UC-NRLF 
 
 B 3 10 fl 177 
 
ftr 
 
THE LIBRARY 
 
 OF 
 
 THE UNIVERSITY 
 OF CALIFORNIA 
 
 PRESENTED BY 
 
 PROF. CHARLES A. KOFOID AND 
 MRS. PRUDENCE W. KOFOID 
 
TH E 
 
 MICROSCOPE, 
 
 AND SOME OF THE 
 
 WONDERS IT REVEALS. 
 
 REV. W. HOUGHTON, M.A., F.L.S. 
 
 SECOND EDITION. 
 
 CASSELL, FETTER, & GALPIN, 
 
 LONDON, PARIS, AND NEW YORK. 
 
LONDON 
 
 CASSELL, FETTER. & GALPINT, BELLE SAUVAGE WORKS, 
 
 LUDGATE HILL, E.G. 
 
 673 
 
CONTENTS. 
 
 CHAPTER I. 
 
 Introduction- Researches of Leuwenhoek, Grew, and Mal- 
 pighi Simple Microscopes Compound Microscopes' 
 Object-glasses Necessary Apparatus Binocular Micro- 
 scopes Instructions in use of Microscope . . Page I 
 
 CHAPTER II. 
 
 The Microscope in Botany Vegetable Cells The Yeast 
 Fungus Circulation in the Cells Hairs Raphides 
 Spiral Vessels Stomata ..... Page 17 
 
 CHAPTER III. 
 
 Sections of Stems, Roots, &c. Pollen Grains Germ Cells 
 of Fucus Spores of Fungi Difference between Spore 
 and Seed Spores of Horse tails (Equisetacece} Seeds 
 of various Plants Diatomaceee and Desmidiacei~e 
 Volvox Globator ...... Page 27 
 
 CHAPTER IV. 
 
 Difference between Plant and Animal Professor Huxley 
 on Protoplasm yEthalium Septicum So-called Monads 
 Collecting Apparatus Infusoria Ophrydium- S ten- 
 tors Vorticella Wheel Animalculae Melicerta Page 3^ 
 
 CHAPTER V. 
 
 Stephanoceros and Floscularia Hydrae Parasite on Hydne 
 Tardigrades Tenacity of Life in Tardigrades. Page 48 
 
 CHAPTER VI. 
 
 Circulation of the Blood as seen under the . Microscope in 
 Tadpoles, Young Newts, Young Fish, Foot of Frog, 
 various Larvae Organs of Insects Eye of Fly Mouths 
 of Insects . . . . , . . . Page 56 
 
 M36O105 
 
IV CONTENTS. 
 
 CHAPTER VII. 
 
 Organs of Insects Wings Function of the Halteres 
 Drum and File of House Cricket Foot of Fly Hind 
 Foot of Bee Stings and Ovipositors Spiracles and 
 Tracheae Pap 71 
 
 CHAPTER VIII. 
 
 Eggs of Insects Of Butterflies, Water Scorpion, Man- 
 gold-wurzel Fly, Gnats Hairs and Scales of Insects, 
 and of Fish Structure of Human Hair, of Bat's Hairs, 
 of Musk Deer Structure of Bone . . . Page 81 
 
 CHAPTER IX. 
 
 Structure of Skin Pigment Cells Change from Black to 
 White in Negro Perspiratory Glands and Ducts 
 Blood Corpuscles The Microscope in detecting Adul- 
 terations in Food and Medicine Crystals . Page 92 
 
 CHAPTER X. 
 
 The Microscope in Geology Fossil Diatomaceae Fora- 
 minifera Polycystina Deep-sea Soundings Chalk 
 Globigerinae Sponges in Flint Xanthidia in Flint 
 Eozoon Canadense ...... Page 105 
 
 CHAPTER XL 
 
 Vegetable Origin of Coal Mineral Composition of Rocks 
 Nature of Animals ascertained by Examination of 
 Minute Fossil Parts Old Red Sandstone of Russia 
 determined by a Microscopic Section of a Tooth Iden- 
 tity of the Keuper Sandstein of Wurtemberg with the 
 New Red Sandstone of Warwickshire similarly deter- 
 mined Page 116 
 
 CHAPTER XII. 
 
 The Collecting and Mounting of Objects Test Fluids 
 Conclusion Page 123 
 
THE MICROSCOPE. 
 
 CHAPTER I. 
 
 INTRODUCTORY. 
 
 I AM supposing, reader, that at present you are almost, 
 if not altogether, unacquainted with the use of that 
 wonderful instrument by means of which objects quite 
 invisible to the unassisted eye become distinctly seen, 
 and their minutest structure understood. It will be 
 my endeavour in this little Elementary Hand-book on 
 the Microscope, its construction and revelations, to 
 put you in possession of such knowledge as shall serve 
 as a basis for further information, and a stimulant to 
 unceasing inquiry. 
 
 The word microscope is of Greek origin, being 
 derived from two words, n<Kpoc, "small," and <nco7re W) 
 " I view." Its name, you will see at once, most 
 appropriately describes its use. I need say very* 
 little of its history. Simple microscopes or magnify- 
 ing-glasses were known to the ancient Greeks and 
 Romans ; while compound microscopes were not in- 
 vented before the end of the sixteenth century. In 
 process of time this instrument, through the successive 
 labours of various men of different ages, has become 
 developed into a very valuable instrument of scientific 
 research, whilst the success that has crowned the efforts 
 of microscope-makers during the last thirty years has 
 
6 THE MICROSCOPE. 
 
 been truly marvellous. There is one point in the 
 history of the microscope which it would be well to 
 bear in mind, because it may show you how much 
 may be done by honest and persevering workers 
 with even inferior instruments. Those who are 
 acquainted with the researches of Leuwenhoek, 
 Grew, and Malpighi, all frequent writers in the early 
 volumes of the Philosophical Transactions, are struck 
 with astonishment at the discoveries they made with 
 instruments so much inferior to those in use at the 
 present day. Truly has an eminent living microscopist 
 and biologist observed with regard to the researches 
 of Leuwenhoek, " That with such imperfect instru- 
 ments at his command, this accurate and painstaking 
 observer should have seen so much and so wetl as to 
 make it dangerous for any one, even now, to an- 
 nounce a discovery without having first consulted his 
 works, in order to see whether some anticipation of it 
 may not be found there, must ever remain a marvel 
 to the microscopist." Of the labours of Grew and 
 Malpighi the same writer remarks "Both were at- 
 tended with great success. The former laid the 
 foundation of our anatomical knowledge of the vege- 
 table tissues, and described their disposition in the 
 roots and stems of a great variety of plants, besides 
 making out many important facts in regard to their 
 physiological action ; the latter did the same for the 
 animal body, and he seems to have been the first to 
 witness the marvellous spectacle of the movement of 
 blood in the capillary vessels of the frog's foot, thus 
 verifying by ocular demonstration that doctrine of 
 the passage of blood from the smallest arteries to the 
 smallest veins, which had been propounded as a ra- 
 tional probability by the sagacious Harvey."* 
 
 A simple microscope is familiar to everybody in the 
 Carpenter on the Microscope, third edition, p. 2, Introduction. 
 
INTRODUCTORY. 
 
 form of a reading-glass or hand-magnifier; perhaps 
 the most useful form for the pocket consists of one 
 or more lenses, which shut up in a tortoiseshell or 
 horny frame, with an intervening perforated plate 
 to act as a diaphragm when the lenses are used alto- 
 gether. The micrpscopist should never be without 
 this little pocket-magnifier ; it will be very useful in 
 examining samples of water containing animalculae, 
 revealing to him the 
 presence or absence of 
 some particular kinds 
 he maybe in search of, 
 or enabling him to gain 
 some clearer idea of the 
 structure of a fern, grass, 
 or flower, than the un- 
 aided eye can afford. 
 Simple microscopes, 
 properly so called, are 
 supported on stands. 
 That one known as the 
 Society of Arts Simple 
 Microscope, manufac- 
 tured by Mr. Field, 
 of Birmingham, is a 
 useful form of simple microscope. It has a tubular* 
 pillar about five inches high, which screws into the 
 lid of the box which contains the instrument when 
 not in use ; a concave mirror is fixed at the lower 
 end of the pillar, while the upper end carries the stage 
 and a short horizontal arm in which the lenses, three 
 in number, may be screwed. A condensing lens, for 
 opaque objects, can be fitted into any of the four holes 
 with which the stage is perforated. This instrument 
 has a range of powers from 5 to 40 diameters. 
 
 What is the difference between a simple and a 
 
 A Simple Microscope. 
 
THE MICROSCOPE. 
 
 compound microscope ? It is this : in the simple 
 microscope you look directly, through the lens, at 
 the object; in the compound microscope you do not 
 
 look directly at the 
 object, but at its 
 image, which has 
 been magnified by 
 another lens placed 
 between the ob- 
 ject and the lens, 
 or "eye-piece," 
 through which you 
 are looking. Of 
 course, great mag- 
 nifying power is 
 thus obtained. 
 
 Here is a figure 
 of a microscope; 
 it represents Na- 
 chet's smaller com- 
 pound microscope. 
 From a careful 
 study of this figure 
 you will soon be 
 able to learn the 
 parts of which it 
 consists, and will 
 gain a general idea 
 of what a com- 
 pound microscope 
 is. It stands, as 
 you see, on a broad foot, a, out of which a pillar, , 
 arises ; at the top of this is a joint, h, supporting the 
 stage, c, and another pillar, d, which carries the body, 
 / with which it is connected by a transverse arm, e. 
 The body slides up or down within the ring of the trans- * 
 
 A Compound Microscope. 
 
INTRO D UC TOR Y. 9 
 
 verse arm, like a telescope ; this motion is for coarse 
 focussing. For fine adjustment it is moved by a milled 
 head, g, which acts upon a screw inside the pillar d. 
 The joint at h enables the observer to place the instru- 
 ment at any angle he may require. The mirror, for 
 throwing light through transparent objects, is seen at 
 k ; a condensing lens, for throwing light upon opaque 
 objects, is seen at i. So much for the mechanical 
 arrangement. But where are the most important parts 
 of the microscope the lenses, upon the combination of 
 which the magnifying power of the instrument depends? 
 These lenses, which are known by the names of " ob- 
 ject-glasses " and " eye-pieces ;; respectively, fit, the 
 former by a screw, into the bottom of the body, /; the 
 latter, m, by sliding into its top portion. I would 
 advise you to learn the names of these different parts 
 of a compound microscope. Of course, I need hardly 
 tell you that there is great difference in the forms of 
 compound microscopes, their mechanical arrange- 
 ments, and so on; but the above description will 
 seive to give you a fair idea of the general plan of a 
 compound microscope. 
 
 Let us now look a little more closely into the struc- 
 ture of the lenses, on which the magnifying power of 
 the microscope depends. I have already told you that 
 these are known by the names of " eye-pieces " and 
 "object-glasses," or "objectives," as they are some- 
 times termed. The names are easy to remember and 
 explain their respective uses, the former being looked 
 through by the eye of the observer, the latter being 
 placed near the object you wish to examine. The ordi- 
 nary eye-piece consists of two plano-convex* glasses, 
 the plane surfaces of each being directed upwards. 
 That one near the eye is the " eye-glass," the one at 
 
 * A plano-convex lens is one which has one of its surfaces plane 
 or flat, the other convex. 
 
IO THE MICROSCOPE. 
 
 the greater distance is called the "field-glass." The 
 object-glasses consist of three lenses, one of which is 
 constructed to correct certain optical defects or 
 "aberrations." Each of these three sets of lenses is 
 itself compound ; and upon the excellence of the lenses 
 especially the merits of a good microscope depend. 
 They ought to define objects with great clearness ; 
 there must be no haziness about the outlines of the 
 images, and plenty of light must be secured. If you 
 notice any coloured rings encircling any object you 
 are inspecting, your object-glass must be discarded ; 
 it has not been corrected for this defect, which is 
 known as " chromatic aberration," and will prove of no 
 value to you. The microscopist will find two object- 
 glasses quite sufficient to begin with ; perhaps the inch, 
 which will magnify, with No. i eye-piece, 30 or 40 
 diameters, and the quarter of an inch, which, with 
 the same eye-piece, will give a power of about 200 
 diameters, will be found the most generally useful. 
 
 I need hardly tell you that a microscope should be 
 perfectly steady, whether the body be inclined at any 
 angle or stand in a vertical position ; no vibration 
 should be communicated to the body when the ad- 
 justment screws are turned for the purpose of focus- 
 sing. Every microscope should be capable of being 
 used in three different positions vertical, inclined, 
 and horizontal. Nachet's microscopes formerly could 
 be used only with the body in a vertical position -one 
 which is very trying to the muscles of the neck of the 
 observer if he is working for some hours at a time ; 
 they are now made to assume the three positions. 
 Then, again, the stage is a very important part of the 
 instrument ; it should be three* inches long, by two 
 and a half broad. Nachet's instruments are too small 
 for working conveniently. Underneath the stage of 
 every microscope there should be a revolving circular 
 
AV7Y? OD UC TOR Y. l^ 
 
 plate, called a diaphragm, in which there are holes of 
 various sizes for the regulation of the required light 
 for transparent illumination ; the observer, however, 
 will often find he can obtain just the quantity and 
 quality of light required without a diaphragm, by in- 
 clining the mirror at various angles, or by shading it 
 occasionally with the hand. A beginner will often 
 find difficulty in getting the focus. Many instruments 
 are provided with two adjustments for altering the 
 focus ; these are the coarse adjustment, which is 
 effected by rack-and-pinion motion ; and the fine ad- 
 justment with very delicate motion. In some micro- 
 scopes the coarse adjustment is obtained by moving 
 the body of the instrument with the hand, as in the 
 figure represented ; but that effected by the rack and 
 pinion is far more pleasant to use. 
 
 For the illumination of opaque objects, the con- 
 densing lens attached to the instrument will be found 
 useful, but, in addition to this, it is very desirable to 
 employ another condensing lens, mounted on a sepa- 
 rate stand, and readily moved in any direction. That 
 known as the bulPs-eye condenser is very convenient 
 and useful ; the lens is a plano-convex one, about 
 three inches in diameter, having a short focus. This 
 lens must be turned with its plane surface to the light 
 or lamp, and its convex side towards the object on 
 the stage of the microscope experience will determine 
 the requisite distance : the rays of light passing through 
 the bull's-eye will form a bright luminous spot upon 
 the object. There are various other contrivances for 
 illuminating opaque objects, but the beginner need 
 not trouble himself with them ; the more simple and 
 the fewer the appliances, the more progress the stu- 
 dent will at first make. I have enumerated, I think, 
 nearly all the apparatus you will find necessary, unless 
 I mention a earner a hicida, or a neutral tint glass 
 
12 THE MICROSCOPE. 
 
 reflector, for drawing the outlines of the magnified 
 images, or for measuring the objects. The camera 
 lucida is a four-sided glass prism, set in a brass frame 
 with a short tube. It is used in this way : you must 
 take off the cap of the eye-piece, and slip the tube of 
 the camera upon the top of the eye-piece ; arrange the 
 microscope in a horizontal position, and look through 
 the camera at a sheet of paper on the table on 
 which you are working ; the magnified image of the 
 object on the stage of the microscope will appear as 
 if it were on the paper below. With a finely-pointed 
 pencil you then proceed to take its outline; do not 
 be disappointed if you cannot see both the image and 
 the pencil ; persevere, and in a short time you will 
 succeed in making your drawing. The neutral tint 
 glass reflector, which is cheaper than the camera lucida, 
 consists of a small piece of slightly coloured glass 
 which fits on the top of the eye-piece ; the micro- 
 scope must be inclined, as before. With a little 
 practice the draughtsman will be able to draw the out- 
 lines on the paper. 
 
 The polarising apparatus, by means of \vhich 
 various splendid colours are made to appear, is a 
 luxury which the beginner may readily dispense with ; 
 though the effects produced, especially when a thin 
 plate of selenite is interposed between the analyser 
 and polariser, are often extremely beautiful ; and 
 though no doubt in some cases the internal structure 
 of transparent objects is rendered very evident, yet 
 for general microscopic work the polarising apparatus 
 is not necessary. 
 
 Various lamps have been suggested as convenient 
 forms for illumination. I do not think you need 
 trouble yourself about a choice ; a moderator or 
 paraffin will serve your purpose well ; only take care to 
 use a lamp, and not candles, the constant flickering 
 
INTR OD UC TOR Y. 13 
 
 of which is trying to the eyes and irritating to the 
 temper. You should provide yourself with the fol- 
 lowing necessary accessories to the microscope, (i) 
 A number of plate-glass slides, three inches in length 
 and one in breadth; they can be bought with the 
 edges ground at about six shillings a gross. On these 
 slides are to be placed the objects you may wish to 
 examine, or to mount for preservation. (2) A quan- 
 tity of thin glass of various degrees of thickness, cut 
 in either square or circular pieces of different sizes. 
 Thin sheets of this glass, called "cylinder glass," are 
 manufactured by the well-known firm of Messrs. 
 Chance, of Birmingham, but they can be procured 
 at any optician's. The pieces should be kept in 
 a box with bran or sawdust to prevent them break- 
 ing, for they are extremely brittle. When an object 
 is placed on a glass slide for examination it should 
 always be covered with a piece of this thin glass, in 
 order to protect the object-glass from injury ; whilst 
 examining drops of water this is especially necessary. 
 
 It would not be easy to do much work satisfactorily 
 without dissecting-needles and a pair of forceps. The 
 dissecting-needles are extremely useful instruments for 
 unravelling entangled objects and various tissues; they 
 can be readily improvised by the student taking some 
 well-tempered needles, nipping off a portion of the 
 heads, and inserting the upper part of the remainder 
 in wooden handles. The forceps may be used inde- 
 pendently, or be attached to the stage, for the pur- 
 pose of holding minute objects under the microscope ; 
 its form will suggest to you various uses to which it 
 may be applied. 
 
 A few watch-glasses will be found convenient for 
 several purposes, and some small glass shades, about 
 five inches in diameter, are useful for protecting from 
 the dust objects you may be ''mounting." I will 
 
THE MICROSCOPE. 
 
 make a few remarks on the "mounting" of micro- 
 scopic objects in another chapter. 
 
 The microscope depicted in the adjoining woodcut 
 represents one of Nachet's stereoscopic binoculars. 
 
 The stereoscopic 
 effect is produced by 
 a peculiar Arrange- 
 ment of prisms. The 
 binocular microscope, 
 though it can hardly 
 be regarded as ne- 
 cessary for the stu- 
 dent, is veiy useful 
 in the examination 
 of opaque objects of 
 solid form, and also 
 of transparent ob- 
 jects, when we wish 
 to ascertain the dis- 
 tinction between 
 their nearer and more 
 distant surfaces. The 
 prolonged use of a 
 binocular is attended 
 with less fatigue than 
 that of the monocular, 
 and should you de- 
 sire to procure one, 
 Messrs. Beck and 
 Beck, or Mr. Crouch, or Mr. Collins, or any other 
 well-known maker, will supply you with an excellent 
 one at the cost of about ten or twelve pounds. An 
 ordinary monocular microscope can be converted into 
 a stereoscopic binocular, should you desire it. The 
 woodcut in page 15 represents three observers using 
 one of the triple- bodied microscopes of M. Nachet. 
 
 A Binocular Microscope. 
 
INTRODUCTORY. 
 
 I will now give you a few short instructions in your 
 use of the instrument. Let it be inclined at a con- 
 venient angle, screw on your low-power objective, and 
 slide the eye-piece into the tube at the top of the 
 body, having previously taken care to see the lenses 
 
 Triple-bodied Microscope. 
 
 are free from dust; place the object you wish to 
 examine on a glass slide, and transfer it to the stage 
 of the microscope ; you will soon learn to obtain the 
 proper focus. If your object is a transparent one, 
 you must turn the mirror under the stage until a clear 
 circular light illumines the field of view; if your 
 object is opaque, you must use the condensing lens or 
 the bull's-eye condenser, and throw the light upon the 
 
1 6 THE MICROSCOPE. 
 
 object. I should recommend you to practise yourself 
 with the examination of objects that require low 
 powers for some time before you try your hand on 
 such as require high powers and very accurate and 
 fine focussing. You will at first mistake small particles 
 of dust, perhaps, for something connected with the 
 object you are examining. In the examination of 
 drops of water, numerous bubbles of air will present 
 themselves in questionable shapes, and you will won- 
 der what they are. In placing the thin glass over the 
 drop of water, be careful to let its edge first touch the 
 water, and then let it slowly fall on it. The surplus 
 water should be wiped off, and care must be taken 
 that the upper surface of the cover does not get wet, 
 otherwise, if you are using a high power, you will get 
 a misty view. Carelessly dropping or flopping the 
 cover upon the drop of water is sure to produce air- 
 bubbles, which may sometimes interfere most inop- 
 portunely and inconveniently with your getting a good 
 view of the organ of some restless little animalcule. 
 Never interfere with the lenses of the object-glasses; 
 all that is necessary is to wipe the lower surface with 
 a clean bit of wash-leather. Never leave the object- 
 glasses uncovered when not in use, and never examine 
 a drop of water without a thin glass cover over it. 
 Do not touch the lenses of the object-glasses, or you 
 will make them dim and misty. Attention to these 
 instructions will repay you for your trouble, and save 
 disappointment and probably expense. 
 
CHAPTER II. 
 
 USE OF THE MICROSCOPE IN BOTANY. 
 
 IT is almost impossible to exaggerate the value of the 
 microscope in vegetable physiology, and the amount 
 of information regarding the minute structure of plants 
 which has been obtained by this instrument. You 
 cannot, I think, do better than begin your microscopic 
 studies with some of the various forms of plant-life 
 that occur abundantly in our ponds, rivers, and 
 ditches. Many of these are of very simple construc- 
 tion, and you may proceed from the investigation of a 
 plant which has a separate existence as a single cell, 
 to that of such complex and highly differentiated 
 forms as the oak, the ash, and other mighty trees of 
 the field or forest. Now the microscope will reveal 
 to you the interesting fact that the origin of every 
 plant is a single cell. Dr. Carpenter has well said, 
 u The plan of organisation throughout the vegetable 
 kingdom presents this remarkable feature of uni- 
 formity that the fabric of the highest and most 
 complicated plants consists of nothing else than an 
 aggregation of the bodies termed cells, every one of 
 which, among the lowest and simplest forms of vege- 
 tation, may maintain an independent existence, and 
 may multiply itself almost indefinitely, so as to form 
 vast assemblages of similar bodies. And the essen- 
 tial difference between the plans of structure in the 
 two cases, lies in this : that the cells produced by the 
 self-multiplication of the primordial cell of the proto- 
 phyte, are all mere repetitions of it, and of one 
 another, each living by and Jor itself; whilst those 
 
 B 
 
1 8 THE MICROSCOPE. 
 
 produced by the like self-multiplication of the pri- 
 mordial cell in the oak or palm, not only remain in 
 mutual connection, but undergo a progressive ' dif- 
 ferentiation ; ' a composite fabric being thereby de- 
 veloped, which is made up of a number of distinct 
 organs (stems, leaves, roots, flowers, &c.), each of 
 them characterised by specialities, not merely of ex- 
 ternal form, but of intimate structure (the ordinary 
 type of the cell undergoing various modifications), and 
 each performing actions peculiar to itself which con- 
 tribute to the life of the plant as a whole. Hence, 
 as was first definitely stated by Schleiden, it is in the 
 life-history of the individual cell that we find the true 
 basis of vegetable life in general."* What a marvel 
 for contemplation, this vegetable cell, this living atom, 
 endowed with such extraordinary and diversified power 
 of reproduction ! 
 
 The cells, as Pouchet observes, " represent little 
 microscopic vesicles, at first globular, but which by 
 increase and mutual compression become many-sided. 
 And these elements, which conceal themselves from 
 our eyes, animated by an inconceivable plastic force, 
 and multiplying at a prodigious rate, cause new worlds 
 to arise. ' Give me a lever and a fulcrum,' said 
 Archimedes, 'and I will lift the globe.' M. Raspail, 
 almost paraphrasing the geometer of Syracuse, was 
 able to say, ' Give me a living cellule, and I will re- 
 produce all creation.' " 
 
 You can readily make yourself acquainted with the 
 form of a simple cell and its growth, by placing a very 
 small quantity of fresh yeast under the microscope, 
 with a power of 400 diameters. The whole substance 
 seems to be nothing but an aggregation of these 
 minute cells. Look at them ; each is like a little 
 
 * " The Microscope," p. 241. Fourth Edition. 
 
