocerum. a, front view, b, end view. PLATE Vlll 5 G.C.W.oW. PLATE !X. CHLOROPHYCE^E. PLATE IX. CHLOROPHYCE/E. Fig. i. Hyalotheca. a, filament, b, end vi.w. x 500. " 2. Desmidium. a, filament, b, end view, x 500. : 3. Sphserozosma. a, filament, b, end view, x 500. : 4. Spirogyra. x 125. : 5. Spirogyra, conjugated form, showing spores. xi2,5 L>* 6. Zygnema. x 125. 7. Vaucheria. x 100. : 8. Conferva, x 125- r 9. Cladophora. x 75- " 10. Ulothrix. x 125. PLATE IX 2 I ' . - a A * -^ , > m 10 / ^MH G.C.W.rfn! PLATE X. CHLOROPHYCE^E. FUNGI. PLATE X. CHLOROPHYCEJE. Fig. i. Draparnaldia. x 125. " 2. Stigeoclonium. x 125. Fig. 4. Saccharomyces. x 500. : 5. Mold hyphae. x 250. 1 6. Penicillium. x 250. Fig. 3. Chsetophora. x 125. FUNGI. Fig. 7. Aspergillns. x 250. " 8. Mucor. x250. PLATE X 6 G.C.W.A/ PLATE XI. FUNGI. PROTOZOA. PLATE XI. FUNGI. Fig. i. Saprolegnia. x 250. Fig. 3. Leptomitus. x 500. " 2. Achlya. X250. PROTOZOA. ig. 4. Amoeba, x 250. Fig. 8. Euglypha. x 250. 5. Arcella, lateral view, x 250 " 9. Trinema. x 250. ( 6. Arcella, inferior view. x25o " 10. Actinophrys. x 250. " 7. Difflugia. X250. PLATE XI G.C.W.oW. PLATE XII. PROTOZOA. PLATE XII. PROTOZOA. Fig. i. Cercomonas. x 500. Fig. 8. Bftacus. x 500. 2. Monas- x 500. " 9. ifeyntira. x 500. : 3. Anthophysa. x 500. " 10. Uvella. x 500. ; 4. Coelomonas. x 500. " 11. Syncrypta. x 500. ; 5. Raphidomonas. x 500. " I2i/fjroglena. x 250. 6. Euglena. x 500. " 13. Uroglena; showing division " 7- Trachelomonas. x 500. of the monads, x 1000. PLATE XII 13 5 . 8 **lil : W?*\\ ikWittfr, G .C.W. del. PLATE XIII. PROTOZOA. PLATE XIII. PROTOZOA. Fig. i/Dinobryon. x 500. Fig. 7. Glenodinium. x 500. " 2>Cryptomonas. x 500. " 8. Euplotes. x 250. " 3. Mallomonas. x 500. " 9. Halteria. x 500. " 4. Chlamydomonas. xiooo. " 10- Vorticella. X25O. " 5> Peridinium. x 500. " n. Epistylis. x 250. *"** 6. Ceratium- X250. " 12. Tintinnus. X250. PLATE XIII. G.C.W.oW. PLATE XIV. PROTOZOA. PLATE XIV. PROTOZOA. Fig. i. Codonella. x 500. Fig. 6. Coleps. x 500. " 2. Stentor. x 50. " 7. Enchelys. x 500. " 3. Bursaria. x 100. " 8. Trachelocerca. x 500. s^ 4- Paramsccium. X250. " 9. Pleuronema. x 500. " 5. Nassula. PLATE XIV. " G .C.W. del PLATE XV. PRO TOZOA . RO TIFERA. PLATE XV. PROTOZOA. Fig. i. Colpidium. x 500. Fig. 2. Acineta. x 500. ROTIFERA. Fig. 3. Floscularia. x 25. Fig. 6. Rotifer, x 100. : 4. Melicerta. x25- " 7. Microcodon. x 150. " 5. Conochilus. x 100. " 8. Asplanchna. x 150. PLATE