THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES MICROSCOPY FOR BEGINNERS OR COMMON OBJECTS FROM THE PONDS AND DITCHES BY ALFRED C. STOKES, M.D. ILLUSTRATED "Tlte microscope is not the mere extension of a faculty ; it is a new sense" " The microscope, frequently and intelligently used, makes nature pellucid" NEW YORK HARPER & BROTHERS, FRANKLIN SQUARE 1887 Copyright, 1887, by HARPER & BROTHERS. All nglitt retmed. 6,2 CONTENTS. FAfll INTRODUCTION ix CHAPTER I. THE MICROSCOPE AKD ITS PAKTS 1 CHAPTER II. COMMON AQUATIC PLANTS USEFUL TO THE MICROSCOPIST 47 CHAPTER III. DESMIDS, DIATOMS, AND FRESH- AY ATER ALGJE 64 CHAPTER IV. RHIZOPODS Ill CHAPTER V. INFUSORIA. . . CHAPTER VI. HYDRAS.. . . . 155 CHAPTER VII. SOME AQUATIC WORMS, CH^TONOTUS, AND CHIRONOMUS LARVA... .. 163 iv CONTENTS. CHAPTER VIII. PAGB ROTIFERS 200 CHAPTER IX. FRESH- WATER POLYZOA 221 CHAPTER X. ENTOMOSTRACA AND PHYLLOPODA 238 CHAPTER XI. WATER-MITES AND THE WATER-BEAR 260 CHAPTER XII. SOME COMMON OBJECTS WORTH EXAMINING 274 GLOSSARY 293 INDEX... .. 299 ILLUSTRATIONS. FIG. p VGE FIG. PAGE 1. A Pocket-lens 3 23. Closterium juncidum . 78 2. A Compound Microscope. . . 9 24. Closterium acerosum . 79 3. A Growing-slide 39 25. Closterium Lunula . 79 4. Air-bubbles 40 26. Closterium Ehrenbergii . . . . 79 6. Reflector for Drawing the 27. Closterium acuminatum. . . . 79 Magnified Object 42 28. Closterium Diana; . ... 79 6. Leaf of Ranunculus anuati- 29. Closterium "Venus 79 lis 49 30. Closterium rostratum . 80 7. Peduncle of Nymphsea odo- 31. Closterium setaceum . 80 rata : transverse section. . 50 32. Micrasterias radiosa 81 8. Whorl of Myriophyllum 33. Micrasterias rotata 81 Leaves 52 34. Micrasterias truncata . 81 9. A Leaf of Utricularia. . . . 53 35. Micrasterias arcuata 82 10. Quadrifid Process from Inner 36. Micrasterias dichotoma . . . . 82 Surface of Utricle of Utri- 37. Micrasterias Kitchelii . 82 cularia 55 38. Micrasterias oscitans . 82 11. Whorl of Leaves of Cerato- 39. Micrasterias laticeps . 82 phyllum ... 56 40. Euastrum crassum 83 12. Letnna pol yrrhiza 57 41. Euastrum didelta . 83 13. Lemna Minor 58 42. Euastrum ansatum . 83 M, Anacharis Canadensis 5'J 43. Tetmemorus granulatus . . . . 84 15. Portion of Leaf of Sphagnum 01 44. Tetmemorus Brebissonii . . . 84 16. Riccia fluitans 02 45 Docidium Baculum 84 17. Didymoprium Grevillii. .... 76 46. Docidium crenulatum . 84 18. Sphserozosma pulehra 76 47. Cosmarium Ralfsii . 85 19. Hyalothcca dissiliens 76 •18. Cosmarium pyramidatum. . . 85 20. Bambusina Brebissonii .... 76 49. Cosrnarium margaritiferum . 85 21. Dcsmidium Swartzii 77 50. Cosmarium Brebissonii . . . . 85 22. Closterium liueatum 78 51. Staurastrum punctulatum . . 86 ILLUSTRATIONS. FIG. PAGE 86 FIG. PAGE 107 86 88 Vaucheria 108 86 109 55. Xanthidium armatum .... 56. Xanthidium antilopaeum . . 57. Arthrodesmus iacus 58. Arthrodesmus convergens. 59. Spirotaenia condensata .... 60. Triploceras verticillatum . . 87 87 87 87 87 87 90. Draparnaldia glomerata. . 91. Bulbochaete 92. Amoeba proteus 93. Vampyrella lateritia 94. Acanthocystis cliaetophora 95. Actinophrys sol 110 110 118 118 120 1-?1 61. Penium Brebissonii 62 Meridion circulare .... 88 94 96. Actinosphaerium Eich- m 63. Diatoma vulgare 64 Bacillaria 94 95 97. Difflugia pyriformis 98 Difflufia corona 124 125 65 and 65a. Fragelaria capucina 66. Ilimantidium pectinale. . . . 95 96 99. Centropyxis aculeata .... 100 Arcella vul^aris 126 T>7 67. Encyonema paradoxa 68 and 68a. Cocconema lanceo- lata 96 96 101. Arcella dentata 102. Trinema enchelys 103 Eu(rlvpha alveolata 127 127 129 69. Gomphoncnm acuminata . . 70. Epithemia turfida 97 97 104. Cyphoderia ampulla 105 Clathrulina ele^ans 129 1BO 97 140 72. Eunotia tctraodon 97 107. Carchesium 141 73. Pleurosigma 98 108. Epistylis 14"! 74 Surirella splendida 98 109. Vorticella 143 99 110 Dinobryon 144 99 111 Va"-inicola 145 77. Piunularia viridis 99 112. Platvcola 146 78. Stauroneis phoenoccntcron. 99 113. Cothurnia 146 79. Sccnedcsmus quadricauda. 80. Pediastrum granulatum . . . 81. Hydrodictyon utriculatum . 101 101 102 114. Stentor potymorphus . . . 115. Stentor Barrett! 116. Stentor igneus 147 148 148 82. Batrachospermum monili- forme 104 117. Astasia 118. Euglena 149 149 83. Anabaena 105 119. Chilomonas IfiO 84. Oscillaria 105 120 Phacus pleuronectes 150 85 Spiro°pyra 106 121 Phacus lonf'icaudus 150 86 Spiro°yra in conjugation 122 Uvella 151 with spores . . , 106 123. Trachelocerca . . 151 ILLUSTRATIONS. Vll FIG. 124. Amphileptus PAGE 159 FIG. 149. Steplianops PAGE 9,17 159 150. Pterodina 918 126 Euplotes 153 151 Dinocharis <>18 127 Stylonycliia 153 152 Polyarthra 218 128. Chilodon 154 153. Brachionus , 9,1ft 129. Loxodes . 154 154. Philodina 990 130. Hydras adherent to Lemna rootlets 130« Hydra stin0" 156 158 155. Pectinatella magnifica . . . 155a. Statoblast of Pectinatella 156 .Plumatella 229 230 231 1306. Trichodina pediculus — 160 157. Paludicella 158. Urnatella 233 935 167 159 Daphnia 947 132 Chsetonotus larus 168 160 Bosmina 249 133. An^uillula 184 161. Cypris 950 134 Snout of a Pristiua 180 162. Camptocercus 951 163 Chj'dorus 251 Pristina 136. Posterior extremity of a 189 164. Alonopsis 165. Diaptomus 251 959 189 166. Canthocamptus 253 167 Cvclops 254 Dcro 199, 167a. Young Cyclops 954 138. Posterior extremity of fin 168. Limnetis 955 Aulophoru.s 139. Podal spines and bristles of Strephuris 193 194 169. Artemia (a female) 170. Branchipus (a male) 171. A Water-mite 256 258 960 140 Nais 198 172 Tlic Water -bear (Macro- 141. Podal Spine of Nais.. . . 100 biotus) 268 142. Stephanoceros 143. Floscularia ornata 144. Actinurus 145. Melicerta ringens . . .. 209 210 211 <>13 173. Coxae of Hydrachna 174. COXJE of Eylais 175. Coxae of Arrenurus (fe- male) 269 270 270 146. Limnias ceratophylli. , .. . 147. Megalotrocha 214 9,15 176. Coxae of Arrenurus (male) 177. Coxa! of Atax. . 271 9,79, 148. Rotifer vulgaris- 216 1 78. Eye- plate of Limnochares. 273 INTRODUCTION. To the beginner in the \\&Q of the microscope, indeed to the beginner in the study of any department of natural history, the name of the specimens found is of the first importance. It is the key that opens the door to further knowledge, and until it is obtained the beginner is helpless; the books are closed to him, all conference with others in reference to the object or specimen is impossible, and, in many, a budding interest that might otherwise bloom and bear fruit is crushed and destroyed. The first question asked is always, " What is it?" and unless the questioner has a kind and experienced friend to whom he can take the specimen, or a book of common objects from which the names of ordinary natural history materials can be ascer- tained, the question is too often unanswered, and the beginner soon loses his relish for the unknown in nature, because to him it always remains the unknowable. In England innumerable little hand-books in all departments of natural science are within the reach of every reader, even the least wealthy. They are written in an attractive style, they are usually accurate as far as they go, and they aim to describe the common objects to be found in the green lanes and the woods, the waters of the ponds and streams, and the shallow bays and inlets of the sea, so that any one with the least inclination towards the study of the teeming world of an- imal and vegetable life can, at slight expenditure of time, labor, and money, learn the names of the commonest things A* X INTRODUCTION. i. surrounding him. Such books, if correct and helpful, arc wor- thy of all praise. That there is a desire for them, even in this fair land of ours, is evident by their importation, and their ap- pearance on the counters of the booksellers and the shelves of the public libraries. But they are seldom adapted to our needs. Their descriptions are commonly too general and diffuse, their writers pay more attention to literary style than to the im- parting of definite information, and the text too often bears internal evidence of having been made to suit certain pictures owned and necessary to be utilized by the publisher. That similar and better books on the life in American fields and streams, and American sea-shores, are so few is much to be re- gretted. There ought to be small and untechnical hand-books adapted to "all capacities, even the meanest," as our forefa- thers used to put it, and in all departments of animal and vege- table life ; books in which the beginner could learn the names of things. " I do beseech you, what is your name?" is the oft- asked question, cot only by the beginner in the use of the microscope, but by the more advanced student in other depart- ments as well. Ernerton's "Life on the Sea- shore," and his " Structure and Habits of Spiders ;" Hervcy's charming " Sea- mosses," Gray's " How Plants Grow," Romyn Hitchcock's "Synopsis of the Fresh-water Rhizopods," Jordan's "Manual of the Vertebrates," are delightful books that approach the ideal nearer than any others published in this country ; indeed, there are no others. There is so much for our learned scien- tists to do in this comparatively unexplored land of ours, that they may have no time to stoop and lend a hand to those who would like to enter a little way into the attractive world of sci- ence, from which faint but pleasant rumors occasionally come. They arc all courteous and communicative when personally ap- proached, but what boy or other young person with an inclina- tion towards "bugs and things" would be willing, or, indeed, INTRODUCTION. xi would know how to seek aid from these celebrated men? And if the student is alone in a country place where Nature smiles her sweetest, but where there are no libraries and no human being to consult, except, perhaps, " the minister," how then shall he learn the name of the flower, the stone, or the bird that at- tracts his attention? "The minister" is usually poor authori- ty on such subjects, and the boy, after wondering and investi- gating in an awkward and boyish fashion, soon gives it up, when he might have become a lover of nature, and perhaps a lover of something even better than nature. The " Agassiz Association," with its clubs and chapters and auxiliary natural history societies, is doing much good in awakening a desire in its young members to know something of natural science, and in doing something to help the young investigators. Yet it can do but little. The workers must depend upon themselves, and the books, of which there are so few adapted to their needs. The microscope is every day becoming a more familiar in- strument to the young. There is a growing interest among the boys and girls, even among those of a larger growth, in the little things of the world, and the number of so-called micro- scopists is rapidly increasing. But the possessor of an instru- ment looks at the two or three mounted objects supplied by the dealer, and then wonders if this is all, and if this is the only foundation for the charming stones he has heard of the charming things to be seen with the microscope. " Will you tell me where I can find a book that will help me to know a microscopic plant from a microscopic animal, and teach me how I can best collect them?" is a question that has often, in some shape, been asked the writer, and has as often remained unanswered, for there is no book on common American micro- scopic objects. It is only possible to direct the questioner to the ditches and the ponds, and to wish him a success that is almost hopeless. In any event, the beginner naturally, and al- xii INTRODUCTION. most instinctively, goes first to the water for liis microscopic objects, probably because lie has heard so much about the " ani- malcules" there. His first examination bewilders him. There is so much life and motion and color, there are so many strange forms; but where shall he turn for help? Since our illustrious scientists have not offered to help him, the writer, who is only a beginner himself, and who makes not the slightest pretensions, has sympathized with the inquirers whom he has been compelled to turn away unsatisfied when they have come for printed help in their microscopical work, and this little book is the result. It claims no literary merit ; it makes no scientific pretensions. Its only aim is to help the beginner to ascertain the names of some of the common mi- croscopic creatures, both animal and vegetable, with which the fresh waters of the land are filled, and it tries to do so in the simplest and most direct way, leaping scientific hedges and trampling on scientific classification in a manner that will dis- may the learned botanist and zoologist. But the botanist and zoologist have weighty books that delight their souls, so why should not the beginner with a microscope have a book to help him to the names of the commonest aquatic objects, and, it is hoped, delight him by smoothing the path that leads to them ? The writer will not be greatly troubled if the learned botanist and zoologist do not like this little book, provided the beginner in the use of the microscope approves it and finds it helpful. It relates almost exclusively to aquatic objects. One reason for this, has already been mentioned. Another and more po- tent one is, that even the beginner knows, in a general way, what he is looking at when he magnifies the common objects of the land, but the microscopic creatures from the water are so truly microscopic, the observer must so often go fishing on faith, and only know the contents of his net by faith and im- agination until he can examine his collection drop by drop with INTRODUCTION. xiii the microscope, that lie is lost at the start unless he has a book to help him, which this one hopes to do. But is it necessary to say that the following pages do not contain notices of ev- erything to be found in the ponds and ditches? The begin- ner will capture many objects which he will not find described here. It is not possible that the matter should be otherwise. The waters are crowded with life, and it is only the common- est objects and those most frequently found, that a little book of this kind can attempt to include. The descriptions of those few have been made as plain as possible. The writer has seldom allowed himself to "fall into poetry," although often sorely tempted. The keys or analyti- cal tables so freely scattered through the pages have been pur- posely made as artificial as they could be. They use the most conspicuous external characters without regard to scientific classification, and without regard to any result but one only—- to help the beginner find the name, at least the generic name, of his specimen. If this is accomplished the book will have attained its purpose. The method of using the keys is ex- plained on page 70. Finally, to the beginners in the use of the microscope, for whom the book has been prepared, the writer would say, as has so often been already said : There is DO royal road. The mother-bird finds and brings the food, but even the youngest nestling opens its own mouth. MICROSCOPY FOR BEGINNERS. CHAPTER I. THE MICROSCOPE AND ITS PARTS. Simple and Compound Microscopes.— Pocket -lens. — " Craig Mi- croscope."—" Excelsior Microscope." — Watch-maker's Glass.— Coddington Lens. — How to Focus a Simple Lens. — Parts of the Compound Microscope. — Draw - tube. — Eye - pieces. — Society - screw.— French Triplets.— Objectives.— Selecting Objectives for the Beginner.— Coarse Adjustment.— Focussing.— Fine Adjust- ment.— The Stage. — Diaphragm. — Mirror and Bull's-eye Cou- densing-lens. — Preparing the Object. — Thin Cover-glass. — Cells. — Cement. — Dry Mounting. — Needles. — Dipping - tube. — Bunsen Burner. —Evaporation from beneath the Cover. —Life -slide.— Growing - cell. — Air - bubbles. — Drawing. — Camera Lucida and Glass Reflector. — Micrometer. — Measuring the Object. — To as- certain the Magnifying Power. — Collecting-bottles. — Books and Magazines for Reference. MICROSCOPES are compound or simple : compound when they consist of two or more glasses, one or more being near the object to be examined, and one or more near the eye of the observer ; simple when they consist of but one double-convex lens to be held near the ob- ject, or of two or more lenses that can be used singly or all at the same time. "When thus used in combination, the two or three simple lenses are not only placed close 1 2 MICROSCOPY FOR BEGINNERS. to each other, but close to the object, the combination acting as if it were a single lens, the magnifying power being much greater than that of but one glass, and the distance from the object much shorter when in focus. In the compound microscope the lenses near the eye magnify the image formed by the lower glasses, and that image is inverted, the upper side of the object then appearing to be the lower, the right-hand side the left, and the left-hand the right. In the simple microscope, however, the image is not inverted ; and in those forms where two or three lenses are combined, the effect is the same as though one glass of great magnifying power were used. But separate the lenses so that the upper shall magnify the image produced by the lower, and you have a simple form of compound microscope. In the simple microscope we see the object itself, in the com- pound we see the enlarged image of the object. As a simple microscope does not seem to invert and reverse the object, and because the distance between the two is long when a low-power glass is in focus — that is, when the glass is in such a position that the magnified object looks clear and distinct to the eye — it is always used for the examination of a flower, the surface of a piece of bark, a stone, an insect, or any other specimen of considerable size, or one that is visible to the naked eye, more extended study being reserved for the com- pound instrument at home. A simple microscope, a "pocket-lens" as it is often and preferably called (Fig. 1), is really indispensable to every one who has a taste for THE MICROSCOPE AND ITS PARTS. 3 nature studies, and a desire to know somewhat of the beauties hidden from our unaided vision; for the sim- plest glass shows the student unim- agined charms in the petal of a flow- er, the sand he walks on, and in the green scum that floats on every sum- J Fig. 1.— A Pocket-lens. mer pool and disgusts him until his little lens reveals its purity and grace. It is always ready for the examination of anything picked up in the fields or woods, it is small, and it is easily carried in the pocket. It can be obtained in a great variety of shapes, so far as the frame that holds the lens is concerned ; it can be had with but one glass, or with two or three of various powers, to be used alone or combined ; it can be bought with a large lens of low power in one end of the frame, and a smaller glass of higher power in the other. But whatever form the beginner selects, he must remember that the larger the simple lens the lower, as a rule, will be the magnifying power, and the longer the working distance, or the space between the glass and the object when in focus ; and the smaller the lens the more con- vex it will be, the greater power it will have, the shorter the working distance, and the less of the object it will show at one view, and consequently the more trouble- some it will be to use. The beginner is advised to pur- chase a good pocket -lens with a working distance, or "focal length" as it is sometimes rather incorrectly termed, of one or one and one-half inches. This is all that is really needed for the examination of botanical 4 MICROSCOPY FOR BEGINNERS. specimens and the thousand and one objects that attract the attention on every summer ramble. The writer personally dislikes the combination pock- et-lens formed of two or three separable glasses. If but one lens of the combination is wanted for immediate use, the entire number must be pushed out of the thick and awkward case, one must be selected and separated, for the perverse thing usually comes out of the pocket upside down, and it is of course desirable that the high- est-power glass shall be next to and nearest the object, while those not needed are turned to one side, making a series of operations that take time, both hands, and con- siderable patience if you are anxious to examine the specimen. Your companion will have finished the work with the single glass, and will be telling you how the ob- ject looks, before your complicated affair is ready to be- gin, provided you are not wise enough to have avoided the combination pocket-lens. And if tire whole number is used at once, the working distance is usually so short that the observer's head or hat-brim shuts off most of the light, so that the object can be seen with difficulty, and a very little of it at that. To see at one view so small a portion as these high-power combinations always show, and to be compelled to pass the lens over so many little parts before an idea of the whole surface can be ob- tained, is, to say the least, not satisfactory ; unless the observer is familiar with the entire object, and the rela- tion and arrangement of all the parts, a low-power pocket- lens is the most useful, and the one to be recommended. THE MICROSCOPE AND ITS PARTS. 5 The reader perceives that this matter of short focus is an important one ; indeed the usefulness of the pock- et-lens to a great extent depends upon it. Reject with- out hesitation the simple lens whose focus is so short that it must be held almost in contact with the object. Not long ago a rather expensive instrument called the " Craig Microscope" was extensively advertised, and sold as a remarkable thing. The lens was a small globule of glass fastened to a glass plate, to give it a flat under-sur- face, and mounted in a brass ring, the whole being sup- ported on an upright brass tube with a plane mirror at the lower end. It was not a compound microscope, but a simple lens with mirror attachment. The object to be examined was suspended from the flat surface of the glass in a drop of water, the focus being so short that it was at the front of the lens, so that nothing could be looked at unless it was adherent to the glass. No mounted object could be satisfactorily studied ; to ex- amine the parts of a flower was impossible, and even when a drop of water was suspended from the lens its contents were distorted almost beyond recognition. The " Excelsior Microscope " makes no false pretences. The instrument consists of a small box which is a recep- tacle for all the parts when not in use, and a support when the steel rod is elevated to receive the combina- tion pocket-lens and the stage, on which the object is to be placed, a small mirror in the front of the box re- flecting the light to the object from below. A great fault is the absence of weight in the instrument. At 6 MICROSCOPY FOR BEGINNERS. the least touch it moves, the light reflected from the mirror is lost, and the object is consequently left in semi- obscurity. It is intended chiefly for the dissection of flowers, grasses, or large insects, and fairly answers the purpose if the observer desires to have both hands free, and cares to screw the box to the table. But it is no better than a good pocket-lens, which, with very little trouble, can be attached to an upright rod and be used for dissections ; in some respects it is much less valuable. The three lenses supplied can be used as a single one or combined. The former is good, the combination of two is not seriously objectionable, but the focus of the united three is, to the writer's eye, only five-sixteenths of an inch, a distance, aside from the small field of view, that effectually prevents its use as a dissecting microscope. "With the lowest-power lens six letters of the type used in this book can be seen, the focal distance being one and one-fourth inches ; with two lenses combined, four letters, with a focal length of about one -quarter of an inch ; and with the three glasses only one letter is vis- ible, the focal distance being five-sixteenths of an inch, when tested by the writer. A " watch-maker's glass," winch is sometimes seen on the microscopist's table, is a simple lens mounted in a short horn or rubber tube, so arranged that it can be held to the eye by the contraction of the muscles of the cheek and brow, while both hands are used for the manipulation of the object. It can be obtained of various powers and focal lengths, but it is scarcely THE MICROSCOPE AND ITS PARTS. 