USE OF THE MICROSCOPE IN BOTANY. 19 
 
 globe, and like most vegetable cells consists of a 
 membranous bag with some fluid contents. The 
 vegetable cell-wall is generally composed of two layers 
 having different properties and composition. They 
 are excessively thin, and difficult of detection, unless 
 you add iodine or other colouring matter. The inner 
 layer, which can only be separated from the outer one 
 "by developmental changes, or by the influence of 
 re-agents which cause it to contract by drawing forth 
 part of its contents," is called the primordial utricle, 
 as " being first formed and most essential to the 
 existence of the cell." The outer cell is supposed to 
 be merely a protective covering ; the contents of the 
 cell consist of colourless protoplasm (organisable 
 fluid), containing albuminous matter in combination 
 with starch, gum, sap, and a green, oily substance 
 called chlorophyl. But let us return to the yeast cells. 
 They are still of the same form as when we looked at 
 them before, and independent of each other. I will 
 add a little newly-made beer, or some albuminous 
 matter mixed with sugar, and what do we see after the 
 interval of a few hours ? No longer single uncon- 
 nected globules, but a number together forming 
 chains. Each cell has budded out one or two little 
 projections, which have developed themselves into 
 complete cells, in their turn giving origin to fresh ones, 
 and so on continuously as long as the fermenting pro- 
 cess continues. When this is stopped, the yeast-plant 
 it is a fungus called Torula cerevisicz returns to its 
 isolated condition once more. In quoting an extract 
 from Dr. Carpenter, I mentioned the term protophyte* 
 The yeast fungus is a good example of organisms 
 designated by this word, which, as its derivation 
 shows, is intended to define the most simple, primi- 
 
 * From TrpoiTor, " first," and <J>VTOV, "a plant." 
 
 B 2 
 
20 
 
 THE MICROSCOPE. 
 
 tive, and elementary forms of vegetation. Vegetable 
 cells are of various shapes and sizes ; they may be 
 globular (Fig. i), or square, hexagonal (Fig. 2), cy- 
 drical (Fig. 3), spindle-shaped, 
 &c. &c. Sometimes the cell- 
 walls grow unequally at different 
 points, so as to produce angular 
 projections by which the cells 
 cohere ; or they grow out into 
 long arms, thus producing stel- 
 late cells, as in the pith of the 
 rush, a thin section of which, 
 when viewed by reflected light, 
 is a very pretty microscopic object. Thin sections of 
 any soft vegetable tissues are readily made with a 
 razor or very sharp knife. Starch is found abun- 
 
 Fig. i. Globular Cells. 
 
 Fig. 2. Hexagonal Cells. 
 
 Fig. 3. Cylindrical Cells. 
 
 dantly in the cells of a great many vegetables. The 
 granules vary much in form and size, and are gene- 
 rally so characteristic of the plants, that it is an easy 
 matter to detect, by means of the -microscope, adul- 
 terations in food. Fig. 4 represents a thin section of 
 a potato, showing the cells and starch-granules con- 
 
USE OF THE MICROSCOPE IN BOTANY. 21 
 
 tained therein. Starch is the most generally diffused 
 substance, except protoplasm,* met with in vegetable 
 cells ; it occurs in all classes of plants, except funguses. 
 It can always be detected by the application of iodine, 
 which immediately turns the granules blue. I should 
 recommend you to make yourself acquainted with 
 
 Fig. 4. Section of Potato, showing Cells and Starch Granules. 
 
 various forms of starch-granules of several common 
 plants, such as wheat, rice, Indian corn, and arrow- 
 root. It is supposed by some microscopists that the 
 structure of a starch-granule is composed of a series 
 of concentric shells or layers, which are firm as they 
 approach the outside wall, but are less dense and 
 more full of water as they approach the centre or 
 nucleus. The granules may be isolated from the 
 cells by macerating slices in water for a few days. 
 
 * The name is applied to the nearly colourless granular viscid 
 substance, nitrogenous in nature, which constitutes the formative 
 matter in the cells. From Trpwror and 7r\tto-/ua, " form." 
 
22 THE MICROSCOPE. 
 
 One of the largest forms of starch-granules is that of 
 tons-. J es-mois ( Canna ) . 
 
 The circulating movement of particles in the cells 
 of certain plants is an extremely interesting sight, and 
 in some can be observed without much difficulty. 
 Those generally selected for exhibiting this phenome- 
 non are Char a nitella and the American weed Ana- 
 charis alsinastrum. The long ribbon-like leaves of 
 Vallisneria spiralis a plant not indigenous in this 
 country, but which may be purchased in Covent 
 Garden and elsewhere show this cyclasis, or circu- 
 latory movement, of chlorophyl particles admirably. 
 You must take a very thin strip or layer from the 
 surface of a youns: leaf, using a sharp knife ; place 
 this upon a glass slide with a drop of water, and cover 
 it with very thin glass, using a power of 300 or 400 
 diameters. The circulating corpuscles will be seen to 
 traverse the cell-walls round and round. Should the 
 circulation stop, you should submit the strip to gentle 
 heat, when it will go on again. The hairs of certain 
 plants exhibit the same phenomenon, such as those 
 of Tradescantia Virginica, the Virginian spider- wort ; 
 Anchusa paniculata, one of the borage family ; the 
 young hairs of the nettle show the same rotation 
 under a very high power. Crystals, or raphides as 
 they are termed, are found in many plants, and are in- 
 teresting microscopic objects. The name " raphides," 
 from the Greek word r aphis, "a needle/' was first 
 applied to crystals having a needle-like form; but it 
 is now used in a general sense to express any crys- 
 talline formation. These bodies are found usually 
 within the cells in almost any part of the plant 
 in the stem, leaves, bark, or pith. In the bulbs of 
 the lily tribe they occur extensively. You can readily 
 see them in the cuticle of the common onion ; strip 
 off a small piece, and view it with a power of 
 
USE OF THE MICROSCOPE IN BOTANY. 2$ 
 
 about 200 diameters, and you will notice some very 
 pretty groups of octahedral or prismatic crystals. 
 They are generally composed of oxalate of lime, or 
 of carbonate, sulphate, and phosphate of lime. Dr. 
 Carpenter says that "certain plants of the cactus 
 tribe, when aged, have their tissue so loaded with 
 raphides as to become quite brittle, so that when some 
 large specimens of C. senilis, said to be a thousand 
 years old, were sent to the Kew Gardens from South 
 America, some years since, it was found necessary for 
 their preservation during transport to pack them in 
 cottcn like jewellery."* What office these crystalline 
 bodies fulfil, or whether they fulfil any at all, is not 
 known. Raphides have been artificially produced 
 within the cells of rice-paper. Mr. Quekett filled the 
 cells with lime-water by means of an air-pump, and 
 placed the paper in weak solutions of oxalic and phos- 
 phoric acids. " The artificial raphides of phosphate 
 of lime were rhombohedral ; while those of oxalate 
 of lime were stellate, exactly resembling the natural 
 raphides of the rhubarb." 
 
 The spiral vessels of plants will amply repay you for 
 investigation by their extreme beauty : they are easily 
 seen by macerating the stems or leaves in water, or 
 by boiling them. These spiral vessels are cylindrical 
 tubes with cone-like ends, within which fibres wind in 
 a corkscrew fashion. In some cases the tube contains 
 only one spiral fibre ; in others as many as twenty 
 have been counted (Fig. 5). These vessels are found 
 in all parts of plants excepting the roots. They a-e 
 very beautiful in the seeds of certain plants, as in the 
 strawberry and hazel-nut. Every one is familiar with 
 the brown coating that surrounds the common nut ; 
 scrape a portion of this membrane off the kernel, and 
 
 * " The Microscope," p. 400. 
 
THE MICROSCOPE. 
 
 soak it in water for a time ; tear it in pieces with a 
 pair of needles, and examine under the microscope 
 with reflected light, you will see a great number of 
 glistening fibres. It seems probable that the use of 
 these spiral vessels is to convey air to the plants, thus 
 
 Fig. 5 Spiral Vessels. 
 
 Fig. 6. 
 
 forming a system of internal respiration, which at once 
 suggests an analogy to that of insects, the tracheae of 
 which very closely resemble the spiral vessels in the 
 vegetable kingdom. Spiral vessels, however, are some- 
 times found to convey fluid. The various kinds of 
 ducts, or the canals through which fluids are carried 
 to different parts of plants, will form objects for study ; 
 spiral, annular, dotted, scalariform, and reticulated 
 ducts are interesting varieties of form. 
 
 Among other important organs, the stomata, or little 
 openings by which almost all leaves with distinct 
 cuticles are perforated, must be mentioned. These 
 organs are really mouths through which respiration 
 
USE OF THE MICROSCOPE IN BOTANY. 25 
 
 and exhalation are carried on in plants ; they lead 
 into cavities beneath the epidermis. The usual form 
 of the stomata consists of a number of rounded cells, 
 bordering the opening, with a couple of kidney-shaped 
 cells of a large size in the centre ; between these is a 
 narrow slit when the mouth is open, and a raised seam 
 when it is shut. In some plants the stomata do not 
 open on the surface of the leaf, but lie in depressions 
 in it ; these are lined and guarded with a number of 
 hairs, as in the oleander (see Fig. 6). You would do 
 well to make yourself acquainted not only with the 
 function, but the various forms of the stomata. The 
 examination of their structure is easy. Take a leaf 
 or flower of almost any plant, tear a thin slice off its 
 under surface, put it in a glass slide with a drop of 
 water, cover it with thin glass, and use a power of 
 about 200 diameters. Examine the outer surface of 
 the object first ; then you will see the cells and slit 
 of which I spoke. Now examine the other side, and 
 notice the cavity into which the slit is directed. 
 Stomata are usually more abundant on the lower sur- 
 face of leaves ; but in plants whose leaves float on the 
 water they are found only on the upper surface, as In 
 the water-lilies ; in plants whose leaves are always 
 submerged there are no stomata ; in grasses and such 
 plants as grow in an erect form they are found on both 
 surfaces equally distributed. As many as 160,000 of 
 these little mouths have been counted on each square 
 inch of surface on leaves of some plants. In the 
 liverworts, as in Marchqntia polymorpha, the stomata 
 are of very complex structure. These organs are not 
 found in the roots of plants, nor in the ribs of the 
 leaves : and they are absent from fungi, lichens, and 
 sea-weeds. 
 
 The study of hairs, which are so abundant on many 
 plants, will afford you much pleasure and instruction, 
 
26 
 
 THE MICROSCOPE. 
 
 so variously formed and beautifully constructed as the 
 microscope shows them to be ; they are generally 
 attached to the cuticle by one end, having the other 
 one free. To the naked eye the hair of the Trades- 
 cantia Virginica, for instance, looks like a single thread- 
 like process ; under the microscope it is found to 
 consist of three or four successive cells. I ought to 
 say that vegetable hairs are always of a cellular cha- 
 racter. Some 
 hairs appear to 
 be attached to 
 the epidermis by 
 their centre por- 
 ' tion, and assume 
 very pretty stel- 
 late or starlike 
 forms. Such cases 
 are, no doubt, 
 merely clusters 
 of hairs each 
 attached by its 
 lower extremity. 
 Fig. 7 represents 
 the sinuous cells and starlike hairs of the leaf of the 
 Deutzia scabra, a very beautiful and favourite micro- 
 scopic object. These hairs are covered with a siliceous 
 coating, and when viewed by reflected light shine with 
 great brilliancy. Hairs may consist of single cells, or of 
 numerous ones arranged one above the other, or they 
 may be branched, or toothed, or plumose ; indeed 
 their forms are almost unlimited. In some hairs you 
 may see a single cell which contains an elastic coiled- 
 up spiral fibre. Hairs may be, as we all know by ex- 
 perience, either harmless to touch, or hurtful. The hair 
 of the common nettle contains at the base a poison- 
 ous fluid, which is conveyed into the wound through a 
 
 Fig. 7. Starlike hairs of Deutzia scabra. 
 
USE OF THE MICROSCOPE IN BOTANY. 2*J 
 
 duct ending at its finely-pointed extremity. We are 
 here reminded of the analogous case of a viper's 
 tooth in the animal kingdom. The phenomenon of 
 cyclosis, of which I have already spoken, takes place 
 probably in all kinds of hairs. Mr. Wenham says, 
 " The difficulty is to find exceptions, for hairs taken 
 alike from the loftiest elm of the forest, to the Humblest 
 weed that we trample beneath our feet, plainly exhibit 
 this circulation." To witness it, however, very high 
 powers of the microscope and great care are neces- 
 sary. In your examination of hairs, remember to tear 
 off a part of the cuticle from which they grow. If you 
 take hold of the hair itself, it will be almost sure to 
 break ; place the piece in a drop of water, with a thin 
 glass covering, and the forms of the various kinds will 
 reveal themselves. 
 
 CHAPTER III. 
 
 USE OF THE MICROSCOPE IN BOTANY (continued}. 
 
 You will, no doubt, be much interested in examining 
 the structure of the hard portions of plants, such as 
 the stems, roots, seeds, &c. In many cases you will 
 find a sharp knife or razor sufficient for making sec- 
 tions of the parts you wish to study ; such substances 
 as the stony fruits of various trees require a more 
 expensive apparatus in order to prepare them for 
 investigation. I shall therefore take no notice of 
 these hard substances at present. You must take care 
 to prepare the stems or roots before you make your 
 sections ; if the wood be green, you must soak it for 
 some days in strong spirit, in order to get rid of any 
 resinous matter it may contain. After this, let the 
 
28 THE MICROSCOPE. 
 
 specimen be macerated in water for a few days ; this 
 will remove the gum. If the portion of wood you 
 wish to study be dry, you must moisten it in water for 
 some time to soften it, then treat it as you would 
 green wood. It may be necessary in some cases to 
 use boiling water to render the stems sufficiently soft 
 for making sections. Wet the surface of the wood, 
 and cut off as thin a transverse section as possible. 
 Instruments called " section instruments " are sold for 
 this purpose, and very handy and useful some of them 
 are ; you can add one to your microscopic apparatus 
 after you have had more experience ; but you will 
 find that, with care and perseverance, you will succeed 
 in making very thin sections of stems, which will show 
 their different parts, such as the pith, medullary rays, 
 bundles of wood and bark, quite satisfactorily. In 
 the examination of the reproductive organs of plants, 
 you will find exhaustless matter for study and contem- 
 plation. Every one is familiar with the dusty particles 
 contained within the stamens of different plants, called 
 pollen (Fig. 8). Various and very 
 beautiful are these pollen forms, and 
 easy enough to examine, so far as 
 the external appearance goes. Per- 
 haps their most common form is 
 spherical or elliptical ; but many 
 beautiful geometrical forms are met 
 L with, such as cubic, tetrahedral, poly- 
 gonal, &c. In structure, the pollen grain generally 
 consists of an internal cell membrane, with one 
 or more outer layers of firmer texture. In some 
 instances, as in the Zostera marina, there is 
 only an inner membrane. The outer covering may 
 be smooth, or rough with numerous spiny pro- 
 jections, or reticulated, or divided into several seg- 
 ments or bands, or beset with numerous pores 
 
USE OF THE MICROSCOPE JN BOTANY. 
 
 2 9 
 
 regularly or irregularly scattered. Pollen grains are 
 developed in the stamens (Figs. 10 and n), which are 
 the pollen-cases ; when they have arrived at maturity, 
 that stage at which they are fitted for the purpose of 
 fertilisation, the pollen-cases burst, and clouds of 
 pollen are shot forth like dust. Have you not often 
 dusted your nose with the yellow pollen of the garden 
 Eschscholtzia ? You have also, I dare say, been often 
 
 Fig. 9 -Pollen mass of 
 Orchis Maculata. 
 
 Fig. ii. Fou reel led 
 Fig. 10.' Stamens of Anther of Persian 
 Iris. Laurel. 
 
 struck with the astonishing quantity of pollen some- 
 times found on a single stamen. A very little is 
 absolutely required for the fertilisation of the pistil : 
 why, therefore, this extraordinary abundance ? A great 
 deal of pollen, as you may suppose, runs to waste. 
 Such is the structure and position of the pistils of many 
 plants, that contact of the pollen-grains with the 
 ovule is often impossible except for the agency of the 
 winds, or of various birds and insects. The internal 
 cell contains a fluid (fovilld) which is supposed to 
 
30 THE MICROSCOPE. 
 
 be the fructifying substance. The development of 
 the pollen-grain after it has touched the soft viscid 
 tissue of the pistil is very remarkable ; one or more 
 
 little processes bud 
 out of the grain (Fig. 
 13); in time this tube 
 or,'process becomes 
 much elongated (Fig. 
 14); it insinuates itself 
 between the cells of 
 the stigma, until, con- 
 tinually elongating it- 
 self, it arrives at the 
 ovule at the bottom 
 of the ovaries which 
 are thus fertilised by it. 
 The illustrations here 
 given will show these 
 changes in the pollen- 
 grain which we have 
 been considering. " In 
 tracing the origin and 
 early history of the 
 ovule, very thin sec- 
 tions should be made 
 through the flower- 
 bud, both vertically 
 and transversely ; but 
 when the ovule is large and distinct enough to 
 be separately examined, it should be placed on the 
 thumb-nail of the left hand, and very thin sec- 
 tions made with a sharp razor ; the ovule should 
 not be allowed to dry up, and the section should 
 be removed from the blade of the razor by a wetted 
 camel-hair pencil. The tracing downwards the 
 pollen tubes through the tissue of the style may be 
 
 Fig. 14. 
 
 Fig. 13. 
 
USE OF THE MICROSCOPE IN BOTANY. 31 
 
 accomplished by sections (which, however, will seldom 
 follow one tube continuously for any great part of its 
 length), or, in some instances, by careful dissection 
 with needles. Plants of the orchis tribe are the most 
 favourable subjects for this kind of investigation, 
 which is best carried on by artificially applying the 
 pollen to the stigma of several flowers, and then 
 examining one or more of the styles daily. i If the 
 style of flower of an Epipactis (says Schacht), to which 
 the pollen has been applied about eight days pre- 
 viously, be examined in the manner above mentioned, 
 the observer will be surprised at the extraordinary 
 number of pollen-tubes, and he will easily be able to 
 trace them in large strings, even as far as the ovules. 
 Viola tricolor (heart's-ease) and Ribes nigrum and 
 rubrum (black and red currant) are also good plants 
 for the purpose ; in the case of the former plant, 
 withered flowers may be taken, and branched pollen- 
 tubes will not unfrequently be met with/ The en- 
 trance of the pollen-tube into the micropyle* may 
 be most easily observed in orchidious plants and in 
 Euphrasia; it being only necessary to tear open 
 with a needle the ovary of a flower which is just 
 withering, and to detach from the placenta the ovules, 
 almost every one of which will be found to have a 
 pollen-tube sticking in its micropyle. These ovules, 
 however, are too small to allow of sections being 
 made, whereby the origin of the embryo may be dis- 
 cerned ; and for this purpose, (Enothera (evening 
 primrose) has been had recourse to by Hortmeister, 
 whilst Schacht recommends Lathr&a squamaria, 
 Pedicularis palustris, and particularly fedicularis 
 
 * From juxpoc, " small," and <7rw\n, "a gate," the minute perfora- 
 tion through the skin of a seed. 
 t Dr. Carpenter on the Microscope, p. 430. 
 
32 THE MICROSCOPE. 
 
 You will find much to attract your attention and 
 excite your admiration in some of the lowest forms of 
 vegetation. The lichens, mosses, sea-weeds, fungi, 
 will all demand your notice, and none will fail to 
 repay you for the pains of a careful investigation. 
 Some of the fresh-water algae are extremely beautiful 
 and readily procurable, whilst, should you pay a visit 
 
 Fig. 15. Receptacle of Fucus, containing Sporangia "germ cells." 
 
 to the sea-side, the "flowers of the sea" when gathered, 
 in some form or other, on every shore, will supply 
 a wide field for investigation. The common Fucus 
 vesiculosiis, whose ovoid capsules you explode at 
 almost every tread of the foot ; or the nearly equally 
 common F. platycarpus will amply repay you for 
 careful research. You will notice the receptacles at 
 the extremity of the fronds ; in the group of Fuci there 
 is no doubt about a true sexual mode of fructification 
 
USE OF THE MICROSCOPE IN BOTANY. 33 
 
 (Fig. 15). The fungi, again, will demand your atten- 
 tion ; the minute reproductive bodies thrown off from 
 the gills of the Agaric group in countless millions, 
 known by the name of "spores," will interest you 
 much. Gather a common mushroom or other fungus, 
 cut off the stem near the gills, place it with the gills 
 downwards on a sheet of paper, black or white ; leave 
 it in this position for several hours ; on taking it up 
 you will notice the gills have deposited a quantity of 
 dust-like stuff upon the surface of the paper. The 
 colour varies according to the families to which 
 the fungi respectively belong; in the mushroom the 
 " spores " are pink, in some fungi they are rust- 
 coloured, in others white, in others black. Just 
 notice how beautifully the deposited spores represent 
 the form of the gills, then scrape a portion off the 
 paper, and submit it to microscopic examination. 
 Bear in mind this distinctive difference between a 
 "seed" and a "spore" a seed contains an embryo, 
 a spore has none. 
 
 The little brown patches on the under side of some 
 of the ferns will attract your attention ; these are the 
 spore-cases of different forms, and variously disposed 
 according to the genus of plant on which they occur. 
 The spore-case, in some genus of ferns, is surrounded 
 by a curious elastic band, which, when the spores con- 
 tained within are ripe, suddenly jerks itself straight, 
 tears open the case, and disperses the minute spores 
 in all directions. You can witness the germination of 
 fern-spores by placing some on a damp surface, and 
 exposing them to light and heat. At first each one 
 puts forth a tubular prolongation ; the cells of the 
 spore multiplying by subdivision both transversely 
 and longitudinally, give rise to a flattened leaf-like 
 expansion, which from its under surface developes 
 both root-fibres and reproductive organs. Every one 
 
 c 
 
34 THE MICROSCOPE. 
 
 is acquainted with those curious-looking plants called 
 horsetails (Equisetacea) ; you will find them interesting 
 microscopic studies. Take hold of one ; you notice 
 how rough it is ; this roughness is caused by a quantity 
 of silex which permeates the whole of the structure of 
 the horsetail. To such an extent does this in some 
 cases take place, that " even when its organic portion 
 has been destroyed by prolonged maceration in dilute 
 nitric acid, a consistent skeleton still remains/' These 
 horsetails are reproduced from spores on a spike at 
 the end of some of the branches. To each spore are 
 attached two pairs of elastic filaments; at first they 
 are coiled up round the body of the spore ; at the 
 liberation of the spore they extend themselves. " If a 
 number of the spores be spread on a slip of glass 
 under the field of view, and whilst the observer 
 watches them a bystander breathes gently upon the 
 glass, all the filaments will be instantaneously put in 
 motion, thus presenting an extremely curious spectacle, 
 and will almost as suddenly return to their previous 
 condition when the effect of the moisture has passed 
 off."* I have frequently witnessed this curious spec- 
 tacle, and you can easily do so yourself by following 
 Dr. Carpenter's directions, which I have just quoted. 
 The Equisetacecz develop themselves from these spores 
 after the manner of ferns ; on this account the name 
 " fern allies " has been applied to their family. 
 
 You will find endless variety of form and markings 
 in the seeds of plants. Seeds as microscopic objects 
 under a low power and by reflected light, or viewed 
 under the binocular, are often extremely beautiful. 
 Take the seed of the poppy ; notice the network 
 markings upon its surface ; or the seed of the carrot 
 with its long starfish-like radiating processes. Make 
 
 * Carpenter, p. 383. 
 
US OF THE MICROSCOPE IN BOTANY. 35 
 
 a transverse section of any seed, you will find it has 
 two coats, an outer and inner membrane called re- 
 spectively testa and tegmen; you will see the embryo 
 either surrounded by albumen or immediately invested 
 by the coats. The following easily procured plants 
 will furnish you with samples of seed-forms : poppy, 
 stitchwort, mignonette, snapdragon, saxifrage, sweet- 
 william, foxglove. You can add to this list almost 
 indefinitely. 
 
 Every stream, ditch, and pond will supply. you ; 
 with many forms of algae, known as Diatomacecz and 
 Desmidiacetz* Once these organisms were supposed to 
 belong to the animal kingdom, on account of some 
 ot them exhibiting motion ; there is no doubt, how- 
 ever, that both these families are true vegetables'. 
 They are found in masses of jelly-like substance 
 attached to the stems or leaves of various aquatic or 
 marine plants, or they envelop any submerged plant 
 with loose brownish flocculent matter. The Diatomacece, 
 or brittleworts, are invested with a covering of silex ; 
 this fact you can readily demonstrate for yourself by 
 boiling the minute plants in nitric acid, having pre- 
 viously washed them well, so as to free them from 
 extraneous matters. The organic vegetable matter 
 is destroyed ; the siliceous portion remains. The 
 Desmidiacece, another family of confervoid algae, are 
 destitute of any siliceous covering ; they are generally 
 of a green colour, and are found, like the Diatomacece, 
 investing submerged plants or other bodies. These 
 microscopic algae, under a power of 300 to 400 
 diameters, are very striking objects; they come "in 
 such questionable shapes " that you cannot help but 
 " speak to them." Now circular, now filamentary, 
 beautifully jointed, now like small boats in outline, 
 now crescent-shaped in fact, every variety of form 
 exhibiting these algae, I have no doubt, will occupy 
 
 C 2 
 
THE MICROSCOPE. 
 
 much of your time. And here I should wish to 
 give you some advice which you will find useful as 
 a beginner. It is well at first to make yourself ac- 
 quainted with various forms of plant-life to run 
 cursorily at first, but mind, only at first, over various 
 objects. You will thus gain a sort of general notion 
 of the interesting field of operations before you. 
 Real special work and I hope you are going in for 
 real work must begin after you have made a general 
 survey of the land in which you wish to make con- 
 quests. It is not well 
 for a beginner to embark 
 all at once, without some 
 general knowledge of 
 the field of labour, into 
 special work. 
 