XV 8 -.7 G.C.W.oW' PLATE XVI. ROTIFERA. PLATE XVI. Figs. A to E. Diagrams of Trochal Disc. (After Bourne.) A, Microcodon. B, Stephanoceros. G, Hypothetical form intermediate between Microcodon and Philodina. D, Philodina. E, Brachionus. Figs. F to I. Diagrams showing Structure of the Foot. (After Hudsor and Gosse.) F, Rhizotic foot (Floscularia). G, Rhizotic foot (Melicerta) H, Bdelloidic foot (Rotifer). I, Scirtopodic foot (Pedalion). Figs. J to P. Diagrams showing Forms of Trophi. (After Hudson and Gosse.) J, Malleate. K, Sub-malleate. L, Forcipitate. M, In- cudate. N, Uncinate. O, Ramate. P, Malleo- ramate. Fig. i. Synchseta. x 100. " 2. Polyarthra. x 200. " 3- Triarthra. x 150. ROTIFERA. Fig. 4. Diglena. x 15- " 5. Mastigocerca. x 150. PLATE XVI H K '> 1 M N 7( I . A G. CW.de/. PLATE XVII. ROTJFERA. CRUSTACEA. PLATE XVIT. ROTIFERA. Fig. i. Brachionus. x 200. VXFig. 3. Anuraea aculeata. x ISO. " 2. Anuraea cochlearis. A, dor- " 4. Notholca. x 200. sal view. B, side view. CRUSTACEA. " Fig. 5. Cyclops, x 25. Fig. 8. Cypris. x 25. ^" 6. Diaptomus. x 25. " 9. Daphnia- x 25. " 7. Canthocamptus. x 25. " !'"> Bosmina. x2$. PLATE XVII. G.C.W.rfrf PLATE XVIII. CRUSTACEA. BRYOZOA. SPONGID^E. PLATE XVIII. CRUSTACEA. Fig. i. Sida. x^S. Fig. 3. Branchipus. x2. " 2. Chydorus. X25. BRYOZOA. Fig. 4. Fredericella. x 5- Fig. 6. Statoblast of Plumatella. " 5. Paludicella. x5- " 7- Statoblastof Pectinatella. SPONGID^:. Fig. 8. Spongilla. x i. " 9. Sponge spicules (skeleton spicules). x 150. PLATE XVIII G.C.W.oW. PLATE XIX. MISCELLANEOUS. PLATE XIX. MISCELLANEOUS. Fig. I. Anguillula. x 100. Fig. 7. Batrachospermum. x 100. " 2. Nais. x 10. " 8. Chara. x 75- " 3. Chastonotus. X250. " 9. Anacharis. x i. " 4- Macrobiotus. x 250. " 10. Ceratophyllum. x I. " 5. Acarina. x2S. " n. Potamogeton. XL " 6. Hydra, x 25. " 12. Lemna. x I. PLATE XIX, G .C.W. M GENERAL LIBRARY UNIVERSITY OF CALIFORNIA BERKELEY RETURN TO DESK FROM WHICH BORROWED This book is due on the last date stamped below, or on the date to which renewed. Renewed books are subject to immediate recall. BidWgy LaiEfifaiy wflK t MOV 6 1954 NOV $ 1954 NOV 8 1954 OCT 2 5 NOV 8 J954 1954 OC NOV 1 1954 9 1954 1955 JUN 1 5 1955 21-100m-l f '54(1887sl6)478 NOV 9 1956 H MAR 12 1964 FED 2 7 1964 MAR .17 '964 MAR 1 8 1964 APRS 1966 AP8 '66BI F 6 1969 MAR 2 ia FEB -2 1972 JAN 2 5 1972 2 U.C.BERKELEY LIBRARIES COMSflDSSbl 891712 "'* BlOLOGy U&fiAitY G THE UNIVERSITY OF CALIFORNIA LIBRARY