7 desirable. The prolonged contraction of the facial mus- cles necessary to keep it in place is very fatiguing, and the vapor always evaporating from the front of the eye being confined within the tube is sure to condense on the lens and obscure the object. Everything a watch- maker's glass will do, a good pocket-lens will accomplish. A "Coddington lens" is admirable in many respects. Its magnifying power is great, the image it forms is ex- cellent, the field of view is good, but the focus is usually unpleasantly short. This, aside from its cost, is its only objectionable feature. It is named after the gentleman who first brought it to the notice of the opticians, and not, as it should have been, after Sir David Brewster, its inventor. It consists of a sphere of glass with a deep groove cut around its centre, and filled with a black ce- ment, which acts as a diaphragm to cut off certain rays of light whose presence and action would be undesira- ble, as they would interfere with the formation of a clear and sharply outlined image. The reader may be surprised to learn that there are people who do not know how to focus a lens. I have seen such persons take the glass as if they were afraid of it. They extend it towards the object in a hesitating way, move it about irregularly for a few moments, throw back the head, look cross-eyed, and say, " Oh yes ; I see. How beautiful! And how very queer it looks!" I once offered a lady an opera-glass, which she put to her eyes and never touched the adjustment wheel that alters the length of the tubes and focuses the lenses on the 8 MICROSCOPY TOR BEGINNERS. actors ; and when she returned it she said, " Thank you. I don't like it much ; I can see a good deal better with- out it." To " get the focus " it is not really necessary to close one eye, although that is usually done. If both eyes are open, the one looking through the lens becomes so interested that the other sees nothing ; or, if you prefer, you may say that the brain becomes so interested in con- templating the image formed on the retina of the eye examining the magnified object, that it fails to note the retinal impressions of the other. But if one eye must be closed, it can be done, after very little practice, with- out clapping your hand over it. This applies equally well to the use of the compound microscope. To focus a pocket-lens hold the object to be examined in the left hand, and while looking through the glass raise and lower it with the right hand until the magni- fied object appears clear and distinct, the outlines sharp, and without a fringe of color, and the surface rough or smooth, rounded or concave, as it indistinctly appears to the unaided eye. The focus cannot be obtained without this experimenting every time the glass is used. A good plan is to place the lens nearer the object than you know to be necessary, but always without allowing the two to come in contact, and then to slowly raise the glass until the image is distinct, when it will be focussed. Keep it steadily in that position and study the object. The compound microscope (Fig. 2) consists of the stand, the eye -piece, and the objective, although the THE MICROSCOPE AND ITS PARTS. 9 word, as commonly used, refers to the entire combination of brass, with or without the magnifying -glasses. But Fig. 2. — A Compotiud Microscope. without the objective the microscope is only the " stand," and is practically useless. The stand alone generally in- cludes the tube or microscope body, the eye - piece, I* 10 MICROSCOPY FOR BEGINNERS. formed of two lenses at the opposite ends of a short tube inserted into the upper end of the body, the arm supporting the body, the stage on which the object is placed to be examined, the mirror to light the object, a movable circular plate, or diaphragm, immediately be- neath the stage, and the foot that supports the whole. The addition of the objective, or magnify ing - glass, at the lower end of the body, makes the stand a compound microscope of the simplest form. The objective is so named because it is near the object to be examined when the microscope is in use, and the eye-piece is so called because it is then near to the observer's eye. Without both of these sets of lenses the instrument is useless. The arm and foot may be made of either brass or iron, and there should be a joint between them so that the upper parts of the instrument may be inclined. The cheapest stands are made without this arrangement, and they must therefore always be used in a vertical posi- tion, the observer being compelled to hold his head and body in a way that soon becomes very wearisome. An iron arm and foot are quite as useful as if made of brass, but no stand should be selected without the joint for in- clination. Brass looks better, and is much more expen- sive than neatly japanned iron, but is practically no more useful. The body should be about ten inches long. In the less expensive stands it is often made in two parts, the upper tube sliding within the other, so that when it is drawn out to its full extent the entire body will then be THE MICROSCOPE AND ITS PARTS. 11 the proper length to obtain the best results from the ob- jectives. In such a stand, when the inner, or " draw," tube is pushed down, the microscope will have the low- est magnifying power obtainable with the eye-piece and objective then in use ; when fully extended, the power of the objective will be greatly increased, so that by varying the length of the body by the use of the " draw- tube," many different magnifying powers may be ob- tained from one objective. In some cases this arrange- ment may be useful ; it is at least not entirely objec- tionable, neither is it very convenient. Stands with an undivided body ten inches long — the standard length — also often have a draw- tube by means of which the body can be enormously lengthened and the magnifying pow- er enormously increased, but usually with a loss of some good qualities in the image. The addition is occasionally useful, but it is not necessary. If the reader selects an instrument with a body of the standard length, and he finds that it is without a draw-tube, he need not be troubled. The stand will be as valuable without as with this secondary part. The eye-piece consists of two lenses at the opposite ends of a. short brass tube divided internally by a dia- phragm. The lens nearest the observer's eye when the instrument is in use is the " eye-glass," the one at the opposite extremity the " field-glass." The price of the stand usually includes one or more eye-pieces. If but one is supplied, it will generally be the lowest power, the two-inch or "A;" if two, the one-and-one-half or 2 12 MICROSCOPY FOR BEGINNERS. one-inch, often also called " B " or " C," will be added. Opticians also make £, f , J, and even ^ inch eye-pieces, most of which are for special kinds of microscopical work, their magnifying power being enormous and the result almost worthless ; indeed, these very high power eye-pieces are usually to be avoided. On no account should they be selected by the beginner in microscopy. Every purchaser of a stand should insist upon having the two-inch, if he can have but one, as it is always use- ful, and is all he will need for a long time, or until he desires to use an eye- piece micrometer for the meas- urement of microscopic objects, when he can add the one-inch, or " B," ocular to his stand. The lower opening in the body always carries a screw to receive the one on the upper end of the objective. Several years ago the size of these screws varied widely in stands and objectives of different makers, so that if the student desired an objective of different make from those accompanying his instrument, he was forced to buy a little piece of apparatus called an adapter, one end of which was made to screw into the microscope body, the other to receive the objective. At the suggestion, however, of the Royal Microscopical Society of London, all objectives and stands now have screws of the size recommended by that society, and therefore called the " society-screw." Only the very cheapest stands of the present day, or those having the least value as instru- ments for serious investigation, are without this screw, and they are usually supplied with what are termed THE MICROSCOPE AND ITS PARTS. 13 French triplets. These are miserable lenses that should always be shunned, as they will do the observer more injury than much time can remedy. It is true that before the optician, especially before the American optician, began to make really good ob- jectives at moderate cost, these French triplets were extensively used, and are said to have done some good work. But at what expense ? Not at the expense of any great amount of knowledge or skill in their manu- facture, for the lenses were ground, mounted singly, and then combined in an experimental way : two or three were selected at random from a basketful, screwed to- gether, and examined on a microscope. If the result was considered satisfactory, all was well ; if not, one or more of the lenses was replaced by others also selected at random, and the experiments were continued until the objective was considered passable and salable. Such, at least, is the credible story. Their expense, therefore, was not in the making ; it was in the imper- fect image, in the great loss of light, in the injury to the eye due to the strain caused by the absence of sharp- ness and brilliancy characteristic of the image formed by even low-priced American objectives, and in the time wasted while unconsciously forming erroneous conclu- sions from the objects so imperfectly seen. The writer is somewhat emphatic on this point. He knows where- of he speaks, for he began the use of the microscope with French triplets, and employed them for years, be- cause he was ignorant and had no teacher. What the 14 MICROSCOPY FOR BEGINNERS. cost was to him lie knows only too well. To the young student who longs for a microscope, I am almost tempt- ed to say, if you cannot afford the cheapest suitable low- power American objective, if you must have the ordi- nary French triplet or none, take none. It is a hard fate, but is not life itself hard ? Fortunately, however, these inferior commercial lenses are not extensively in the market at the present day. Yet the purchaser of a microscope already fitted out with objectives, should inquire whether he is buying French triplets. If so, then as his experience, knowledge, and skill increase, so will his dissatisfaction increase. An intelligent boy had been using these poor lenses for some time, and doing work that, under the circumstances, was commendable, when he for the first time looked through a good low- power (one-inch) objective. After a momentary exam- ination, he glanced at me in a wondering way as he said : " How beautifully bright and clear it looks ! My microscope is different. I think it needs cleaning !" Modern objectives are the result of the most consum- mate skill of the accomplished optician. There is no chance work in his methods. Every curve is mathe- matically exact, and is calculated and positively known before the glass comes to the grinding-tool. Objectives are usually a combination of several lenses, but the union is not accidentally perfected. The maker's knowl- edge of abstruse optics tells him the precise result to expect from the combination of lenses of certain forms made from glass of a certain chemical composition. He THE MICROSCOPE AND ITS PARTS. 15 is the master ; his objective is a masterpiece. The own- er of a good objective must not treat it carelessly. He should treasure it, for it is not a common thing. "When not on the stand in use, it should be kept in the brass box supplied for that purpose, and it should never be left on the stand when not in actual employment. That part of the brass mounting of the objective which bears the screw is the back ; the opposite end that shows a small flat surface of glass is the front, or, as it is often styled, the front lens. The glass of this part is soft and easily scratched, therefore take care not to let it touch anything hard ; especially avoid any gritty substance, or dirty rag that may hold a minute parti- cle of sand or hard dust.; and never touch it with the lingers, as the oily exudation from the skin will soil it and interfere with the clearness and beauty of the image. If the front lens becomes accidentally stained, or soiled by long use, the objective should be sent to its maker, who can clean it without the great risk that its owner would expose it to if an attempt should be made to wipe the glass. If fine dust adheres too closely to be dislodged by the breath, ravel out the edge of a piece of very clean old linen or muslin, and with the fringe thus obtained gently sweep the surface. "When the objective is to be taken from its box, un- screw the cover and tip the lens into the palm of the left hand, supporting it with the fingers ; pick it up with the thumb and finger of the right hand against the sides of the tube or brass mounting, and it will be ready, 16 MICROSCOPY FOR BEGINNERS. when reversed, to be screwed to the stand. If it is not to be returned to the box immediately after use, as will often happen if the student has more than one, and he desires to examine the object with another power, stand it on its screw end on the table, and to protect it from dust invert its box over it. The latter can be lifted off in a moment, and the objective will then be ready to be picked up as before. What objectives should the beginner select ? If pos- sible, he should have two, a low and a moderately high magnifying power. If unable to purchase both at once, let him by all means first take what is called the one- inch objective ; if he can also buy a high - power, the £ or % will be the proper glass. But for this he can wait. There is so much to be examined with the one- inch objective that, for a long time, he will scarcely feel the need of another. The inch, if properly selected, need not be expensive, but it should be a good and sat- isfactory glass, not only at the outset, but when the stu- dent becomes an expert microscopist ; it will then always be useful. Such objectives are made by several Ameri- can opticians, and included in what they call their " Stu- dents' Series." "When in focus, the distance between the front lens and the surface of the object — the "working distance " — is large, so there will be no trouble in using it; and with the two-inch, the "A" eye-piece, the mag- nifying power will be about forty-five diameters, or a little more than two thousand times. After the student has been using the one-inch objec- THE MICROSCOPE AND ITS PARTS. 17 tive for some time, and his eye lias become educated, he will begin to catch glimpses of minute objects beyond the ability of the low-power glass to properly exhibit. Then he will wish for something more, so that he can look deeper into the little things of nature. What shall it be ? The opticians make ^, T^, and even -^ inch ob- jectives, which magnify enormously, cost frightfully, and can be successfully used only by accomplished mi- croscopists on large and first-class stands. To the be- ginner, even after considerable experience with the low-power, any objective higher than the £ or -§- will be useless. With these glasses he will be well equipped for quite extensive microscopical study, until he is ready to undertake original work in some unexplored depart- ment of science, or in some partially neglected corner, of which there are many in every scientific field, how- ever well cultivated. Like the one -inch, the % or -J- will always be useful. As the observer's eye becomes better educated, when it learns, as it will, to see minute parts of delicate objects, which at the start were entire- ly, overlooked, the high -power objective will not be thrown aside, the student will not become disgusted with it as lie would with a high-power French triplet, but his quickened sight will again catch glimpses of beauty to be examined, and mystery to be unravelled, which are beyond the power of his best objective, and he will almost unconsciously have advanced another step. Personally the writer prefers the ^ inch objective to the ^, and such a glass need not be expensive to be good 18 MICROSCOPY FOU BEGINNERS. (several opticians' "Students' Series" include them), the working distance is not too short, or need not be, and with the two-inch eye-piece it will give a magnifying power of about two hundred and fifty diameters. "The coarse adjustment" is the expression usually applied to the rapid movement of the body produced by turning the large milled heads, one of which is on each side of the instrument. It is used in focussing, that is, in obtaining a distinct image of the object when seen through the eye-piece and objective. The image then appears surrounded by a circle of light called the "field of view," or simply "the field." Yery few, ex- cept the small, vertical "boys' microscopes," and some of the cheapest and least desirable American or English stands, are without the coarse adjustment. Occasionally a stand will be seen in which this part is replaced by a broad, cloth-lined, or tightly-fitting collar, through which the body slides, the movement being made by hand. This is very unsatisfactory, and such stands should be avoided, if possible, as, sooner or later, the body is sure to be suddenly pushed too far down, the objective then coming in contact with the object : an accident to be al- ways guarded against with the greatest care, as the ob- jective, or the object, or both, may be injured. If the object is destroyed it may possibly be replaced, but a scratched or broken objective can be remedied only by buying a new one. Of course the microscope body may, by a careless student, be forced against the object by the use of the milled heads, and equally, of course, a THE MICROSCOPE AND ITS PARTS. 19 man may fill his stomach with gravel-stones or powder- ed glass ; but no sane man will so maltreat that organ, and no sane microscopist will so maltreat his objective as to drive it against the object on the stage when the risk is so great. The only proper way to use the coarse adjustment is to always focus upward. When the object to be ex- amined has been placed on the stage, and the light from the mirror is properly arranged, the microscope body, with the eye-piece and objective, is racked downward by means of the milled heads until the front of the objec- tive almost touches the object, the observer carefully watching that they do not come in contact. Then place the eye at the eye-piece, and nothing will be visible ex- cept the brightly illuminated field of view ; but, while looking into the microscope, slowly raise the body until the image appears sharp and clear, in other words until the objective is focussed. It makes no difference wheth- er the distance between the front lens, when focussed, and the object is two inches or the one-hundredth part of one inch, always rack the objective down while you are looking at it, and focus upward while you are look- ing through it. This is the single rule that must never be forgotten. It has been said in a joking way, "that nothing will throw a microscopist into a chill more quickly than to see a friend look into his microscope and focus down with the coarse adjustment." Yet men who ought to know better have been seen to do this reprehensible thing. 20 MICROSCOPY FOR BEGINNERS. In the older stands a single small milled head will be found on the front of the body near the lower end, just above the society-screw. In more recent stands it will be on the arm at the back of the instrument. This is the "fine adjustment screw ;" and although it adds somewhat to the cost, it should always be on the stand if the pur- chaser desires to use even moderately high-power objec- tives. For low-powers it is not necessary. The fine ad- justment screw is so made that by turning its milled head the objective, if the adjustment is at the front, or the entire body, if it is at the back, is slowly raised or low- ered. When the high-power objective has been imper- fectly focussed by racking the body upward^ it seldom happens that the image is as distinct as is desirable ; therefore the microscopist, by a few gentle turns of the fine adjustment screw, raises or lowers the objective, un- til the magnified image has its outlines as sharply de- fined as the figures in the best steel engravings. With the one-inch objective, or others still lower (two, three, or even four inch), the focus can be accurately obtained by the coarse adjustment alone, but with the £ or £ the fine adjustment must always be used. It is a great mistake made by some who ought to know better, to try to examine an object not distinctly in focus. In such cases the strain on the eye is severe and injurious, while the pleasure of examining the preparation is much lessened. The changes made for the better by a few delicate touches of the fine adjust- ment can be appreciated only when seen. Always try THE MICROSCOPE AND ITS PARTS. 21 to have the image as distinct as possible. If in doubt as to the focus, after obtaining what seems to be a moderately good appearance, give the fine adjustment a turn or two one way or the other, noticing whether the image becomes sharper in outline and clearer in its gen- eral aspect, or whether it grows cloudy and indistinct. If the last, the focus has not been improved, and was probably correct at first. A very little experience will make the beginner an expert in this important matter. The stage, on all but the largest and most expensive instruments, is a square or circular piece of thin metal, with a large central circular opening for the passage of the light from the mirror. Sometimes the metal stage has a glass plate made to slide over it easily. This is a convenience and a desirable luxury, but it is by no means necessary. The strip of glass that bears the ob- ject to be examined can just as readily be slipped about under the objective by the fingers directly, as it can be if supported on this movable glass stage. These finger movements require a little practice, but the student will so soon become accustomed to them that he will change the position of the object without consciously thinking of it, and his touch will become so delicate that he will be able, with the slightest pressure, to move the object for a distance so small that it would be invisible to the naked eye. All this is rather awkward at first, because the object must be moved while the eye is looking through the microscope ; and, in addition, if it is to be pushed to what appears to be the left-hand side of the 22 MICROSCOPY FOR BEGINNERS. field of view, it must actually be pulled towards the ob- server's right hand ; and if the image is to travel up the field, that is, away from the observer as he sits at the microscope, the object must really be slipped towards him, because the lenses reverse the image. This seems a very complicated proceeding, but it soon becomes the easiest thing imaginable. At the first trial the object will be sure to leap entirely out of the field, because it will be too rapidly moved, and the motion is magnified as well as the object ; but the student will become so expert that before very long he will be able to make on the stage of his microscope complicated dissections with fine needles of the internal organs of the house- fly, or some other equally small insect. The stage will probably have two springs on the up- per surface, one on each side. These "spring clips" are to keep the glass slide holding the object in position, unless intentionally moved. The slide is put under the clips, and the object, provided it is itself stationary, will remain in the field, where it can be examined quietly and comfortably. The diaphragm should always be present. It will be pierced near the edge with a series of openings of vari- ous sizes, to modify the amount of light thrown on the object, the largest opening admitting the greatest amount. The beginner will at first be disposed to use too much light ; indeed this is a fault of many older mi- croscopists. More can be seen with a moderately light- ed field than when the eye is dazzled and half blinded THE MICROSCOPE AND ITS PARTS. 23 by a fierce glare. Such a blaze is objectionable, not only because it tends to obscure the finer parts of the object, but it may lead the student or his friends to condemn the microscope as injurious to the sight — an unjust accusation more than once made. If too much light is undesirable, do not go to the opposite extreme and strain the eye by forcing it to work in semi-dark- ness. Keep the field sufficiently lighted to be pleasant to the sight. Turn the diaphragm until the opening giving the most agreeable effect and illuminating the object enough to show the parts clearly is under the centre of the stage opening. If the object is very thick or opaque, more light will be needed than if it were per- fectly transparent ; in such cases use a larger diaphragm opening. The mirror is one of the most important parts of the stand. It should have both a concave and a plane sur- face, and it ought not to be less than two inches in di- ameter, so that it may reflect enough light and be easily handled. In the newest styles of stands the mirror is arranged to swing from side to side, so as to throw an oblique beam of light on the object, as well as to rise above the stage, so that light may be reflected down upon an opaque specimen, since it is used below the stage for the illumination of transparent substances only. This swinging arrangement is very convenient, and should be had if possible. It is, however, not absolute- ly necessary, as similar illumination of opaque bodies can be obtained by the "bull's eye condensing lens," a 24: MICROSCOPY FOR BEGINXERS. rather expensive piece of apparatus, and somewhat diffi- cult to manipulate successfully. But as the newest and best stands have the swinging mirror, the condensing lens need not be described, especially since the beginner will not care to examine many opaque objects that will demand stronger illumination than that of ordinary dif- fused daylight or common lamplight. When ready to examine an object, the stand is placed near the window, or, if at night, the lighted lamp is stood near the instrument on the left-hand side and one or two inches in front of the mirror, and the objective is screwed on. The microscope is inclined at a conven- ient angle ; the mirror is moved in various directions, until the light is reflected from a white cloud, if possi- ble, or from the lamp, onto the front of the objective, where it can be easily seen. The eye is then placed at the eye-piece, and if the field is but partially lighted, as it probably will be, perhaps one-half of it being in shadow, or only a faint trace of light visible at one side, the mirror is slowly moved until the field is brightly and evenly illuminated, when every part of the circular bright space within the instrument is as well lighted as every other part. The position of the diaphragm is then changed, to be further altered, if necessary, after the object has been placed on the stage. This even il- lumination may at first be a little troublesome to obtain, but as in so many other actions in connection with the microscope, a very little practice will overcome every difficulty. The fingers are soon taught; they speed- THE MICROSCOPE AND ITS PARTS. 