 All these plants, you 
 will see, evolve oxygen 
 when exposed to the 
 light of the sun ; those 
 bubbles which bespangle 
 that brown-coated stem 
 from the confervae are 
 bubbles of oxygen, which 
 at once disclose, even 
 
 in the absence of further proof, their vegetable nature. 
 Many other forms of undoubted vegetable nature 
 which have been, at one time or another, claimed by 
 the zoologists as belonging to the animal kingdom, 
 might be enumerated. Prominently we may notice 
 that curious protophyte not uncommon in stagnant 
 water, called Volvox globator. Look out for specimens 
 in the spring and summer months ; they are easily 
 seen where they abound, about the size of a small 
 pin's head, and of a greenish colour : they will attract 
 your eye when they roll along in the glass bottle in 
 
 Volvox Globator. 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 37 
 
 which you have collected some specimens. I have 
 generally found Volvox globator in stagnant ponds 
 containing a profusion of aquatic vegetation. The 
 ordinary size is about -^ of an inch in diameter. 
 " When examined with a sufficient magnifying power, 
 the volvox is seen to consist of a hollow sphere, 
 composed of a very pellucid material, which is 
 studded at regular intervals with minute green spots, 
 and which is often, but not constantly, traversed by 
 green threads connecting these spots together. From 
 each of the spots proceed two long cilia; so that 
 the entire surface is beset with these vibratile fila- 
 ments, to whose combined action its movements are 
 due. Within the external sphere may generally be 
 seen from two to twenty other globules of a darker 
 colour and of varying sizes ; the smaller of these are 
 attached to the inner surface of the investing sphere, 
 and project into its cavity; but the larger lie freely 
 within the cavity, and may often be observed to revolve 
 by the agency of their own ciliary filaments. After 
 a time the original sphere bursts, and the contained 
 spherules swim forth, and speedily develop themselves 
 into the likeness of that within which they have been 
 evolved." When you see, as you will do, various 
 organisms swimming freely about in a drop of water, 
 you will be inclined to put them down as belonging to 
 the animal kingdom. Suspend your judgment; it is 
 quite probable what you see are motile cells of certain 
 vegetable organisms. What is the difference between 
 a plant and an animal ? 
 
 * Carpenter, " Microscope," p. 251. 
 
CHAPTER IV. 
 
 USE OF THE MICROSCOPE IN ZOOLOGY. 
 
 IN the last chapter I asked the question, "What is 
 the difference between a plant and an animal?" a 
 question more easily asked than satisfactorily answered, 
 for when we examine very low organisms, we seem to 
 touch the confines of the two kingdoms ; but these 
 confines are very difficult to determine indeed, some 
 scientific men have denied any absolute distinction 
 between the two kingdoms. They assert that, not- 
 withstanding the manifold differences in form and 
 structure, there is a " physical basis of life underlying 
 all the diversities of vital existence;" that "a three- 
 fold unity namely, a unity of power or faculty, a 
 unity of form, and a unity of substantial composition 
 does pervade the whole living world." According to 
 that eminent biologist, Professor Huxley, the formal 
 basis of all life is protoplasm, simple or nucleated ; 
 and in the lowest plants, as in the lowest animals, 
 a single mass of such protoplasm may constitute the 
 whole plant, or the protoplasm may exist without 
 a nucleus. How, then, it is asked, is one mass of 
 non-nucleated protoplasm to be distinguished from 
 another? Why call one plant and the other ani- 
 mal? The only reply is that, so far as form is 
 concerned, plants and animals are not separable, and 
 that in many cases it is a mere matter of con- 
 vention whether we call a given organism an animal 
 or a plant. There is a living body called &thalium 
 septicum, which appears upon decaying vegetable sub- 
 stances, and in one of its forms is common upon 
 the surfaces of tan-pits. In this condition, it is to 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 39 
 
 all intents and purposes a fungus, and formerly was 
 always regarded as such ; but the remarkable in- 
 vestigations of De Bary* have shown that in another 
 condition the ^Ethalium is an actively locomotive 
 creature, and takes in solid matters, upon which 
 apparently it feeds, thus exhibiting the most charac- 
 teristic feature of animality. Is this a plant, or is it 
 an animal ? Is it both ; is it neither ? Some decide 
 in favour of the last supposition, and establish an 
 intermediate kingdom, a sort of biological No Man's 
 Land, for all these questionable forms. But as it is 
 admittedly impossible to draw any distinct ' boundary 
 line between this No Man's Land and the vegetable 
 world on the one hand, or the animal on the other, it 
 appears to be that this proceeding merely doubles the 
 difficulty, which before was single, t 
 
 Notwithstanding, however, the great difficulty, if 
 not impossibility, of drawing a distinction between 
 some of the lowest forms of the animal and vegetable 
 kingdoms, as a general rule the boundaries are suffi- 
 ciently distinct. I have called your attention to the 
 remarks of Professor Huxley on this subject, in order 
 that you may see what great problems the microscope 
 helps to solve. I will now direct you to a considera- 
 tion of some of the minute forms of undoubted animal 
 life which every pond or ditch contains in endless 
 variety and profusion. Of so-called monads extremely 
 minute organisms found in water containing decom- 
 posed vegetable or animal matter, several supposed 
 species of which have been described I need say but 
 little. There can be no doubt, notwithstanding the 
 opinion of Ehrenberg, that the Monadina family con- 
 
 * "Die Mycetozoen." Leipzig, 1864; also an abstract in Hoff- 
 meister's "New System of Botany." 
 
 t "Oft the Physical Basis of Life." Fortnightly Review, Feb., 
 1869. 
 
40 THE MICROSCOPE. 
 
 sists of a heterogeneous group, some forms of which 
 may be the zoospores of algse, others the germs of 
 animalcules. The Monadina, which quite recently 
 have been regarded as the most minute living crea- 
 tures discovered, comprising several distinct genera 
 such as Monas, Euglena, Uvella, Syncrypta, Chlamydo- 
 monas, Bodo, and many more can no longer stand as 
 a family representing different mature animal forms. 
 
 For obtaining microscopic objects from the pond, 
 stream, or ditch, all you want is a wide-mouthed bottle 
 or two, a bit of wire, a walking-stick, a lens, and a 
 canvas or strong muslin net. A cutting hook to screw 
 into the end of your walking-stick will be useful in 
 nipping off the stems of aquatic plants, which always 
 harbour many forms of animal life. Several kinds of 
 animalcules, wholly invisible to the unaided eye as 
 single objects, are discernible as groups ; among which 
 I may mention to you the green masses of Ophrydium 
 versatile, and various Vorticellce, which may be fre- 
 quently seen encircling submerged stems or other 
 bodies with a dirty-white flocculent mass. Ophrydium 
 versatile lives in societies of many thousands together, 
 in balls of a whitish jelly-like substance. The colour 
 of the animalcules is green, and this gives the colour 
 to the masses of jelly in which they live. The size of 
 these balls varies from that of a pea to that of a man's 
 fist. In form each individual is very like a Stentor, 
 especially when it is free for these little creatures 
 can leave the jelly-like ball, and swim treely in the 
 surrounding fluid but as long as an Ophrydium is an 
 inmate of the jelly ball, it possesses, at the hinder 
 end, a very long thread-like tail, much longer than 
 itself; this tail seems to anchor the animalcule securely 
 in the gelatinous substance. You may meet with 
 these balls in clear water in the spring and early sum- 
 mer months. 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 
 
 1 he little creatures called Stentors are very interest- 
 ing to study. Each one looks like a miniature 
 green trumpet, and is visible to the unassisted eye. 
 Look carefully at the engraving : you notice that 
 the goblet-shaped mouth is sur- 
 rounded with a circle of hairs ; these 
 are called cilia, from the Latin word 
 meaning eyelashes, a designation 
 appropriate enough. There are 
 many curious forms of these ciliated 
 protozoa, and it will be a source of 
 much pleasure to you to make their 
 acquaintance from time to time. 
 The whole body of the stew tor is, as 
 you observe, covered with cilia 
 organs which play a very useful and 
 prominent part in these creatures' 
 lives. They serve both for the pur- 
 poses of progression for by these 
 numerous hairs the animalcules row 
 themselves about with wonderful 
 rapidity and also, when arranged 
 in a circlet round the mouth, for 
 obtaining food. The constant lash- 
 ing of these cilia produces currents of water, which 
 convey to the animalcule particles of food, whether 
 of an animal or vegetable nature. These Stentors are 
 of various colours it is supposed there are many 
 species of the genus ; five or six have been described 
 either white, black, blue, or green; and like their 
 relations, the Ophrydia, are capable of assuming 
 various forms. They increase, like numerous othei' 
 forms of low animal life, by self-division. Such split- 
 ting may take place either longitudinally or obliquely, 
 and each part may form a perfect animal. You will 
 often witness animalcules in the act of separating into 
 
 Fig. 16. Stentor. 
 
42 THE MICROSCOPE. 
 
 two portions ; this method of reproduction is ana- 
 logous to that of the budding of plants. But even in 
 animals so small as, and even much smaller than, a 
 Stentor, a true sexual reproduction takes place. It is 
 to the researches ot Balbiani that we are indebted 
 for our knowledge of this most interesting fact. It 
 seems pretty certain that, both in the case ot animals 
 and plants, a contact of sperm-cell with germ-cell is 
 at times absolutely necessary for the continuation of 
 the species. You will be able to make yourself satis- 
 fied of the existence of this phenomenon amongst the 
 infusoria, after some experience in the use of the 
 microscope; so at present I will not make further 
 remarks on the subject. Great patience is necessary 
 if you would gain an accurate idea of the structure or 
 functions of any minute organ of these little crea- 
 tures. In no case is the old Latin proverb, "Nil 
 sine labore," more true than in microscopic work ; 
 and the same may be said of the converse, " Labor 
 omnia vincit." 
 
 What strange form of animal life am I gazing at 
 now ? A group of some dozen or more of creatures, 
 each growing from a long, spirally-twisting stalk ; some 
 individuals, you see, are in the act of splitting, others 
 have left the stalks; some are just beginning to 
 uncoil, others are partly, others wholly uncoiled. The 
 mouths, you observe, are surrounded with cilia. I 
 will rub a little paint, say carmine or indigo, on this 
 glass slide, and dip my camel-hair brush into it ; now 
 I let a little drop of this find its way between the 
 glass cover and the slide on which the specimens I 
 am examining lie. Now you see the action of these 
 cilia. How the particles of colour are whirled about 
 in all directions ! How wonderfully rapid is the move- 
 ment of these spiral stems, or foot-stalks ! The name 
 of this little creature is Vorticella^ or the Bell Flower 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 
 
 43 
 
 Animalculse (Fig. 17). Other interesting forms of the 
 Vorticellina family you are sure to meet with, such as 
 Epistylis and Carchesium. In individuals of the former 
 genus, the 
 flowers droop 
 from a stem 
 in a tree-like 
 form, the foot- 
 stalks having 
 no retractile 
 power; in Car- 
 chesium the 
 bells orflowers 
 spring from a 
 single non-re- 
 tractile trunk, 
 but the stems, 
 which are very 
 numerous, are 
 all retractile. 
 On the stems 
 and leaves of various aquatic plants you will see 
 other interesting little creatures of the same family 
 each inhabiting a tube. A great number of species 
 
 have been described ; 
 but you will recognise 
 the general form when I 
 tell you that the animal- 
 cule is like a Stentor. It 
 is very curious to witness 
 this animal protrude itself 
 out of its case. Within 
 its case, which is often 
 very transparent, and 
 which perhaps would es- 
 Fi g . ig.-carchesium. cape your detection were 
 
 Fig. 17. Vorticella. 
 
44 
 
 THE MICROSCOPE. 
 
 it not for the small particles of dirt which have 
 attached themselves to it, the animal is seen as a 
 round mass. By-and-by it slowly extends itself till it 
 reaches the open mouth of the tube ; then the an- 
 terior orifice expands, the circlet of cilia is put in 
 active motion, currents of food-producing water are 
 brought within the action of the cilia, and, all of a 
 sudden quick as lightning the little creature, by 
 
 contraction of its 
 muscular tissues, 
 subsides into the 
 form of a ball, as 
 before. From 
 their habit of living 
 in a sheath these 
 creatures are 
 called Vaginicoltz. 
 The wheel-ani- 
 malcules (Rotiferd) 
 will afford you un- 
 limited amusement 
 and instruction. 
 You will recognise 
 their form from 
 the accompanying 
 figure. We advance a step most decidedly here. The 
 animals that have hitherto come before our notice 
 are of low organisation compared with the Rotifer a. 
 How shall we describe the structure of a Stentor 
 or an Ophrydium ? Imagine an animated mass hol- 
 lowed out into one large general cavity. There 
 is a mouth, with its circlet or circlets of cilia, 
 and a stomach some animal organisms, such as 
 amseba and sponge, have not got so much even as 
 this a contractile vesicle, apparently the rudiments 
 of a circulating system, and two nuclei, which represent 
 
 Fig. 19. Wheel-animal culae. 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 45 
 
 the reproductive apparatus ; but in the wheel-animal- 
 cule, and other Rotifers, you will see a differentiation 
 of parts and a specialisation of organs. There is evi- 
 dently an integument or skin through which certain 
 viscera or internal organs can be discerned ; one of 
 the most conspicuous organs is what is sometimes 
 badly named the gizzard. This piece of organic 
 machinery, consisting of strong muscular substance, fur- 
 nished, according to the species, with various pointed 
 teeth, seems in these animals to be always going \ its 
 function is manifest even at a glance. You will notice 
 that various substances, drawn down in the vortex 
 caused by the action of the cilia, pass through this 
 manducatory organ, which, like a pair of miniature 
 mill-stones, grinds the food as it passes between them. 
 You will often notice both eggs and young ones 
 within the bodies of the wheel-animalcules, and very 
 curious it is to see under the microscope the move- 
 ments and contortions of a restless embryo rotifer. 
 The Rotifera possess, moreover, an intestinal canal, 
 a water-vascular system, and longitudinal muscles. 
 There is much difference of opinion as to their 
 proper place in the zoological scale. Some naturalists 
 think that these wheel-animalcules have their affinities 
 with worms, others with crabs. 
 
 You will be almost in ecstacies of delight at first 
 becoming acquainted with the Melicerta ringens, an 
 exquisite little creature, pretty common in pools and 
 ditches, where it may be found sometimes in extra- 
 ordinary profusion, attached to the stems and leaves 
 of various aquatic plants. The Melicerta is a worm- 
 like creature, about as thick as a horsehair, and the 
 twelfth part of an inch in length^ It is itself the 
 architect of a very pretty little tubular house in which 
 it dwells. You should try to make the acquaintance 
 of Melicerta, for in the whole aquatic world there is 
 
46 THE MICROSCOPE. 
 
 scarcely a more interesting object for contemplation. 
 Search for these creatures in mill-pools and ponds 
 through which a current of water gently flows. If a 
 portion of water-weed be brought home and placed in 
 a glass vessel, and the leaves of the plants be care- 
 fully examined with a lens the long thread-like leaves 
 of the water crowfoot (Ranunculus aquatilis) are a very 
 favourite habitat you will probably detect delicate 
 projecting objects of a reddish-brown colour, light or 
 dark, however, according to the nature of the bottom 
 of the pool. These are the tubular cases of Meliccria. 
 If one of these, still attached to the bit of weed, be 
 placed on a slip of glass, and viewed under the micro- 
 scope with a power of about 50 diameters, you will 
 notice that this tube is made of several series of round 
 clay or mud pellets. By-and-by, if you will be careful 
 not to shake the table on which the specimen is 
 placed (for Mdicerta is a coy and timid creature), you 
 will see the occupant slowly unfold the anterior portion 
 of its body from the orifice of the tube. At first, as 
 Mr. Gosse has well described it, "a complicated mass 
 of transparent flesh appears involved in many folds, 
 displaying at one side a pair of hooked spines, and at 
 the other two slender truncate processes projecting 
 horizontally. As it exposes itselt more and more, 
 suddenly two large rounded discs are expanded, 
 around which at the same time a wreath of cilia is 
 seen performing its surprising motions. Often the 
 animal contents itself with this degree of exposure, 
 but sometimes it protrudes further, and displays two 
 other smaller leaflets, opposite to the former, but in 
 the same place, margined with cilia in like manner. 
 The appearance is now not unlike that of a flower of 
 four unequal petals ; from which resemblance Linnaeus, 
 who compared it to a ringent labiate corolla, gave it 
 the trivial name of ringens, by which it is still known.'* 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 47 
 
 By continuing to gaze on this marvel of creative skill, 
 you will notice that it every now and then bends its 
 corolla-shaped head down upon the tube, holding it 
 there a second or two, and then raising it up again. 
 What is the meaning of this ? Melicerta is adding a 
 brick to its house ; sometimes you will see the bricks 
 roll off after deposition, in consequence of the material 
 not being sufficiently tenacious. The bricks are 
 made of the same substance so generally used by 
 human architects namely, of clay, the only difference 
 being that the bricks of the rotifer are round and soft. 
 Under a power of about 200 diameters you will 
 observe a singular cavity below the large discs of the 
 head ; this cavity gradually becomes filled with 
 particles of clay ; a number of cilia line the cavity, 
 and by their action cause the particles of clay to 
 rotate rapidly and to be consolidated. When the 
 brick is formed the animal bends down its head and 
 fixes it to the tube, and then begins to form another 
 pellet. The particles of clay, or other adhesive 
 material, are drawn into the cavity where the bricks 
 are formed, by the ciliary action of the discs, a small 
 channel conducting them from the upper portion of 
 the disc to the cavity in question. If portions of 
 indigo or carmine be mixed with the water in which 
 the Melicerta lies, the animal will make use of them, 
 and add rings of red or blue to its dwelling-place. It 
 is impossible, I think, to imagine a more interesting 
 instance of animal architecture than that exhibited by 
 this little creature. 
 
 The Rotifera, from their great transparency, are 
 excellent objects for study ; many, forms, moreover 
 are readily obtained the scum attached to aquatic 
 plants, the dirt in your pipes on the roof of your 
 house, the soil on the roots of the moss of your slated 
 roof, the mud at the bottom of ponds and ditches, will 
 
48 THE MICROSCOPE. 
 
 afford many specimens for examination. There is 
 every variety of form : some are naked ; others are 
 loricated, or have a consolidated integument encircling 
 their bodies; others construct houses in which they 
 reside. Two beautiful forms, the Floscularia and Ste- 
 phanoceros, will demand a short notice in the next 
 chapter. 
 
 CHAPTER V. 
 
 USE OF THE MICROSCOPE IN ZOOLOGY (continued). 
 
 THE Stephanoceros and Floscularia are both very 
 beautiful and delicate little creatures ; they should be 
 examined, to get a general idea of their form and 
 characters, with a power of about 60 diameters. The 
 former animal has an oblong body on a long tapering 
 stalk ; a circlet of fine elegant tentacles, with two rows 
 of cilia on the sides, surrounds its upper portion ; like 
 the Melicerta^ this little creature dwells in a tube, but 
 not mechanically constructed, like that of the first- 
 named animal. You will not easily satisfy yourself 
 of the existence of this tube, so extremely transparent 
 as it is ; but by turning the mirror at different angles, 
 you will notice a jelly-like case, which appears to be a 
 secretion from the animal's body. Groups attached 
 to weeds are visible to the naked eye; they prefer 
 clear water, and may be kept alive for weeks in a 
 vessel of water. On the slightest alarm, the Stepha- 
 noceros retreats within her cylindrical tube. Floscu- 
 laria is another exquisite microscopic object, and 
 common enough on the stems or leaves of water- 
 plants. This creature, too, dwells in a transparent case ; 
 in form, it is like Stephanoceros, except that the head- 
 portion is divided into six lobes or projections, each 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 49 
 
 one having an immense quantity of extremely fine 
 bristles. As the animal protrudes itselt out of its case, 
 these hairs appear in a dense mass, but soon the lobes 
 separate, and the tufts of bristles on each spread them- 
 selves out in a graceful fan-like torm. What is the 
 use of these long bristles ? I am unable to tell you. 
 Although the animal is destitute of the ciliary wheel- 
 like wings that characterise the Rotifera generally, its 
 whole organisation, and the mechanism and functions 
 of the grinding jaws or gizzard, clearly indicate its 
 relationship with that class ot animals. We must not 
 linger more on these and similar exquisite little forms 
 of animal life ; let me direct your attention to a very 
 strange-looking creature called the Hydra, of which 
 genus there are three well-marked British species 
 namely H. viridis, H. vulgaris, and H.fusca. The first 
 is of a beautiful grass-green colour, the second and third 
 of a pale brown, sometimes nearly white. The arms or 
 tentacles of the last-named species are very long. These 
 animals are found only in fresh water, and generally 
 such as flows very slowly or is quite still. As you will 
 find the study of these creatures full of the deepest 
 interest, I will give you a description somewhat fully. 
 
 The best way to obtain specimens is to take a 
 handful of weeds from any clear pond or ditch, and 
 place it in a glass vessel of water. After waiting 
 half an hour the hydrae will probably be seen in 
 various attitudes, some hanging loosely down, others 
 gracefully curving themselves upward and throwing 
 out tentacles many times longer than their bodies; 
 others shooting up their arms above their heads ; 
 others contracting themselves into mere jelly-like dabs ; 
 others attaching themselves by both extremities to the 
 side of the glass ; others floating on the surface of the 
 water, their-tail ends preserving them from sinking. 
 Their colours, too, may be nearly as various as their 
 
 D 
 
THE MICROSCOPE. 
 
 attitudes white, red, light flesh, or beautiful grass- 
 green. The body of the hydra is of a gelatinous 
 nature, altering in shape as it changes its position ; 
 when contracted, in some species a mere tubercle with 
 short radiating papillae ; when extended, becoming a 
 
 narrow cylinder. 
 One end expands 
 and forms an ad- 
 herent disc j the 
 other has a mouth 
 surrounded by nu- 
 merous exceedingly 
 contractile arms or 
 tentacles, varying 
 in number accord- 
 ing to the age and 
 species of the in- 
 dividual. The 
 hydra's body is 
 composed of two 
 membranes, techni- 
 cally termed ecto- 
 derm and endoderm, 
 the former being 
 the external cover- 
 ing, the latter the 
 internal lining of the cavity. The tentacles are tubes, 
 which are, in fact, prolongations of these two mem- 
 branes. They are the arms by which the animal seizes 
 its prey, and they are placed a little, below the mouth, 
 which, when closed, protrudes like a snout above them. 
 Both membranes have irregularly rounded nodules on 
 their surface. These nodules, especially in the tenta- 
 cles, contain capsular bodies (thread-cells), in which 
 may be seen (the hydra being crushed between bits of 
 glass, under a high microscopic power) curious organs. 
 
 Hydra attached to a Weed. 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 51 
 
 consisting of spines and filaments, supposed by some 
 to have the power of stinging. There are traces of 
 muscular fibres in the tentacles, but whether sufficient 
 to account for their extraordinary extensibility is 
 doubtful. Some have supposed their elongation to be 
 caused by the water, which, finding its way into the 
 hydra's body through the mouth, may pass through 
 extremely narrow channels into the tentacles. The 
 tentacles of Hydra fusca are the most wonderfully 
 extensible of all; growing gradually finer than the 
 lightest gossamer, they become invisible except to 
 the eye of the microscopist. 
 
 The hydrae are very voracious, and readily kept in 
 confinement for some time. They feed on small 
 Entomostraca ', and on minute larvae of gnats and naid 
 worms. Their stomach is a simple cavity. Some 
 authors speak of a short narrow duct leading from the 
 stomach to the centre ot the disc, whence they say 
 through a tiny aperture excrementitious particles may 
 be seen to pass. Of this intestinal canal I have never 
 discovered any sign in the species I have examined. 
 Food is quickly assimilated by the hydra, and the 
 indigestible portion expelled through the mouth, as 
 in the Actinice. The movements of the hydra are 
 very slow, but performed in the same manner as those 
 of the leech, their position being also varied by a 
 gliding motion of the disc. Sometimes this disc, 
 protruded above the water, acts as a float, and the 
 animal is borne along on the current. Hydrae may be 
 found in spring, summer, or autumn, and in the latter 
 season they give birth to eggs and die. I have found 
 H. viridis in very mild winters. Their mode of in- 
 crease is twofold gemmation and the ordinary mode 
 of reproduction. The first takes place throughout 
 the summer, the latter only at the end of autumn. 
 When increasing by gemmation, a small swelling first 
 
 D 2 
 
52 THE MICROSCOPE. 
 
 appears on the hydra's body; this grows larger, and 
 divides at its apex into several minute papillae, which 
 afterwards become the tentacles. When reproducing 
 by ova, the observer will notice certain peculiar eleva- 
 tions on the body of the hydra, some, in the middle 
 of the body, round; others, at the bases of the 
 tentacles, of a conical shape; perhaps one or two ot 
 each kind. The round elevations contain the ova; 
 the conical, the spermatozoan bodies. The ovum, 
 when ripe, pushed through the body-wall, and impreg- 
 nated, becomes attached to some water-weed, and 
 awaits the warm spring to be developed into the young 
 hydra. But I have never succeeded in meeting with 
 these detached ova, and they appear to have been 
 only noticed by few. Trembley and Baker record 
 many and various experiments practised by them on 
 the hydra; and the former gives us a number of 
 admirably executed figures. The result of these ex- 
 periments may be summed up in the language of 
 Dr. G. Johnston: "If the body is halved in any 
 direction, each half in a short time grows up a perfect 
 hydra ; if it is cut into four or eight, or even minced 
 into forty pieces, each continues alive and developes 
 a new animal, which is itself capable of being mul- 
 tiplied in the same extraordinary manner. If the 
 section is made lengthways, so as to divide the body 
 into two or more slips, connected merely by the tail, 
 they are speedily re-soldered, like some heroes of fairy- 
 tale, into one perfect whole ; or if the pieces are kept 
 asunder, each will become a polype, and thus we may 
 have two or several polypes with only one tail between 
 them ; but if the sections be made in the contrary 
 direction from the tail towards the tentacula you 
 produce a monster with two or more bodies and one 
 head. If the tentacula the organs by which they 
 take their prey, and on which* their existence might 
 
USE OF THE MICROSCOPE IN ZOOLOGY, 53 
 
 seem to depend are cut away, they are reproduced, 
 and the lopped-off parts remain not long without a 
 new body. If only two or three tentacula are em- 
 braced in the section, the result is the same, and a 
 single tentaculum will serve for the evolution of a 
 complete creature. When a piece is cut out of the 
 body, the wound speedily heals, and as if excited by 
 the stimulus of the knife, young polypes sprout from 
 the wound more abundantly, and in preference to 
 unscarred parts ; when a polype is introduced by the 
 tail into another's body, the two unite and form one 
 individual ; and when a head is lopped off, it may 
 safely be engrafted on the body of any other which 
 may chance to want one. You may slit the animal 
 up, and lay it out flat like a membrane with impunity ; 
 nay, it may be turned inside out, so that the stomachal 
 surface shall become the epidermis, and yet continue 
 to live and enjoy itself, and the animal suffers very 
 little by these apparently cruel operations, 
 
 'Scarce seems to feel, or know 
 His wound,' 
 
 for, before the lapse of many minutes, the upper half 
 of a cross section will expand its tentacula and catch 
 prey as usual \ and the two portions of a longitudinal 
 division will, after an hour or two, take food and 
 retain it. A polype cut transversely in three parts 
 requires four or five days in summer, and longer in 
 cold weather, for the middle piece to produce a head 
 and tail, and the tail part to get a body and head, 
 which they both do in pretty much the same time." 
 
 You will often notice some very interesting para- 
 sites upon the various species of Hydra. One very 
 curious little fellow delights to run up and down .the 
 hydra's tentacles, like a miniature railway-truck. In 
 form the creature resembles a dice-box, only it is as 
 
54 THE MICROSCOPE. 
 
 broad as it is long ; a wreath of cilia surrounds both 
 the top and the bottom edges. Now it leaves the 
 hydra, soon, however, to return to it again. The 
 name of this little parasite is Trichodina pediculiis. I 
 am of opinion that these hydra-lice are indicative of 
 a not very healthy condition of their hosts ; but 
 whether they are annoying or not I cannot say. 
 The curiously-formed stinging organs of the hydra 
 seem to be of no service in warding off these minia- 
 ture Trichodina. 
 
 There is one curious creature which I must intro- 
 duce to your notice, and which you may not unfre- 
 quently find in the surface mud of any pond. I shall 
 never forget my first acquaintance with this animal, 
 about twenty years ago. So struck was I with its 
 absurd and grotesque appearance, having at that time 
 but little acquaintance with microscopic forms, that I 
 could hardly believe the evidence of my senses, and 
 I called in a servant to look at the strange creature, 
 and to tell me that I was not dreaming. Well, what 
 was the creature ? It was a Tardigrade, a very " slow- 
 goer" indeed, but the strangest of beasts ; it was 
 something like a naked sloth, only it had four pairs 
 of legs instead of two. These legs such things to call 
 legs were each provided with four claws ; there was 
 no tail ; its mouth was changeable in form, now 
 blunted, now pointed with pouting lips. A curious 
 oval-shaped muscular body, with peculiar style-like 
 appendages was very conspicuous ; this was the ani- 
 mal's gizzard. The style-like processes, or horny rods, 
 are said to be protrusile ; but though I have fre- 
 quently examined tardigrades since I first made their 
 acquaintance, I do not think I ever saw these rods in 
 a protruded state. 
 
 These animals, like the rotifers, are capable of 
 bearing exposure to very great heat without being 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 55 
 
 any the worse for it; indeed, they were believed to 
 be capable of resuscitation. Spallanzani has a chapter 
 with the following heading : " Animals which can be 
 killed and resuscitated at pleasure." Of course such 
 an idea is absurd; the fact, however, remains that 
 certain creatures, rotifers, tardigrade s, anguillulae, can 
 be reduced by great heat to almost thorough dryness, 
 can be kept in this condition for a length of time, and 
 yet will revive on the application of moisture. Every 
 one who is acquainted with the history of these animals 
 is aware of the experiments made on them by M. 
 Pouchet, so I shall conclude this chapter with an 
 extract -from 
 "The Uni- 
 verse" of that 
 distinguished 
 French savant: 
 " It is true we 
 
 are, in OUr A Tardigrade. 
 
 day, obliged to 
 
 erase the charming romance of palingenesis, with 
 which our forefathers amused themselves. Still, we 
 must say that, although the Rotiferae cannot be resus- 
 citated when they are once dead, their tenacity of life 
 is one of the most extraordinary phenomena. Their 
 resistance to cold is something marvellous, and we do 
 not even know where it stops ; the lowest temperature 
 that we can obtain in our laboratories does not seem 
 to have any effect upon them. I have seen these 
 animals defy a cold which would kill a man a hundred 
 times over. Rotiferae placed in an apparatus where 
 the temperature was 40 below zero, Centig. (40 
 Fahr.), issued from it full of vitality."* 
 
 " The natural history of the Rotiferae is a 
 
 * "The Universe,'.' p. 56. 
 
^ 6 THE MICROSCOPE. 
 
 marvel from beginning to end. I have sometimes 
 removed them quickly from the freezing apparatus, 
 and thrown them into a stove heated to 80 u Centig. 
 (176 Fahr.); when they emerged from this they 
 were seen to recover their animation, and run about 
 full of life. In this twofold test t and formidable 
 transition from cold to heat, these Microzoa passed 
 rapidly through a change of 120 Centig. (216 
 Fahr.) without being in the least inconvenienced by 
 it." After what I have said and quoted, I am sure 
 you will wish to make a few " slow-going" acquaint- 
 ances. 
 
 CHAPTER VI. 
 
 USE OF THE MICROSCOPE IN ZOOLOGY (continued}. 
 
 ONE of the most interesting spectacles afforded by 
 the microscope is that which is furnished by the cir- 
 culation of the blood. This may readily be seen in 
 the gills of the tadpole or newt, in the tail of the tad- 
 pole, the foot and tongue of the frog, in newly-hatched 
 fish, such as young trout, perch, sticklebacks, &c. 
 The tadpole in its early stages of existence is essen- 
 tially a fish, breathing the air contained in the water 
 by means of external gills alone. If you will examine 
 a very young tadpole, you will see these gills in the 
 form of a pair of fringes at the sides of the head ; at 
 the bases of these are also the rudiments of the in- 
 ternal gills. The external gills rapidly disappear at 
 the end of four or five days; but the internal gills, 
 which were mere rudiments at first, are undergoing 
 rapid development. " It is requisite," says Dr. Car- 
 penter, " that the tadpole subjected to observation 
 
Circulation of Blood in a young Tadpole. 
 
58 THE MICROSCOPE. 
 
 should not be so far advanced as to have lost its early 
 transparence of skin ; and it is further essential to the 
 tracing out the course of the abdominal vessels, that 
 the creature should be kept without food for some 
 days, so that the intestine may empty itself. This 
 starving process reduces the quantity of red corpuscles, 
 and thus renders the blood paler ; but this, although 
 it makes the smaller branches less obvious, brings the 
 circulation in the larger trunks into more distinct 
 view." The circulation of blood in a young tadpole 
 is a most astonishing spectacle. The plate will serve 
 to give you some slight notion of the internal organs ; 
 by-and-by, when you become more experienced, you 
 should read Mr. Whitney's remarks on that subject 
 in Vol. X. of the Transactions of the Microscopical 
 Society, 1862. If you desire to study the circulation 
 of blood in a frog's foot, you should select a young 
 specimen with a thin web. But how are you to keep 
 the frog quiet under inspection ? Microscope-makers 
 sell an especial apparatus for this purpose, called a frog- 
 plate ; but you can easily cut out a wooden imitation, 
 which will serve your purpose completely. Provide 
 yourself with a piece of thin wood or cork, about nine 
 inches long and three inches wide; towards the middle 
 of its length cut a hole about half an inch in diameter. 
 Wrap the whole of the frog, except one leg, in a piece 
 of wet calico, and fasten him, but not too tightly, on 
 the cork-plate ; spread out the exposed foot over the 
 aperture, and by means of a few small pins fasten the 
 foot to the cork. Then put the cork-plate upon the 
 stage of the microscope, and secure it by means of 
 tape. Moisten the frog's web with a spot of water, 
 and examine it under the microscope with a power of 
 about 100 diameters, and you will see a wonderful 
 sight. Torrents of blood flow with great rapidity, 
 crossing and re-crossing each other ; sometimes there 
 
USE OF THE MICROSCOPE I XT ZOOLOGY. 59 
 
 is a momentary check, and the blood-corpuscles col- 
 lect together in one spot. Perhaps the frog is too 
 tightly fastened, or alarm may have interfered with 
 the heart's action. You will notice several dark 
 opaque bodies in the substance of the frog's feet ; 
 these are pigment cells. 
 
 The water larvae of various kinds of insects, small 
 Crustacea, such as Daphnia pulex, &c., will reward you 
 for a patient study of the circulatory system in these 
 creatures. Both in the larva, pupa, and imago stages 
 insects have not a heart, but a long dorsal vessel, which 
 is really made up of a series of contractile cavities, 
 one for each segment of the body, opening one into 
 another from behind forwards, the whole being divided 
 by valvular partitions. This is the typical form of the 
 circulatory system. It must be confessed, however, 
 that there is much difficulty in always making out 
 these valvular partitions. The larvae of any of the 
 EphtmcricUz are capital objects for examination. A 
 smaller specimen laid upon a glass slide, with a drop 
 of water and a thin glass cover over it, will serve well 
 to show you the circulation of blood in insects. You 
 will notice that the blood is almost colourless, that the 
 corpuscles are oat-shaped. " The current enters the 
 dorsal vessel at its posterior extremity, and is propelled 
 forwards by the contractions of the successive cham- 
 bers, being prevented from moving in the opposite 
 direction by the valves between the chambers, which 
 only open forwards. Arrived at the anterior extremity 
 of the dorsal vessel, the blood is distributed in three 
 principal channels ; a central one, namely, passing to 
 the head, and a lateral one to either side, descending 
 so as to approach the lower surface of the body. It 
 is from the two lateral currents that the secondary 
 streams diverge, which pass into the legs and wings, 
 and then return back to the main stream. It is from 
 
6o 
 
 THE MICROSCOPE. 
 
 these also that in the larva of the Ephemera margin ata 
 the smaller currents diverge into the gill-like append- 
 ages with which the body is furnished." 
 
 The various organs of insects will supply you with 
 inexhaustible subjects for study and interest. A com- 
 mon fly from your window pane will furnish you with 
 
 Eye of Fly magnified. 
 
 matter for examination for some time ; and I would 
 recommend the common fly as a sample of insect 
 structure. Under a simple lens you will observe the 
 numerous facets of the eyes, the number and position 
 of the nervures on the wings ; you may then select its 
 various members for examination. Cut off the head, 
 and view it as an opaque object by reflected light; 
 you. will notice that each eye is made up of numerous 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 6 1 
 
 little hexagonal figures, forming so many eyes, or ocelli, 
 as they are termed. In the common fly the two eyes 
 contain about 4,000 of these hexagonal facets, or ocelli. 
 The eyes of insects differ according to the species, 
 both in position, number, form, and colour. The eyes 
 of the common white butterfly are composed of about 
 17,000 ocelli; in the dragon-fly there are upwards 
 of 20,000. 
 
 By making a very careful vertical section you will 
 discover that each ocellus is in shape like a pyramid ; 
 the upper part, or corneule, forming the base, the apex, 
 or lower part, which is drawn to an extremely fine 
 point, coming in contact with some delicate extremi- 
 ties of nerve-fibres which branch out from the optic 
 nerve. It has been shown that each corneule is a 
 double-convex lens, made up of the junction of two 
 plano-convex lenses possessing a different refractive 
 power, by which arrangement, probably, the aberra- 
 tions are diminished, as they are by the combination of 
 "humours" in the human eye. "That each 'corneule' 
 acts as a distinct lens may be shown by detaching the 
 entire assemblage by maceration, and then drying it 
 (flattened out) upon a slip of glass ; for, when this is 
 placed under the microscope, if the point of a knife, 
 scissors, or any similar object, be interposed between 
 the mirror and the stage, the image of this point will 
 be seen, by a proper adjustment of the focus of the 
 microscope, in every one of the lenses."* 
 
 The pyramids, which consist of a transparent sub- 
 stance, representing, it is supposed, the " vitreous hu- 
 mour," are separated from each other by a layer of 
 dark pigment, which at one point closes in, but leaves 
 very minute papillary apertures for the entrance of rays 
 from the corneule, which, passing down the pyramids, 
 
 * " The Microscope," p. 662. 
 
6? THE MICROSCOPE. 
 
 impinge upon the nerve-fibres at the apex of the pyra- 
 mid. " Thus the rays which have passed through 
 the several 'corneules' are prevented from mixing 
 with each other, and no rays, save those which pass 
 in the axes of the pyramids, can reach the fibres of the 
 optic nerve. Hence it is evident that, as no two 
 ocelli on the same side have exactly the same axis, no 
 two can receive their rays from the same point of an 
 object, and thus, as each composite eye is immovably 
 fixed upon the head, the combined action of the entire 
 aggregate will probably only afford but a single image, 
 resembling that which we obtain by means of our 
 single eyes."* 
 
 In other words, this explains the reason, and 
 answers the question often asked. Why insects, which 
 have so many eyes, do not see images of the same 
 object as numerous as their eyes? I should mention 
 that, besides these composite eyes, insects possess also 
 rudimentary single eyes, like the spiders; these are 
 situated on the top of the head ; they are termed 
 stemmata, and are generally three in number. It is a 
 curious fact that the larvae of insects undergoing a 
 complete metamorphosis have these single eyes (stem- 
 mata) only; the two large composite eyes are de- 
 veloped during the latter part of the pupal life. If 
 you have gained a fair knowledge of the structure of a 
 fly's eye, you can pass on to another organ for study. 
 Let us take the proboscis, with which we are all so 
 familiar. The parts of the mouths of insects cannot 
 fail to afford you an almost boundless source of grati- 
 fication and delight, and notwithstanding their almost 
 infinite varieties, they are always composed of the 
 same essential elements. " You would not think so 
 indeed ; you would naturally suppose, looking at the 
 
 * Dr. Carpenter, " The Microscope," page 663. 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 63 
 
 biting jaws of a beetle, the piercing proboscis of a 
 bug, the long elegantly-coiled sucker of a butterfly, 
 the licking tongue of a bee, the cutting lancets of a 
 horse-fly, and the stinging tube of a gnat, that each of 
 these organs was composed on a plan of its own, and 
 that no common structure could exist in instruments 
 so diverse."* But such is the case ; underlying the 
 great varieties of form in the details there is a com- 
 mon type. In order, therefore, to get some good 
 definite idea of the typical insect mouth, you should 
 examine the parts in that of a beetle, which possesses 
 them in their most distinct form. You will notice, 
 then, in a beetle (i) an upper lip, or labrum; (2^ a 
 lower lip, or labium; (3) a pair of jaws, or mandibles, 
 which frequently are provided with strong teeth, and 
 open laterally on either side of the mouth ; (4) a pair 
 of secondary jaws, maxillce, situated beneath the 
 mandibles ; these serve to hold the food, the man- 
 dibles or biting jaws working on it, and to convey it 
 to the mouth ; (5) one or two pairs of jointed appen- 
 dages attached to the maxillae, called maxillary palpi ; 
 (6) a pair of labial palpi. The. under lip, or labium, 
 is generally composed of several parts, the basal part 
 being called the chin, or mentum a wide horny piece 
 the upper part being often much prolonged, forming 
 what has been termed the ligula. Now, it is this 
 tongue-shaped organ that we see so highly developed 
 in the common fly, blow-fly, and other relatives. The 
 plate, p. 64, represents a magnified view of the under side 
 of the fly's tongue. The broad dark part at the bottom 
 of the figure is the mentum \ b is the portion formed 
 by the metamorphosis of the maxillae, being modified 
 into a kind of sheath for the mandibles, which, in the 
 fly, assumes the form of a pair of sharp cutting lancets. 
 
 * Gosse's " Evenings at the Microscope," page 168. 
 
Proboscis of Fly. 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 65 
 
 If you have ever been bitten by a horse-fly, you will 
 have a lively appreciation of the effects of these 
 lancets piercing your skin. At c you will notice the 
 maxillary palpi. But by far the most beautiful piece 
 of mechanism in the mouth of the fly is the end of 
 the labium, which consists of two lobes forming the 
 ligula (a). It is a wide muscular membrane, which con- 
 tains a number of delicate semi-spiral tubes, through 
 which the little insect sucks up fluids. These tubes 
 remind one strongly of the trachea, those exquisite 
 little spiral vessels by means of which insects breathe, 
 only there is this difference in their construction in . 
 the tracheae the rings are a continuous spire, in the 
 ligula they are distinct, and do not, as in the tracheae, 
 surround the whole tube, but perform about two-thirds 
 of a circle. 
 
 " In the Diptera, or two-winged flies, generally, the 
 labrum, maxillae, mandibles, and the internal tongue 
 (where it exists), are converted into delicate lancet- 
 shaped organs, termed setce, which, when closed 
 together, are received into a hollow on the upper side 
 of the labium, but which are capable of being used 
 to make punctures in the skin of animals or the 
 epidermis of plants, whence the juices may be drawn 
 forth by the proboscis. Frequently, however, two or 
 more of these organs may be wanting, so that their 
 number is reduced from six to four, three, or two. In 
 die Hymenoptera (bee and wasp tribe), however, the 
 labrum and the mandibles much resemble those of 
 mandibulate insects, and are. used for corresponding 
 purposes. The maxillae, c, (see page 66), are greatly 
 elongated, and form, when closed, a tubular sheath for 
 the ligula (e), or ' tongue/ through which the honey is 
 drawn up ; the labial palpi (), which are greatly deve- 
 loped and fold together like the maxillae, so as to form 
 an inner sheath for the ' tongue,' while the ligula itselt 
 
 E 
 
66 
 
 THE MICROSCOPE. 
 
 Mouth of Bee. 
 
 (e) is a long, tapering, muscular organ, marked by an 
 immense number of short annular divisions, and 
 densely covered over its whole length with long hairs. 
 It is not tubular, as some have stated, but is solid ; 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 
 
 when actively employed in taking food, it is extended 
 to a great distance beyond the other parts of the mouth ; 
 but when at rest it is closely 
 packed up and concealed 
 between the maxillae. 
 ' The manner/ says Mr. 
 Newport, ' in which the 
 honey is obtained when 
 the organ is plunged into 
 it at the bottom of a 
 flower, is by "lapping," 
 or a constant succession 
 of short and quick exten- 
 sions and contractions of 
 the organ, which occasion 
 the fluid to accumulate 
 upon it, and to ascend 
 along its upper surface 
 until it reaches the orifice 
 of the tube formed by the 
 approximation of the 
 maxillae above, and of the 
 labial palpi and this part 
 of the ligula below/ " * 
 
 The head of the gnat 
 is a wonderful organ, and 
 is provided with numerous 
 sharp instruments, the 
 effect of which when punc- 
 turing the skin is known 
 to everybody. I ought, Head of Gnat, 
 
 however, for the credit of 
 
 the sex, to say it is the female alone that practises 
 blood-letting, the males being harmless in this respect. 
 
 * Carpenter's " Microscope," page 667. 
 
 E 2 
 
68 THE MICROSCOPE. 
 
 The hemispherical head of the gnat, with its two large 
 compound eyes, will be seen at once to be furnished with 
 a long, cylindrical proboscis (<:), a pair of antennae (<?), 
 and a pair of labial palpi (b\ This cylindrical probos- 
 cis is the homologue of the labium, or lower lip ; it is 
 covered with lined scales for a considerable portion of 
 its length, and is expanded at the tip into three pairs 
 of concave leaves. On the upper side of this pro- 
 boscis is a groove, out of which spring six long, thin 
 filaments (d\ representing the mandibles, maxillae, 
 tongue, and labium. " The labium," writes Mr. Gosse, 
 " does not enter the wound. If you have ever had 
 the philosophic patience to watch a gnat while punc- 
 turing your hand, you have observed that the knob 
 at the end of the proboscis is applied to the skin, and 
 that then the organ lends with an angle more and 
 more acute, until at length it forms a double line, 
 being folded on itself, so that the base is brought into 
 close proximity to the skin. Meanwhile the lancets 
 have all been plunged in, and are now sunk into your 
 flesh to their very bottom, while the labium, which 
 formed merely the sheath for the whole, is bent up 
 upon itself, ready again to assume its straight form as 
 soon as the disengaged lancets require its protection."* 
 The proboscis, or hausiellum, of the Lepidoptera 
 (butterfly and moth tribe) will furnish you with a large 
 stock of interesting matter for study. The long spiral 
 organ must be familiar to the most castia', observer. 
 An examination of the structure of a butterfly's mouth 
 will show us that the most important organs are here 
 represented by the maxillae, which are immensely 
 elongated. The labrum and mandibles have their 
 homologues in three small triangular plates, not easy to 
 discover ; the labial' palpi appear one on each side of 
 the spiral coil. The maxillae are united, and form a 
 * " Evenings at the Microscope," page 183. 
 
USE OF THE MICROSCOPE IN ZOOLOGY. 69 
 
 tube by the union of their grooves; the juices of the 
 flowers are sucked up by means of the proboscis, but 
 what the precise mechanical action may be is a matter 
 of doubt. On the tips of the haustella of some of 
 the Lepidoptera are small papilliform bodies, project- 
 ing at a considerable angle ; it has been conjectured 
 that they are organs of taste, but nothing is known as 
 to their functions. 
 
 In the flea, the mandibles are represented by a . 
 pair of very sharp, razor-like instruments, which are 
 situated on each side of the tongue ; the maxillae, 
 which appear in the form of a pair of elongated 
 flattened bands, serve as sheaths for the mandibles. 
 The labial palpi also, in the flea, are cutting instru- 
 ments. You must not expect to be able to make out 
 all these details without a good deal of patient care, 
 and without many failures at first ; but persevere, and 
 you will be rewarded by success in time. I would 
 recommend you to begin with the study of the struc- 
 ture of insects' mouths, by selecting some large beetle, 
 as a cockchafer. After you have killed it, cut off the 
 head, and examine the various parts with a low power 
 of the microscope. Place the head in a gutta-percha 
 trough of water, and with dissecting-needles separate 
 the component parts, viewing the insect's head first 
 on the dorsal aspect, then on the ventral ; be careful 
 to notice the relative position of the parts, and do 
 not proceed to the examination of another species 
 till you have thoroughly mastered one. You lose 
 no time by such a proceeding ; oh the contrary, you 
 are really saving time, because the knowledge acquired 
 by such thorough kind of work will so imprint itself 
 on your mind, that you will be saved much time that 
 would otherwise be lost, from repeated attempts to 
 verify some point which a careful preliminary study 
 would have settled at a glance. 
 
CHAPTER VII. 
 THE MICROSCOPE IN ZOOLOGY (continued). 
 
 EVERY part of an insect is worthy of attentive study ; 
 the head with its various appendages, the wings, legs, 
 eyes, spiracles, stings, and ovipositors, &c. &c., will 
 come under your examination. You. must often have 
 been struck with the extraordinarily rapid movements 
 of various insects through the air. You have been 
 lying awake in an early morning on your bed, and 
 have noticed the ease and grace with which the little 
 house-fly performs, in company with his companions, 
 his dancing gyrations. Now one individual darts 
 backwards with the rapidity almost of thought, and 
 another is soon seen to accomplish the same feat. 
 Her gauze-like wings, moved by the strong muscles 
 of the thorax, vibrate 600 or 800 times in a single 
 second, and even considerably more if she will it. 
 Our little fly, say Kirby and Spence, in her swiftest 
 flight will go more than the third of a mile a 
 minute. Now compare the infinite difference of the 
 size of the two animals (ten millions of the fly would 
 hardly counterpoise one racer), and how wonderful 
 will the velocity of this miniature creature appear! 
 Did the fly equal the racehorse in size, and retain its 
 present powers in the ratio of its magnitude, it would 
 traverse the globe with the rapidity of lightning. The 
 organs by means of which such wonderful results are 
 accomplished must be worthy of your patient ex- 
 amination. The wings of many insects, as bees and 
 
 " Introduction to Entomology," vol. ii., p. 362. 
 