25 ily do their work without their owner's conscious bid- ding. The specimen to be studied may be permanently pre- served, or "mounted," on a slip of glass, under a thin cover and surrounded by Canada balsam, glycerine, or some other preservative, thus forming preparations called " slides/' or " mounted slides," the plain piece of glass without the object being a "slip." The addition of the object therefore changes the slip into a slide. It is well to remember this distinction in talking with the dealers or sending orders by mail. Slides can be made by the student, although to do the work neatly and well demands some skill and considera- ble preliminary study of the object before it can be pre- pared for the mounting processes ; or the slides may be purchased. It is much better arid, in the end, more sat- isfactory to the owner of the slides to prepare them himself. Certain rare objects, if desired, must be bought already mounted, but any small object naturally dry can be so easily mounted by placing it in a drop of Can- ada balsam from the druggist's, and covered by a cover of thin glass from the optician's, that for the beginner to spend his money for " the foot of a fly," " dust from a butterfly's wing," " the sting of a bee," or similar slides crowding the dealers' lists and drawers, is non- sense, unless he lives alone in the wilderness, and is ig- , norant of the appearance of a slide ; in such a case, to buy the mounted foot of a fly may be useful to show what is to be aimed at in the preparation of ordinary 26 MICROSCOPY FOR BEGINNERS. objects. A few properly mounted slides, however, usu- ally accompany the stand as specimens, or the dealer will supply them if asked. It is better to do than to buy, and so much has been written on the subject of microscopic mounting, and indeed all advanced workers with the microscope are such " good fellows," they are always so generous in giving away for the asking infor- mation that has cost much time and labor to obtain, that the young student need never despair, nor be at a loss as to where to go for help, if he possesses the name and address of some microscopist and a postage-stamp or two. Cheap little hand-books on the subject are acces- sible, microscopists are numerous and willing, so why should the beginner ever be discouraged ? and why should he buy what he can make ? It always adds a zest to this work if the worker can make his own tools, and es- pecially if he can prepare his own objects. Almost ev- ery tool needed at the beginning can be made at home. Slides must be made at home if one desires to examine any of the endless variety of the invisible animal and vegetable life with which the great world teems. All the objects referred to in this book can be studied when only temporarily mounted ; indeed, no method of pre-. serving some of them has yet been discovered or invent- ed. They must, therefore, be studied alive or not at all. And for the beginner this is not only the easiest, but it is the most inspiring way. Some things can be examined when dry. Such an object is simply laid on a slip, placed under the spring THE MICROSCOPE AND ITS PARTS. 27 clips, and the low-power objective used. The ripe seeds of wild plants are easily studied in this way, and some of them are marvellously beautiful. Small insects can also be looked at when dry, but the result is not always entirely satisfactory unless they are viewed as opaque objects. Usually most objects appear better and show more of their structure if examined under a disk of thin glass and surrounded by water. But seeds, scales from butterfly's wings, and many other things, can be viewed and preserved in a dry state by enclosing them in a cell with a thin glass cover fastened above. This " cell " and "cover" and fastening process will be described presently. All plants and animals living in water must be ex- amined in water. To dry them and expect to learn anything about them, or even to obtain a correct idea of their true appearance, is a waste of time, and worse. When your wet specimens get dry on the slide, and you think you are seeing some wonderful things, add a drop of water, and save yourself a probable blunder. Cer- tain objects, naturally dry, will look better and will re- veal their secrets sooner if examined wet. This is due to optical reasons not necessary to explain here. The observer, if he is seeking information, and not merely pretty things to please the eye and the aesthetic fancy, will do well if he examines naturally dry objects both in and out of water; but things naturally wet must never be seriously studied in a dry condition. The most convenient size for slips is three inches in 28 MICROSCOPY FOR BEGINNERS. length by one in width. Some microscopists use and recommend them two and one-half inches long by one- half an inch wide, and this will probably be the size of the slides accompanying the student's stand. They are, however, much too small ; it will be better for the be- ginner to at once select the standard, three inches by one inch, size. These can be bought, and the writer would advise that they should be, as the edges will then be ground smooth and perhaps polished, although the last is not necessary. Slips can be cheaply cut by any glass-dealer who has a diamond or glass-cutting wheel, and if thus made, the best, whitest, smoothest, and thin- nest glass should be selected. The rough edges of the home-made slips, however, are not pleasant to handle, the student who uses them taking the risk of cut fin- gers. Otherwise, unless they have a green color, they are as useful as the more expensive ones sold by the dealers. A drop of water on a slip of smooth glass is not easi- ly kept in position. "When the slide is placed on the stage, and the microscope is inclined for use, the water will surely run away, and probably carry the object with it. If the microscope is not inclined, the convex sur- face of the drop, and its tremulous movements, will so affect the light that the image will be distorted, and the observer will obtain erroneous impressions. A piece of glass placed over the water will flatten the surface, the distortion of the image will be partially counteracted, and capillary attraction will keep the liquid from en- THE MICROSCOPE AND ITS PARTS. 29 tirely running away. But ordinary glass is too thick for this purpose, consequently thin glass prepared for microscopical use must be purchased. This varies in thickness from No. 1, measuring about r^ to ^ihr inch or thinner ; No. 2, about T^ ; and 'No. 3, from ^V to TV inch. ~No. 2 glass will be the proper thickness. It can be obtained either in circles of various sizes or in squares. For permanent mounts the circles are usually employed. For temporary purposes, for the examina- tion of an object that is not to be preserved for future use, or when many examinations of separated parts of the same large specimen are to be made, the writer much prefers thin squares, and always uses them. They are pleasanter to handle, they are more easily wiped dry and with less liability to breakage, and their cost is somewhat less than circles of the same thickness. The matter of cleaning thin glass is an important one, and unless the " knack " is soon learned, the beginner will be surprised at the rapidity with which his covers will disappear. This skill, however, is readily attained. The writer has had the same thin square of No. 1 glass in use for three months continuously, frequently remov- ing and reapplying it during the five or six hours of daily evening work in which it did important service, and in the end he became quite attached to it as to a good friend. But a hasty move while cleaning it, or a little undue pressure, finally sent it on the way that -thin covers often travel. To clean without much risk of breaking, take the square with two opposite edges, that 30 MICROSCOPY FOR BEGINNERS. is, with the edges where the glass was cut, between the thumb and finger of the left hand, and with a piece of soft, old muslin held smoothly over the thumb and fore- finger of the right hand, gently wipe both surfaces at once, rotating the square when necessary. The secret of success is care, gentleness, and no wrinkles. It was probably a wrinkle in the muslin that ruined my three months' old pet cover. But a punishment is a good thing sometimes ; the microscopist who should begin to think that he was skilful enough to avoid breakage of covers for more than three months, might become in- sufferably conceited and a nuisance to his friends. But a glass square, however thin, dropped on a deli- cate animal or plant will often crush it, and destroy all resemblance to anything that ever lived. Some means must be devised for supporting it at a very short dis- tance above the slip, so that the living creatures may have room to move about, and the plants may not be too much flattened. This is done by making a ring of cement on the slip, and thus enclosing a circular space called a cell, which can be made of any depth by apply- ing more cement after the first application has dried, or by using the cement very thickly. The opticians offer several kinds of cement for sale, all of which are useful for special purposes ; but the one that seems most convenient, and one that can be easily prepared by the beginner, is simply shellac dissolved in alcohol. The solution can be made as thick as is desired by allowing some of the alcohol to evaporate, or it can THE MICROSCOPE AND ITS PARTS. 31 be thinned by the addition of more. It should be thick enough to flow freely from a small camel's-hair brush, but not so thin as to spread in an irregular film over the glass. As shellac dissolves slowly in alcohol, it is better to add more of the latter than will be needed, and to thicken the solution by evaporation. It will keep for any length of time in a tightly closed bottle. A ring can be built up with a camel's-hair brush, and this cement, either by the hand alone, or by a little ma- chine called a " turn-table," manufactured for the pur- pose. These turn-tables are as nice and neat and beau- tiful as can be imagined, and they cost — the cheapest that I can find in the catalogues costs $2.50. They spin perfect circles exactly in the centre of the slip, and the result is very pretty and very desirable if the be- ginner can afford one, but he can get along right well without. If you have none, draw in the centre of a strip of white pasteboard the size of a slip, a circle in black ink, and use it as a guide to the brush with which you make the ring after the slip is laid on the paste- board. Of course the hand cannot be as steady as a flat disk rapidly rotating on a central pivot, and the cir- cles will not be as perfect, but they will be practically as useful. To get the inked circle in the centre of the paper, draw a lead-pencil line diagonally across it from each upper corner to the opposite lower one, and use the point at which the two lines cross each other as the cen- tre of the circle. The glass slip can be kept in better position, and the whole can be turned about, if the paste- 32 MICROSCOPY FOR BEGINNERS. board is fastened to a strip of wood, and a small pin is driven into each corner. "When the ring is made, put the slip in a warm place until the cement is hard, or hold it over the lamp flame for a few moments at a time, taking care not to allow the shellac to boil, or the bubbles will never disappear and the ring will be weak- ened. These lamp-dried rings are hard as soon as cold, and they adhere so firmly that they can only be scraped off with a knife and hard work. They have the further advantage of being rapidly made. A deeper and perhaps a somewhat neater cell can be formed from paper. Cut a circular disk, of the diameter of the ring required, from porous paper as thick as the depth of the desired cell, and from the centre cut out a smaller disk, leaving a ring with a narrow rim. Soak this ring in thin shellac cement until its pores are filled with the liquid, and hang it on a pin in a warm place to dry. Several can be prepared at once, and can be of different sizes and thickness. They are fastened to the slip by touching one side with a little shellac and pressing the glass on it and allowing it to dry, or by gently heating the slip and ring over the lamp. It is a good thing to prepare several slips at one time, so as to have them ready for an emergency, as, for instance, after an excel- lent gathering of microscopical material has been made, and the student is so anxious to see what he has that he cannot take time to clean the slide and cover after a hasty glance for rarities, but must have another ready at a moment's notice. THE MICROSCOPE AND ITS PARTS. 33 To permanently mount dry objects, such as pollen, seeds, scales from insect wings, and other things suita- ble for this method of preservation, arrange the specimen in the cell, place the cover over it — preferably a circle in this case, the diameter of the cell being a little greater than that of the cover — so that the cement shall project a short distance beyond the edges of the thin glass, and with a camel's-hair brush paint a thin layer of shellac over the place where the cover and ring meet. There should be but little cement on the brush for the first coat, because if too much is used, or it is too thin, it will probably run into the cell by capillary attraction and spoil the object. This is one great trouble in all microscopical mounting. But after the first coat is dry, another is to be added, and repeated until the cover is firmly fastened to the ring. "Brown's Rubber Ce- ment," for sale by the dealers, is useful for this pur- pose, as it is very fluid, dries with great rapidity, and has little tendency to " run under." The cell having been made, the object is to be placed within it in a drop of water, the thin cover dropped over it, and the preparation will then be ready for ex- amination. But how is this minute, generally invisible object to be got into the cell ? A glass tube about one- tenth inch in inside diameter, and as long as may be convenient, several needles in wooden handles, and a camel's-hair brush, with a small smooth stick thrust into the quill, will be needed. The needles are used for spreading any small mass 34 MICROSCOPY FOR BEGINNERS. evenly over the cell, and in disentangling and arranging the parts of any comparatively large object, as well as for lifting the thin cover from the cell so that it can be easily seized by the fingers, or for tilting it up in the box, where the thin squares should always be kept. Fresh-water Algae (Chapter III.), for instance, found so abundantly in almost all still water, where they often form delicate green clouds, or thread-like streamers adhering to other plants, dead leaves, or waterlogged sticks, are almost sure to be transferred to the slip in a heaped up and tangled mass, which only two needles with gently persuasive movements can straighten out for microscopic study. If an attempt is made to exam- ine such a confused heap, the thin cover cannot be forced to lie flat without crushing the delicate speci- mens, and if the cover is tilted the objective cannot be properly focussed. To make these useful tools, with pliers thrust fine needles head first into parlor-matches, after the phosphorous ends have been cut off. These round sticks make handles convenient in length and pleasant to use. It is well to have half a dozen or more of these needle-bearing matches lying where they can be picked up whenever wanted. If the student desires to dissect insects, nothing can be so useful for cutting and tearing minute parts and for separating delicate tis- sues or organs as fine needles. !N~o knives have been made to equal them for this purpose. The glass tube is the "dipping-tube." It is really one of the most important little pieces of apparatus that THE MICROSCOPE AND ITS PARTS. 35 the microscopist can have on his table, if he intends to study aquatic life. "With it he can pick up any small object that may be visible in the water, transfer any se- lected matters to the slip, or make the dip that is made by faith, with the assurance that although the tube may seem to be filled with water only, it will be pretty sure to have captured something interesting, novel, or beau- tiful. He can fill the tube with water, and allow it to escape in a miniature torrent, or drop by drop, or he can allow a drop to enter and a drop to flow slowly out at his will. Some workers prefer a tube with a hollow rubber bulb attached, by which the water and contained objects are drawn up by the expanding ball, and forced out by its compression. The writer is prejudiced in favor of the simple tube, as it is less complicated, more easily cleansed, and its contents are more completely under control. To use it, place the tip of the forefinger firm- ly over one end, and dip the other into the water above and near to the object desired ; lift up the finger, and the water will rush in until it is level with that on the out- side ; close the upper end again, remove the tube, and the water will remain in it as long as the finger stops the upper opening ; remove the finger and the water will at once flow out. By the proper regulation of the pressure and movements of the finger, the water can be made to escape drop by drop or in a sudden rush. In this way any small aquatic object can be easily trans- ferred to the slip, and as readily washed off by a sudden outward flow from a full tube. 3 36 MICROSCOPY FOR BEGINNERS. Until recently I supposed this little affair was com- mon property, and that the principle on which it acts was understood by everybody. But when I called on a gentleman, a member of a scientific society, to obtain some water in which certain plants were growing, he ex- pressed surprise at the performance, and called his wife to witness a new and curious method of taking up wa- ter with nothing but a glass tube and a finger. His as- tonishment was amusing ; but how much more so was that of a druggist who had a teaspoonful of deposit at the bottom of a conical glass vessel with a quart of wa- ter above it, and who, after running about for bottles and jars to hold this water, which he thought must be poured off, returned to find the deposit removed, and in a small phial in my pocket, the quart of water re- maining undisturbed. " Why," he said, " that is strange. I never saw the like before. How did you do it ?" - It is often convenient to have several dipping-tubes, some straight, others drawn out to a point, and some curved so as to be readily directed into a narrow corner. A glass tube is easily pulled out to a fine extremity, or variously curved when softened in an alcohol flame. But a spirit-lamp may not always be within reach, and is not necessary, for the student can make a Bnnsen burner almost without cost, and use it successfully if his home is supplied with illuminating gas. Prof. Aus- tin C. Apgar, in Science News and Boston Journal of Chemistry, has, under the title " A Bunsen burner for two cents," recently described a simple piece of appara- THE MICROSCOPE AND ITS PARTS. 37 tus that is a boon to any one desiring to do a little ama- teur glass-blowing. A strip of tin about six indies long and two wide is rolled, without solder or fastening of any kind, into a tube about half an inch in diameter, after two holes, each about one-fourth inch in diameter, have been punched so that they shall be on opposite sides of the tube, and high enough to be a short dis- tance above the tip of the gas-burner. This simple ar- rangement is forced over an ordinary burner, so that the holes are just above the tip, the spring of the tin hold- ing it in place; the gas is lighted at the upper end, where it burns without smoke and gives a strong heat, the flame being easily regulated, and, with ordinary care, not flashing into the tube. It is entirely successful. Evaporation of the water will take place from be- neath the thin cover, sometimes quite rapidly, and the observer will at first be surprised at the way in which his objects will be swept out of the field before an ad- vancing wave that leaves the glass nearly dry behind it. The water in the cell is drying up, and a fresh supply must be added if the objects are not to be entirely lost. Here is another advantage in using square covers on cir- cular cells. The four corners project beyond the cement ring, and by applying the camel's-hair brush, wet with water, to the slide beneath any one of these projections, the drop will run in and fill the cell by capillary attrac- tion. This supply is much more easily added than if circular covers are used, and after a little experience the fresh drops can be applied while the eye is at the eye- 38 MICROSCOPY FOR BEGINNERS. piece, the hand alone guiding the wet brush, and the eye taking note of the rush of the incoming wave and the result. The student will soon become such an adept that he will be able to add so small a supply at each touch of the wet brush that the movement of the cap- illary wave will not be strong enough to float the ob- ject out of the field. But it often happens that a certain specimen is to be studied for a long time, a whole evening, for instance, and to be continually supplying the loss by evaporation is not convenient — the student often becoming so ab- sorbed that he forgets this one of nature's laws until he suffers the penalty, and probably loses his object. At such a time an arrangement is wanted for supplying fresh water continuously and without demanding much attention, and such a contrivance is easily made. With a triangular file cut one of the smallest homoeopathic phials in two, throw away the upper half, and cement the lower to a little oblong or square piece of ordinary glass or broken slip. Attach this to the slide by a drop of glycerine, taking care not to use too much, or the square will glide out of place when inclined. Fill the bottle with water, coil into it one end of a doubled, loosely twisted thread of sewing-cotton, and place the other end in contact with one side of the cover, as shown in Fig. 3. The water will pass down the thread to one edge of the cell, where it will flow under as it evapo- rates from the other three sides. This usually works well, the secret of success being to have the reservoir THE MICROSCOPE AND ITS PARTS. Fig. 3.— A Growing-slide. not more than three-quarters of an inch from the cell, to keep it always full of water, and to have the doubled thread applied closely against the cover. If the water supply is too great, and the cell is disposed to over- flow, shorten the end of the thread against the cover ; if not enough, lengthen it, and do not allow the thread to touch the slide in its course from the reservoir to the cell. Again, the observer frequently wants to make a grow- ing-cell of the slide on which he may accidentally have placed a desirable or beautiful object ; that is, he desires to preserve the specimen for several days in the cell without disturbing it, and so taking the risk of losing the invisible thing. He may also wish to watch its growth and development. A reservoir for 'a water sup- ply is necessary ; an " individual " butter-dish makes a good one. Place the slide across the dish, apply a dou- bled thread of sewing-cotton along one side of the square cover, so that each end shall hang down into the dish, and fill the latter with water, which will then pass up and along the thread, and keep the cell full for as long as may be desired. The only objection to this little af- fair is that, after a few days' use, the salts in the water will crystallize on the cover, and so cut off part of the oxygen supply. But no growing-cell is free from some 40 MICROSCOPY FOR BEGIXXERS. objectionable features ; none can quite imitate the natu- ral conditions, and the animal or plant dies before long, either falling to pieces or becoming buried beneath a mass of fungi. This one will supply an abundance of water, if the water in the dish is always kept in contact with the lower surface of the slide. This, and the ab- solute contact of the thread with the edge of the cover, are the only things whose absence will result in defeat. As the reader already understands, the object must never be examined in water without being covered by either a thin glass circle or square ; the importance of this little piece of glass must not be forgotten. But very often, in lowering it over the wet specimen, small bubbles of air will be caught and not noticed until mag- nified, when, if seen for the first time, they appear won- derful, if not startling. Some strange statements have been made, and discoveries announced whose only foun- dation has been minute air-bubbles that the observer did not recognize. A man once described a marvellous something that he had found in a cancer, which turned out to be a magnified air- bubble. These little air-drops always play an amusing part at the beginning of the microscopist's career. In Fig. 4 are shown several of different sizes. Let Fig. 4.