THE MICROSCOPE. 
 
 wasps, dragon-flies, two-winged flies, are made up of 
 a double layer of membrane, with a number of veins 
 or " nervures," within which there are generally found 
 air-vessels, or tracheae. These nervures, by their 
 
 Common Fly. 
 
 subdivision and reunion, form in some cases an ex- 
 ceedingly beautiful network ; this is especially ob- 
 servable in some of the smaller Neuroptera. Besides 
 spiral vessels, or tracheae, the nervures contain a fluid 
 supplied from the body, so that both air and blood 
 circulate in them ; the membrane of the wing often pre> 
 sents an appearance of cellular areolation, as you will 
 see in the above figure of the common fly. Although 
 to the unassisted eye the membrane appears to be 
 clear, transparent, and homogeneous, under the micro- 
 scope you will see it is covered with short stiff hairs ; 
 in the fly there is a single hair in each areola, of the 
 form of a curved spine. In the wings of the Hy- 
 
THE MICROSCOPE IN ZOOLOGY, 73 
 
 menoptera as the bees, wasps, &c. there often exists 
 a beautiful apparatus for connecting together the two 
 wings on either side, so that they may present one 
 large flat surface wherewith to strike the air and not 
 overlap one another ; along the front edge of the hind 
 wing there is a row of curved hooks ; the front wing 
 near its base is doubled over so as to form a groove 
 or slit into which the hooks fasten. You will see this 
 structure readily enough in the wings of the wasp. 
 In some insects the wings are strengthened by a thick 
 layer of horny substance intervening between the two 
 membranes, as in the Coleoptera, or beetle tribe, where 
 the front wings are no longer instruments of flight, 
 but coverings for the hind wings. In the Orthoptera 
 (grasshoppers, crickets, &c.) the front wings contain 
 much horny matter, but they are not consolidated to 
 the same extent as in the beetle tribe. If you will 
 examine a fly or other two-winged insect, you will 
 notice at the base of each of the front wings two 
 small projecting organs (halteres), the rudimentary 
 representatives, it is believed, of the posterior wings. 
 What is the function of the halleres ? Dr. Braxton 
 Hicks considers they minister to the sense of smell. 
 Mr. Lowne, in his recent excellent monograph on the 
 anatomy of the blow-fly, thinks they are organs of 
 hearing. Each haltere is a little fleshy cylinder ter- 
 minating in a small knob, having a thickened base 
 clothed with fine hairs. The globular extremity is 
 hollow, according to Mr. Lownes, and contains 
 numerous round spots, which he regards as otoconia. 
 The wing of the house-cricket contains the apparatus 
 by means of which its well-known characteristic 
 sounds are produced. I have a specimen before me 
 as I write. On each of the upper wings there is a 
 large clear space of a sub-triangular form, bounded 
 on one side by a thick dark-coloured nervure with 
 
74 THE MICROSCOPE. 
 
 three or four longitudinal ridges ; the inner margin 
 of this nervure spreads out into a thin, narrow mem- 
 brane ; other nervures, much smaller than the dark 
 one, border the space which forms a drum, or tym- 
 panum. In front of the drum is clearly to be seen a 
 transverse side with numerous file-like teeth, from the 
 middle portion of which side there proceed three 
 nervures ; two are simple ; the other, which is con- 
 nected at the base to the file by three short and 
 strong processes, branches into two parts. All these 
 three nervures are strong at the base, and then become 
 attenuated ; they stretch across the tympanum till they 
 touch and become part of the narrow membrane of 
 the large dark nervure spoken of above. The insect 
 then produces the sound by rubbing the wings to- 
 gether; the files are rapidly drawn one across the 
 other, and the sound greatly intensified by the action 
 of the drum, or tympanum, I have endeavoured to 
 describe. I ought, however, to say that some ob- 
 servers believe the sound is produced by the rubbing 
 of the file across the large longitudinally -ridged 
 nervure. It would be difficult to decide the point, 
 but I can readily conceive either mode would produce 
 the well-known sound. 
 
 You will be struck with the beautiful iridescent 
 hues observable in the wings of some insects. The 
 aphides, or plant-lice those noxious pests known to 
 farmers as " smother fly/' and to the popular mind as 
 "blight" exhibit this iridescence in a remarkable 
 degree. By turning the wing you may be examining 
 to various directions, you will ascertain the angle at 
 which the iridescent hues are best seen. 
 
 The feet of insects will be sure to occupy your 
 attention, and their study to afford you delight. The 
 foot of the house-fly is a very common microscopic 
 object, and one especially interesting. It has long 
 
THE MICROSCOPE IN ZOOLOGY. 
 
 75 
 
 Plant Lice. 
 
 been a question how the fly and other insects can 
 maintain their position in an inverted attitude. The 
 foot, or tarsus, of the fly consists of five pieces, " the 
 first of which contains a pair of muscles which move 
 the second upon it, but the remaining four contain 
 none," The last joint has a pair of pads (pulvillt)^ 
 
76 THE MICROSCOPE. 
 
 and above them a pair of sharp hooks. On the. 
 interesting question alluded to above, I shall give you 
 what Mr. Lownes has lately written thereon. " The 
 foot-pads are amongst the most interesting parts of 
 the insect, because they enable it to walk upon 
 smooth surfaces in an inverted position, apparently 
 in defiance of the laws of gravity. Long ago this was 
 first ascribed, by Dr. Derham, to the exhaustion of 
 air from the foot-pads ; recently it has been supposed 
 to be due to the exhaustion of air from the extremities 
 of the hairs with which the pad is closed; others 
 have ascribed it to the hold which these minute hairs 
 take of trifling irregularities of surface; but none of 
 these explanations are correct, and one of the earliest 
 notions upon the subject is the nearest to the truth 
 that is, that the feet secrete a glutinous fluid which 
 glues them to the surface on which the insect walks. 
 When the pads are carefully examined, it will be seen 
 that they have no cup -shaped cavity beneath them, 
 but that they are hollow with a nipple-like pro- 
 tuberance projecting into each. This will be seen 
 more plainly by pressing upon the tarsus which forces 
 it into the pad ; by cutting off the end of the pad 
 first it may be exposed in this manner, and will be 
 found to consist of a closed sac. This sac fills the 
 whole of the last four tarsal joints, and is lined with 
 pavement epithelium; it secretes a perfectly clear viscid 
 fluid, which exudes from it into the pad, and fills its 
 cavity, as well as the hollow hairs with which its under 
 surface is covered. These hairs open by trumpet- 
 shaped mouths, and the disc of each mouth is kept 
 full of the fluid. Sometimes, when the insect is cap- 
 tured and held between the finger and thumb, it 
 exudes so rapidly that the pads are soon covered with 
 a little glistening drop of it, which may be collected 
 upon a glass slide, where it rapidly solidifies. It is 
 
THE MICROSCOPE IN ZOOLOGY. 
 
 77 
 
 insoluble in water, and solidifies under that fluid. 
 The whole contents of the tarsus becomes solid very 
 rapidly as soon as the insect is dead, or the part is 
 removed. 
 
 " There is no essential difference in the pads of flies 
 and the pulvilli of beetles, moths, and other insects ; 
 the same fluid is secreted in all. The 
 only difference is that the pads of flies 
 are membranous and transparent, in- 
 stead of hard and opaque. 
 
 " The feet of the smaller house-fly 
 are the best to show the manner in 
 which the viscid fluid exudes from the 
 extremities of the trumpet-shaped hairs, 
 as they are \ery large in this species, 
 and a glistening bead of fluid can be 
 seen plainly at the extremity of each 
 hair by placing the living insect under 
 the microscope. The footprints left 
 upon glass by flies consist of rows of 
 dots corresponding to these hairs ; this 
 is best seen in those of the lesser house- 
 fly from their greater size. The whole 
 appears precisely analogous to the 
 manner in which caterpillars and spiders 
 suspend themselves by silken threads. 
 In both cases the fluid is exuded from minute pores, 
 and bears the weight of the insect, the only difference 
 being in the nature and quantity of the fluid exuded. 
 Much discussion has arisen as to the manner in which 
 flies liberate their feet, and it has even been objected 
 that they would become so firmly adherent after a 
 time that the insect would be glued to the spot. 
 Nothing can be simpler than the arrangement by 
 which the foot is liberated, and in the healthy insect 
 the secretion probably never becomes solid as long as 
 
78 THE MICROSCOPE. 
 
 it remains in contact with the foot. It is sufficiently 
 glutinous, even in the fluid, or rather semi-fluid, state 
 it assumes as it exudes, to sustain the weight of the 
 insect, when the strain is put equally upon all the 
 hairs, of which there are about 1,200 on each pad; 
 but when the pad is removed obliquely, so that each 
 row is detached separately, the resistance amounts 
 practically to nothing. A neat experiment will 
 demonstrate this, even to the most sceptical. If a 
 piece of adhesive label be cut for convenience into a 
 pear-shaped disc, an inch in diameter, and caused to 
 adhere to the hand by slightly damping it, a force of 
 many pounds applied to the narrow extremity in the 
 axis of the paper- will not stir it, whilst it is imme- 
 diately removed with very little resistance, when the 
 force is applied so as to lift it gradually up., 
 
 " The direction and length of the hairs upon the pad 
 are so adapted to the oblique direction in which the 
 strain is put upon them when the tarsus is straight, 
 that the insect has a perfectly secure hold; this is 
 immediately released as soon as the tarsus is curved, 
 which is effected by the long slender tendon already 
 mentioned. In the small house-fly, the pads them- 
 selves are capable of being curved, for the tarsal tendon 
 branches, and is inserted into the distal extremity of 
 the pad."* 
 
 I will select one more insect's foot for examination, 
 and that shall be the hind-foot of the bee. I have 
 just caught a hive-bee as it was gathering pollen from 
 mignonette, a flower to which bees resort much for 
 the sake of the pollen-grains. I see on each of the 
 hind-legs a reddish-yellow globular mass of substance 
 adhering to its middle portion. After killing the bee 
 by putting it under an inverted tumbler with some 
 
 * "Anatomy of the Blow-fly ; " pp. 20 22. 
 
THE MICROSCOPE IN ZOOLOGY. 
 
 79 
 
 bruised laurel leaves (the effect of the fumes of prussic 
 acid on bees is very rapid), I 
 cut off its hind-legs, and with 
 a camel's-hair brush and water 
 wash away that pollen mass. 
 At the juncture of the femur 
 and tibia I notice a deep nick 
 or cavity, and on submitting 
 this to microscopic investiga- 
 tion, I find a number of red- 
 dish-coloured spines arranged 
 around the cavity of the femur; 
 the upper part of the tibia is 
 also hollowed out into a cavity ; 
 the remaining part of the tibia 
 contains a number of brushes 
 or hairs, by means of which the 
 pollen is taken from the flowers 
 of various plants. But how 
 does the pollen get from the 
 brushes into the pocket? It 
 is evident this cannot be done 
 from the same leg. The bee 
 rubs the pollen-grains off one 
 leg into the pocket of the other, 
 and the series of strong comb- 
 like spines render material aid 
 in their deposition there. When- 
 the bee is loaded, off she flies 
 to the hive, where the pollen 
 mass is mixed with honey, de- 
 posited in cells, forming the 
 "bee-bread" with which the 
 young bee-grubs are fed. 
 
 The stings and ovipositors of insects are very inte- 
 resting objects to study. The Hymenoptera will afford 
 
 Hind Foot of Bee. 
 
8o THE MICROSCOPE. 
 
 numerous forms of these instruments. In the bees, 
 wasps, hornets, ants, the last segment of the body is 
 provided with a sting ; the ichneumon, saw-flies, gall- 
 flies, are furnished with an ovipositor; in external 
 form there is not very much difference between an 
 ovipositor and a sting. The sting consists, in wasps, 
 bees, &c., of two very sharp dart-like organs, with 
 barbed teeth at their points ; this apparatus is enclosed 
 in a horny, elongated sheath; near the root of the 
 sting you will find a membranous bag, which contains 
 a poisonous fluid ; between the darts there is a canal, 
 down which the venom is poured into the wound 
 made by them. The ovipositors of insects differ 
 somewhat in form, but they all consist of a long tube 
 protected and covered by a cleft sheath. That curious 
 hymenopterous insect, not uncommonly met with in 
 this country, the Sir ex gigas, and generally taken for 
 some kind of hornet by the ignorant of such matters, 
 has a very strong ovipositor, by means of which the 
 insect can bore into hard timber. The Cynipidtz, or 
 gall-insects, so extremely common on various parts of 
 the oak, have a very delicate ovipositor, with a toothed 
 edge ; using this instrument as a kind of saw, the little 
 insect bores a hole in some part of the tree, and 
 deposits therein its egg. It is supposed that some 
 irritating fluid is dropped into the hole at the same 
 time as the egg, which produces what are known as 
 " galls." These serve both as shelter and food for the 
 young grubs of the gall-flies. You will be struck with 
 the beauty of the spiracles and tracheal system of in- 
 sects, the apparatus by means of which the respiration is 
 carried on. In insects the blood is oxygenated by the 
 admission of air into every part of the body, even into 
 the most minute; the air enters through the spiracles, 
 which are situated at each side of the body, and pass- 
 ing down the tracheae, which branch off into numerous 
 
THE MICROSCOPE IN ZOOLOGY. 8* 
 
 ramifications, is conveyed to every part of the system. 
 " The structure of the air-tubes," as Dr. Carpenter 
 says, " reminds us of that of the spiral vessels in 
 plants, which seem destined (in part at least) to perform 
 a similar office ; for. within the membrane that forms 
 that outer wall, an elastic fibre winds round and round, 
 so as to form a spiral closely resembling in its position 
 and functions the spiral wire-spring of flexible gas- 
 pipes ; within this again, however, there is another 
 membranous wall to the air-tubes, so that' the spire 
 winds between their inner and outer coats." There is 
 much difference in the form of the spiracles, or stigmata, 
 as they are also called ; but in most cases the opening 
 is protected by a sieve or grating formed by hairs or 
 branches of the integument; these prevent particles 
 of dust, &c., from getting into the air-vessels. Some 
 of the large caterpillars of the Sphinx-moths show the 
 stigmata very clearly even to the naked eye. 
 
 CHAPTER VIII. 
 THE MICROSCOPE IN ZOOLOGY (continued). 
 
 You will find much to admire in the examination of 
 the eggs of insects, which are often of great beauty. 
 The butterfly tribe (Lepidopterd) furnish some of the 
 most interesting forms, and those ot the garden white 
 or cabbage butterfly are too common on the leaves of 
 that vegetable. The eggs of the water-scorpion (Nepa 
 cinered) are very curious ; they are of an oval form, 
 and one end is surmounted by seven stiff reflexed hairs 
 or filaments. The eggs of the mangold-worzel fly 
 (Ant homy ia beta) have their surfaces very symmetri- 
 cally marked. In the summer of 1861 these flies 
 
 F 
 
82 
 
 THE MICROSCOPE. 
 
 were so numerous that they committed serious damage 
 on the crops in many parts of England. From the 
 eggs are produced small larvae, which at once bore a 
 hole in the leaves, and tunnel between the cuticles ; 
 
 Egg of Mangold- Worzel Fly magnified. 
 
 whole fields soon present an appearance as if the 
 leaves of the plants had suffered from some scorching 
 influence. The larvae, when full grown, drop out of 
 the leaves and turn to pupae in the earth. The eggs 
 
 of the common gnat 
 ( Ctilex pipietis} are de- 
 posited, by the aid of 
 the insect's hind-legs, 
 in a small boat-shaped 
 mass, which floats upon 
 the surface of the water. 
 They are of a longish 
 oval form with a small 
 knot at the top, and all 
 are packed closely to- 
 The larvae, whose peculiar twistings and 
 
 The Boat, Eggs, and Egg of a Gnat. 
 
 gether. 
 
 jerkings must be familiar to everybody who has ever 
 looked into a rain-tub, are very active little creatures, 
 and interesting objects for microscopic study. 
 
 The hairs and scales which beset the surface of 
 many insects will long afford you delight. The dust 
 which so readily comes off the wings of butterflies and 
 moths will be found to exhibit, under the microscope, 
 very beautiful forms. These scales are deposited in 
 regular layers upon each side of the membranous 
 
THE MICROSCOPE IN ZOOLOGY. 83 
 
 wings for if you rub the dust off the wings, you will 
 see they are membranes like the tiles on the roof of 
 a house. It is the scales that give the brilliant hues 
 to the wings; one patch being red, another green, 
 another brown or yellow. There is great variety of 
 form in the scales even of the same insect ; those on 
 the wings are generally broad, those on the legs long 
 and slender. Now examine carefully the form of a 
 
 The Gnat and her Boat of Eggs. 
 
 single scale ; you will see that each one is furnished 
 with a short pedicel or foot-stalk ; carefully wash 
 away all the dust off the wing you are examining, and 
 attend to the membrane only, You will see regular 
 rows of small sockets ; into' these sockets the foot- 
 stalks of the scales are fitted. The foot-stalks of the 
 scales vary according to the species. The little azure 
 blue butterfly (Polyommatus Alexis)^ so common in the 
 summer months, will supply you with a form of scale 
 termed "battledore scale," the footstalk of which 
 forms quite a long handle. These scales are marked 
 by longitudinal ribs, which swell into round elevations 
 
84 THE MICROSCOPE. 
 
 at intervals, each with a black point in its centre. 
 The metallic lustre of the scales of the diamond 
 beetle -of South America (Curculio imperialis) will 
 astonish you from its gorgeous magnificence. I have 
 a specimen before me as I write, but I cannot de- 
 scribe it better than in the words of Mr. Gosse. " We 
 look at it by reflected light, with a magnifying power 
 of 130 diameters. We see a black ground on which 
 are shown a profusion of what look like precious 
 stones, blazing in the most gorgeous lustre. Topazes, 
 sapphires, ametl.ysts, rubies, emeralds seem here sown 
 broadcast, and yet not wholly without regularity, for 
 there are broad bands of the deep black surface where 
 there are no gems, and, though at considerable diversity 
 of angle, they do all point, with more or less precision, 
 in one direction viz., that of the bands. These gems 
 are flat, transparent scales, very regularly oval in form, 
 for one end is rather more pointed than the other ; 
 there is no appearance of a foot-stalk, and by what 
 means they adhere I know not. They are evidently 
 attached in some manner by the smaller extremity to 
 the velvety black surface of the wing-case. The 
 gorgeous colours seem dependent in some measure on 
 the reflection of light from their polished surface, and 
 to vary according to the angle at which it is reflected. 
 Green, yellow, and orange hues predominate ; crim- 
 son, violet, and blue are rare, except upon the long 
 and narrow scales that border the suture of the wing- 
 cases, where these colours are the chief reflected."* 
 Mr. Gosse, however, thinks there is some positive 
 colour in their substance. 
 
 The scales of fish, the feathers of birds, the hairs of 
 insects, insect-larvae, and mammalia, will afford you 
 matter for contemplation and study. Scales of fish 
 
 * " Evenings at the Microscope," page 99. 
 
THE MICROSCOPE IN ZOOLOGY. 85 
 
 are developed in the substance of the true skin ; but 
 those of reptiles, the feathers of birds, the hairs, nails, 
 claws, and horns of mammalia, are developed, not 
 within, but upon the surface of the true skin. The 
 scales of fish are either ctenoid, i.e., furnished at their 
 posterior extremities with comb-like teeth, as the 
 scales of the sole ; cycloid, having scales more or less 
 round, as in the salmon, roach, herring, &c. ; ganoid 
 (from a Greek word ganos, " splendour "), having scales 
 whose substance is essentially bony, hard, and highly 
 polished (this kind has few existing representatives, 
 but numbers are found as fossils) ; or placoid, i.e., 
 having scales separately embedded in the skin, and 
 projecting from its surface in various forms. "In 
 studying the structure of the more highly developed 
 scales, we may take as an illustration that of the carp, 
 in which two very distinct layers can be made out by 
 a vertical section, with a third but incomplete layer 
 interposed between them. The outer layer is com- 
 posed of several concentric laminae of a structureless 
 transparent substance, like that of cartilage ; the outer- 
 most of these laminae is the smallest, and the size of 
 the plates increases progressively from without in- 
 wards, so that their margins appear on the surface as 
 a series of concentric lines, and their surfaces are 
 thrown into ridges and furrows which commonly have 
 a radiating direction. The inner layer is composed of 
 numerous laminae of a fibrous structure, the fibres of 
 each laminae being inclined at various angles to those 
 of the laminae above and below it. Between these 
 two layers is interposed a stratum of calcareous con- 
 cretions, resembling those of the skin of the eel; 
 these are sometimes globular or spheroidal, but more 
 commonly 'lenticula/ that is, having the form of a 
 double-convex lens."* The scales of the eel are con- 
 
 * Dr. Carpenter, page 702. 
 
86 THE MICROSCOPE. 
 
 cealed within the skin; they are oblong in shape, 
 and seem to be composed principally of round cal- 
 careous bodies, arranged in many regular concentric 
 series. The scale of the eel is a beautiful object for 
 the polariscope. 
 
 If you will pluck a hair out of your head, and hold 
 it between your forefinger and thumb, with the root of 
 the hair upwards, and then move your finger and 
 thumb up and down, you will notice the hair to 
 ascend ; now do the same with the root downwards, 
 and the hair descends. How is this ? Let us examine 
 its structure under the microscope. Under a magni- 
 fying power of about 400 diameters, you will notice 
 that the outer surface of the hair is marked by irregular 
 lines, the indications, as Dr. Carpenter remarks, of 
 the imbricated arrangement of the flattened cells or 
 scales which form the cuticle layer, for all hairs 
 essentially consist of two elementary parts, a ciiticle, or 
 investing substance, of a dense horny structure, and a 
 medullary, or pith-like substance, usually of a much 
 softer texture, occupying the interior. The cuticle 
 part consists of flattened scales arranged in an imbri- 
 cated manner ; the medullary substance is composed 
 of large spheroidal cells. In human hair the cuticle 
 layer is very thin ; the medullary portion, which is of 
 a fibrous nature, constitutes the principal part of the 
 shaft of the hair. These fibres may be separated from 
 each other if the specimen be macerated in sulphuric 
 acid for a time, and then crushed between two pieces 
 of glass. Each fibre is a long spindle-shaped cell. 
 The imbricated scales of the cuticle layer may be 
 isolated if the specimen be treated with an acid or an 
 alkali. It is in consequence of the position of these 
 imbricated scales that the upward or downward motion 
 of the hair, when moved between the finger and 
 thumb, takes place, the ed^es of the scales being 
 
THE MICROSCOPE IN ZOOLOGY. 87 
 
 arranged in the direction of the apex of the hair. The 
 colour of the hair is due to the presence of pigment- 
 granules and air-cells diffused through its substance. 
 The hairs of bats are very curious ; they have projec- 
 tions on their surface, formed by extensions of the 
 scales of the cuticle layer. The hair of a species of 
 Indian bat reminds one of the branch of an equisetum, 
 long, narrow, leaf-like scales being arranged round the 
 shaft in regular whorls. In the mole and other 
 insectivora the cells of the medulla are very distinct. 
 Amongst ruminant animals great variety occurs in the 
 structure of the hair, whilst the camel's hair exhibits 
 pretty nearly the same structure as that of the higher 
 classes. The musk-deer's hair consists almost entirely 
 of the inner medullary layer ; the cuticle layer is 
 nearly absent. Nor must we regard this structure of 
 the hair of animals merely as an interesting subject, 
 for as Mr. Gosse has well said, in his charming " Even- 
 ings at the Microscope," England's time-honoured 
 manufacture, that which affords the highest seat in 
 her most august assembly, depends on the imbricate 
 surface of hairs. "The hat on your head, the coat on 
 your back, the flannel waistcoat that shields your 
 chest, the double hose that comfort your ankles, the 
 carpet under your feet, and hundreds of other neces- 
 saries of life, are what they are because mammalian 
 hairs are covered with sheathing scales. 
 
 " It is owing to this structure that those hairs which 
 possess it in an appreciable degree are endowed with 
 the property of felting; that is, of being, especially 
 under the combined action of heat, moisture, motion, 
 and pressure, so interlaced and entangled as to be- 
 come inseparable, and of gradually forming a dense 
 and cloth-like texture. The ' body/ or substance, of 
 the best sort of men's hats is made of lamb's wool 
 and rabbit's fur, not interwoven, but simply beaten, 
 
88 THE MICROSCOPE. 
 
 pressed, and worked together between damp cloths. 
 The same property enables woven woollen tissues to 
 become close and thick ; every one knows that worsted 
 stockings shrink in their dimensions, but become much 
 thicker and firmer, after they have been worn and 
 washed a little; and the ' stout broadcloth' which has 
 been the characteristic covering of Englishmen for 
 ages, would be but a poor open flimsy texture but for 
 the intimate union of the felted wool-fibres, which 
 accrues from the various processes to which the tabric 
 has been subjected. 
 
 " In a commercial view, the excellence of the wool 
 
 Hair of Larva of Dermestes. 
 
 is tested by the closeness of its imbrication. When 
 first the wool-fibre was submitted to microscopical 
 examination, the experiment was made on a specimen 
 of merino : it presented 2,400 serratures in an inch. 
 Then a fibre of Saxon wool, finer than the former, and 
 known to possess a superior felting power, was tried : 
 there were 2,700 serratures in an inch. Next a speci- 
 men of Southdown wool, acknowledged to be inferior 
 to either of the former, was examined, and gave 2,080 
 serratures. Finally, the Leicester wool, whose felting 
 property is feebler still, yielded only 1,850 serratures 
 per inch. And this connection of good felting quality 
 with the number and sharpness of the sheathing scales 
 is found to be invariable." 
 
 The hairs of insects, caterpillars, &c., are of infinite 
 variety of form. The hairs of the larva of the bacon 
 beetle (Dermestes} are of two kinds : in one, the shaft 
 is covered with minute spinous secondary hairs closely 
 
THE MICROSCOPE IN ZOOLOGY. 89 
 
 packed together ; the spines or scales in the others are 
 placed in regular whorls, the highest of which is .com- 
 posed of knobby spines, the whole shaft being " sur- 
 mounted by a curious circle of six or seven large fila- 
 ments attached by their pointed ends to its shaft, 
 whilst at their free extremities they dilate into knobs." 
 I have no doubt that you will find much to occupy 
 your attention, and to afford you delight in the exami- 
 nation of thin sections of bone. " Bone consists of a 
 hard and soft part ; the hard is composed of carbonate, 
 phosphate, and fluate of 
 lime, and of carbonate and 
 phosphate of magnesia, de- 
 posited in a cartilaginous 
 or other matrix ; whilst the 
 soft consists of that matrix, 
 and of the periosteum which 
 invests the outer surface of 
 the bone, and of the me- 
 dullary membrane which 
 
 lines its interior or medullary cavity, and is continued 
 into the minutest pores." You can, if you like, pre- 
 pare the sections of bone for examination, or you can 
 buy specimens already ground and mounted at a small 
 cost. With a thin sharp saw you must make as thin 
 a section as possible, and this must be ground down 
 on a hone, or be rubbed between two smooth hones 
 till you get the desired tenuity. Let the specimen 
 be further polished on a piece of plate glass, in order 
 to obliterate the scratchings caused by the friction on 
 the hone. If it is a long bone you wish to examine, 
 you should make a longitudinal section ; if a flat bone, 
 the section should be made parallel to its surface. 
 You will then see it is traversed by a great number of 
 canals, called Haver sian canals, after their discoverer, 
 Havers. These canals are in connection with the 
 
9 o 
 
 THE MICROSCOPE. 
 
 central cavity, and like it are filled with marrow. By 
 examining a transverse section of a long bone you 
 will see that the small orifices of the canals are in the 
 centre of the layer forming the bone, which is arranged 
 round them in concentric rings ; between these layers 
 are small open spaces called lacuna. They are cavi- 
 ties from which the canaliculi extremely minute 
 spider-like tubules, which perforate the bony layers and 
 communicate with the central Haversian canal pro- 
 ceed. Blood-vessels, from the membrane surrounding 
 the bone termed the periosteum, are traceable intQ the 
 Haversian canals. The canaliculi are too small to 
 allow the admission of blood-corpuscles. I may here 
 mention the effect of madder, when given to- an animal 
 in its food, upon the osseous system. The bones 
 become coloured with a 
 deep red tinge. The bones 
 of a pigeon were rendered 
 red in about twenty-four 
 hours ; it took three weeks 
 to colour the bones of a 
 young pig. Both the external 
 and internal laminae of the 
 bone are found to be affected 
 by the colouring matter, 
 proving thereby that the 
 action takes place on those 
 parts which lie in contact 
 with blood-vessels. 
 
 You will be interested to 
 hear that an intimate know- 
 ledge of the structure of bone, as acquired by 
 the aid of the microscope, has proved of immense 
 value in determining the tribe of animals to which 
 bones belonged. I shall quote Dr. Carpenter's graphic 
 words : " From the average size and form of the 
 
 Section of Humerus of Turtle. 
 
THE MICROSCOPE IN ZOOLOGY. 91 
 
 lacuna, their disposition in regard to each other and 
 to the Haversian canals, and the number and course 
 of the canaliculi, the nature of even a minute fragment 
 of bone may often be determined with a considerable 
 approach to certainty, as is shown by the following 
 examples, among many which might be cited Dr. Fal- 
 coner, the distinguished investigator of the fossil re- 
 mains of the Himalayan region, and the discoverer of 
 the gigantic fossil tortoise of the Sivalik hills, having 
 met with certain small bones about which he was doubt- 
 ful, placed them in the hands of Professor Quekett 
 for minute examination; and was informed, on micro- 
 scopic evidence, that they might certainly be pronounced 
 reptilian, and probably belonged to an animal of the 
 tortoise tribe ; and this determination was fully borne 
 out by the evidence, which led Dr. Falconer to con- 
 clude they were toe-bones of his great tortoise. Some 
 fragments of bone were found some years since in a 
 chalk-pit, which were considered by Professor Owen 
 to have formed part of the wing-bones of a long- 
 winged sea-bird allied to the albatross. This deter- 
 mination, founded solely on consideration derived 
 from the very imperfectly preserved external forms of 
 these fragments, was called in question by some other 
 palaeontologists, who thought it more probable that 
 these bones belonged to a large species of the extinct 
 genus Pterodactylus, a flying lizard, whose wing was 
 extended upon a single immensely prolonged digit. 
 No species of Pterodactyle, however, at all comparable 
 to this in dimensions was at that time known ; and the 
 characters furnished by the configuration of the bones 
 not being in any degree decisive, the question would 
 have long remained unsettled, had not an appeal been 
 made to the microscopic test. This appeal was so 
 decisive by showing that the minute structure of the 
 bone in question corresponded exactly with that of 
 
92 THE MICROSCOPE. 
 
 the Pterodactyle bone, and differed essentially from 
 that of every known bird that no one who placed 
 much reliance upon that evidence could entertain the 
 slightest doubt on the matter. By Professor Owen, 
 however, the validity of that evidence was questioned, 
 and the bone was still maintained to be that ot a bird ; 
 until the question was finally set at rest, and the value 
 of the microscopic test triumphantly confirmed, by 
 the discovery of undoubted Pterodactyle bones of cor- 
 responding, and even of greater dimensions, in the 
 same and other chalk quarries."* 
 
 CHAPTER IX. 
 
 THE MICROSCOPE IN PHYSIOLOGY. 
 
 BY the aid of the microscope we become acquainted 
 with the wonderful structure of skin and other animal 
 tissues. This figure represents a section of human skin, 
 which is found to consist of two principal layers the 
 cutis vera, or true skin, and the cuticle, or epidermis, 
 which covers it. A thin vertical section of the skin 
 of the finger shows the upper layer, or cuticle, at a; the 
 lower part, or cutis vera, at b; sweat-glands, e, with 
 their ducts, at c, leading to the orifices ; the small 
 granular clusters at / are fat-cells ; the dull-coloured, 
 wavy portion at b is the rete mucosum, or stratum 
 Malpighii. Mingled with the cells which make up 
 the epidermic covering are found others, which, from 
 their secreting colouring matter, are called pigment- 
 cells. An extraordinary number of blood-vessels, 
 twisting so as to form a complete network of capillaries 
 and numerous nerves, are distributed through the cutis 
 
 * Dr. Carpenter, page 764. 
 
THE MICROSCOPE IN PHYSIOLOGY. 
 
 93 
 
 rera, and you know it is impossible to prick any part 
 of your finger with the fine point of a needle without 
 piercing some of these capillaries and drawing blood. 
 The cuticle, or outer covering, is destitute of blood- 
 vessels and nerves ; it consists of a series of layers of 
 
 .a 
 
 cells " that are continually wearing off at their outer 
 surface, and renewed at the surface of the true skin, 
 so that the newest and deeper layers gradually become 
 the oldest and most superficial, and are at last thrown 
 off by desquamation. In their progress from the 
 internal to the external surface of the epidermis, the 
 cells undergo a series of well-marked changes. When 
 
94 THE MICROSCOPE. 
 
 we examine the innermost layer, we mid it soft and 
 granular, consisting of germinal corpuscles in various 
 stages of development into cells, held together by a 
 tenacious semi-fluid substance. This was formerly 
 considered as a distinct tissue, and was supposed to 
 be the peculiar seat of the colour of the skin ; it 
 received the designation of Malpighian layer, or rete 
 mucosum. Passing outwards, we find the cells more 
 completely formed ; at first nearly spherical in shape, 
 but becoming polygonal where they are flattened one 
 against the other. As we proceed further towards the 
 surface, we perceive that the cells are gradually more 
 and more flattened until they become mere horny 
 scales, their cavity being obliterated; their origin is 
 indicated, however, by the nucleus in the centre of 
 each. This change in form is accompanied by a 
 change in the chemical composition of the tissue, 
 which seems to be due to the metamorphosis of the 
 contents of the cells into a horny substance identical 
 with that of which hair, horn, nails, hoofs, &c., are 
 composed."* You will notice, on reference to the 
 figure, that the lower stratum of the epidermis i.e., 
 the Malpighian layer is regularly hollowed out into 
 small depressions, into which the upper surface of the 
 cutis vera rises in the form of little ridges, or papilla, 
 from which nerves and blood-vessels arise. The colour- 
 ing matter contained in the " pigment-cells " is most 
 abundant in the Malpighian layer ; they are generally 
 polygonal in form, and contain a number of extremely 
 minute roundish black granules. I have before me a 
 small portion of the dark-coloured vascular membrane 
 of the eye of a sheep, called the choroid, and see the 
 numerous cells of the layers of pigment very plainly. 
 In dark-coloured races the pigment cells of the skin 
 
 * Carpenter on the Microscope, p. 718. 
 
THE MICROSCOPE IN PHYSIOLOGY. 95 
 
 are black ; in white races they are pink. It is clear 
 that these pigment cells are confined to the cuticle 
 and Malpighian stratum alone ; for the cutis vera of 
 a negro is as pink as that of the fairer races, so that 
 the colour is not even " skin deep/' The subject of 
 epidermic pigment-cells has always appeared to me to 
 be full of deep and curious interest. How are these 
 pigment-cells affected ? Why are they black in the 
 negro, olive in the Mongolian, copper-coloured in the 
 North American, pink in the Saxon ? Why are they 
 altogether absent in the Malpighian layer of albinoes ? 
 The sun would appear to have the power of darkening 
 the pigment-cells, for the exposed parts of a negro 
 are blacker than those which are unexposed. The 
 Jews, moreover, who settled centuries ago in India, 
 "have become as dark as the Hindoos around them." 
 But even in the same individual these epidermic pig- 
 ment-cells are subject to change. " Can the Ethiopian 
 change his skin ? " asks the Hebrew prophet. Cases 
 of such change of colour have occasionally occurred. 
 " One case is that of a negro slave in Kentucky, aged 
 forty-five, who was born of black parents, and was 
 himself perfectly black until twelve years of age. At 
 that time a portion of the skin, an inch wide, encircling 
 the cranium, just within the edge of the hair, gradually 
 changed to white, also the hair occupying that locality. 
 A white spot next appeared near the inner canthus of 
 the left eye ; and from this the white colour gradually 
 extended over the face, trunk, and extremities, until 
 it covered the entire surface. The complete change 
 from black to white occupied about ten years ; and 
 but for the hair, which was crisped or woolly, no one 
 would have supposed at this time that his progenitors 
 had offered any of the characteristics of the negro, 
 his skin presenting the healthy vascular appearance of 
 that of a fair-complexioned European. When he was 
 
g6 THE MICROSCOPE. 
 
 about twenty-two years of age, however, dark copper- 
 coloured or brown spots began to appear on the face 
 and hands, but these have remained limited to the 
 portions of the surface exposed to light. About the 
 time that the black colour of the skin began to dis- 
 appear, he completely lost his sense of smell ; and 
 since he has become white, he has had measles and 
 hooping-cough a second time." This occurred in 
 1852. A case of partial disappearance of the black 
 colour of the negro's skin was brought by Dr. Inman 
 before the Zoological section of the British Association 
 at Liverpool in 1854.* 
 
 You notice the perspiratory glands and ducts figured 
 in the engraving at c and g. By means of these organs 
 a transpiration of fluid holding excrementitious matters 
 in solution takes place. -The glands consist of a 
 number of long convoluted tubes, at first dividing into 
 two branches, and then re-uniting into a single tube or 
 duct opening at the surface of the epidermis. The 
 number of these perspiratory pores is enormous. 
 " To arrive at something like an estimate of the value 
 of the perspiratory system," says Mr. Erasmus Wilson, 
 " I counted the perspiratory pores on the palm of the 
 hand, and found 3,528 in a square inch. Now each 
 of these pores being the aperture of a little tube of 
 about a quarter of an inch long, it follows that, in a 
 square inch of skin on the palm of the hand there 
 exists a length of tube equal to 882 inches or 7 3! feet. 
 The number of glands in other parts of the body is 
 sometimes greater, sometimes less than this ; 2,800 
 may be taken as the average number of pores in each 
 square inch throughout the body. Now the number 
 of square inches of surface in a man of ordinary 
 stature is about 2,500 ; the total number of pores, 
 
 * Carpenter's " Principles of Human Physiology," p. 851, note. 
 Sixth Edition. 
 
THE MICROSCOPE IN PHYSIOLOGY. 97 
 
 therefore, may be about seven millions, and the length 
 of the perspiratory tubing would thus be 1,570,000 
 inches, or nearly 28 miles. " 
 
 I have in a previous chapter called your attention 
 to the circulation oi the blood in various animals ; the 
 blood itself is an interesting subject for study. Blood 
 consists, in a great measure, of numerous floating cells, 
 called corpuscles. These are of two kinds, the red and 
 the white. The former are always in the shape of a 
 flattened disc, but they differ in size and configuration: 
 In man and in most of the mammalia they are circular; 
 in the camel tribe, however, they are oval, as they are in 
 birds, reptiles, and fishes. In the blood of oviparous 
 vertebrata, the blood-corpuscles have a dark central 
 spot, or nucleus, composed apparently of a mass of 
 small granules. If a drop of acetic acid be added 
 to the blood-discs under examination, this will be 
 distinctly seen, the opacity of the nucleus being 
 increased. The average size of human corpuscles 
 nas been estimated at about -g-gVo f an mcn m dia- 
 meter. " The smallest red corpuscles known," says 
 Dr. Carpenter, " are those of the musk-deer, whilst the 
 largest are those of that curious grcup of batrachian, 
 (frog-like) reptiles which retain their gills through the 
 whole of life ; and one of the oval blood-discs of the 
 Proteus, being more than thirty times as long and 
 seventeen times as broad. as those of the musk-deer, 
 would cover no fewer than 500 of them. According 
 to the recent estimate of Vierordt, a cubic inch of 
 human blood contains upwards of -eighty millions of 
 red corpuscles, and near a quarter of a million of the 
 white." 
 
 A small drop of blood should be placed on a glass 
 slide, and carefully protected by a thin glass cover, 
 taking care to exclude air-bubbles ; the red corpuscles 
 will be seen, many adhering together like rolls of 
 
98 THE MICROSCOPE. 
 
 coins ; by gently moving the glass together you will 
 cause them to separate and to roll over. The blood- 
 discs of mammals are entirely destitute of the granular 
 nucleus spoken of above. The discs of the blood- 
 corpuscles of the mammalia are double-concave in 
 form, and the dark spot in the centre is merely an 
 effect of refraction, for by adding a little water to 
 them, they gradually become flat and then double- 
 convex, the dark spot disappearing. They can be 
 made to assume the concave form again by treating 
 them with fluids of greater density than their own 
 contents. 
 
 The white corpuscles are much fewer in number 
 than the red, usually not more than as i to 350 ; they 
 are for the most part globular in form, though subject 
 to much variation. 
 
 In a medico-legal point of view, it is obvious that a 
 knowledge of the shape and relative sizes of the red 
 corpuscles might be of great use. Suppose, for instance, 
 that a man was brought before the magistrates on a 
 charge of murder ; certain marks of blood are found 
 upon his clothes. He insists, it may be, that they are 
 blood-stains of some bird, say a pheasant. The 
 microscope shows the form of the corpuscles to be 
 circular ; clearly, then, the stains in question are not 
 those of any bird, which has oval corpuscles. Intimate 
 acquaintance with the forms of the blood-discs of 
 many animals would decide the animal from which 
 they came. 
 
 The microscope has been much used in the exami- 
 nation of articles of food and medicine, and has re- 
 vealed the existence of a great deal ot fraudulent 
 practices on the part of unscrupulous tradesmen, who 
 are in the habit of adulterating different productions. 
 " The happy application of the microscope," says Dr. 
 Hassall (" Adulterations Detected in Food and Medi- 
 
THE MICROSCOPE IN PHYSIOLOGY. 99 
 
 cine "), " to the subject of adulteration, has furnished 
 the means of detecting a host of adulterations, the 
 discovery of which had before, for the most part, 
 been considered to be impossible." By means of the 
 microscope, the various forms of cellular and other 
 tissue, starch granules, woody fibres, spiral vessels, &c. 
 &c.,are revealed; as the various substances have their 
 distinctive characteristic forms, a mixture of one or 
 more substances with what is sold as a pure and 
 unadulterated substance, becomes evident. The fol 
 lowing remarks of Dr. Hassall, one of our highest 
 authorities on food adulteration, will be read with 
 interest : 
 
 "When we survey with our unaided vision any 
 animal or plant, we detect a variety of evidences of 
 organisation or structure ; but there is in every part 
 of every animal or vegetable production an extra- 
 ordinary amount of organisation wholly invisible to 
 the unarmed sight, and which is revealed only to the 
 powers of the microscope. Now this minute and 
 microscopical organisation is different in different parts 
 of the same animal or plant, and different in different 
 animals and plants, so that by means of these 
 differences, rightly understood, the experienced micro- 
 scopical observer is enabled to identify in many cases 
 infinitely minute portions of animal or vegetable tissues, 
 and to refer them to the parts or species to which they 
 belong. 
 
 " Thus by means ot the microscope, one kind of 
 root, stem, or leaf may generally be distinguished from 
 another ; one kind of starch or flour from another ; one 
 seed from another, and so on. In this way, the micro- 
 scope becomes an invaluable and indispensable aid 
 in the discovery of adulteration. 
 
 " Applying the microscope to food, it appears that 
 there is scarcely a vegetable article of consumption, 
 
 G 2 
 
100 THE MICROSCOPE. 
 
 not a liquid, which may not be distinguished by means 
 of that instrument. Further, that all those adultera- 
 tions of these articles which consist in the addition 
 of other vegetable substances, and which constitute by 
 far the majority of adulterations practised, may like- 
 wise be discovered and discriminated by the same 
 means. 
 
 "The same remarks apply to all the vegetable 
 drugs, whether roots, barks, seeds, or leaves. We are 
 not acquainted with one such drug which may not be 
 thus distinguished. 
 
 "The seeds even belonging to different species of the 
 same genus may frequently be distinguished from each 
 other by the microscope a point in some cases of very 
 great importance. A remarkable instance of this has 
 fallen under our observation. The seeds of the dif- 
 ferent species of mustard, rape, &c., may all be distin- 
 guished under the microscope by differences in their 
 organisation. To show the importance of the dis- 
 crimination in some cases, the following instance may 
 be cited. Some cattle were fed with rape-cake, and 
 died with symptoms of inflammation of the stomach 
 and bowels. Nothing of a poisonous nature could 
 be detected on analysis ; but it was suspected that the 
 cake might be adulterated with mustard-husk, al- 
 though even this point could not be clearly established 
 by chemical research. Under these circumstances 
 the cake was sent to the author for examination, who 
 had but little difficulty in ascertaining that it was 
 adulterated with mustard-seed, which, from the large 
 quantity consumed, was doubtless the cause of the 
 fatal inflammation. Not only can the seeds of dif- 
 ferent plants of the same genus be frequently discrimi- 
 nated by the microscope, but in some cases those 
 belonging even to mere varieties of species. T ne 
 microscope in some cases can even inform us of the 
 
THE MICROSCOPE IN PHYSIOLOGY. IOI 
 
 piocesses or agents to which certain vegetable sub- 
 stances have been subjected. Illustrations of this are 
 afforded by the starches of wheat and barley ; it can be 
 determined by the microscope whether these are raw, 
 baked or boiled, or whether malted or unmalted."* 
 
 Cocoa adulterated with Potato Starch. 
 
 This figure shows a sample of cocoa adulterated with 
 potato-flower ; at a you will notice the starch-granules, 
 cells, and spiral vessels of cocoa ; at b you will see 
 the large characteristic granules of potato-starch. 
 
 Milk is a substance very frequently adulterated. 
 " If the testimony of ordinary observers, and even of 
 many scientific writers, is to be credited, there are few 
 
 * "Adulterations Detected in Food and Medicine," pp. 44, 45. 
 
102 
 
 THE MICROSCOPE. 
 
 articles of food more liable to adulteration and this 
 of the grossest description than milk." In a sample 
 of good milk shown below you will observe myriads 
 of beautifully-formed globules of fatty matter, of 
 various size, and reflecting the light strongly. Some- 
 
 Milk, showing fat-globules (a) and pus corpuscles (b). 
 
 times the milk is rendered unwholesome from the 
 presence of a number of pus corpuscles, as in the 
 figure ; where the fat-globules are few, the milk is 
 poor or deficient in cream, representing the state 
 known popularly known as " skim milk." 
 
 " The most prevalent and important adulteration of 
 
THE MICROSCOPE IN PHYSIOLOGY. 103 
 
 milk is that with water. Now, some few persons who 
 have not reflected closely upon the matter, may be 
 disposed to make light of the adulteration of milk with 
 water, and to speak in rather facetious terms of the 
 cow with the iron tail ; but it is surely no light matter 
 to rob an important article of daily consumption, like 
 milk, of a large portion of its nutritious constituents. 
 But the adulteration with water is not the only adul- 
 teration to which milk is liable ; the large addition of 
 water frequently made to it so alters its appearance as 
 to cause it to assume the sky-blue colour so familiar to 
 us in our school-boy days, and so reduces its flavour 
 that it becomes necessary to have recourse to other 
 adulterating ingredients namely, treacle, to sweeten it, 
 salt, to bring out the flavour, and annatto, to colour it. 
 Further, there is no question but that chalk, cerebral 
 matter , and starch have been, and are occasionally, 
 though rarely, employed in the adulteration of milk. 
 With regard to the use of chalk, a manufacturer of pre- 
 served milk recently informed us that it sometimes 
 happened to him to find carbonate of lime or chalk at 
 the bottom of the evaporating dishes or pans on the 
 evaporation of large quantities ot London milk." 
 
 These remarks will be sufficient to show you the 
 use of the microscope in the detection of adulteration 
 in food. Dr. Hassall's book will supply you with 
 abundance of information on the subject, should your 
 microscopic predilections point that way. 
 
 It is very curious to see the formation of crystals 
 taking place under the microscope. If you evaporate 
 a solution ot common salt on a glass slide, and allow 
 it to cool, and then cover it with a bit of thin glass, 
 you will see some beautitul cubes of chloride of sodium. 
 In the same simple way you may obtain crystals of 
 several salts for examination. On the other side are 
 represented forms of the crystals of ammonio-phosphate 
 
104 
 
 THE MICROSCOPE. 
 
 of magnesia, the prismatic form* of which are extremely 
 beautiful when viewed with the polariscope (a). The 
 other forms depicted are those of oxalate of lime, 
 which, it will be seen, assume various shapes (b). When 
 
 occurring in the cells of plants these crystals are fre- 
 quently deposited in a needle-shaped form (raphides), 
 or they may be rectangular or rhombic prisms with 
 pyramidal ends, often forming groups radiating from 
 a centre. The formation of the crystals of silver is a 
 beautiful thing to see. Place a solution of nitrate of 
 
THE MICROSCOPE IN GEOLOGY. 105 
 
 silver on a glass slide, drop a few copper filings upon 
 it ; a brilliant arborescent form of crystallisation takes 
 place, growing rapidly as you look at it. This is an 
 interesting case of affinity. The nitric acid imme- 
 diately combines with the copper, and the silver 
 appears in the metallic state. 
 
 CHAPTER X. 
 
 THE MICROSCOPE IN GEOLOGY. 
 
 THE geological student will gather a vast amount of 
 information by means of the microscope. He will be 
 able to determine the nature of the minute animal and 
 vegetable remains that are found in various strata ot 
 the earth's crust, as well as the composition of many 
 of the strata themselves. Huge mountains have been 
 shown, by the aid of the microscope, to be composed 
 of countless millions of minute organisms, such as 
 Diatomacecz, Foraminifera, &c. " Startling and almost 
 incredible as the assertion may appear to some," as 
 Mr. Hogg truly observes, " it is none the less a fact 
 established beyond all question by the aid of the 
 microscope, that some of our most gigantic mountain 
 ranges, such as the mighty Andes, towering into space 
 25,250 feet above the. level of the sea, their base occu- 
 pying so vast an area of land, as also our massive 
 limestone rocks, the sand that covers our boundless 
 deserts, and the soil of many of our wide extended 
 plains, are principally composed of portions of in- 
 visible animalcules. And, as Dr. Buckland truly 
 observes, ' The remains of such minute animals have 
 added much more to the mass of materials which com- 
 pose the exterior crust of the globe than the bones of 
 elephants, hippopotami, and whales/ " In some cases 
 
io6 
 
 THE MICROSCOPE. 
 
 these remains consist for the most part of the siliceous 
 shells of the Diatomaceae, at one time supposed to be 
 of animal origin, but now of undoubted vegetable 
 nature ; in other cases, enormous deposits are found 
 to consist principally of the shells of the Foraminifera, 
 minute animals of low organisation. Chalk hills are 
 
 Forms of Diatomaceae. 
 
 formed almost entirely of the remains of these little 
 creatures, whose shells are often of most exquisite 
 forms. Ehrenberg has computed that a cubic inch 
 of chalk may contain the remains of a million 
 of these creatures. "The Paris basin, 180 miles 
 long and averaging 90 in breadth, abounds in in- 
 fusoria and other siliceous remains. Ehrenberg, on 
 examining the immense deposit of mud at the har- 
 bour of Wismar, Mecklenburg-Schwerin, found one- 
 
THE MICROSCOPE IN GEOLOGY. IOJ 
 
 tenth to consist of the shells of infusoria, giving a 
 mass of animal remains amounting to 22,885 cubic 
 feet in bulk, and weighing forty tons, as the quantity 
 annually deposited there. How vast, how utterly in- 
 comprehensible, then, must be the number of once 
 living beings, whose remains have in the lapse of time 
 accumulated." Richmond, in Virginia, is built upon 
 a stratum, the so-called " infusorial earth," which is 
 eighteen feet thick, and extends over a wide area ; 
 this is found to consist principally of the siliceous 
 shells of Diatomaceae. 
 