— Air-bubbies. the student examine a drop of saliva or of soapsuds, and he will in future be able to recognize the troublesome things. Pictures or words cannot convey so true an idea of their appearance as a THE MICROSCOPE AND ITS PARTS. 41 single sight of the bubbles themselves. At times they become entangled in the parts of an object in such num- bers as to interfere with its examination. In these cases nothing can be done except to lift the cover on the point of the needle, and slowly lower it, or remove it entirely, add more water, and reapply it carefully. In appearance the bubbles are usually circular, with a broad black border which varies in width and depth of color as the objective is raised or lowered. Near the margin is a bright ring, and in the centre a bright spot. They often float about, and this movement adds much to the wonder with which the beginner usually regards them. If the student will have a note-book in which to jot down his observations, or to keep a list of the objects examined, it will not only aid him in forming habits of accurate observation, but will be of great interest when he has become an accomplished microscopist. The en- try may be very simple, and may be made to serve as a memorandum of items to refresh the memory. Here is an example from a boy's note-book: "June 15, 1884 — Came across a pool near the toll-gate with the water colored green, and found the color was caused by a great quantity of Volvox — small green globes rolling about in the water. Volvox is said to be a plant. Wonder if it is. What are the darker balls inside of some of them ?" He answered all these queries later in his experience. If you can draw the microscopic objects that interest you most, although the sketches may not be quite artis- tic they will help you to remember, and a collection 42 MICROSCOPY FOR BEGINNERS. of such drawings will be as interesting and valuable as the note-book. In talking to friends about microscopic matters, a single rough drawing will do more to help them understand than many words. And if you can look at the object and make the sketch, you will like it better and do yourself more good than if you bought and used the drawing apparatus called a camera lucida, for sale by the dealers. This camera lucida is a glass prism, so arranged that when it is put over the eye-piece, and the microscope is placed in a horizontal or inclined position, the magnified image seems to be reflected down on a sheet of paper spread on the table just under the camera, but of course with a space of several inches be- tween them. By placing the eye in the proper position, and looking down towards the table through the edge of the prism, the image and the pencil-point can both be seen at once and the outlines traced. It is a rather ex- pensive apparatus, and difficult to use without a good deal of practice, but if you want a simple arrangement that you can make, try the one shown in Fig. 5. From a piece of thin sheet brass or tin, cut with scissors a strip half an inch wide and long enough for B. — Reaector for one end to pass around the upper Drawing the Magni- . fled object. part oi the eye-piece, and the other to be bent into a handle like a small hollow square. Cut another strip about one inch long and one-fourth wide, and double it lengthwise so that it THE MICROSCOPE AND ITS PARTS. 43 will still be an inch long, but one-eighth of an inch broad. Take one of the small brass hinges to be had for a cent, solder one end to the hollow handle and the other to the narrow doubled strip; into this narrow piece place a thin glass square, the thinner the better, and the instru- ment is done. To use it, turn the microscope horizontal, have a faint light on the object and a strong one on the paper, bend the strip of brass around the upper part of the eye-piece so it will not slip, the hollow handle and hinge being directed towards the table, and move the hinge until the thin cover is placed obliquely in front of the eye-glass of the eye-piece. Look down through the glass square towards the paper on the table, and the image of the object on the stage will seem to be thrown on the white surface, where it can be traced with a pen- cil. The image is really reflected from the surface of the thin square, and the pencil is seen through it, but the eye unconsciously combines them so that both are seen together. The secret of success here is a faint light on the object, a strong one on the paper, and a thin glass square. A long, sharp pencil-point is also an advantage. A micrometer is for measuring objects under the mi- croscope. It is made by ruling a number of short lines on glass, the spaces between the lines varying from j^-g- to 1016&- inch or less. Micrometers are said to have been ruled with one million lines to the inch, but no human eye using the best and highest power objectives has ever seen them. All micrometers are ruled by a machine made for the purpose. 3* 44 MICROSCOPY FOR BEGINNERS. The beginner will not need one, but ho may desire to know how to use it. Place the micrometer on the stage, turn the microscope horizontal with the reflector referred to above, fitted to the eye -piece. "With the low-power objective focus the lines that are yfg- inch apart, and draw them on the paper. Do the same with every objective, drawing the y^ inch spaces with the £ or £ lenses. These drawings will form the scale for measuring the drawings of the magnified objects. Thus, if the magnified object, when drawn, occupies two spaces of your paper scale made from the y^-g- inch micrometer spaces, the object will measureyl-j, or -^ inch in length ; if five spaces of your scale, then it will measure yjj-^, or •g1^ inch long ; if only one-half a space of your scale, then it will measure one-half of y^- of an inch ; if one- fourth of your scale space, then its actual length will be •j-J-5- inch. If the £ or -^ objective is used in making your scale from the 10*00 inch micrometer spaces, then each division on the paper will represent 10*00 inch, and if the drawing of the object measures two of these spaces on your scale, the real length of the object will be y^j- inch, or Tfj-. It is perceived that the stage micrometer cannot be used for measuring objects direct- ly, but only by applying the drawing of the magnified micrometer spaces to the drawing of the magnified ob- ject. The micrometer can also be used to ascertain the power of the microscope. If each of the y^-g- inch spaces measures, when drawn on the paper, T^ inch, that com- THE MICROSCOPE AND ITS PARTS. 45 bination of eye-piece and objective will have a magnify- ing power of ten diameters ; if each y^- inch microm- eter space measures -^ inch, the power will be forty diameters ; each, therefore, corresponds to ten times. If the YoVtf mch micrometer spaces measure, when drawn, Y1^ inch, then each tenth corresponds to a power of one hundred times ; therefore, if the ^-^ inch spaces, when magnified, measure ten-tenths, the power of that eye- piece and objective is of course one thousand diameters, or ten times one hundred ; if five-tenths, then five times one hundred. The owner of a microscope should never take a walk in the country without one or two wide-mouthed bot- tles in his pocket. Empty morphia bottles, to be had of any druggist, are convenient for small collections ; for greater quantities an empty quinine bottle, and for still larger gatherings of aquatic plants the ordinary glass fruit-jar is admirable if a string is added for a han- dle. No bottle should be entirely filled and corked, or all animal life will be animal death before the micro- scope is reached. Leave a large space for air between the cork and the water. Those desiring information as to the optical construc- tion of the compound microscope, the uses of the numer- ous pieces of apparatus often used for advanced work, and about the methods of permanently mounting micro- scopic objects, may advantageously consult the follow- ing publications : 46 MICROSCOPY FOR BEGINNERS. ''How to Use the Microscope." 16mo. By John Phinn. New York. " How to See with the Microscope." 12mo. ByDr.J. E. Smith. Chicago. "How to Work with the Microscope." 8vo. By Dr. Lionel S. Beale. London. "The Microscope." Small 4to By Dr. W. B. Carpenter. London. " The Micrographic Diction - ary." 8vo. London. "Manual of Microscopic Mounting." 8vo. By John N. Martin. Philadelphia. " The Preparation and Mount- ing of Microscopic Objects." 16mo. By Thomas Davies. London. The American Monthly Microscopical Journal. Washington, D. C. The Microscope: an Illustrated Monthly Journal. Ann Arbor, Mich. AQUATIC PLANTS USEFUL TO THE MICROSCOPIST. CHAPTER II. COMMON AQUATIC PLANTS USEFUL TO THE MICROSCOPIST. Ranunculus. — Nymphaea. — Myriophyllum. — Utricularia. — Cerato- phy Hum. — Lernna. — Anacbaris. — Vallisneria. — Sphagnum. — Ric- cia. THERE are several common plants floating freely in the water, or more or less firmly rooted in the mud at the bottom of shallow ponds and slowly flowing streams, that are important to the student of microscopic aquatic life. This may be either through their own interesting or peculiar structure, or on account of the minute plants and animals living among their tangled leaves or at- tached to the stem and other parts, these entangled ob- jects being, therefore, more easily and surely captured by transferring the larger visible growths to a small vessel of water than in any other way. Most of these aquatic plants have their leaves divided into fine, thread- like leaflets. They have " dissected leaves," as the bot- anist names them, and they become the favorite resorts of invisible animals which attach themselves to the nar- row divisions, and feed on the free-swimming kinds that also find the same places attractive. So, if the student desires to gather microscopic material, let him find any of the following plants and he will be quite sure to get what he wants. But he must remember that by lifting 48 MICROSCOPY FOR BEGINNERS. them out of the water very many of the creatures he most desires will be washed away. The plants should be slowly and carefully drawn to the shore, and lifted out in a tin dipper and poured into a wide -mouthed bottle. The small tin dipper will prove a very conven- ient implement for all kinds of microscopical collecting, as a handle of any length can be made by thrusting a stick into the hollow handle of the dipper. If the lat- ter, however, is not accessible, the plants may be gently pushed into the bottle, after it has been partly sunk so that it lies parallel with the surface of the water. Many of our commonest aquatic plants have no com- mon English names, probably because most of them bear the smallest and least showy flowers of all bloom- ing plants, and therefore do not attract the attention of the ordinary observer. In referring to them, the begin- ner must use the scientific names, or learn the meaning of the Latin words and use the translation, usually with awkward results. It sounds better and is quite as easy to speak of Myriophyllum as of the " thousand-leaved plant," which the word means. Many plants might be styled thousand-leaved; another common aquatic one, for instance, which often grows in the same pond with Myriophyllum, the Ceratophyllum, called "hornwort" because the leaves are rather stiff and horny ; and Lem- na, as a word, is prettier and more appropriate than "duckmeat," an ugly term and meaningless, because ducks have nothing to do with the plant. If the reader is not already familiar with the appear- AQUATIC PLANTS USEFUL TO THE MICROSCOriST. 49 ance of the following forms, he need have no trouble in learning their names, although he may not have studied botany ; he has only to compare the leaves with the figures in this chapter. It is, of course, understood that there are many aquatic plants not here referred to, only those being included in this list which afford the most certain supply of microscopic life. The leaves of many water-plants fall against the stem and cling together when lifted into the air ; but if the student will place a small part of the plant in a saucer ("individual" butter dishes are good for this purpose), he can float them out against the white surface and so compare them with the figures. RANUNCULUS AQUATILIS (Fig. 6). A part of the stem and a single leaf of this plant are shown about natural size in the figure (Fig. 6). It is quite common in ponds and slowly flowing streams: The leaves are dissected into fine, rather stiff and hair -like parts, to which many minute animals, such as Rotifers (Chapter VIIL), Vorticellas (Chapter V.), and Stentors (Chapter V.) are fond of attaching themselves. The leaves are placed above each other on opposite sides of the rather brittle stem, and usually quite wide apart. Fig. 6.— Leaf of Ranunculus nqndtilis. 50 MICROSCOPY FOR BEGINNERS. The whole plant is under water except at flowering- time, when it raises a delicate stalk above the surface, and blooms with a single white flower closely resem- bling the common yellow " buttercup " of the fields. NYMPHJEA ODORATA (Wmra WATER-LILY, Fig. 7). Every one is familiar with this beautiful flower, that " marvel of bloom and grace," and the large, almost cir- cular, floating leaves. It is to the under-surface of the latter that the microscopist often goes for several forms of case-building Rotifers, with the certainty of always finding them, together with many and various kinds of minute animal life. It is also an excellent place to search for worms. You will usually find these creat- ures if the surface is gently scraped and the dark mass obtained is examined in water. But if the scented blossom is beautiful to the ordi- nary observer, the interior of the flower-stems and leaf- stalks lias charms known only to the microscopist. Gut a thin slice from either of those parts and examine it. The sides of the wide openings made by cutting across the internal tubes are studded with crystal- line stars (Fig. 7). Three-point- ed, four and five pointed, they Fig . r.-pedancie of Nymphsea sparkle there like diamonds, yet odorata ; transverse section. they were formed in darkness, and in darkness act their part in the life of the AQUATIC PLANTS USEFUL TO THE MICROSCOPIST. 51 plant. What that part is we can only guess. Botan- ists call them internal hairs ; but they are hard, sharp, and brittle. They are hollow, too, and their surface is roughened by minute elevations, as though fairy fingers had sprinkled them with crystal grains. I never see a white water-lily without in imagination seeing those long stalks rising out of the black mud up through the dark water, with their entire length illuminated by the sparkling of these internal star-like gems. The whole plant contains them, even the root. The common " spat- ter-dock " — hideous name ! — the Nuphar, also conceals similar stellate hairs within its stems, but they are there larger and coarser, as becomes a coarser plant. The leaves of the Nuphar, however, are not a good micro- scopical hunting-ground, as they usually stand high above the water. MYRIOPHYLLUM (Fig. 8). This is not rare in shallow ponds and slow streams ; it even occurs in running water, but there it is not worth gathering, so far as any adherent microscopical life is concerned. Indeed, no running water is a good locality for free-swimming creatures, because the current sweeps them away, and so scatters them that it is not possible to make a collection. But where Myriophyllum grows it usually grows abundantly. It forms long green streamers, round and thick, sometimes more than an inch in diameter and several feet long, yet it looks soft and feathery. The leaves are very numerous, and each 52 MICROSCOPY FOR BEGINNERS. Fig. 8.— Whorl of Myriophyllnm Leaves. set is arranged in a circle around the stem ; they are in "whorls," as the botanist calls the arrangement. One such whorl is shown in Fig. 8. Five dissected leaves are there drawn, but whorls sometimes occur with three or four, the number helping to distinguish the species, of "which there are several. They all resemble one anoth- er when in the water. The parts of the leaf are fine, soft, and hair-like, those near- est the stem of the plant being the longest. They are very numerous and close to- gether, thus giving the floating streamers their pecul- iar thick and soft appearance, and making them an ex- cellent place for the microscopist to explore. To compare with Fig. 8 a feathery plant which the collector does not know, select a circle of leaves, cut the stem close above and below it, and after floating the separated whorl in a saucer as already directed, or spread- ing it out on white paper, compare its leaves with those figured. The leaves vary in size in different parts of the plant, the uppermost being smallest and youngest, the lower the oldest arid largest. There is another rather common aquatic plant called Proserpindca, or " mermaid- weed," which so closely re- sembles Myriophyllum when in the water that it has AQUATIC PLANTS USEFUL TO THE MICROSCOPIST. 53 often been mistaken for it. To make such an error is of no great consequence, unless it should lead the ob- server to imagine, as it once did the writer, that he has found a rare species of Myriophyllum. Yet it is always pleasant, if nothing else, to feel sure, and it is more than pleasant to have a reputation for accurate observation. Proserpinaca, however, is as useful a trap as Myriophyl- lum, and it can be easily distinguished because the dis- sected leaves are not in an exact circle around the stem : one is on one side, the next a little further round and a little higher on the stem, another still further round and nearer the first, but still higher. They are what the bot- anist calls alternate. Either of these plants is a specially good place for attached diatoms (Chapter III.). UTRICULARIA (Figs. 9 and 10). Of all our water-plants with finely divided Utricularia is probably the most interesting in and one that can always be recog- nized at a glance. It is found in long, somewhat branching streamers, floating freely below the surface or very slightly rooted. A leaf of Utri- cularia vulgdris, a common species, is shown somewhat enlarged in Fig. 9, with the peculiar hollow bladders, or " utricles," that distinguish it from all other plants, and give it one of its leaves, itself, Fig. 9 A Leaf of Utricn- laria. 54 MICROSCOPY FOR BEGINNERS. scientific names. These utricles are almost always con- spicuous when the plant is taken from the water, as small, green, semi-transparent particles attached to the leaves. They are not unlike small pieces of jelly in appearance, until examined with the microscope, when their remarkable structure is seen. Until within a few years they were supposed to act as air-sacs to help the plant float. It was even said that they became filled with air or gas at flowering-time, and so lifted the flow- er-stalk and the bloom above the water. This was in- teresting, but the truth is more interesting and star- tling. The plant actually feeds on animals. These bladder-like bodies are the food-traps, the mouths and the stomachs of the Utricularia. Under the microscope they are seen to be hollow, oval bodies, with a narrow, almost straight anterior end, and several long bristles projecting forward or away from the utricle, these bristles probably serving as a guide to an opening at their base. The little animal swims or crawls against a bristle, and naturally moves down it towards the opening in the utricle, which it finds closed by a transparent colorless curtain ; this it pushes aside and passes on into the trap. The curtain-like valve is at- tached by its upper and lateral margins, therefore hang- ing before the opening in the utricle, and swinging in- ward, but so arranged that it cannot be forced outward by any creature small enough to pass within. Indeed, the power that the valve seems to exert is somewhat astonish- ing. Small fish have been found with the tail or even the AQUATIC PLANTS USEFUL TO THE MICROSCOPIST. 55 head inside tlie utricle, and firmly held by the pressure of the valve. In these cases, however, it seems proba- ble that the struggles of the dying fish may have wedged it fast, rather than that the valve has held it. Small worms and worm-like larvae have been found half in and half out of these fatal traps, for once past the curtain- like valve the little animal never escapes. ,And no sooner has it entered than it begins to show signs of discomfort ; if it has a shell it withdraws its legs and head and closes the shell ; if a worm or animalcule it speedily becomes languid, its movements cease, and it finally dies, as does every creature that ventures into Utricularia's utricles, which evidently contain something more than simple water. If these bladders are torn to pieces under the microscope with the needles, the remains of many kinds of minute creatures will be seen, the soft parts of the captives having been dissolved and absorbed, and gone to nourish the FitT10 _ plant The whole inner surface of the fid Process n-om . ,. , , . Inner Surface of utricles is lined by innumerable colorless utricle of utri- four-parted bodies, one of which is shown much magnified in Fig. 10. They are distinctly visible only when the utricle is torn to pieces. They are said to absorb the fluid in which the entrapped animals are dis- solved. CERATOPHYLLUM DEMERSUM (Fig. 11). This is commoner and more abundant than Myrio- phyllum, for which it is often mistaken, although the 56 MICROSCOPY FOR BEGINNERS. two have only a remote general likeness. The leaves of Myriophyllum are fine and soft, those of Ceratophyllum rather coarse and stiff. In the latter they are whorled with six to eight in each circle, but instead of being di- vided on each side down to the middle line (the midrib), as in Myriophyllum, they appear to separate into two narrow parts near the stem, while each division then often divides into two other parts. Both these arrangements are represented in Fig. 11, where the whorl is shown separated, as was Fig. 11.— whori of Lcaves^of done in Myriophyllum. The leaves always bear several very small but visible spines on their sides, as in the figure, and when taken from the water they usually do not fall against the stem. The plant is found in still, shallow places, growing in thick masses and often considerably branched. It makes an excellent retreat for certain Rotifers and worms, but the leaves are so heavy and stiff that they are not as easily prepared for microscopical examination as are those of Myriophylluin ; they often refuse to lie flat, and thus tilt the cover glass and allow the water to run away. But with neither of these plants will the student try to place an entire whorl in the cell. It is always best to clip off with scissors a part of a single leaf, and examine it for whatever may be attached. Work with the microscope is delicate work, and the smaller the ob- AQUATIC PLANTS USEFUL TO THE MICROSCOPIST. 57 jectj within certain limits, the better. Many beginners make the mistake of trying to examine too large a speci- men or too much of a mass at once. LEMNA POLYRRHfZA (Fig. 12) AND LEMNA MfNOR (Fig. 13).- DUCKMEAT. These are small plants, very common, and often so abundant that the entire surface of large ponds is cov- ered by them as by a green carpet. The water in such cases is so completely covered and concealed that the observer is for a moment tempted to step on it. The above two species resemble each other, yet they differ so widely that a glance will distinguish them. Each consists of a small green, more or less oval leaf or frond floating on the water, with one or more rootlets hanging from beneath, but never taking root in the mud. Usually two, three, or four fronds are attached together, so as to form an ir- regular star. Lemna poly rrhiza, the many- rooted one (Fig. 12), has the largest fronds, is a deeper green, and, as its specific name Fig. 12.