 The mountain meal (bergh-mehl) of Norway, Lap- 
 land, Saxony, sometimes forming a stratum nearly 
 thirty feet thick, is similarly composed. Most of these 
 deposits consist of marine forms of Diatomaceae, but 
 in our own islands, as at Dolgelly in North Wales, 
 Mourne Mountain in Ireland, Mull in Scotland, depo- 
 sits of fresh-water origin have apparently been formed. 
 In the Foraminifera the skeleton usually consists of a 
 many-chambered calcareous shell investing a jelly-like 
 body ; many of these are perforated with numerous 
 little apertures. In the Polycystina, an allied group of 
 the same rhizopod type of animal life, the investing 
 shell is perforated with very large apertures, and it is 
 siliceous ; " the apertures are often so large and nu- 
 merous that the solid portion of the shell forms little 
 more than a network, thus indicating a transition to 
 the succeeding group, the Porifera, or sponges. The 
 Polycystina possess wonderful beauty, and are capital 
 objects for the binocular microscope ; its stereoscopic 
 perfection, as Dr. Carpenter remarks, causing them 
 to be presented to the mind's eye in complete relief, 
 so as to bring out, with the most marvellous and 
 beautiful effect, all their delicate sculpture. 
 
 The Polycystina are probably as widely diffused 
 as the Foraminifera ; they have been brought up by 
 
I08- THE MICROSCOPE. 
 
 the sounding-lead from the bottom of the Atlantic, at 
 depths of from 1,000 to 2,000 fathoms. We are told 
 that they were probably more abundant during the 
 later geological periods, having been detected by Pro- 
 fessor Ehrenberg in the chalks and marls of Sicily and 
 Greece, and of Oran, in Africa, and also in the 
 diatomaceous deposits of Bermuda, and Richmond 
 (Virginia). 
 
 " It is an admitted rule in geological science, that the 
 past history of the earth is to be interpreted, so far as 
 may be found possible, by the study of the changes 
 which are still going on. Thus when we meet with 
 an extensive stratum of fossilised Diatom acese in what 
 is now dry land, we can entertain no doubt that this 
 siliceous deposit originally accumulated either at the 
 bottom of a fresh-water lake, or beneath the waters of 
 ' the ocean ; just as such deposits are formed at the pre- 
 sent time by the production and death of successive 
 generations of these bodies, whose indestructible casings 
 accumulate in the lapse of ages, so as to form layers 
 whose thickness is only limited by the time during which 
 this process has been in action. In like manner, when 
 we meet with a limestone rock entirely composed of 
 the calcareous shells of Foraminifera, some of them 
 entire, others broken up into minute particles, we 
 interpret the phenomenon by the fact that the dredg- 
 ings obtained from some parts of the ocean-bottom 
 consist almost entirely of existing Foraminifera, in 
 which entire shells, the animals of which may be yet 
 alive, are mingled with the debris of others that have 
 been reduced by the action of the waves to a frag- 
 mentary state. Now in the fine white mud which is 
 brought up from almost every part of the sea-bottom 
 of the Levant, where it forms a stratum that is con- 
 tinually undergoing a slow but steady increase in 
 thickness, the microscopic researches of Professor 
 
THE MICROSCOPE IN GEOLOGY. 1 09 
 
 Williamson have shown that not only are there multi- 
 tudes of minute remains of living organisms, both 
 animal and vegetable, but that it is entirely, or almost 
 wholly, composed of such remains. Amongst these 
 were about twenty-six species of Diatomaceae (sili- 
 ceous), eight species of Foraminifera (calcareous), and 
 a miscellaneous group of objects, consisting of calca- 
 reous and siliceous spicules of sponges and Gorgoniae, 
 and ot fragments of the calcareous skeletons of echi- 
 noderms and mollusks. The deep-sea soundings which 
 have recently been obtained from various parts of the 
 ocean-bed afford results more or less similar; the variety 
 of form, however, usually showing a diminution as the 
 depth increases. From an extensive comparison of 
 the forms of recent Foraminifera brought up from dit- 
 ferent depths, Messrs. Parker and Rupert Jones con- 
 sider themselves able to predicate the range of depth 
 within which any particular collection may have been 
 taken ; and thus to determine, in the case of deposits 
 of fossil Foraminifera, within what range of depth they 
 were probably formed."* 
 
 Very interesting results have attended the various 
 deep-sea expeditions that have taken place the last 
 few years in different parts of the Atlantic. It has 
 been estimated that nearly two hundredweight of the 
 sea-bottom, revealing, contrary to preconceived notions, 
 a submarine life at a depth of more than 2,000 fathoms, 
 has been dredged up and examined. One of the 
 most curious questions relates to the deposits in the 
 deep water of the Atlantic, and their connection with 
 the Cretaceous period of geologists. For very many 
 years the origin of chalk has been a point of discus- 
 sion. If you will rub a bit of whiting in a drop ot" 
 water on a glass side, cover with thin glass, and use a 
 
 * Carpenter on the Microscope, p. 755. 
 
HO THE MICROSCOPE. 
 
 power of 400 or 500 diameters, you will notice a great 
 quantity of rounded flattened bodies. Ehrenberg, I 
 believe, was the first person to observe and describe 
 these little particles. Formerly these bodies were sup- 
 posed to be mineral concretions of particles derived 
 from organic bodies. They were called crystalloids, 
 and are thus described in the " Micrographic Dic- 
 tionary," under the word chalk: "The cementing 
 material of chalk consists of very minute, numerous, 
 and remarkable bodies, called crystalloids; they are 
 elliptical, or rounded and flattened, from TOO^O to 
 a-gVo in length, the most numerous perhaps -^Q-Q. 
 Some of them consist of a simple ring ; in others it is 
 marked with pretty regular transverse lines, so as to 
 make it appear jointed; in others, again, there is a 
 thinner central portion, often exhibiting one or more 
 granules. M. Ehrenberg regards these as arising from 
 the disintegration of the microscopic organism forming 
 the chalk into much more minute calcareous particles, 
 and their reunion into regular elliptical plates (or 
 discs) by a peculiar process, differing essentially from 
 and coarser than that of crystallisation, but com- 
 parable with it ; one probably preceding all slow crys- 
 talline formation, and causing, but not alone, the 
 granular state of solid inorganic matter." Recent 
 investigations, however, afforded by the mud, or ooze, 
 obtained from the deep sea, have been supposed by 
 some to confirm the opinion, first, I believe, made 
 public by the Rev. J. B. Reade, that these so-called 
 crystalloids are organic. They are now known by 
 the name of coccoliths and coccospheres, and have 
 been found abundantly in the sticky mud of the 
 Atlantic sea-bed. These bodies, be they animal or 
 vegetable, are of extreme low organisation, and are 
 not confined to deep water, for Dr. Wallich has ob- 
 tained them off the coast of Plymouth at about seven- 
 
THE MICROSCOPE IN GEOLOGY. I J I 
 
 teen fathoms. Whatever be their nature, whether 
 organic or not, it is certain that these bodies abound 
 in extraordinary numbers in chalk and in the ooze at 
 the bottom of the Atlantic, and seem to indicate a 
 similar origin and an essential identity of the chalk 
 with modern deep-sea mud. But besides these cocco- 
 liths and coccospheres so called, chalk contains other 
 bodies round in form, having many chambers in 
 communion with each other, of microscopic size and 
 beautiful construction. These calcareous bodies are 
 of various forms. Professor Huxley very aptly com- 
 pares one of the commonest to a badly-grown rasp- 
 berry, being formed of a number of nearly globular 
 chambers of different sizes congregated together. These 
 bodies have hence been called Globigerincz, and some 
 specimens of chalk consist of little else than Globi- 
 gerinae and the granular bodies already mentioned. 
 What a subject for contemplation have we here ! 
 Immense chalk cliffs extending for hundreds of miles, 
 the vast fabric the work of minute creatures invisible 
 to the naked eye ! In England this chalk formation 
 extends diagonally from Lulworth, in Dorset, to Flam- 
 borough Head, in Yorkshire, a distance of over 280 
 miles "as the crow flies. In some places it is more 
 than a thousand feet thick. Nevertheless, as Pro- 
 fessor Huxley says, "it covers but an insignificant 
 portion of the whole area occupied by the chalk forma- 
 tion of the globe ;" for if all the points at which true 
 chalk occurs were circumscribed, they would lie within 
 an irregular oval about 3,000 miles in long diameter, 
 the area of which would be as great as that of Europe, 
 and would many times exceed that of the largest exist- 
 ing inland sea the Mediterranean ; and all this wide- 
 spread component of the earth's surface consists for 
 the most part of the skeletons or calcareous shells of 
 Globigerinae ! But recent investigations have shown 
 
112 THE MICROSCOPE. 
 
 that the chalk-forming process is even now going 
 on at the bottom of the North Atlantic Ocean 
 over an immense area, and this is brought about for 
 the most part by the same agencies as built up the 
 hills and deposits of the Cretaceous period. This 
 deep-sea mud is substantially chalk, and covers an 
 area of about 1,700 miles from east to west. " It is a 
 prodigious plain one of the widest and most even 
 plains in the world. If the sea were drained off, you 
 might drive a wagon all the way from Valentia, on the 
 west coast of Ireland, to Trinity Bay, in Newfound- 
 land. And except upon one sharp incline about 200 
 miles from Valentia, I am not quite sure that it would 
 be necessary to put the skid on, so gentle are the 
 ascents and descents upon that long route. From 
 Valentia the road would lie down-hill for about 200 
 miles to the point at which the bottom is now covered 
 by 1,700 fathoms of sea-water. Then would come 
 the central plain, more than a thousand miles wide, 
 the inequalities of the surface of which would be 
 hardly perceptible, though the depth of water upon it 
 now varies from 10,000 to 15,000 feet; and there are 
 places in which Mont Blanc might be sunk without 
 showing its peak above the water. Beyond this, the 
 ascent on the American side commences, and gradually 
 leads, for about 300 miles, to the Newfoundland shore. 
 " Almost the whole of the bottom of this central plain 
 (which extends for many hundred miles in a north and 
 south direction) is covered by a fine mud, which, when 
 brought to the surface, dries into a greyish-white friable 
 substance. You can write with this on a blackboard 
 if you are so inclined, and to the eye it is quite like 
 very soft, greyish chalk. Examined chemically, it 
 proves to be composed almost wholly of carbonate of 
 lime ; and if you make a section of it, and view it with 
 the microscope, it presents innumerable Globigerinae 
 
THE MICROSCOPE IN GEOLOGY. 113 
 
 embedded in a granular matrix."* These calcareous 
 shells, which belong to the Foraminiferous group, con- 
 tain living inhabitants ; at least, those which lie on the 
 surface layer of the ooze do, whilst deeper layers are 
 chiefly made up of the empty shells of Globigerinae. 
 The animal is "a mere particle of living jelly, without 
 defined parts of any kind, without a mouth, nerves, 
 muscles, or distinct organs, and only manifesting its 
 vitality to ordinary observation by thrusting out and 
 retracting, from all parts of its surface, long filamentous 
 processes which serve for arms and legs. Yet this 
 amorphous particle, devoid of everything which in the 
 higher animals we call organs, is capable of feeding, 
 growing, and multiplying ; of separating from the ocean 
 the small proportion of carbonate of lime which is 
 dissolved in sea-water ; and of building up that sub- 
 stance into a skeleton for itself, according to a pattern 
 which can be imitated by no other known agency." 
 And here I must guard you against Dr. Carpenter's 
 opinion, that the deposit of Globigerina-mud " has 
 been going on over some part or other of the North 
 Atlantic sea-bed from the Cretaceous epoch to the pre- 
 sent time as there is much reason to think that it did 
 elsewhere in anterior geological periods this mud 
 being not merely a chalk formation, but a continuation 
 of the chalk formation, so that we may be said to be 
 still living in the Cretaceous period" an idea which, 
 to use Sir Charles Lyell's words, is as inadmissible in a 
 geographical as a geological sense. You are doubt- 
 less familiar with those flinty nodules so extremely 
 abundant in the chalk formation ; you are certainly 
 familiar with that common, but very interesting article, 
 a sponge. What connection has the framework of the 
 softest of animals with one of the hardest of stones ? 
 The microscope reveals the fact that flint contains 
 
 * Huxley's " Lay Sermons," &c. " On a Piece of Chalk." 
 
 H 
 
114 T HE MICROSCOPE. 
 
 the remains of sponges, for it is not uncommon to 
 find the external forms and markings characteristic 
 of their organisms preserved, whilst thin sections of 
 flint show a spongeous texture in the interior. Fora- 
 miniferal shells, and bodies termed Xanthidia^ with 
 their long spinous projections (the sporangia of Des- 
 midiaceae), are often found embedded in flint. The 
 siliceous spicules of sponges are also found in jaspers 
 and agates. The pretty little round concretions of the 
 Oolitic formation, so conspicuous in Bath stone, have 
 been formed concentrically round a nucleus which is 
 often a foraminiferal shell. The green sands which 
 occur in various deposits from the Silurian to the 
 Tertiary period, and which, when occurring beneath 
 the chalk, are known as the Greensand formation, 
 have been shown by the microscope to consist of the 
 siliceous casts, coloured by silicate of iron, of fora- 
 miniferal shells, or those of minute Mollusca. I must 
 not forget to mention the discovery in late years, by 
 Dr. Carpenter, of the nature of the serpentine limestone 
 in the Laurentian formations of Canada. This deposit 
 consists of a regular series of stratified rocks, and 
 underlies the equivalents, not merely of the Silurian, 
 but also of the Upper and Lower Cambrian systems 
 of this country. We are told that these rocks spread 
 over an area of 200,000 square miles, and that they 
 are composed of a species of foraminiferal shell called 
 Eozoon Canadense. "The geological position of this 
 fossil, indicating the vast remoteness in time of its exist- 
 ence as a living organism, is scarcely more remarkable 
 than its zoological relations ; for at what (so far as we 
 at present know) was the dawn of animal life upon 
 our globe, it affords evidence of a most extraordinary 
 development of that rhizopod type of animal life, 
 which now presents itself only in forms of compara- 
 tive insignificance, a development which enabled it to 
 separate carbonate of lime from the ocean-waters, in 
 
THE MICROSCOPE IN GEOLOGY. 11$ 
 
 quantity sufficient to produce masses rivalling in bulk 
 and solidity those of the stony corals ot later epochs, 
 and thus to turnish (as there seems good reason to 
 believe) the materials of those calcareous strata, ot 
 whose occurrence in the Laurentian series it had pre- 
 viously been impossible to give a satisfactory account."* 
 Wonderful, truly, it is to reflect that such enormous 
 results are brought about by the operations of an 
 animal of such extreme simplicity. These rhizopods 
 seem to have performed in the seas ot the Laurentian 
 epoch the same part in the production of limestone 
 rocks which was subsequently taken by coral polypes, 
 echinoderms, and mollusks, as well as by minuter 
 forms of Foraminifera ; " and it is a fact not without 
 an important significance/' Dr. Carpenter also remarks, 
 " that this the lowest type of animal life known to the 
 physiologist, should have thus culminated in the very 
 earliest period in the history of the life of our gldfoe 
 with which the palaeontologist is at present acquainted. 
 . , . . . The physiologist has here a case in which 
 those vital operations which he is accustomed to see 
 carried on by an elaborate apparatus, are performed 
 without any special instruments whatever a little 
 particle of apparently homogeneous jelly, changing 
 itself into a greater variety of forms than the fabled 
 Proteus, laying hold of its food without members, 
 swallowing it without a mouth, digesting it ^ without a 
 stomach, appropriating its nutritious material without 
 absorbent vessels or a circulating system, moving its 
 parts without muscles, feeling (if it has any power to 
 do so) without nerves, propagating itself without a 
 genital apparatus, and forming a shelly covering that 
 possesses a symmetry and complexity not surpassed by 
 those of any testaceous animals. "t 
 
 * Dr. Carpenter in Intellectual Observer, vii. 278. 
 ^ Introduction to the Study of the Foraminifera. Ray Society, 
 p. vii. 
 
 R 2 
 
CHAPTER XI. 
 
 THE MICROSCOPE IN GEOLOGY (continued). 
 
 IT has long been suspected that the extremely useful 
 substance called coal is nothing else than a con- 
 solidated mass of decomposed vegetable matter ; it 
 is not, indeed, uncommon to find certain markings or 
 indications of a vegetable origin in a lump of coal, 
 and the microscope has enabled us to determine the 
 nature of that vegetation by revealing its structure. 
 It shows us that the coal vegetation was in a great 
 measure coniferous in its nature, "that it probably 
 approximated most nearly to that group of existing 
 Coniferae to which the Araucaria belong." It is one 
 characteristic of coniferous wood to exhibit a number 
 of glandular dots on the woody fibres ; now these 
 glandular dots are often to be seen in sections of coal. 
 Owing to the extreme friability of coal, its examination 
 is attended with some difficulty, for it is no easy 
 .matter to reduce slices to the necessary degree of 
 tenuity. The following mode of examining the 
 structure of coal is taken from the " Micrographic 
 Dictionary:" "The coal is macerated for about a 
 week in a solution of carbonate of potash ; at the end 
 of that time it is possible to cut tolerably thin slices 
 with a razor. These slices are then placed in a watch- 
 glass with strong nitric acid, covered, and gently 
 heated ; they soon turn brownish, then yellow, when 
 the process must be arrested by dipping the whole 
 into a saucer of cold water, or else the coal would 
 be dissolved. The slices thus treated appear of a 
 darkish amber colour, very transparent, and exhibit 
 the structure when existing most clearly. The speci- 
 
THE MICROSCOPE IN GEOLOGY. 117 
 
 mens are best preserved in glycerine, in cells ; we find 
 that spirits render them opaque, and even Canada 
 balsam has the same effect." 
 
 Mr. David Forbes, in a very interesting paper 
 "The Microscope in Geology" in the Popular Science 
 Review for October, 1867, has shown how much may 
 be learnt of the mineral composition of rocks by a 
 careful and patient use of the microscope. Previous 
 to Mr. David Forbes' application of the microscope 
 to determine the composition of rocks, very little 
 appears to have been done, with the exception of Mr. 
 Sorby's memoirs on such special points of inquiry. 
 Mr. David Forbes' collection of sections of rocks and 
 their constituent minerals were, for the most part, 
 made by himself; it amounted, in 1867, to upwards of 
 2,000, and represents a wide geographical distribution. 
 " As long as the geologist encounters in the field any 
 rocks of so coarse or simple a structure as to admit 
 of their being resolved by the naked eye into their 
 constituent mineral species, or of distinguishing the 
 fragments of previously existing rocks, of which they 
 may have been built up, he may speculate with a fair 
 chance of success as to their probable origin or mode 
 of formation. When, however, as is often more the 
 rule than the exception, rocks are everywhere met 
 with presenting so fine-grained and apparently homo- 
 geneous a texture as to defy such attempts at ocular 
 analysis, all speculations as to their nature and for- 
 mation, based merely upon observation in the field, 
 can but be compared to groping in the dark, with the 
 faint hope of stumbling upon the truth. 
 
 " In these cases the geologist must call in the aid of 
 chemistry and the microscope ; by chemical analysis 
 he learns the per-centage composition of the rock in 
 question, and the microscopic examination informs 
 him how the chemical elements are mineralogically 
 
Il8 THE MICROSCOPE. 
 
 combined, and at the same time affords valuable in- 
 formation as to the physical structure and arrangement 
 of the components of the rock mass, tending to 
 elucidate its formation and origin." Let me select 
 one or two instances out of several given by Mr. 
 D. Forbes. You are, perhaps, acquainted with the 
 mineral termed Obsidian, or Volcanic glass, which is 
 produced by the fusion of felspathic rocks or those 
 which contain alkaline silicates. The glassy appear- 
 ance testifying to an apparently complete vitreous 
 condition would, at first sight, defy all attempts to 
 discover the structure ; nevertheless, some part of the 
 mass will be found to be sufficiently devitrified to 
 allow of its structure and mineral composition being 
 recognised, and Mr. D. Forbes has figured a very 
 pretty section of obsidian in which the pyroscenic and 
 felspathic constituents of the rock are very clearly 
 apparent. Rocks, according to their structure, fall 
 naturally into one or other of two great classes (i) 
 Primary, or Eruptive; and (2) Secondary, or Sedi- 
 mentary. Now, in some cases it is impossible to 
 determine by mere ocular inspection to which of 
 these classes a certain rock may belong. Microscopic 
 examination shows that whatever be the geological 
 age of these primary rocks, or from whatever part of 
 the earth's surface they may be taken, they " possess 
 certain general and definite structural characters dis- 
 tinguishing them at once from all other rocks." 
 
 There occurs, either found embedded in or breaking 
 through the coal-measures of Staffordshire, a rock 
 popularly termed " White Horse," from often having 
 the appearance of a whitish clay ; the coal-measures 
 at points of contact with the rock are frequently burnt 
 and altered. " The origin of this rock, whether sedi- 
 mentary or igneous, was disputed until the more 
 recent geological and chemical examinations of it 
 
THE MICROSCOPE IN GEOLOGY. 1 1 9 
 
 have proved satisfactorily its identity with the Rowley 
 basaltic rock." In external appearance, the mineral 
 uralite resembles augite, but its chemical composition 
 is that of hornblende ; the microscope distinctly re- 
 veals the fibrous structure characteristic of the horn- 
 blende. 
 
 Some years ago, you may remember, a geological 
 heresy was maintained by some, that granite had not, 
 after all that had been said, an igneous origin. Let 
 us see what part the microscope played in determin- 
 ing the question. Mr. Sorby discovered in the quartz 
 of granites numerous minute fluid cavities, thus show- 
 ing that granites have solidified at a heat far below 
 the fusing points of their constituent minerals, and at 
 such a pressure as to enable it to entangle and retain 
 a small amount of aqueous vapour, which naturally 
 must have been present during its liquefaction. 
 " The presence of these fluid cavities in the quartz of 
 granite was immediately blazoned forth as proof posi- 
 tive of the non-igneous origin of granite ; whereas, if 
 Mr. Sorby' s memoir had actually been read, it would 
 have been seen that he had found fluid cavities per- 
 fectly identical with those of granite, not only in the 
 quartz of volcanic rocks, but also in the felspar and 
 nepheline ejected from the crater of Vesuvius; and 
 that the presence of fluid, vapour, gas, and stone cavK 
 ties are common both to the volcanic quartz-trachytes 
 and to the oldest granites ; and the inference drawn 
 by Mr. Sorby from the results of his researches, is 
 that both these rocks were formed by identical agen- 
 cies." As with regard to- the volcanic, so with the 
 sedimentary rocks ; a microscopic examination alone 
 will afford correct information as to their origin; but I 
 must refer you to Mr. David Forbes' most interesting - 
 memoir for further details. Mr. D. Forbes gives 
 the following instructions how to prepare rock sec- 
 
120 THE MICROSCOPE. 
 
 tions : "A fragment, from one quarter to three- 
 quarters of an inch square, and of convenient thick- 
 ness, is chipped off the rock specimen in the direc- 
 tion of the required section, and ground down upon 
 an iron or pewter plate in a lapidary's lathe, with 
 emery, until a perfectly flat surface is obtained. This 
 surface is then worked down still finer by hand on a 
 slab of black marble, with less coarse emery; then 
 upon a Water of Ayr stone, with water alone, and lastly 
 finished by hand with water on a slab of black marble. 
 By these means the surface acquires a sufficient 
 polish, without being contaminated with rouge or 
 other polishing-powder or oil, as is sometimes the case 
 with purchased sections of rocks. This side of the 
 rock is now cemented by Canada balsam on to a small 
 piece of plate glass,, about i| in. square, and fin. 
 thick, which serves as a handle when grinding the 
 other side on the emery plate as before. This grind- 
 ing is continued until the section is so thin as to be 
 in danger of breaking up from the roughness of the 
 motion, upon which it is completed, by further grind- 
 ing with emery by hand on marble, and finished first 
 upon Water of Ayr stone with water, and afterwards 
 upon black marble, as before described. The section 
 is now removed from the plate glass, and mounted in 
 Canada balsam on a slide, covering its upper surface 
 with a thin glass as usual/' 
 
 By the aid of the microscope the geological investi- 
 gator is able to ascertain the nature, and even to con- 
 struct the entire form of an animal long ago extinct, 
 by the examination of minute parts that have been 
 preserved in the tomb of the earth. Fossil corals, 
 fragments of the shells or spines of Echinodermata, 
 and of such molluscous shells as present distinct ap- 
 pearances of structure, may be identified by its 
 means. A knowledge of the structure of teeth, 
 
THE MICROSCOPE IN GEOLOGY. 121 
 
 bones, the dermal skeleton of vertebrate animals, will 
 enable the microscopist to name the animal to which 
 the parts belonged. You are, of course, aware that 
 the different strata are more or less characterised by 
 the organic remains which they contain. In some 
 cases the strata may be so similar in composition, that 
 it is impossible to determine its position on the geo- 
 logical chart in the absence of organic remains. Many 
 thousand pounds would have been saved to the 
 pockets of certain land proprietors had they con- 
 sulted the geologist or microscopist before they sank 
 shafts for coal in beds which could not possibly con- 
 tain any. Extending over many parts of Russia, there 
 occurs a certain rock formation, whose mineral cha- 
 racters might justify its being likened either to the 
 Old or New Red Sandstone of this country, and whose 
 position relatively to other strata is such, that there is 
 great difficulty in obtaining evidence from the usual 
 sources as to its place in the series. The nature of 
 this formation could be determined by the organic 
 remains which it might yield, but in this case they 
 were few and fragmentary, and consisted chiefly of 
 teeth which were seldom found entire. It was at first 
 supposed from the great size of these teeth, that they 
 belonged to Saurian reptiles ; hence the formation 
 must have been considered New Red. External form 
 may be deceptive ; so recourse was had to a micro- 
 scopic section of the tooth, the result of which was to 
 show that it belonged to an undoubted fish, called, 
 from the dendritic disposition of the tissues, by the 
 name of Dendrodus. This decided the all-important 
 point, for as the genus Dendrodus is exclusively 
 Palaeozoic, the rock in question belonged not to the 
 New, but to the Old Red formation ; therefore there 
 would be no possibility of finding coal in it. 
 
 You will be interested in another similar case. The 
 
122 THE MICROSCOPE. 
 
 identity of the Keuper Sandstein of Wirtemburg, with 
 the New Red Sandstone of Warwickshire, has been 
 satisfactorily demonstrated by means of the micro- 
 scope. Some years ago, Professor Jaeger found in 
 the German Keuper formation some remarkable fossil 
 teeth, which were of great size, conical or canine in 
 form, and distinctly striated. In 1840 Professor 
 Owen found similar teeth in the New Red Sandstone 
 of Coton End quarry, Warwickshire. What was the 
 nature of the animal to which these teeth belonged ? 
 From external characters it had at first been inferred 
 that the teeth were those of some Saurian reptile ; but 
 the results of a microscopic examination of the teeth, 
 both from the German Keuper and the New Red Sand- 
 stone of Warwickshire, revealed a very remarkable 
 and complicated structure; hence, provisionally, the 
 creature to which the teeth were supposed to belong 
 was named Labyrinthodon, by Professor Owen ; but 
 this peculiar internal structure of the tooth a structure 
 formed by "the convergence of numerous inflected 
 folds of the external layer of cement towards the 
 pulp cavity" is typically presented also in the teeth 
 of fish-lizards and lizard-like fish ; hence it might be 
 reasonably inferred that the labyrinthodon would 
 combine with its reptilian characters an affinity with 
 fish. The subsequent discovery of some of the bones 
 of the labyrinthodon, as the vertebrae, jaws, hume- 
 rus, femur, and toes, &c., have gone far to establish 
 this inference ; and there is much reason to believe 
 that that strange creature, the labyrinthodon, was a 
 gigantic frog-like animal five or six feet long, with a 
 mixture of fish and crocodilian characters, and that in 
 all probability it was identical with the animal whose 
 footprints have been discovered in the quarries of the 
 grey quartzose and red sandstone of Saxony, and in 
 the sandstone quarries of Stourton, in Cheshire. 
 
CHAPTER XII. 
 
 THE COLLECTION AND MOUNTING OF OBJECTS TEST- 
 FLUIDS. 
 
 THERE is little need that I should say much on the 
 collection of objects you may wish to examine ; a 
 little experience will prove the best instructor. If 
 you wish to collect Desmidiacese and Diatomaceae, 
 you should take with you two or three wide-mouthed 
 bottles with corks, a tin scoop, a sharp hook for cut- 
 ting off stems of aquatic plants, which are often covered 
 with minute vegetable organisms (these two last should 
 be made to screw on to a long light bamboo rod), 
 and a lens. The Desmidiacese occur in slow-running 
 rivers, pools, ditches, especially those on boggy moors. 
 They often form a greenish cloud on the stems and 
 leaves of water-plants, or on the ground. They may 
 be taken up from the ground by the scoop, or from 
 the stems of plants by your fingers. If placed in 
 bottles and exposed to the light, these vegetable forms 
 will grow, and you may employ your time advan- 
 tageously in studying the development. Diatomaceae 
 are also found in profusion on the stems and leaves 
 of aquatic plants, presenting themselves as coloured 
 fringes, or forming a covering to stones or rocks in 
 cushion-like tufts, or spread over their surface as 
 delicate velvet, or depositing themselves as a filmy 
 stratum on the mud, or intermixed with the scum of 
 living or decayed vegetation on the surface of the 
 water. They are often mixed with sand and mud; 
 and the best way to get rid of these impurities is to 
 place the lot in a saucer of water, and expose it to the 
 light, when the diatoms may be skimmed from the 
 surface. Various beautiful forms occur upon sea* 
 
124 THE MICROSCOPE. 
 
 weeds, and on the mud at the bottom of the sea. 
 You may also procure numerous forms from the 
 stomach of various sea-creatures, such as oysters, 
 sea-cucumbers, sea-squirts, soles, and other flat-fish. 
 It is a distinctive character of this group to have 
 encircling their various forms an external coat of silex, 
 which would appear to be almost indestructible. We 
 have seen how an accumulation of them give rise to 
 deposits of considerable thickness ; and guano, it is 
 well known, contains many forms, some of extreme 
 beauty. If you wish to collect Diatomacese from 
 guano, you should wash a portion several times in 
 water, and stir it well ; then let it rest for some hours, 
 so as to give the lighter forms time to sink; then 
 pour off the water, and if necessary give the sediment 
 another washing. You must now use strong acids; 
 the deposit is to be placed in a test-tube with hydro- 
 chloric acid, and gently heated. After the sediment 
 has subsided, pour off the acid, and heat it with a 
 fresh dose ; pour off again, and heat with nitric acid 
 two or three times, and apply heat for three or 
 four hours of about 200; then wash the sediment 
 till the acid is removed. "The separation of siliceous 
 sand, and the subdivision of the entire aggregate of 
 diatoms into the larger and the finer kinds, may be 
 accomplished by stirring the sediment in a tall jar of 
 water, and then, while it is still in motion, pouring oft 
 the supernatant fluid as soon as the coarser particles 
 have subsided ; this fluid should be set aside, and as 
 soon as a finer sediment has subsided, it should again 
 be poured off; and this process may be repeated 
 three or four times at increasing intervals, until no 
 further sediment subsides after the lapse of half an 
 hour. The first sediment will probably contain all 
 the sandy particles, with perhaps some of the largest 
 diatoms, which may be picked out from among them ; 
 
TEST- FLUIDS. 125 
 
 and the subsequent sediments will consist almost ex- 
 clusively of diatoms, the sizes of which will be so 
 graduated that the earliest sediments may be ex- 
 amined with the low powers, the next with the medium 
 powers, while the latest will require the higher powers 
 a separation which is attended with great conve- 
 nience/'* small portions of the sediment should then 
 be mounted in Canada balsam, or set up dry between 
 two pieces of thin glass. For mounting microscopic 
 objects you will require a pair of fine-pointed forceps 
 for holding the objects to be mounted, a pair of stout 
 needles fixed in handles, a spring dipt for holding 
 down the covers whilst the balsam is cooling, and a 
 small spirit-lamp. 
 
 Canada balsam a natural combination of resin 
 with the essential oil of turpentine may be procured 
 from any druggist It is thick and viscid, but becomes 
 softer on the application of heat ; you must be careful 
 to keep it very clean and to exclude the air, which 
 would render it too thick for immediate use. To 
 mount in Canada balsam, place a drop on the glass 
 slide by means of a glass rod, then apply gentle heat, 
 immerse the object in it, and if there are no air- 
 bubbles, place the glass cover on, apply the spring 
 clip, and set aside for the balsam to harden. You will, 
 however, have need to exercise much patience ; for 
 no sooner is the object placed in the balsam than all 
 at once many air-bubbles make their unwelcome ap- 
 pearance ; you must, therefore, boil the balsam over 
 the spirit-lamp, if the texture of your object will allow 
 you to do so, and the heat will probably drive out the 
 intruding bubbles. It is advisable to prepare some 
 objects before mounting in Canada balsam by soak- 
 ing in oil of turpentine for some minutes. Insect 
 
 * Carpenter, page 315. 
 
 Sold by Messrs. Baker, Mr. Collins, and others. 
 
126 THE MICROSCOPE. 
 
 structures, Foraminifera, &c., may be thus treated; 
 the oil of turpentine entering into the cavities or 
 tissues, excludes the air. 
 
 Spirit and distilled water form an excellent medium 
 for preserving animal tissu'es; one part of alcohol, 
 60 over proof, to five parts of distilled water, will 
 t>e found of sufficient strength for preserving many 
 substances. Methylated alcohol, which pays no duty, 
 answers very well, and it may be obtained at the 
 price of five shillings and sixpence per gallon. A drop 
 of this dilute alcohol is to be placed, by means of a 
 glass rod, on the glass slide, the tissue is to be sunk 
 into it, and covered with thin glass ; care must be 
 taken to exclude air-bubbles, the superfluous fluid 
 drained off, and the edge of the glass cover and ad- 
 jacent portion of the slide wiped quite dry. A ring 
 of cement gold size may be especially recommended 
 is to be laid round the edge of the thin glass, so as 
 to fix the cover on the slide. After this coating has 
 hardened, apply a second and a third. 
 
 A solution ot glycerine with camphor-water is another 
 valuable fluid for preserving structures. Price's gly- 
 cerine is superior to any other for microscopic pur- 
 poses. The proportion of glycerine and camphor- 
 water will depend on the nature of the object to be 
 mounted ; for general purposes, one part of glycerine 
 to two parts of camphor-water will be found useful. 
 There are various other preservative fluids and cements 
 which are very useful in microscopic work, but those 
 I have named will be sufficient for most practical 
 purposes. 
 
 Test-liquids are of immense use to the microscopist ; 
 they are employed to remove certain substances which 
 he wishes to get rid of, or to detect the presence of 
 particular substances in the object under examination. 
 For instance, suppose I wish to obtain the animal 
 
TEST-FLUIDS. 127 
 
 basis of a bone or shell, I must dissolve the calcareous 
 portions by means of a mixture of hydrochloric and 
 nitric acid ; if I wish to get rid of the organic matter 
 in sponges, so as to obtain the mineral portion in a 
 separate state, I can do so by boiling the objects in 
 a solution of caustic potash; if it is desirable to 
 harden animal tissues, this can be done by maceration 
 in strong alcohol, or in a solution of chromic acid, 
 "so dilute as to be of a pale straw colour, which 
 is particularly efficacious in bringing into view the 
 finer ramification of nerves." If, on the other hand, 
 I wish to detect the presence of some particular sub- 
 stance in the object I am examining say of starch 
 granules I apply a solution of iodine in water (i gr. 
 of iodine, 3 grs. of iodide of potassium, i oz. of 
 distilled water), and the starch is turned blue; if 
 albuminous substance is present, the test gives it an 
 intense brown. Acid nitrate of mercury colours 
 albuminous substances red. A solution of caustic 
 potash or soda, by means of its solvent power, is ex- 
 tremely useful in rendering animal and vegetable 
 structures transparent. If you wish to clean any glass 
 slides or covers, and to get rid of the Canada balsam 
 or cement, you can readily do by means of spirits 
 of turpentine. 
 
 I shall conclude this very imperfect sketch of some 
 of the marvels of the microscope by quoting some 
 very valuable words of advice of an eminent micro- 
 scopist, Dr. Lionel S. Beale, F.R.S. : 
 
 " No one engaged in the pursuit of any branch of 
 natural science is more tempted to be led into too 
 hasty generalisation than the microscopic observer. 
 It is his duty, therefore, to avoid drawing inferences 
 until he has accumulated a vast number of facts to 
 support the conclusions at which he has arrived. True 
 generalisations and correct inferences promote the 
 
128 THE MICROSCOPE. 
 
 rapid advancement of scientific knowledge, for each 
 new inference may form the starting-point of a fresh 
 line of investigation ; but, on the other hand, every 
 false statement, regarded as an observed fact, forms 
 a terrible barrier to onward progress, since, before 
 the slightest useful advance can be made, it is neces- 
 sary to retrace our steps, it may be for a long way, 
 before we can hope to recommence our onward course. 
 Again, a much greater amount of evidence is always 
 required to overthrow a false conclusion than is 
 sufficient to propagate the original mistake, and 
 there can be no task more unsatisfactory than that 
 of being called upon to controvert the opinions and 
 deductions. of others. Years must be passed in patient 
 investigation before a man can expect to be able to 
 trust himself as an observer of facts, and it is only by 
 careful and unremitting exercise that he will gradually 
 acquire habits of attentive observation and the power 
 of thoughtful discrimination, which can alone render 
 his conclusions reliable. Indeed, though he labour 
 hard and earnestly, he will scarcely have properly 
 educated himself ere his powers begin to decay, and 
 he become liable to err from the natural deterioration 
 in structure of the organs upon which the observation 
 of his facts entirely depends." 
 
 * "How to Work with the Microscope," Fourth Edition, pp. 
 i33, 189. 
 
INDEX. 
 
 ^Ethalium septicum . 
 Algse ...... 
 
 Anacharis alsinastrum 
 Anchusa paniculata . 
 Animalcules 
 
 PAGE 
 
 39 
 
 35 
 
 . 22 
 . 22 
 40 
 
 Anthomyia betae, Eggs of 81 
 Apparatus for Microscope 13 
 
 Bats, Hairs of .... 87 
 Bell-flower Animalcules . 42 
 Blood, Circulation of . . 56 
 Bone, Structure of . . . 89 
 Butterfly, Eggs of . . 8 1, 83 
 
 Cactus, Raphides in . . 22 
 
 Camera Lucida .... 1 1 
 Canada Balsam . . .125 
 
 Carchesium .... 43 
 
 Cells, Vegetable ... 17 
 
 Chalk 109 
 
 Chara nitella .... 22 
 
 Cilia ....... 41 
 
 Circulation in Plants . . 22 
 
 Coal 116 
 
 Collecting Apparatus . . 123 
 
 Condensing Lens ... 1 1 
 
 Corpuscles of Blood . . 97 
 
 Cricket, Drum and File of 73 
 
 Crystals 104 
 
 Cutis vera 92 
 
 Cynipidse 80 
 
 Deep-sea Soundings . . 109 
 
 Dendrodus 121 
 
 Dermestes, Hairs of . . 88 
 
 Desmidiaceae .... 35 
 
 PAGE 
 
 Deutzia, Hairs of . . . 26 
 Diatomaceae . . .35, 105 
 Difference between Animal 
 and Plant .... 38 
 
 Eel, Scales of .... 86 
 
 Eggs of Insects .... 82 
 
 Eozoon Canadense . . 14 
 
 Epipactis 31 
 
 Epistylis 43 
 
 Equisetum, Spores of . 34 
 
 Eyes of Insects ... 60 
 
 Fat-cells in Human Skin. 92 
 Ferns, Spores of ... 33 
 
 Flea 69 
 
 Floscularia 48 
 
 Fly, Foot of .... 74 
 Food, Adulterations in . 98 
 Foot of Frog, Circulation 
 
 of Blood in ... 58 
 Foraminifera . . . .109 
 Fossil Diatomaceae . .105 
 
 Fucus 32 
 
 Fungus 33 
 
 Glass Covers .... 13 
 Globigerinae . . . .ill 
 Gnat, Head of .... 67 
 Grew, Researches of . . 6 
 
 Hairs, Structure of , . 86, 87 
 Halteres, Functions of . 73 
 Hind-foot of Bee ... 79 
 Hydra ..... 49 
 
 Hymenoptera, Stings of . 80 
 I 
 
130 
 
 INDEX. 
 
 p 
 Illumination of Objects . 
 
 AGE 
 
 II 
 
 40 
 
 122 
 
 12 
 122 
 6 
 
 6 
 25 
 
 45 
 
 8 
 14 
 
 117 
 
 39 
 
 "5 
 
 62 
 
 95 
 
 81 
 
 10 
 
 123 
 
 121 
 
 40 
 30 
 
 93 
 94 
 
 12 
 
 28 
 107 
 
 39 
 
 p 
 Quekett on Artificial Pro- 
 duction of Raphldes . 
 
 AGE 
 
 23 
 22 
 
 122 
 
 44 
 
 85 
 83 
 84 
 27 
 80 
 93 
 24 
 80 
 
 "3 
 
 4i 
 48 
 
 79 
 24 
 
 56- 
 54 
 
 iS 
 
 121 
 
 80 
 
 22 
 
 22 
 36 
 
 43 
 
 44 
 
 72 
 
 114 
 18 
 
 Keuper Sandstein . . . 
 
 Lamps for Microscope 
 Labyrinthodon .... 
 Leuwenhoek .... 
 
 Malpighi, Researches of . 
 Marchantia 
 
 Red Sandstone, New, of 
 Warwickshire . . . 
 
 Scales of Fish .... 
 
 : Butterflies . . 
 - Dj^uiond Beetle 
 
 Sections of Stems, &c. . 
 Sirex gigas 
 Skin, Structure of . . . 
 Spiral Vessels .... 
 Spiracles 
 Sponges in Flint . 
 Stentors 
 
 Melicerta 
 Microscope, Simple . . 
 
 
 Mineral Composition of 
 
 
 Stephanoceros .... 
 
 Mounting Objects . . . 
 Mouths of Insects . . . 
 
 Negro, Change from Black 
 to White in .... 
 Nepa, Eggs of .... 
 
 Object-glasses .... 
 Objects, Collecting of . 
 Old Red Sandstone . . 
 
 
 Tadpole, Circulation in . 
 
 Tenacity of 
 
 
 Test Fluids 
 Tooth of Dendrodns . . 
 
 Tradescantia .... 
 
 Vallisneria spiralis . . 
 Volvox globator . . . 
 
 Ovules of Pollen-grains . 
 
 Perspiratory Glands and 
 Ducts .... 
 
 Wheel Animalcules . . 
 Wings of Insects . . . 
 
 Xanthidia in Flint . . . 
 Yeast Fungus .... 
 
 Pigment- cells . . . 
 Polarising Apparatus . 
 Pollen-grains . . . 
 Polycistina .... 
 Protoplasm .... 
 
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 Monthly Parts at 6<t. 
 
 Notable Shipwrecks. Being Tales of Disaster and 
 Heroism at Sea. By UNCLE HARDY. 320 pp., crown Svo. With 
 Frontispiece. Second Edition. Cloth, 53. 
 
 Soldier and Patriot. The Story of George Washington. 
 By F. M. OWEN. Illustrated. 256 pp., crown Svo, cloth, 35. 6d. 
 
 Half-Hours with Early Explorers. By T. FROST. 
 
 Containing Narratives of the Adventures and Discoveries of the Early 
 Explorers. Profusely Illustrated. 240 pp., fcap. 410, cloth, 55. 
 
 Stories about Animals. By the Rev. T. JACKSON, 
 
 M. A. A Familiar Description of the Life and Habits of the different 
 varieties of the Animal World. Profusely Illustrated. 256 pp., extra 
 fcap. 410, cloth, 55. 
 
 Stories about Birds. By M. and E. KIRBY, Authors 
 
 of " Chapters on Trees," &c. &c. An Interesting Account of the Life 
 and Habits of the various descriptions of the Feathered Tribes. 
 Profusely Illustrated. 256 pp., extra fcap. 410, cloth, 55. 
 
 The Old Fairy Tales. A Choice Collection of Favourite 
 
 Fairy Tales. Edited by JAMES MASON- With 24 full-page and 
 numerous other Illustrations. Super-royal i6mo, cloth, 25. 6d. 
 
 Pictures of Sohool Life and Boyhood. Being 
 
 Selections from the Best Authors, Edited by PERCY FITZGERALD, 
 M.A., F.S.A. Crown Svo, 256 pp. and Frontispiece, cloth gilt, 33. 6d. 
 
 Great Lessons from Little Things. By JOHN TAYLOR. 
 
 A Series of Practical Lessons on Bible Natural History. Full of 
 Illustrations. 176 pp., extra fcap. 410, cloth gilt, 35. 6d. 
 
 Patsy's First Glimpse of Heaven. By the Author 
 
 of " Scraps of Knowledge." Illustrated, is. 
 
 The History of a Book. By ANNIE CARRY. Illustrated 
 
 throughout. Extra fcap 4to, cloth, 35. 6d. 
 
 Peeps Abroad for Folks at Home. By CLARA 
 
 MATEAUX. Profusely Illustrated. Fcap. 4to, cloth. 55. 
 
 Home Chat with Our Young Folks. By CLARA 
 
 MATEAUX. Fifik Edition. With Two Hundred Engravings. Fcap. 
 4to, cloth lettered, 260 pages, 55. 
 
 Sunday Chats. By CLARA MATEAUX. Profusely Il- 
 lustrated. Second Edition. Fcap. 4to, cloth gilt, 55. 
 Leslie's Songs for Little Folks. With Twelve Pieces 
 
 of Music by HEMRY LESLIE, and Frontispiece by H. C. SELOUS. 
 Illustrated. Secc nd Edition. Cloth gilt, 35. 6d. 
 
 Cassell, Fetter 6 Galpin : London, Paris 6 New York. 
 
THE "LITTLE GEMS" SERIES. 
 
 Cloth, 6d. ; or cloth gilt, gilt edges, is. each. 
 
 Shall weKnow One Another? 
 
 By the Rev. Canon RYLE, M.A. 
 
 Twenty-fifth Thousand. 
 Home Religion. By the late 
 
 Rev. W. B. MACKENZIE, M.A. 
 
 Sixteenth Thousand. 
 The Grounded Staff. By the 
 
 Rev. ROBERT MAGUIRE, M.A. 
 
 Second Edition. 
 
 Words of Help for Every- 
 day Life. By the Rev. W. M. 
 
 STATHAM. Third Edition. 
 
 The Voice of Time. By J. 
 
 STROUD. Twenty-fourth Thou- 
 sand. 
 Pre- Calvary Martyrs, and 
 
 other Papers. By the late Rev. J. 
 
 B. OWEN, M.A. Second Edition. 
 All Men's Place. With other 
 
 Selections from the Sermons of 
 
 GEORGE WHITEFIELD. 
 God's New World. With other 
 
 Selections from the Sermons of 
 
 JOHN WESLEY. 
 
 TALES ON THE PARABLES. 
 
 By ISA CRAIG-KNOX. Consisting of Stories of Modern Life, illustrative of 
 * the Truths taught in the Parables of the New Testament ; each being 
 
 i_i_ : ;.__ir ;__ /SJ i. . 
 
 complete in itself, price 6d. each : 
 
 Seed-time and Harvest. 
 Cumber er of the Q-round. 
 The G-ood Samaritan. 
 Lost Silver. 
 The Pearl. 
 
 Yes or No. 
 
 The Covetous Man. 
 
 Leaven. 
 
 The Debtors. 
 
 Old Garments. 
 
 . The Series can be also had in Two Volumes, cloth gilt, is. 6d. each. 
 
 THE "GOLDEN CROWNS" SERIES. 
 
 Being -a-^eries of Short Tales for Sunday Reading. By Rev. COMPTON 
 READ?, M.A., Chaplain of Magdalen College, and some time Vicar of 
 Cassington, Oxon. Illustrated with Frontispiece in each book, and 
 bound in cloth, each book being complete in itself. Price 6d. each- 
 
 1. The Maiden's Crown. i 4 The Father's Crown. 
 
 2. The Wife's Crown. 5. The Little Girl's Crown. 
 
 3. The Orphan's Crown. I 6. The Poor Man's Crown. 
 
 %* The Complete Series in One Volume, cloth gilt, gilt edges, is. 6d. 
 
 *& The following CATALOGUES of Messrs. CASSELL, 
 FETTER & GALPIN'S PUBLICATIONS are now ready, and may be 
 procured from all Booksellers, or post free from the Publishers: 
 
 CasselTs Complete Descriptive Catalogue, contain- 
 ing a List of their numerous Works, including Bibles and Religious 
 Literature, Children's Books, Editcational Works, Fine Art Volumes, 
 Serial Publications, &*c. 
 
 CasselFs Educational Catalogue, containing a Descrip- 
 tion of their numerous Educational Works, with Specimen Pages and 
 Illustrations, and also supplying particulars of CASSELL, PETTER & 
 GALPIN'S Mathematical Instruments, Water- Colours, Drawing Boards, 
 
 T Squares, Set Squares, Chalks, Crayons, Drawing Books, Drawing 
 " ' ;ls, Drawing Pencils, &c. &c. 
 
 Cassell, Fetter 6 Galpin : London, Paris &> New York.