— Lemna signifies, has many rootlets, often a dozen, hanging in a cluster from each. It can always be known by this root-cluster and by the dull purple color of the lower surface. It seems to like the sun better than Lemna minor, and is oftener found abundantly on open ponds, while the latter appears to prefer ditches with high banks and shade. Lemna minor (Fig. 13) has smaller, more oval and 58 MICROSCOPY FOR BEGINNERS. thinner fronds. It is lighter green in color, the lower surface is never purplish, and it has but one rootlet to each frond. Both species have a curious little ^^ cap on the free end of each rootlet. It is more easily seen with the naked eye on Lemna polyr- rhiza, where it is usually darker than the rest of the rootlet. There are several other species, but they are so seldom found that they are not included in Xlg. 13. — L6mna this list. They all multiply by the growth of young fronds from the edges of the old and mature. This accounts for the clusters so commonly seen. They also bloom, but the flowers are extremely small and are rarely observed. The student will be fort- unate to find specimens in blossom. The flowers burst out of the margin of the frond, and consist of only those parts needed to fertilize and mature the few small seeds. The rootlets are valuable to the microscopist, as they are favorite places for many just such creatures as he most wants. The lower surface of the fronds, especially of Lemna polyrrhiza, should be gently scraped in a drop of water for Rotifers not often found elsewhere. It is also much visited by small worms, but not so frequently as the leaves of the white water-lily. ANlCHARIS CANADENSIS (Fig. 14). This is readily recognized by the arrangement of the leaves in circles, or whorls, of three each, two of which AQUATIC PLANTS USEFUL TO THE MICROSCOPIST. 59 are shown in Fig. 14. The stem is brittle, and frag- ments easily take root, so that the plant spreads rapidly. Having been accidentally introduced into England, it is said to have grown so fast that it has choked up some of the shallow- er streams and to have become a nuisance. It is abundant in this its native country, but it never acts so badly here. The whole chads cana- plant is semitransparent, with leaves about half an inch long springing directly from the stem, and tapering to the point. These leaves, under the micro- scope, exhibit a remarkable phenomenon. All plants are formed of cells, or cavities of various sizes and shapes, surrounded on all sides by a delicate membrane called the cell wall. The cells are seldom empty. Their contents are chiefly the soft, colorless, jelly-like substance called vegetable protoplasm, and the small green grains (the chlorophyl) which give the green color to the plant. In Andcharis the walls of the leaf -cells are transparent, so that the microscope shows a part of what is taking place within the cell ; and it is a wonderful sight, for the protoplasm is slowly moving around the walls, carrying the chlorophyl grains with it. Up one side of that microscopic cell travels the strange procession ; across, down, and up, slowly and steadily the stream and the grains move round and round. Sometimes a little thread of colorless protoplasm leaves the main current and starts across by a shorter road, and sometimes the current pauses, stops, 60 MICROSCOPY FOR BEGINNERS. and refuses to move again. The streams in two cells lying side by side may flow in the same or in opposite directions, with only the thin wall between them. What causes these remarkable movements is not known. Cold seems to retard, and warmth to hasten the flow, and often, when the chlorophyl has increased so that the green grains crowd the cells, the circulation ceases, ap- parently because the chlorophyl has not enough space for free movement. The botanists call this circulation of the protoplasm cyclosis. It is also finely seen in the long, narrow, ribbon-like leaves of Vallisneria, an abun- dant and common plant in slowly flowing streams. To show the cyclosis, the Anacharis leaf needs only to be cut close to the stem, placed in the cell in water, covered by a thin glass, and examined by a high-power objective. The one-inch glass will not show it. . The plant is a fruitful source of supply for our two common species of Hydra (Chapter YL), which often oc- cur there so plentifully that two or three hang from al- most every leaf. SPHAGNUM MOSS (Fig. 15). On the wet shores of shady bogs this pale -green moss grows in great patches, thick, soft, and elastic. It is a beautiful plant anywhere, but it is especially so when it appears greenly glimmering beneath the shallow water, while the shadows of elder and azalea, and the broad leaves of the tangled smilax vines, make the neighboring thicket dim and cool, even when the hot sun smites the bordering fields. In such pleasant sur- AQUATIC PLANTS USEFUL TO THE MICROSCOPIST. 61 roundings Rhizopods (Chapter IY.) and Infusoria (Chap- ter "V.) are found in abundance. For the former it is an unfailing source of supply. The water pressed out of a little pinch of the moss will be sure to contain many individuals and species. From a single small bunch Dr. Leidy, when studying the Rhizopods, ob- tained thirty-eight species and many individuals of those animals, besides numerous active diatoms (Chapter III.) and desmids (Chapter III.). The leaves make exquisite microscopic objects, on ac- count of their curious and beautiful structure. Each leaf is formed of two kinds of cells, a and & (Fig. 15). The large ones, a, will, when magnified, immedi- ately attract the attention. They are hollow, and usu- ally empty, and they have a spiral thread running around the walls. At cer- tain stages of growth the cell -wall also has one or more small openings, c, so that the water is able to pass in and fill the cell. This may explain why the Fig" 15-p-tio» of Leaf of sphagnum, plant retains moisture for so long, and why it is so easily wetted. The second kind of cells, 5, are found between the 62 MICROSCOPY FOR BEGINNERS. large ones. They are much smaller, narrower, and com- monly contain chlorophyl grains, which, while usually not abundant enough to tint the whole moss a bright green, yet give it that beautiful pale hue almost charac- teristic of it. These cells will probably need to be searched for the first time the beginner studies a sphag- num leaf, as they are not apt to catch the eye. The moss seems to have no roots. The lowest parts of the thick mass which it makes are usually dark and partially decayed, and it is there that the Rhizopods are most abundantly found, although many sun-loving forms are equally numerous in the brighter, better lighted up- per parts. On no account should the student pass a sphagnum swamp, nor even a little patch in those places where it grows more rarely, without taking some to be examined at home. Such a gathering will always pay. R1CCIA FLUITANS (Fig. 16). Near the writer's home this little floating plant (pro- nounced ricksia) is so abundant that it often covers small pools with a layer two inches deep. Elsewhere, on larger ponds, it is not un- common. It often comes to the collect- ing-bottle tangled in the leaves of Utricu- laria, Myriophyllum, or Ceratophyllum, Fig. 16.— Kiccia flfi- or it floats on still waters in little patches iUms. like islands. Its form is seen in Fig. 16. It has no leaves, indeed it is all leaf ; the botanist calls it a radiately expanding frond, with narrow divisions, AQUATIC PLANTS USEFUL TO THE MICROSCOP1ST. 63 whose ends are notched. The plant is green, and may be an incli or more wide when spread out. It is often larger and more branched than shown in the figure. It has no roots, but floats freely wherever the currents or the winds send it. Shady places seem its favorite haunts. As a microscopic object it is rather large and thick, but it forms a good place to examine for certain Algae (Chapter III.) which tangle themselves about it in fine green threads, appear to favor it, and may often be seen with the naked eye if the single frond is placed in water above a wliite surface. 64: MICROSCOPY FOR BEGINNERS. CHAPTER III. DESMIDS, DIATOMS, ASTD FRESH-WATER ALG.E. THE desraids and diatoms are two closely related groups of minute aquatic plants which the beginner will at first probably have some trouble to distinguish from each other ; yet after a very little experience he will be able to recognize them at a glance. Both are plants formed of only a single cell, but their beauty and variety of form, their peculiar movements and wonder- ful structure, place them among the most attractive of microscopic objects. And they are among the most fre- quent. Scarcely a drop of water from a pool in spring or summer can be examined without showing a desmid or a diatom. The desmids are usually found in the freshest and sweetest water. In salt or brackish marshes, where di- atoms flourish as well as in a mill - pond, desmids never occur. They also seem to prefer open pools on which the sun is brightest and the shadows fewest, where they probably seek warmth rather than the strong light, for they seldom form patches on the mud as the diatoms do, but adhere to the stems of other plants in a green film, or conceal themselves among the dissected leaves of the aquatic vegetation, or among tangled masses of DESMIDS, DIATOMS, AND FRESH-WATER ALG.E. 65 A living desmid is always green ; a living diatom is always brown. This difference in color makes it easy to distinguish the two groups of plants, but there are other points that can be used by even a color-blind student. The cell- wall of the desmid— that is, the thin sack which surrounds the soft green contents — is soft and flexible. If the cover-glass is pressed down firmly with a needle the desmid can be flattened or squeezed out of shape, and the cell-wall can often be broken, so that the green and colorless mixture of jelly-like matter filling the plant is forced out. The cell-wall of a diatom is hard and brit- tle. The cover-glass may be pressed upon until the glass breaks, yet the diatom will not be flattened nor its shape changed. It may roll over and look quite different in form when viewed in another position, but it will prob- ably roll back and appear as at first. It can be broken, however ; and it does so as if made of glass or some other hard and brittle material, and the yellowish-brown con- tents may flow out, but the broken place will not be a hole with irregular edges, as it was in the crushed des- mid ; the edges will be sharp and angular, and the dia- tom will probably break into several fragments. Yet with the most skilful manipulation it is rather difficult to purposely break any but the largest of the diatoms, few of which are visible to the unaided sight of the acutest eye. The little hard-coated plants are often found in fragments, but according to the writer's experience they are broken accidentally, either by being piled on top of each other and so crushed by the cover -glass, 66 MICROSCOPY FOR BEGINNERS. or by the rough contact with one another when gath- ered. The desmids float freely in the water ; many diatoms do the same. Several species of desmids are attached to each other side by side to form long bands ; many diatoms are arranged in a similar way. Some desmids are surrounded by a colorless jelly-like coating ; so are some diatoms. The desmids never grow on the ends of stems secreted by themselves, and attached to other plants or submerged objects ; many diatoms are found growing on the extremities of long colorless and branch- ing stalks like microscopic trees, these stems being fast- ened to other objects in the water. Some of the common- est diatoms will be found in great abundance growing in this way on the leaves of Myriophyllum. Any object that may apparently be either a desmid or a diatom is not a desmid if it is on the end of a stem of its own formation. Most desmids have the ability to voluntari- ly change their position. They can move from place to place, as they frequently do when under the micro- scope, slowly travelling across the field of view in a very interesting way. "When mixed with mud or dirt, as they often are when gathered and carried home in a bottle, they will gradually work themselves 'to the sur- face and collect in a green film or line on the side of the bottle next the window, whence they can be easily taken by the dipping -tube. Diatoms have a similar power of movement ; but they are usually much more active, and their motions more rapid than those of des- DESMIDS, DIATOMS, AND FRESH-WATER ALG^E. 67 mids. And wliile the desmids move stately and slowly in one direction, a diatom may travel quickly half-way across the field of view, and without a moment's hesita- tion, and without turning round, may at once return by its former path or dart off obliquely. A moving diatom always seems to have important business on hand, and to be anxious to accomplish it. An object, therefore, that may be either a desmid or a diatom is not a desinid if it moves rapidly and changes its course suddenly and quickly. The cause of this motion is in either case a mystery. Many theories have been proposed to explain it, but none are satisfactory. If the reader can discover how the desmids and diatoms move themselves his name will be remembered among naturalists to the end of time. The surface of a desmid may be smooth, finely stri- ated lengthwise, roughened by minute dots or points, or it may bear several wart-like elevations or spines of dif- ferent shapes ; its edges may be even or notched, pro- longed into teeth, or variously cut and divided. It is these ornaments, in connection with the graceful form and the pure homogeneous green color, that make the desmids so attractive to every student of microscopic aquatic life. Fresh-water diatoms occasionally have tooth- like processes, but they are never spine-bearing ; yet the markings of their surfaces are among the most exquisite of Nature's handiwork, and the most varied. Dots, hem- ispherical bosses, hexagons, transverse and longitudinal lines of astonishing fineness, are among their many 4* 68 MICROSCOPY FOR BEGINNERS. surface sculpturings, the delicacy and the closeness of which defy description. So fine and close together are the surface lines of some that they are used to test the good qualities of the best and highest power objectives: There are no perfectly smooth diatoms, although many may appear so to a low-power lens ; but the splendid glasses of the best American makers will compel any diatom to show just how it is marked and roughened. In each end of many desmids, especially in the cres- cent-shaped ones, is a small colorless, apparently circu- lar space containing numerous very minute black parti- cles in incessant motion. These little granules, which are said to be crystals, are sometimes so few that they can be counted if sufficiently magnified, while in other individuals they are innumerable. Their motion resem- bles the swarming of microscopic bees. It can scarcely be described, but once seen it can never be forgotten. The spaces containing them are called vacuoles, and are never present in diatoms. It is true that in some of the latter, when dying or dead, many minute black par- ticles are visible, dancing and swarming in clusters with- in the cells, but this is common to many microscopic creatures after death. In the desmids there is also often seen a circulation of the protoplasm similar to the cy- closis in the leaf-cells of Anacharis, a movement of the cell contents never observed, so far as I am aware, in any diatom. Between the cell-wall and the green col- oring matter, the chlorophyl, there seems to be a nar- row space filled with colorless protoplasm, and it is here DESMIDS, DIATOMS, AND FKESH-WATER ALG.E. 69 that the circulation takes place. It is a steady, quite rapid flow, several currents streaming lengthwise up and down the cell, carrying the minute starch grains and other enclosed particles in their course. It has been said that these currents sometimes enter the vacuoles, and that the latter obtain their supply of swarming granules from the particles in the streams ; it has also been stated that occasionally one or more of the swarm- ing granules leaves the vacuole, enters the current, and journeys round the cell. These statements are rather doubtful. But with a high -power objective (the one- fifth, for instance) it is not difficult to select a granule, and follow it as the current carries it down one side to the vacuole, where, according to the writer's observation, it never enters, but passes into an ascending current, and continues the round. The vacuoles themselves are visible with a good low-power objective, but to see the swarming granules and the general cyclosis a one-fourth or one-fifth is needed. In addition to the desmids and diatoms, almost every pond and stream contains other minute plants of interest to the microscopist, called the fresh-water Algae, which he probably already knows, if not by this name, at least by their general appearance, for they form those green masses floating like a scum on the surface, or soft green clouds attached to sticks and stones and dead leaves. The Algse often have a disgusting appearance as they collect in thick and heavy patches, but under the micro- scope they reveal beauty undreamed of. All those slimy, 70 MICROSCOPY FOR BEGINNERS. slippery streamers usually so abundant in still water dur- ing the summer are Algse. The beginner need have no trouble to recognize them as Algse after a little experi- ence, but since he at first may be somewhat uncertain as to which of the three classes of plants his specimen belongs, the following Key has been constructed to aid him. To use it, compare the plant with it in the fol- lowing way : Suppose the specimen is a single cell, shaped like a crescent, as described in the first sentence of the Key. The reader will notice (a) at the end, meaning that he shall now seek a description somewhere in the table be- low with a at the head of the line. Finding three such lines, he reads the first, "Color green," which is the color of the specimen under the microscope ; " the plant a floating hollow sphere," which does not describe it, since it is crescent-shaped. He then reads the second "a" line : " Color green, the plant not a hollow sphere," which is of course right, as his plant is not a sphere. The (£>) at the end refers to another line below headed by 5. There being but one such, the plant must be a desmid ; but to learn which of the numerous desmids it is, he turns to Section I. of this chapter, where is another Key to help him find the name of the genus. Again, sup- pose he obtains a floating mass which, when lifted on the hand or in the dipper, he sees to be a fine, delicate green net. To find the section to which this belongs, read each numbered sentence at the beginning of the Key : 1 will not do, since the specimen is not spherical, crescentic, DESMIDS, DIATOMS, AND FRESH-WATER ALG.E. 71 nor circular ; 2 will not do, because the plant is not in long threads ; 3 and 4 do not describe it, because it is neither star -shaped nor formed of oval cells with two bristles on each end ; but 5 calls for a green net often visible to the naked eye, which describes the specimen, giving the name of its genus, Hydrodictyon, and refer- ring the student to the Algse, Section III. of this chap- ter. After using this preliminary Key for a few times, he will be able to .decide at a glance through the micro- scope to which section his specimen belongs. Key to the Desmids, Diatoms, and fresh-water Algce. 1. Plants formed of a single, crescent-shaped, spherical, barrel - shaped, oblong and constricted, or circular and flattened, cell, sometimes arranged side by side in long ribbons, but seldom end to end ; color green or brown (a). 2. Plants formed of many cells arranged end to end in long threads ; coloring matter usually green, often in spiral bands or other patterns on the cell-wall (d). 3. Plants formed of several green cells grouped in the shape of a flat disk with six to many short blunt star- like points ; floating free. Pedidstrum (Algce, III.). 4. Plants formed of two to eight narrowly -oval green cells placed side by side, each terminal cell with two curved colorless bristles; floating free. See* nedesmus (Algce, III.). 5. Plants forming a green net visible to the naked eye. Hydrodictyon (Algce, III.). 72 MICROSCOPY FOR BEGINNERS. a. Color green, the plant a floating hollow sphere. V61VOX (AlffCB, III.). a. Color green, the plant not a hollow sphere (5). a. Color golden-brown (c). 1). Cell-wall smooth, rough, warty, or spine-bearing, also soft and flexible; always floating freely, never growing on stems permanently attached to other objects ; a vacuole with swarming granules often present in each end. (Desmids, /.) c. Cell-wall marked transversely, often also longitudi- nally, by lines, smooth bands, or dots; never spine-bearing ; cell-wall also hard and brittle ; floating freely, or growing on colorless stems permanently attached to other objects. (Dia- toms, II.} d. Plants forming cloud-like clusters, long streamers, or scum-like floating masses visible to the naked eye ; color bright green or olive, sometimes al- most black ; the cells under the microscope unit- ed end to end to form long, sometimes branching filaments. (Algce, III.) 1. DfcSMIDS. As the desmids are singly invisible to the naked eye, the student can know what he has gathered only after reaching home, except in those rare instances where the little plants have become congregated together in such quantities that a good pocket-lens will show their forms. I have more than once found Clostirium in this profu- DESMIDS, DIATOMS, AND FRESH-WATER ALG^E. 73 sion, but never any other. The early spring, as early as the last of March or the first of April, in the writer's locality (New Jersey), is the best time of the year to gather them, or indeed any of the Algae. At that time all these plants seem more vigorous, their vital functions are performed more actively, and the observer is then almost sure to see in some of them the conjugation, or union, of two separate cells and the formation of the spores. This spore formation, however, is much more frequently seen in the thread-like Algae than in the sin- gle-celled desmids. There are more than four hundred known species of desmids. Perhaps an undue proportion has been in- cluded in the subsequent list, but nature offers them 'so freely and abundantly, and they are so attractive, that they must be their own excuse. The following Key to the genera is to be used as directed for the " Key to the Desmids, Diatoms, and Fresh-water Algae," except that when the name of the genus has been found, the reader should then refer to the paragraph on the following pages headed by that name, where he will find one or more species described and figured. Thus, if he has a green half-moon-shaped plant under the microscope, to learn its name turn to this Key, the second line of which describes it, since it is not in ribbons or bands ; he then refers to the lines headed by d, the first one describing his plant as a " cell more or less crescent-shaped," giving the generic name Closterium, 6 being the number of the paragraph fur- 74 MICROSCOPY FOR BEGINNERS. ther on in this section of the chapter, where several species are noticed. Key to Genera of Desmids. 1. In ribbons or narrow bands (a). 2. Not in ribbons nor bands (d}. a. In a transparent, jelly-like sheath (5). a. Not in a jelly-like sheath (c). I. Each cell with two teeth on eacli narrow end. Didymoprium, 1. 5. Each cell deeply divided almost into two parts. Sphcerozosma, 2. b. Each cell without teeth and not divided. Hyalo- theca, 3. c. Cells barrel-shaped, the band not twisted. Bam- busina, 4. c. Cells not barrel-shaped, the band twisted. Desmi- dium, 5. d. Cell more or less crescent -shaped. Closterium, 6. d. Cell cylindrical, spindle-shaped, hour-glass, or dumb-bell shaped (/). d. Cell flattened, oblong, circular, or often divided into arms (e). e. Mostly circular or broadly elliptical, often cut and divided by slits and depressions ; marginal teeth usually sharp. Micrasterias, Y. e. Mostly oblong or elliptical, the margin wavy, the depressions rounded. Euastrum, 8. DESMIDS, DIATOMS, AND FRESH-WATER ALG.E. 75 f. Cell constricted in the middle ; no arms nor sharp spines (g). f. Cell constricted in the middle, with arms or sharp spines (A). f. Cell not constricted in the middle ; no arms nor sharp spines («"). g. Ends notched, cell cylindrical. Tetmemorus, 9. g. Ends not notched, cell cylindrical. Docidium, 10. g. Ends not notched ; cell more or less dumb-bell or hour-glass shaped (I). h. Arms three or more, radiating, tipped with one or more points. Staurastrum, 12. h. Arms none, spines four, two on each end. Ar- throdesmuSj 14. h. Arms none; spines several, on the edges; a round- ed, truncate, or denticulate tubercle in the centre of each semi-cell. Xantladium, 13. *. Chlorophyl in a spiral band, cell cylindrical. Spi- rotcenid, 15. *. Chlorophyl not in a spiral band, cell cylindrical (&). k. Surface roughened by tooth-like elevations. Tri- ploceras, 16. ~k. Surface smooth, ends rounded, neither divided nor notched. JPenium, 17. L End view three to six or more angular (m). I. End view not angular, margins smooth, dentate, or crenate, without spines; ends always entire. Cosmdriwn, 11. 76 MICROSCOPY FOR BEGINNERS. m. Angles obtuse, acute, or with horn-like prolonga- tions. Staurdstrum, 12* 1. DlDYMOPRITJM. Each cell in the band longer than broad ; two round- ed or angular teeth on each narrow end ; case or sheath distinct, colorless. D. Gremllii, Fig. 17. Fig. IT.— Didym6prium Grevillii. Fig. IS.— Spbserozosma pnlchra. 2. SPH^EROZOSMA. Each cell in the band about twice as long as broad, divided on both ends almost to the middle ; sheath large, colorless. Three cells are shown in the figure. S. pul- chra, Fig. 18. 3. HYALOTHECA. The ribbons are often very long, and the narrow ends of each cell are sometimes slightly constricted, as shown in the lower part of the figure, but the depression is never deep enough to form teeth ; sheath colorless. H. dissiliens, Fig. 19. Fig. 19.-IIyalotheca dissiliens. Fig. 20.— Bambnsina Brebissunii. 4. BAMBUSINA. The cells somewhat resemble barrels or casks joined DESMIDS, DIATOMS, AND FRESH-WATER ALG.E. 77 end to end, with two narrow hoop-like elevations around the middle of each. J2. Brebissonii, Fig. 20. 5. DESMIDITJM. The twisted appearance of the band is due to the fact that each cell is triangular, as may sometimes be seen when they break apart and float over on end, but the three angles are not all in the same line, each cell being turned a little to one side. When the side of the band is looked at, it is these Fig.2i.-Desmidium Swartzii. angles that are seen like a dark ob- lique or zigzag line traversing the ribbon. Each cell is slightly toothed on both the narrow ends. Common. D. Swartzii, Fig. 21. 6. CLOSTERIUM (Figs. 22 to 31). All the species of this genus are more or less cres- cent-shaped, some being more curved than others, but none having exactly straight sides. In each end of al- most every one will be seen a clear circular vacuole con- taining many small, dark, swarming granules. These have already been referred to, as has the movement of the protoplasm between the cell-wall and the layer of green coloring matter. Closterium is the only desmid in which this cyclosis can be seen easily, if it ever oc- curs in others. There are thirty-five species of the genus, the following being some of the commonest. The most convex margin is called the " back ;" the con- cave border the " ventrum." 78 MICROSCOPY FOR BEGINNERS. Some Species of Closterium. 1. Ends not lengthened out into a colorless beak (a). 2. Ends lengthened out into a colorless beak (/"). a. Back slightly convex, the whole cell slightly curved (&). a. Back strongly convex, ventrum nearly straight ( ^^ &TQ geveral species which closely resemble each other (Fig. 83). 3. OSCILLARIA (Fig. 84). These plants are found almost everywhere in the wa- ter. They often form thick floating mats of a dark purplish almost blackish color, or they are entangled among other plants in a dark green film. Under the microscope they consist of filaments composed of very many short cells that vary a good deal in width accord- ing to the species, of which there are several. They can usually be known by the bluish-green color and their characteristic motions. Some are like straight rods of cells bending slowly from side to side ; others twist and writhe and coil them- selves into circles, only to slowly uncoil and repeat the move- ments. Some glide slowly for- ward, the tip end gradually bend- ing and curving. The move- ments, when the plants are in a healthy condition, are incessant. The beginner need never be at a loss to rec- ognize one of the several species of Oscillaria. Three forms are shown in the figure. (Fig. 84.) 106 MICROSCOPY FOR BEGINNERS. Fig. 85.— Spirogyra. 4. SPIROGYKA (Figs. 85, 86). The SpirogyrcB are easily recognized by the beautiful spiral bands of green within each cell, as shown in Fig. 85. There may be one, two, or several of these spirals winding around the cell -wall, the num- ber helping to de- termine the species, of which there are many. The plants usually grow iu masses, and especially form those soft green clouds ap- parently floating in the water. They are often attached to submerged objects, but almost as often free. Their manner of producing spores is remarkable, but not confined to them, as other Algae have a similar method. The cells of two filaments lying side by side begin, usually at the same time, to throw out from those sides nearest each other a narrow tube. These tubes meet and grow together, so that the two filaments soon resemble a lad- der, the original filaments forming the sides, the tubes being the rounds. The coloring matter then falls away from the cell-walls, and the entire contents of the cells of one filament pass through the rungs of this living ladder into the opposite cells, where the contents of both mingle. From this mixture the spore is formed, one in each cell, and is, when ripe, oval and dark brown. This conjugation, as it is called, and the result- DESMIDS, DIATOMS, AND FRESH-WATER ALG.E. 107 ing spores are shown in Fig. 86. The plants are often found in this condition in June and July. 5. ZYGNEMA (Fig. 87). This usually floats unattached. The cells are rather wide and short, the inter- nal stellate masses being a deep green in color. The formation of the spores re- Fig. ST.-Zygneraa insigne.. sembles that of Spirogyra. It is found in conjugation in April. Z. insigne, Fig. 87. 6. VAUCHERIA (Fig. 88). A deep green mat growing on the mud in shallow water, and resembling felt both to touch and sight, will usually prove to be Vaucheria. The filaments are very long, with few branches. The green matter is diffused over the cell- wall, and when the latter is broken, flows out and often forms green globules. The spores are produced in two ways, both of which the beginner will see, as they are not rare early in the season. In one the end of a filament enlarges and becomes club-shaped, while a partition grows across it near the handle of the club. The contents of this new cell become very dark, opaque, and hardened. The free end of the cell then breaks, and the spore slowly passes out, being squeezed into an hour-glass shape as it does so. No sooner is it free than it is off like a flash, being covered by cilia. But it soon settles down, and finally develops into a fil- 108 MICROSCOPY FOB BEGINNERS. amcnt like the parent. In the other method the -fila- ment produces from the side, as shown in Fig. 88, a small oval cell, and near it a narrow curved or coiled tube. Presently the free ends of each of these cells open, and the contents of the tube pass into the oval cell, in which a spore without cilia is finally formed. Fis. S3.— Vancheria. This spore is said to fall in the mud and to remain unchanged for many months, sometimes all winter, but at last developing into another Yaucheria. In some of the species the oval cells are several in a cluster, and the whole, with the coiled tube, is raised above the filament on the end of a short stem. 7. CH^ETOPHOR.V (Fig. 89). The light green jelly-like masses into which this Alga grows are found attached to submerged leaves of grass, twigs, or other small objects. They are often almost spherical, varying in size from that of a pin-head to that of a marble. The surface is smooth, and so slippery that to pick up one of these Chatfdphora jellies is next to im- possible. The plant within the jelly is formed of fine branching filaments usually radiating in all directions from a common centre, the branches being shorter and most numerous near the surface of the gelatinous mass, DESMIDS, DIATOMS, AND FRESH-WATER ALG^E. 109 their ends bearing a fine, colorless hair or bristle. Tin- der a low -power objective the plant, if carefully flat- rig. 89.— Chsetophora elegans. tened out, is very beautiful, gant." Ch. elegans, Fig. 89. It is justly named " ele- 8. DRAPAUNALDIA (Fig. 90). There need be no trouble in recognizing this Alga. It grows attached to many objects, the fine branches giving it a delicate feathery appearance to the naked eye. Under the microscope it is seen to be much branched, the branches being arranged in clusters, and formed of cells smaller than those of the main stem, and filled with chlorophyl, while each terminal cell is ended by a long, colorless hair. The cells of the stem are but little longer than wide, and are colorless except for a narrow, light green chlorophyl band surrounding the centre. D. glomerate^ Fig. 90. 110 MICROSCOPY FOR BEGINNERS. Fig. 90.— Draparnaldia glomerata. 9. BULBOCH^TE (Fig. 91). This genus can always be known by the swollen or bulbous bases of the long hairs that tip many of the .cells. It grows on larger Algae, or on the leaflets of Ceratophyllum or other aquatic plants (Fig. 91). Fig. 91.— Bulbocbrete. RHIZOPODS. Ill CHAPTER IV. KHIZOPODS. THE Khizopods are the lowest animals in the scale of life. Scarcely more than a drop of jelly-like protoplasm, the lowest of these lowly creatures live, move, eat, and multiply. Some are so far down in the scale that they are actually only a particle of soft and unprotected protoplasm, moving, like the common Amoeba, which is one of the Rhizopods, by protruding long, thread-like projections of its own substance from any part of its body, and withdrawing them again into its substance, where they entirely disappear. These protruded parts, by means of which the creatures move and capture their food, are called pseudopodia, from two Greek words, meaning false feet. And since they often extend to long distances from the body of the animal, dividing and branching somewhat after the manner of roots, the group of lowly animals producing these pseudo- podia is named the Rhizopods, or root-footed, a word also from the Greek. The Amo3ba, and those Rhizopods nearest to it in structure, are formed of naked protoplasm; they are simply a drop of living jelly. But some higher in the same group secrete or build around their soft bodies a protective shell, often of exquisite form and remarkable 112 MICROSCOPY FOR BEGINNERS. construction. Thus the members of one genus, Difflu- gia, build themselves shells of sand grains cemented together with the most perfect regularity, every grain exactly fitting to its place. Yet, when the young Dif- flugia happens to be where suitable sand is scarce, it will build its shell of diatoms, often using those that are longer than the completed covering, attaching them lengthwise, side by side, and parallel to each other. An- other genus, Arcella, secretes from its body a brown shell of delicate membrane which, with a high power, is seen to be formed in minute hexagons. And still another, Clathrulina, the most beautiful of all the fresh- water Ehizopods, lifts itself on a long stem, and there surrounds its body by a hollow latticed sphere, and through the openings in the walls extends its pseudo- podal rays in search of food. In the unprotected forms — those without a shell — the pseudopodia are protruded from any part of the body ; in those preparing shells they are protruded from that portion of the body immediately in contact with the mouth of the shell, through which they often extend for a long distance as very fine, branching threads. "With a few exceptions the bodies of the Rhizopods are colorless ; in those exceptions the coloration is usually due to the presence of colored food, and so is diffused throughout the entire protoplasm, or it is confined to the parts near the surface, the central portion being nearly colorless. The pseudopodia are never colored. Not only do the Rhizopods move by means of these RHIZOPODS. 113 " false feet," but they capture food with them, consum- ing both plants and animals. Diatoms, Desmids, Infu- soria (Chapter V.), Eotifers (Chapter VIII.), almost any living thing small enough to be seized, is accepta- ble. When a desirable morsel is found, the end of the pseudopodium touching it usually expands, and a wave of the body substance flows along it until the object is surrounded, like an island of food in a sea of proto- plasm. The whole broadened pseudopodium is then withdrawn into the body, carrying the food with it ; or, if the captured object is unusually large, or if it strug- gles a good deal, several pseudopodia may come to the assistance of the first, or a great wave-like outflow from the body may envelop both pseudopodia and food. These curious animals have no distinct mouth and no distinct stomach. The mouth in the shell-less ones is formed at any point on the surface wherever the creat- ure chooses to open itself and take in the food parti- cle; and the stomach is in any part of the internal substance ; the food is digested wherever it may hap- pen to enter and remain. They have no eyes, yet they seem to direct their course and avoid unpleasant or in- jurious obstacles. They have no nerves, yet when dis- turbed they contract into a small ball-like mass, or with- draw themselves into their shell. They also appear to feel some sort of sensation of hunger, for they are often seen to take food, and they select what they like. They are very numerous and common. They are to be found in any shallow pond, or pool, or body of 114 MICROSCOPY FOR BEGINNERS. still water. They glide among aquatic plants and Algae, especially on the lower surface of water-lily leaves, and among Myriophyllum and Ceratoph}7llum. Sphagnum moss is sure to contain them in abundance, as has al- ready been stated on page 61. But the mud is an ac- cessible and fruitful source of supply. To obtain them, gently scrape with a big iron spoon or the edge of a tin dipper the surface of the ooze from the mud in shal- low ponds, and transfer it to the collecting-bottle. Let the muddy mixture stand for a few minutes until the Rhizopods settle towards the bottom, and carefully pour off some of the water, adding more ooze if desired. Pour the mud and water into saucers, and set them near the window, when the Rhizopods will make their way to the surface, and may be removed by the dipping- tube. Do not place the saucers in the sunlight ; Rhiz- opods prefer a little shade. They are invisible, conse- quently the collector must collect on faith, as he must usually do when out on a microscopical fishing tour. But he will seldom be disappointed if he gathers the surface ooze from the edges of somewhat shady ponds, and avoids those places long exposed to the sun, and never sinks the dipper into the thick black mud, which contains no animal life of any kind. They are small and easily overlooked in the field of the microscope, but when one of the unprotected forms and a single shell-bearing Rhizopod is recognized, the beginner will never again overlook any of them in the material on his slide. The Amoeba will probably be RHIZOPODS. 115 the first seen, as a colorless, jelly-like body, very soft, and changeable in shape, slowly moving forward and suddenly altering its course and extending itself in nu- merous long, blunt, finger-like pseudopodia, lengthening or shortening at the creature's will. Or he may see a small pear-shaped collection of sand-grains slowly mov- ing about the slide, apparently without a cause, but a careful examination of the narrow or stem end of the pear will show the long, fine, and colorless pseudopodia issuing from the mouth, and he will know it to be a Rhizopod. After he has recognized a living shell he will have no trouble thereafter in knowing a dead one, and by referring to the following Key he will be able to learn its name, unless it is a very uncommon species. Key to Genera of Rhizopods. 1. Body without a shell (a). 2. Body with a shell (e). a. "Without fine, hair -like rays; pseudopodia thick and blunt (b}. a. With fine, hair-like rays on all parts of the body w- I). Body colorless, very changeable in shape. Amoe- ba, 1. c. Body orange or brick -red, with pin -like rays. Vampyrella, 2. c. Body colorless or greenish (d). d. Eays stiff, forked at the ends ; body often green. Acanthocystis, 3. 6* 110 MICROSCOPY FOR BEGINNERS. d. Kays flexible, not forked. Actinophrys, 4, or Actinosphcerium, 5. e. Shell formed apparently of sand-grains (/). e. Shell not formed of sand-grains (g). e. Shell a latticed globe on a long stem. Clathru- lina, 12. /. Not inclined ; pear-shaped, or globular with spines at the summit. Diffiugia, 6. f. Inclined; circular or oblong, thicker and with spines at the rear. Centropyxis, 7. g. Shell brown (A). g. Shell colorless, ovoid, not curved (*). g. Shell often yellowish, ovoid, curved (retort shaped), mouth circular. Cyphoderia, 11. h. Circular, with or without marginal teeth. Ar- cella, 8. i. Mouth smooth, circular; shell inclined, without spines. Trinema, 9. i. Mouth serrated ; shell not inclined, formed of hex- agonal plates ; often spinous. Euglypha, 10. 1. AMCEBA (Fig. 92). There is hardly a living animal so soft and changea- ble in shape as this. It may not retain the same form for a second at a time. The soft body protrudes thick, blunt, finger-like pseudopodia from any part of its sur- face, but usually from the front margin, or that edge at the forward part of the moving creature. The front may, with scarcely a warning, become the rear as the RHIZOPODS. 117 animal changes its course, by emitting pseudopodia from gome other portion, travelling off in the direction tow- ards which they extend. The semi-fluid contents of the body are colorless, unless tinged by the food or by the presence of numerous dark particles. The movements are sometimes quite rapid, the Amoeba extending its pseudopodia, keeping them extended in advance, and glid- ing along as though the body were formed of the white of egg. In the figure it is shown with many short pseudopodia, as it often appears immediately after it is placed on the slide, and before it has learned where it is, and has prepared to move in some definite direction. The posterior extremity, when the Amoeba is in motion, may be entirely smooth, or it may show a cluster of very short pseudopodia, giving it a velvety or mulberry ap- pearance. Suddenly a blunt, thick finger projects from the part, and Amoeba at once reverses its course, the pseudopodia at the front being withdrawn, and disappear- ing in the substance of the body. The observer can never predict what an Amoeba will do next. It is very common in the ooze of shallow ponds and on the leaves of many aquatic plants. Its body usually contains a number of diatoms, which form part of its favorite food, and it is a strange fact that the food is usually taken by what, at the time, is the posterior extremity. There are several species. 1. Body large, colorless or blackish ; pseudopodia finger- like, blunt. Amosba proteus, Fig. 92. 2. Body small, colorless, rather sluggish ; often floating 118 MICROSCOPY FOR BEGINNERS. freely, and star-shaped, with several conical, acute, straight, or curved pseudopodia radiating from the spherical cen- tral body. The form changes very slowly. A. radiosa. 3. Body irregular in shape; pseudo- podia usually few, short, thick, and directed forward ; posterior Fig. 92. — Amceba pr6- portion of the body with a vil- lous or velvet -like patch of very short, colorless pseudopodia. A. villosa. 2. VAMPYRELLA LATERI'TIA (Fig. 93). A red or orange colored, Amoeba-like creature with this name is not uncommonly found in early spring among thick growths of Spirogyra, for which it has a special fondness. It does not very quickly nor frequent- ly change its shape, yet its movements are quite rapid. Its pseudopodia are colorless and transparent, being formed by a short outward flow of the colorless central body substance, the red color being confined chiefly to the sur- face. It also has .short, fine rays like threads, and many pin-like projections, Fig. 93.-varapyreiia by which, in connection with its color, Vampyrella may be easily recognized. These pin-like rays consist of a short, fine stem with a little bulb on the end, so that each looks very much like a pin with a big head. They may appear on all RHIZOPODS. 119 parts of the body, but usually they are on the rear end only when the animal is moving. They often appear very suddenly, and as quickly disappear. Yampyrella's favorite food seems to be the cell con- tents of Spirogyrse. It selects a fresh and healthy plant, and settling down upon it, proceeds to perforate the cell- wall, and to remove the color bands with the entire cell contents by drawing them into its body, leaving the cell quite empty, with a ragged hole in the side. I have seen one Vampyrella remove the contents from seven Spiro- gyra cells in succession before its appetite was satisfied. 3. ACANTHOCYSTIS CH^ETOPHORA (Fig. 94). Body spherical, soft, usually colored green by the numerous green granules within. When the animal changes its shape, which it seldom does, it only becomes oval or slightly irregular in outline. The pseudopodia are very fine and hair-like, springing from all parts of the surface, but the peculiarity by which it may easily be known is the dense growth of spines covering the entire body, their ends being forked or divided into two short, straight, diverging branches. To see these forked ends demands a rather high-power objective, as they are small, butf the spines themselves are apparent to a com- paratively low -power. They seem not very securely fastened to the animal ; some of them quite often be- come loosened and drop off, especially if the Rhizopod is not in a healthy condition. When food is to be taken into the body, a part of the 120 MICROSCOPY FOR BEGINNERS. surface with the adherent spines is lifted up, carrying the spines to one side, and a wave of protoplasm, the body substance, flows out to receive and surround the food brought down by the pseudopodia. It is drawn into the body, the surface closes, and the spines again cover the sPot Tllis may happen at any Part of the surface. Acantfwcystis is often found among the leaflets of Myriophyllum, the roots of Lemna, or floating freely in quiet water. It is rarely found in the mud. 4. ACTINOPHRYS SOL (Fig. 95). This is one of the commonest of aquatic microscopic animals. It may be found floating in every quiet pond or pool, or swimming among the leaflets of nearly every gathering of water-weeds. Its body is usually colorless and almost transparent, seeming to be formed of a col- lection of small bubbles, so that it has a foamy appear- ance. It bristles with numerous long, fine rays spring- ing from the whole surface. It moves in a slow, gliding way that has not been satisfactorily explained, but which can hardly be produced by the hair-like rays, for they are motionless, and apparently used only for capturing food. Yet it slowly floats across the field of view, sel- dom changing its shape; or it remains suspended al- most stationary in the water with all its rays extended, and so resembling the pictures of the sun in an almanac KHIZOPODS. 121 that it has received the name of the " sun animalcule." The rays are seldom entirely with- drawn. It feeds on smaller animals and the spores of Algae. When an animalcule comes in contact with the rays it seems to lose some of its power of motion. It appears to , ,• -II i ITT Fig. 95.— Actiuophrys sol. become partially paralyzed, gliding down the ray, often surrounded by a small drop of pro- toplasm, until it nears the body, when a larger wave flows out and receives it. The little masses of digest- ing food can be seen inside the body, where the green coloring usually turns to brown. 5. ACTINOSPH^EUIUM: EICHHORNII (Fig. 96). At first the beginner will confound this Rhizopod with Actinophrys sol, which it resembles in appearance when seen with a low-power objective. It is larger than the "sun animalcule," but this is a distinction of no value unless the observer has happened to find Actinophrys first, and to have become familiar with its appearance and structure. In Actinosphcerium, however, the ray- like pseudopodia are quite large and coarse, and they ta- per to their free end from a thickened base at the sur- face of the body. The body itself, as the student will notice if he uses a % or ^ inch objective, is formed of an external layer of large vesicles or bubbles, and a central mass of smaller bubbles. In this bubble -like 122 MICROSCOPY FOR BEGINNERS. structure it also resembles Actinophrys, but it seems less like a drop of froth, for the bubbles are larger, and the two distinct layers of two different sizes at once show that the Khizopod is Actinosphserium. But there is another and more impor- tant difference, which the be- ginner will not observe un- less he searches for it with a high-power (^ or £) object- ive. Each ray has a thread Fig. 96 Actiuosphserium Eichh6rnii. or fine rod running length- wise through its middle, and differing slightly in color from the softer part of the ray. This rod begins within the body below the outer layer of larger bubbles, pass- ing between them and extending almost to the end of the pseudopodal rays, which are seldom entirely with- drawn into the body. Actinosphaerium is sluggish, moving slowly and often remaining motionless for a long time in one spot. It is frequently found in company with Actinoplirys, among Lemna and other aquatic plants. It feeds on other animals as well as plants, taking larger victims than the "sun animalcule." The Roti- fers (Chapter VIII.) seem its favorite food. A free swimming animalcule or Rotifer coming in contact with the long rays seems, as with Actinoplirys, to become in- capable of escape ; it is then slowly drawn into the body and digested. RHIZOPODS. 123 6. DIFFLUGIA (Figs. 97, 98). Shell brown, pear-shaped, ovoid or nearly spherical, and formed of angular sand -grains cemented togeth- er. The upper part, the summit, may be rounded, and roughened only by the edges of the sand -grains, or rounded and bearing several pointed spines also form- ed of sand. The lower part may be prolonged as a short neck, at the end of which is the mouth for the passage of the pseudopodia, or the shell may have no part resembling a neck. The animal which builds this protective case lives inside of it, and is a little mass of colorless, or sometimes greenish, protoplasm, somewhat resembling an Amoeba, and almost entire- ly filling the cavity of the shell. The mouth is circu- lar, and may be either smooth or with several rounded teeth or lobes on its inner edge. No .part of the ani- mal in any of the shell-bearing forms, except the pseu- dopodia, ever passes through the mouth. When the shell is made the animal never leaves it, unless it is broken by the cover-glass ; then it will at times creep out and die. The pseudopodia are blunt and colorless. They drag the shell about with the mouth downward, and capture food as in the naked Khizopods. When they are with- drawn, the shell appears like a dead thing, and may roll about the slide at the will of the observer or the mercy of the currents. But often while the student is looking at an apparently dead shell of sand, a blunt little color- less wave issues from the mouth, lengthens and narrows, 124 MICROSCOPY FOR BEGINNERS. is followed by another and another, until the shell is raised and moved slowly away. There are several species of the genus Difflugia, of which the following are about the commonest. They are found abundantly in the mud and among Sphagnum. 1. Shell pear-shaped (Fig. 97), without spines, although the summit may be prolonged into one or two points ; usually formed of sand-grains, sometimes with adherent diatoms ; oc- casionally formed entirely of diatoms ; mouth at the narrow end, circular, smooth, without teeth or lobes. The body within the shell is usually green, sometimes colorless ; pseudopodia col- orless, thick, blunt. It is almost as fond of the cell contents of Spirogyra as is Yampyrella, and obtains them in a similar way ; but instead of appearing to suck them out of the cell, Difflugia jpyriformis pierces the wall, inserts its pseudopodia, with them surrounding the color bands and other cell contents, lifts the whole out and passes it into the body within the shell. I have seen a single Difflugia empty four Spirogyra cells in succession. This species is common. Difflugia pyriformis, Fig. 97. 2. Shell nearly spherical, with from one to twelve, usu- ally three or seven, pointed spines arranged in a circle around the upper part, and formed of sand- grains. These spines are hollow, and communicate RHIZOPODS. 125 with the cavity of the shell, but the animal proba- bly builds them for ornament, as it does not seem to use them. The mouth of the shell occupies the end opposite to the spine - bearing summit, and when the shell is turned over so that this opening is directed upward, it will be seen to be lobed or scalloped, the lobes varying from six to sixteen, being usually about twelve. They may in some forms be rather sharp -pointed, almost like short teeth. They are directed towards each other across the opening. It is a difficult matter to get the shell in such a position that the observer can look down into the mouth, but it may sometimes be done by tapping the cover-glass with a needle so as to roll the Khizopod about, and occasionally, by one of those lucky accidents that some- times occur, it places itself in good position. The soft body is colorless or brownish, and the pseudopodia are thick, blunt, and numerous. The species is common in the ooze. D. corona, Fig. 98. 3. Shell spherical, without spines ; mouth circular, smooth, without lobes or teeth. This species is found with the preceding. D. globulosa. 4. Shell long and narrowly pear-shaped, the summit prolonged into a central sharp point ; mouth circu- lar, smooth, without teeth or lobes. Common. D. acumindta. 126 MICROSCOPY FOR BEGINNERS. 7. CENTROPYXIS ACULEATA (Fig. 99). The shell of this Rhizopod is usually formed of sand- grains, and is brown in color, but sometimes it consists of a brown membrane with scattered adherent sand- grains. I have also met with shells formed entirely of small diatoms fitted together as beautifully and accu- rately as the sand-grains of Difflugia. These diatom shells were found in an aquarium, and were probably built of these plants because suitable sand was not to be had. Centropyxis, when seen in side view, ap- pears as if it had once been a hemi- sphere with the mouth near one side of the flat surface, but that while it was soft the convex part had in some way been pushed over towards one side, thus leav- ing the shell oblique or inclined, the back part being much thicker than the front, the upper surface sloping down from the deeper rear to the thin front margin, the circular or oval mouth remaining nearer the thin border. The figure shows the under part of a shell, which, in this position, ap- peal's almost circular. The spines on the thick part are usually sharp-pointed, and vary in number from one to nine. The body of the animal is colorless, and the pseudopodia are blunt and finger-like. This is the only known species. Common. 8. ARCELLA (Figs. 100, 101). "When seen from above or below, the shell of Arcella, RHIZOPODS. 127 seems like a disk with a pale circular spot in the mid- dle. When seen in side view it has a flat lower surface and a more or less strongly convex or elevated upper surface. In color it is usually some shade of brown, but may be almost black. In very young specimens the shell is often nearly colorless. It is generally trans- parent. The mouth of the shell, in the centre of the flat surface, is circular and smooth. The body of the animal is colorless, and is attached to its home by fine threads of its own substance. There are several species, recognizable by the form of the shell. 1. Margin of the shell smoothly circular. Common everywhere. Arcella, vulgdris, Fig. 100. 2. Margin of the shell with several teeth, so that it re- sembles, when seen from above or below, a wheel with pointed cogs. Not as common as the preced- ing. A. dentdta, Fig. 101. 3. Shell somewhat balloon - shaped when seen in side view ; higher than wide, the sides often depressed in wide facets. Not rare. A. mitrdta. Fig. 101.— Arcel- Fig. 100.— Arcella vulgaris. la dentata. Fig. 102.— Tnuema Suchelys. 9. TRINEMA ENCHELYS (Fig. 102). This shell is pouch-shaped, colorless, small, and in- 128 MICROSCOPY FOR BEGINNERS. dined, so that when in motion with the mouth down- ward against the slide the rounded summit is lifted obliquely upward. It is somewhat narrower at the lower part, and the mouth is a short distance within the shell, the front or lower edges seeming to curve in- ward to meet it. The body of the animal is colorless. The pseudopodia are very fine, thread-like, and few in number. The Rhizopod is common everywhere in wet places ; it is also one of the smallest, and the shell is often found dead and empty. The figure shows it in side view. The aperture of the shell is seen to be bead- ed when examined with a high-power objective. 10. ETJGLYPHA (Fig. 103). The shell of Euglyplia is ovoid, colorless, and trans- parent. Under a high power it is seen to be composed of many oval or hexagonal plates arranged in rows, those towards the widest part of the shell overlapping those in front. The mouth is circular or oval, but the projecting points of the plates give it a toothed, saw- like edge. There are several species, but they all may be known as Euglyphae by this serrated or saw-toothed mouth. The upper part and the borders of the shell are either with or without spines, or they may bear fine hairs. The animal itself is colorless, and almost entire- ly fills the cavity of the shell, to which it is attached, apparently by the summit only. The pseudopodia are very delicate and often branched. The animal moves, like all the shell-bearing forms, with the mouth of the RHIZOPODS. 129 shell against the slide or other object over which it creeps. 1. Shell without spines, or with four or six near the summit and arranged in a circle at equal distances apart, pointing upward and varying some- what in length. Quite common in the ooze of ponds. Euglypha alve- m«. m- oldta, Fig. 103. alveol*ta- 2. Shell with a cluster of spreading spines springing from the centre of the summit. Common in Sphagnum. K cristdta. 3. Shell with the summit and sides fringed with bris- tles. Common in Sphagnum. E. cilidta. 11. CYPHODEKIA AMPULLA (Fig. 104). Shell yellowish, or sometimes colorless, shaped like a chemist's retort, the mouth being at the narrow, curved end. The summit is rounded, sometimes with a cen- tral point or small knob. The shell, when highly mag- nified, is seen to be formed of minute hexagons. The animal is, as usual, colorless, and nearly fills the semi- transparent case. The pseudopodia are numerous and often forked. When mov- ing> the mouth of the shell is in contact deria ampulla. wjth ^ object oyer whjcll faQ RhizO- pod is travelling, and the body of the shell is held obliquely upward or almost parallel with the slide. The figure shows an empty shell. There is but one 130 MICROSCOPY FOR BEGINNERS. species, which is quite frequent in the ooze of ditches and ponds. 12. CLATHRULINA ELEGANS (Fig. 105). A hollow globe of silicious lattice-work elevated on a crystalline stem. Within this exquisite dwelling the spherical, colorless animal lives, extending its fine long pseudopodal rays through the almost circular windows in search of food. The stem is attached to aquatic plants or other submerged objects. Cloth- rulma is the only fresh-water Rhi- zopod that is not free - swimming. It is common in many ponds, at- tached to the rootlets of Lemna. In this small book it is only possi- ble to refer to a very few of the com- monest of these beautiful and in- teresting animals, about whose life history very little is known. They PI'S. 105.— ciathrniina eie- form a department in which there is room for much original inves- tigation. Those who desire to pursue the subject, or to know more of the Rhizopods than can be included here, would do well to refer to Dr. Leidy's " Fresh-water Rhizopods of North America," published by the United States Geological Survey of the Territories, or to Mr. Romyn Hitchcock's " Synopsis of the Fresh-water Rhizo- pods," a useful condensation of Dr. Leidy's splendid work. INFUSORIA. 131 CHAPTER V. INFUSOKIA. THE reader probably knows the Infusoria under the name of animalcules, a word only meaning small ani- mals, which the Infusoria certainly are. But a mouse is also a small animal ; so is a Water-flea (Chapter X.) and a Rotifer (Chapter VIIL). Infusorium for a single one of a group of certain microscopic creatures, and In- fusoria as the plural, are better words than animalcule, with no danger of conveying an incorrect meaning. The Infusoria were so named because they were first discov- ered in infusions, that is, water in which animal or vege- table substances had been soaking and decaying. Since that time the creatures have been obtained in great abundance and variety in even the sweetest of fresh wa- ters, although they abound in astonishing numbers in many infusions. The beginner has only to place a hand- ful of hay in a tumbler of water, and allow it to soak for a week or two, when he will have as many Infusoria as he may want for examination. They are also plenti- ful in every ditch and pool of still water. ~No collec- tion of Algse, aquatic plants, or Rhizopods, can be made without, at the same time, gathering very many Infusoria. One of the best ways to collect the little creatures is to gather aquatic plants and Algae without taking them 7 132 MICROSCOPY FOR BEGINNERS. from the water. If the plants among which they con- ceal themselves and search for food are lifted out of the pond, the water running off washes away all the animals you are seeking. So take the water in the dipper, or float the plants into the bottle, which should never be entirely filled, nor corked for any length of time. The Infusoria are very fond of fresh air ; they rapidly ex- haust the oxygen in solution in the water, dying quickly, and going to pieces almost as soon as dead. Give them plenty of air in the collecting-bottle, and at home pour the gathering into a broad dish so as to have a wide sur- face exposed to the atmosphere. The plants as well as the Infusoria do better in such quarters. They are also usually fond of the light, and will soon make their way to the side of the vessel nearest the window, and the dipping-tube put in at that side will often capture creat- ures that avoid the shadier parts. To obtain those that are free-swimming, that is, those that are never perma- nently adherent to the leaflets of plants nor the fila- ments of Algae, as many of the most interesting are, they can be transferred to the slide by the dipping-tube, and the drop covered by the thin glass, when they are ready for study. Those attached to plants can be found only by cutting off a small piece of Myriophyllum or other water -weed and examining it under the micro- scope. In these cases it is necessary to lift the piece of weed from the water, but it can be moved gently, and at once placed in a drop ready for it on the slide. Some of the most interesting kinds of Infusoria are found ad- INFUSORIA. 133 herent to Ceratophyllum and other plants with finely divided leaves. Every part should be searched with the microscope, especially the angles between the leaflets. The bodies of the Infusoria are usually very soft and delicate. Some of them are so flexible that they can double and twist themselves almost as well as a worm. Others are hard, and some are even covered by a transparent case secreted from their own body. This case is called a lorica, and is used as a shelter for the soft and otherwise defenceless animal. When fright- ened it quickly withdraws itself to the bottom of the lorica, and remains there in a little, almost shapeless, heap, until the danger is past. Then it slowly rises up to the front of the lorica, protrudes the front part of the body, opens the organs by which it creates currents in the water,, and so fishes for the food those currents bring to its mouth. These loricae are usually perma- nently attached to plants or other submerged objects. They are also generally transparent and colorless, but sometimes, as they become old, the color changes to a rich, translucent chestnut brown. In other Infusoria the loricse are not hard and transparent, but soft and delicate. These are usually made of innumerable little particles of dirt fastened together by a sticky substance secreted from the animal's body. Almost any small particles floating about and striking against the sticky mass will be quite sure to adhere, and so help build up the soft sheath that serves the Infusorium as a protect- ive covering, and sometimes effectually conceals it from 134: MICROSCOPY FOR BEGINNERS. the microscopist who may be seeking it. But they are not formed entirely by accident. They are built chiefly of those little particles brought to the animal by the currents produced by the organs it has for that purpose. These currents contain the food which the Infusorium cannot go to seek as the free-swimming kinds can do, for the loricas building animals are almost as perma- nently fastened to their loricse as is a snail to its shell. Sometimes the Infusorium will leave its lorica when the water has lost most of its oxygen, and the poor thing is nearly smothered, and it leaves only to die. But it generally prefers to die at home, for when the time comes the little creature retires to the bottom of the lorica, contracts into a heap, and quietly goes to pieces. There are also some that form loricse and are still free - swimming, carrying the house about with them. They also retire to the rear when frightened, and some even have a little piece of hard substance on the front of the body with which they plug up the entrance, and so make all secure. There are others that form a stem and branches like the trunk and limbs of miniature trees, the colorless animals being fastened to the ends like so many leaves. In some of these the animals can contract themselves into little balls when frightened ; in others the branches contract into coils and pull the animals away from harm ; in still others the whole tree-like colony, stem, branches, and animals, contract and pull themselves down against the plant to which the stem is attached. And in still INFUSORIA. 135 others, the Vorticellce, there is but one stem with a sin- gle bell-shaped body on the end, but the stem contracts into close spirals and suddenly draws the animal down. When the danger is past, the stem slowly uncoils, the branches spread themselves, the animals expand, and all is as before. Indeed, the variety of form and habit in: the Infusoria is almost infinitely great. The general opinion is that "animalcules" have no color. This is a mistake. The majority are almost col- orless, but green, crimson, yellow, indigo blue or almost black Infusoria are not uncommon, and the loricse, as" stated, often become brown. The free-swimming Infusoria are more abundant than the attached ones, and much more difficult to examine because they will never stand still. But how do these creatures, all of which are invisible without the micro- scope— how do they move ? For this purpose they have organs of two kinds, and they are separated into two great classes according as they possess the one kind, or the other. In some there are one or more long, color- less lashes which extend from the front of the body> beat against the water, and so row the animal about very rapidly. Each of these lashes is called zflagellum (ipln- T2\, flagella). In others there are on the body short, very fine hairs, which are continually vibrating so rap- idly that they are often invisible even under a high- power objective. The short hairs are called cilia, and it is their action on the water that urges the animal about even more quickly than the flagella. The cilia may be 136 MICROSCOPY FOR BEGINNERS. confined to a circle around one end, or they may be on the lower surface only, or the whole body may be cov- ered with them. Infusoria with cilia are more numer- ous than Infusoria with flagella. They are, however, not the only ciliated animals. The Eotifers are well supplied, and certain small aquatic worms have the en- tire body ciliated. Although the Infusoria are so abundant that scarcely a drop from any pond or ditch can be examined with- out exhibiting some, the beginner will, I fear, have trou- ble in studying them, they are so lively and so small. The stage must be kept in continuous motion to coun- teract the motions of the Infusorium and keep it in the field, so it can be seen as anything more than a whirling speck, and high-powers are needed to examine it. But the beginner's object will be gained if he learns to know an Infusorium when he sees one, and if he learns the names of some of the largest and commonest. Many can be seen with a one-inch objective, but to ascertain whether any special one has cilia or flagella will demand a one-fifth inch or higher power lens, and without know- ing this the Infusorium cannot be identified. But "it is only the first step that costs." Any work or study is always hardest at the beginning. When the student has identified one Infusorium he will have little trouble with what comes after. The attached forms will not be very difficult even at the first, if a sufficient magnifying pow- er is used, for since they are fastened by stem or lorica to another object, they can be examined at leisure. INFUSORIA. 137 None of these creatures can be preserved as perma- nently mounted objects. Many chemical solutions and mixtures have been recommended for killing and keep- ing them, but none are satisfactory, the soft bodies go- ing to pieces and melting away almost as soon as after a natural death. If the beginner is very much annoyed by the incessant movements of the free-swimming kinds, and he desires to see how they look when quiet for a moment, the following solution will help. It answers the purpose well in some cases, while in others it is worthless. It always kills, but does not always preserve after death. It is used by allowing a small drop to run. under the cover-glass and to mingle with the drop of water containing the Infusoria. Any druggist can make it, but caution him to use not more than half a drachm (half a teaspoonf ul) of water, or you will be terrified by his bill. If this small quantity is made it is not expen- sive. To the half drachm of water add as much iodide of potassium as it can be made to dissolve, and to this so- lution add as much iodine as the .solution can be forced to dissolve. This ends the druggist's part. It only re- mains for you to add enough of the mixture to clean water to make the color a rather deep amber. The proper strength can be learned by experiment. If it kills, and then destroys too quickly, add more water ; if it does not kill quickly enough, drop in a little more of the iodine mixture. A weak solution in water of the^r-chloride of iron 138 MICROSCOPY FOR BEGINNERS. Las also been recommended for this purpose, but its ac- tion is similar to that of the iodine solution, and not more satisfactory. The following Key refers to only a few of the com- monest Infusoria in fresh water and vegetable infusions. To include a tithe of those most frequently seen in such places is an impossibility. When the beginner learns that there are fifty known species of Yorticella alone, and about thirty of Monad, he will see that it is possi- ble to refer in the most superficial way to only a very few of these abundant and attractive creatures. Key to some Genera of Infusoria. 1. Free-swimming (f). 2. Not free-swimming; singly or in clusters on a stem (a). 3. Not free - swimming ; in a transparent or granular lorica (&). a. Stem much branched, neither it nor the animals contractile. Dendromonas, 1. a. Stem much branched, both it and the animals con- tractile. Carchesiitm, 2. a. Stern much branched, only the animals contrac- tile. Epistylis, 3. a. Stem not branched, contracting into spirals. Vor- ticella, 4. b. Loricse vase-shaped, transparent (c). 5. Loricee soft, granular, brownish (e). c. Attached to each other to form colonies. Dino- bryon, 5. INFUSORIA. 139 c. Not attached to each other (d). d. Lorica without a stem, adherent by the narrow base. Vagiiucola, 6. d. Lorica without a stem, adherent by the broad side. Platycola, 7. d. Lorica with a short stem. Cothurnia, 8. e. Extended animal trumpet-shaped. Stentor, 9. f. With one or more flagella at the front (g). f. Without flagella, but with cilia (A). g. Body very changeable in shape, colorless. Asia- sia, 10. g. Body very changeable in shape, green or red. Euglena, 11. g. Body not changeable in shape, colorless, notched in front. Chilomonas, 12. g. Body not changeable in shape, green, with a short, stiff, colorless tail. P hocus, 13. g. Body not changeable in shape, green, united in a revolving colony. Uvella, 14. h. Cilia on the entire surface (i). h. Cilia confined to the lower or flat surface (&). i. Neck long, very elastic and extensile. Trachelo- cerca, 15. i. Neck long, flattened, not extensile. Ampkileptus, 16. i. Body brownish, slipper-shaped. Paramcecium, 17. i. Body green, red, blue or almost black ; ovoid or trumpet-shaped ; cilia largest on the front. Sten- tor, 9. 140 MICROSCOPY FOR BEGINNERS. k. Cilia large, few, scattered (I). k. Cilia fine, numerous (m). 1. Body more or less circular in outline. Euplotes, IS. I. Body more or less oblong in outline. Stylonychia, 19. m. Month followed by a conical tube of rods. Chi- lodon, 20. m. Mouth followed by a brown, sickle-shaped mem- brane. Loxodes, 21. 1. DENDKOMONAS (Fig. 106). The stem is many times divided into numerous branches, and the branches themselves are also much divided, with one small Infusorium at the end of each. The whole has a beautiful but colorless tree-like appearance, the stem being often found attached to Ceratophyllum. The animals have each two flagella, but they are visible only to a high-power objective. There is no special mouth. A particle of food dashed down by the flagella against any part of the body sinks into its soft side and is thus swallowed without a throat. The whole colony is often more branched than is shown in the figure. It can be recognized with a good one-inch objective. 2. CARCHESIUM (Fig. 107). The stem, attached to plants or other submerged INFUSORIA. 141 objects, is divided at the summit into many branches, with one Infusorium at the end of each, and many oth- ers scattered along them with shorter branches of their own. Through the main stem and through all the branches there extends a cord-like muscular thread that suddenly contracts when the animals are frightened or disturbed, and pulls the whole colony down towards the point of attachment to the plant. But the branches may contract one at a time and draw their bur- den of Infusorial fruit down to the main stem without disturbing any other portion of the col- ony, or all the branches may contract at once. Therefore, while the ani- F,g toT._Carch6gium. mals on the branches are connected together, they are still somewhat independ- ent. The front border of each body is surrounded by a circle of cilia visible under a high power. They are the only cilia on the body. When the animal is contracted they are folded together, each body then resembling a little ball. They vibrate rapidly, produc- ing circular currents that bring to the mouth any food- particles that may be in the vicinity. The entire col- ony is colorless, and may include as many as a hundred Infusoria on the branches. It can be seen by a low- power objective. The independent contraction of the 142 MICROSCOPY FOR BEGINNERS. branches and the stem will distinguish it from all other tree-like Infusoria. 3. EPISTYLIS (Fig. 103). As in the two preceding, the stem of Epistylis is also often much branched. The Infusoria at the ends of the branches can alone contract, which they often do with a jerk, settling back as if they meant to impale themselves, or dropping and nodding like flowers fad- ing on their stems. The bodies of the expanded ani- mals are somewhat bell-shaped, their widest part being the free end which closes when the body contracts. The front border is encircled by a row of cilia, to be properly discerned only by a high-power objective. The one-inch glass, however, will show the rapid currents pro- duced, because all small particles in their neighborhood are caught up and dashed around in the mimic whirlpools. The ani- mals select from these streams anything they may want and let the rest sweep by. They have a distinct mouth near the centre of the front part. The entire colony is usually colorless. It is often attached to Ceratophyllum. 4. VORTICELLA (Fig. 109). The unbranched stem of Vorticella contains a zigzag muscular thread like a thin cord, which contracts into close coils very suddenly, and draws the Infusorium INFUSORIA. 143 down with it. The Yorticellse are very common, scarce- ly a leaflet of any aquatic plant is without them. They are usually colorless, although green ones do occur. The body is bell-shaped, the narrow part of the bell be- ing fastened to the top of the stem. The front border is surrounded by a circle of fine cilia which need a high power to show them. They produce currents in the water similar to those of Epistylis, and for the same food-collecting purposes. The contractions are surprising in their suddenness. While the observer is quietly gazing at the graceful creature whirling its cilia and making tre- mendous whirlpools on a small scale, it dis- appears like a flash, and the student feels like looking for it on the table. But pres- ently it slowly begins to rise from the plant against which it was crouching, and the coiled stem lengthens as it straightens. Yery often it hardly extends before it again leaps out of sight, or close to the object supporting the stem; "When the stem throws itself into spirals, the body of the animal folds together into a ball. This will probably be one of the first Infusoria to at- tract the beginner's attention, and he will think it a wonderful thing, as it is. The figure shows some ex- tended and some contracted. They are often found in clusters, sometimes of a hundred or more, all bobbing and swaying in a very curious way, for when one con- tracts it usually sets them all off. 144 MICROSCOPY FOR BEGINNERS. 5. DINOBRYON (Fig. 110). In the early spring, as early as March, among the Algae then found so abundantly in the shallow pools, colonies of very small, vase-shaped loricse are often ob- tained. They are sometimes attached to a plant or fila- ment of alga, or as often they float freely through the water, being fastened to the plant by a very slight hold. The loricae are transparent and colorless, and may be overlooked, but the Infusorium within each one is rather conspicuous to even a low-pow- er objective, for it has a narrow green band on each side of the body, and often a minute red eye-like spot in the centre of the front border. The loricse are united together by one or two being attached to the front edge of the one behind them, until branching colonies of some size are formed. The front border of each en- closed Infusorium bears two flagella, one long and one short, but they are seen with difficulty even with a mod- erately high-power objective. The lashing of all the flagella in a large colony urges it quite rapidly through the water. According to my experience Dinobryon is seldom found in the summer. 6. VAGINICOLA (Fig. 111). The lorica is colorless, transparent, and about three times as long as broad. In form it is long, vase-shaped, or nearly cylindrical, the base, or the part fastened to the plant or other object, being usually rounded. The INFUSORIA. 145 animal, when it projects, extends for a considerable dis- tance beyond the opening at the front of the lorica. When frightened, or disturbed in any way, it quickly closes up its broader front part, and retreats as far into the lorica as possible. When recovered from its fright it slowly ascends to the opening, expands it- self and resumes its fishing operations. It is fastened to the extreme end of the lorica by the tip of the body ; from the sides it is en- tirely free. On its front border it has a wreath of fine cilia in continuous motion Fls-ni— Va- ginicola. when the animal is extended. The body is soft and flexible, and is sometimes of a pale greenish tint, but the lorica, I think, seldom changes color with age. It is not uncommon to find two bodies in one sheath, where they seem to live together in peace and harmony. This may be an advantage to both, for two wreaths of cilia can, of course, produce stronger cur- rents, and so bring more food to the mouths of the always hungry creatures. Vayinwola is quite common on Lemna and Myriophyllum. 7. PLATYCOLA (Fig. 112). The lorica is flattened, and is in outline almost circu- lar. It is always adherent to some submerged object by the broad flat side, the opposite or upper surface being convex. The opening, through which the animal ex- tends itself as in Yaginicola, is at one end, and is often prolonged into a short neck. The figure shows a side 146 MICROSCOPY FOR BEGINNERS. view with tlie animal extended. When young the lor- ica is colorless, but it very soon changes to a deep brown, often becoming so opaque that the body of the Infusorium cannot be seen through its walls. The body is Fig. 112. —Platycola. 6 . J usually colorless ; it is attached by its tip to the side opposite the mouth of the lorica. When frightened it darts back into the shell as Vaginicola does. Two animals are not seldom found in one lorica. It is not uncommon on Ceratophyllum and other aquatic plants. 8. COTHTJRNIA (Fig. 113). The beginner may mistake this for a small Vaginicola, as the loricae somewhat resemble each other in shape ; but Cothurnia can always be known by the little stem or foot-stalk that lifts it a short distance from the plant to which it is attached. This foot-stalk in some species is very short, and must be especially looked ffor. The lorica is vase -shaped, often with the sides variously curved. It changes to a brown color as it grows old. The body of Fig. us. the enclosed Infusorium-is not colored. In its actions it resembles Yaginicola and Platycola, being similarly attached to the posterior end of the lor- ica, and having a similar circle or wreath of cilia around the front border. Two animals are sometimes found in one lorica. 9. STENTOR (Figs. 114, 115, 116). The Stentors vary a good deal in shape in the same INFUSORIA. 147 species, the bodies of all being somewhat changeable in form. The largest ones are trumpet-shaped, and are usually attached to some object by the narrow .end of the body. They also commonly form a soft, brownish, granular sheath or lorica, to the bottom of which they retreat when disturbed, folding together the wide trum- pet-shaped front border. The entire surface of the body in all the species is ciliated, but the cilia are very small and fine. Around the edge of the front border is a cir- cle of longer and larger vibratile hairs, visible with a moderately low power. The Stentors are all common. The following Key may help the beginner to recognize some of those most frequently seen. Key to some species of Stentor. 1. Attached, and usually forming a short, soft sheath (a). 2. Free-swimming, more or less ovoid ; green, red, blue or almost black (J). a. Body large, trumpet-shaped, greenish • often without a visible sheath, and when one is formed it is sometimes soon abandoned, the Stentor swim- ming about freely. The body is slightly changeable in shape. Sev- eral Stentors of this species are often found close together, having formed a very soft sheath divided into irreg- ular compartments, one for each Infusorium. S. polymorphus. Fig. 114:. 148 MICROSCOPY FOR BEGINNERS. a. Body long, and narrowly trumpet-shaped, the front divided into two lobes, one of which is almost at right angles to the other. The body has many long, fine hairs projecting from it, and visible under a high-power (^ inch) ob- jective. The sheath is always present. It is narrow, cylindrical, brown, and about one-half as long as the extended body. This Stentor is never free-swim- .— ming> and ig never found in company ntor wjtjj others of the same species. It is Barretti. not uncommon on Ceratophyllum. S. Barretti, Fig. 115. J. Body green or red, the red color often being lim- ited to the part just beneath the wide front bor- der where the circle of large cilia is. Sometimes the red color is diffused over the whole body, but usually the green matter so obscures it that it is invisible. This species is often ex- ^ tremely abundant at the bottom of Jfjp' shallow ponds in early spring. The r green color then always entirely con- stentor ceals the red. S. igneus, Fig. 116. igneu8' b. Body large, indigo blue. This in shape resembles Fig. 114 when extended ; when contracted it is not unlike Fig. 116. Yery common in some lo- calities. S. ccerideus, b. Body dark brown, almost black. This also resem- bles Fig. 116. Common. S. niger. INFUSORIA. 149 10. ASTASIA (Fig. 117). Body long and narrow, very soft, and changeable in shape, altering its form as it glides over the slide, which it does quite rapidly. It has one long straight flagellum at the front. It is quite common. Fig. 117.— Astteia. Fig. 118.— Euglena. 11. EUGLENA (Fig. 118). Body long and rather narrow, being widest in the middle and tapering to both ends. It is very change- able in form, and bright green or red in color. The front end is seen witli a high power to be notched as if the Infusorium had two lips, the long, vibrating, and colorless flagellum appearing to issue from the notch. There is sometimes a small red spot near the front end, supposed to be an imperfect eye. It is often absent in an old Euglena. At the posterior end is a short, point- ed, stiff, and sometimes curved tail, which is usually col- orless. The Infusorium is common, occasionally occur- ring in such immense numbers that it tinges the water green. There is another species, or another variety of this species, whose body is bright crimson. It also is so abundant at times that it colors the water blood red. 12. CHILOMONAS (Fig. 119). This colorless little creature is very common in vege- table infusions. It may be recognized by the notch at the widest or front end, and the curve of the back 150 MICROSCOPY FOR BEGINNERS. which makes it look almost hunch -backed. Under a high power it shows two flagella, one of them throwing itself into a coil or loop when the Infusorium settles down to rest, which, by -the -way, it quite frequently does. The body is filled with small colorless disks which the iodine solution turns blue, showing that they are starchy. Fig. 119.— Chil • i ,> i t i i • • , tcriorextrem- podal fascicles forward, and hooking into jtyofanAui6- the surface on which it is creeping, and Phoru8« then contracting the fore part of the body and drag- ging along the back part enclosed within the tube."* It often helps itself along by clinging to the slide by its protruded throat or pharynx. The podal spines vary in number from five to nine in each cluster. The fascicles of bristles are each accompanied by from one to three rudimentary spines, which are nearly straight, and end in a broadened, spade-like expansion. The blood is red. 7. STREPHURIS (Fig. 139). The podal spines and bristles are arranged alternately with each other, as in Fig. 139, and together form a single * Dr. Leidy, in the American Naturalist, June, 1880. 194 MICROSCOPY FOR BEGINNERS. row of clusters on each side of the lower surface of the body. The spines are slightly curved, long and forked, the bristles being three times their length. The mouth is triangular. The blood is bright red and the vessels large. The body is thread-like, transparent, and may be from one to two inches in length. The front end is whitish, the tail end yellow- ish. It lives in the mud beneath shallow Fig. 139.— PO- water, and buries itself with about two-thirds and bristles °^ *ne tail end protruding and constantly vi or strephu- brating. When disturbed it disappears into its burrow with astonishing rapidity. Dr. Leidy, who discovered this curious creature, says, " While walking in the outskirts of the city [Philadelphia] I no- ticed in a shallow ditch numerous reddish patches of from one to six inches square, which, supposing to be a species of alga, I stooped to procure some, when to my surprise I found them to consist of millions of the tails of Strephuris dgilis, all in rapid movement. The least disturbance would cause a patch of six inches square so suddenly to disappear that it resembled the movement of a single body." 8. -2EOLOSOMA. The bristles are of unequal length, and are arranged in clusters of four bristles each, the clusters forming a single row on both sides of the body. There are none in advance of the mouth, which is large U-shaped, the arms of the TJ pointing forward, the whole being sur- SOME AQUATIC WORMS, ETC. 195 rounded with a thick border. The pharynx is broad and ciliated within. The body is colorless, the brick- red spots scattered over the internal surface giving the worm a beautiful appearance. ^Eolosoma is found in ditches among Algae, on which it feeds. It is not very active in its movements. The blood is colorless. Among the Sphagnum in the writer's locality there not uncommonly occurs a worm which I have ventured to identify as a member of this genus. It externally differs from the species referred to above in having fewer and larger red spots, which seem to be on the outer surface of the skin, where they are most abun- dantly collected near the two extremities, being fewest on the central region of the body. The bristles are so arranged that they appear to form two rows of clusters on each side, being separated into two groups in each cluster. The worm thus seems to have four rows in- stead of the two, as in the preceding species. Its movements are also much more active. It is also a vegetarian. 9. OCNEBODRILUS. This remarkable worm has thus far been found only in Fresno County, California, where it was obtained among fine Algse growing to the sides of a submerged wooden box, and also occasionally in the mud, with a part of the tail end protruding and motionless. The body is rather less than an inch long, one-twelfth of an inch wide, and presenting the peculiar color mentioned in the Key. Its movements are very slow. 196 MICROSCOPY FOR BEGINNERS. The podal spines are slightly curved, but not forked at the ends. They are arranged in clusters of four spines each, the clusters forming two rows, one on each side of the body. The O3sophagus is long and remarkably muscular. It is surrounded and somewhat obscured by a pair of large glands, and has near its posterior extremity two large appendages similar in structure to the oesophagus itself. The blood is yellowish-red. The dorsal vessel, at some distance behind the front end of the body, divides into three branches, which pass forward, and near the anterior border unite by means of a net-work of fine vessels. The worm has four hearts, two on each side of the dorsal vessel, one pair being near the eighth, and one pair near the ninth cluster of podal spines. The dorsal vessel divides in front of the first pair of hearts. The ventral blood-vessel is forked, but with only two branches. 10. TUBIFEX. A common and, in some places, a very abundant little worm, measuring from one-half to one and one-half inches in length. The body is thread-like in its nar- rowness, and is transparent and colorless, although the bright crimson blood gives it a hue so vivid to the naked eye that, where the worms are numerous, it often seems to tinge the mud in which they live. They are seldom found free-swimming, but live a comparatively seden- tary life, with about one-half of the body buried in their burrow, the remaining parts protruding into the water, SOME AQUATIC WORMS, ETC. 197 and constantly waving to and fro beyond the edge of the little tubular chimneys which they erect. These little towers are often conspicuous objects on the sur- face of the mud in shallow still water, the worms in- stantly disappearing into them at the slightest disturb- ance. Among certain French and German writers on the subject, there is a difference of opinion as to which end of the worm is buried and which end protrudes into the water. As the protruding parts are continually moving, and as the worms also dart into the mud with such astonishing swiftness, to decide the matter is rather difficult. The bristles are comparatively short, and appear to be arranged in a single row on each side of the body, whereas there is really an additional row of podal spines on both sides of the worm. These podal spines are en- tirely retractile, and are therefore often overlooked un- less specially searched for. Even then it will perhaps be necessary to compress the worm rather forcibly be- tween the slide and the cover-glass before they will be- come conspicuous. They are forked, and but slightly curved. With very high magnifying power (about eight hun- dred diameters) some of the bristles present a curious aspect. The free extremity is widened and forked, the two prongs of the fork being apparently connected by a thin membrane which is longitudinally striated. Some- times this membrane splits into fine hairs. These wid- ened bristles are most common on the young worms. 198 MICROSCOPY FOR BEGINNERS. The bright red blood is contained in two principal tubular vessels, one above, the other below the tortu- ous intestine. The upper, or dorsal one, has connected with it near the anterior end of the body two little con- tractile hearts, one on each side, which can be seen through the hyaline animal throwing out the blood with considerable force. The two vessels are connected with each other by smaller ones, a pair in each segment or body-ring, one being on each side. There is also on each side of the body — two in each segment — a narrow colorless tube, ciliated within, and resembling those found in Nais and other aquatic worms. They are most conspicuous in the posterior rings, and are sup- posed to represent kidneys in function. Tubifex is reproduced by eggs, which probably make their escape after the parents' death, and after the body lias fallen to pieces, as the living creature has no passage for their exit. Huxley, however, says that they pass out through the segmental organs — the ciliated tubes just referred to. 11. NAIS (Figs. 140, 141). Body whitish or yellowish, usually very active. The podal spines and bristles are each arranged in a row on both sides of the worm, the bristles near the front end usually be- ing longest. Each cluster of podal spines contains four or more. The mouth is round, the front border of the SOME AQUATIC WORMS, ETC. 199 body bearing numerous fine, short hairs. Two dark or black eye-spots are generally present, one on each side in advance of the mouth. The blood is red. Many narrow, colorless tubes, with a ciliated lining, are to be noticed on both sides of the intes- tine. They are much looped and twisted, and are supposed to play some part in respiration, or to represent the kidneys of animals higher in the scale. They are bathed in the color- less fluid filling the cavity of the body, and change their position rapidly as this fluid flows to and fro, following the movements of the worm. Ndis is the commonest of the aquatic worms, being very frequently found among Algae in shallow water, or on the leaflets of various plants, especially, according to the writer's experience, in Sphagnum, in company with Pristina and Chaetogaster. Dr. Joseph Leidy?s papers, published in the Journal of the Academy of Natural Sciences, Philadelphia, and elsewhere, are the only ones to which the student can be referred for further information in connection with the aquatic bristle -bearing worms, as Dr. Leidy is the only naturalist who has seriously studied the American forms and published the results of his work. 200 MICROSCOPY FOR BEGES'NERS. CHAPTER VIII. KOTIFEKS. WHEN these transparent microscopic animals are swimming or taking food, there is usually an appear- ance of two, small, rapidly rotating wheels on the front border of the body, an appearance that suggested the name of Rotifera, or Wheel -bearers, for the group. The two organs certainly do seem like rapidly revolv- ing wheels when viewed under a low power, but they are in reality two disks or lobes surrounded by wreaths of fine cilia, which vibrate so quickly that the eye can perceive the effect only. It is by the action of these cilia that the Rotifer swims and captures food, the cur- rents produced by them when the animal is at rest set- ting in towards the mouth, usually situated between the ciliary (or cilia-bearing) disks, and carrying particles of food which the Rotifer accepts or rejects. As a rule the ciliary disks are two separate organs, but they may be united into one, or the Rotifer may have the front margin of the body bordered by a single line of cilia, or the disks may be entirely absent, and replaced by long arms, as in Stephanoceros, or by clusters of long, fine hairs, as in Flvsculdria, both of which are Rotifers. Most of these animals have eyes at some period of their life, or little red specks supposed to be imperfect KOTIFERS. 201 eyes. They are often to be noticed near the front of the body in young individuals, but in the old they are as often absent. Their number and position are some- times used as characters by which the genera and spe- cies are classified, but, since they disappear with age, they cannot be of much value for this purpose, certainly not to the beginner. The body is inclined to be cylindrical, yet there are some resembling flat disks and oblong figures. Neither are they all free-swimming. Some are permanently ad- herent to the leaflets of aquatic plants or other sub- merged objects, but these generally form a protective sheath about themselves, into which they retire when frightened or disturbed, in a manner similar to that of some Infusoria ; and, as in the Infusorial loricse, the sheaths may be formed of a stiff membrane, or of the softest and most gelatinous material, or they may be built of particles of dirt or rejected food fragments. In all instances the sheaths are the work of the Rotifers inhabiting them, and none of the Sheath-building Roti- fers are free-swimmers.* Most of the free swimmers, however, may become temporarily adherent by means of their foot and toes. The body of these free-swimming forms may be soft and flexible, and without any greater protection than is afforded by the skin, or it may be en- closed within a hard, shell-like coating called a carapace. The bodies of all the sheath-building Rotifers are with- * Since the above was written three have been discovered in Eng- land. But this need not trouble the beginner. 202 MICROSCOPY FOR BEGINNERS. out a carapace, the lorica being a sufficient protection. In the other kinds the carapace is colorless and trans- parent as a glass box, all the creature's organs being plainly visible through its walls. The front part of the body, which bears the cilia or the ciliary disks, and often the long tail-like prolongation of the posterior part, can be drawn within the carapace, and the Eotifer thus shut in and protected from harm. The soft-bodied forms have a similar habit of drawing in the two ends, taking advantage of the hardened skin. This is one of the Rotifer's characteristics. The long tail-like part at the posterior end of the body is called the foot, and the two or more short divis- ions at the free end of the foot are, of course, the toes. The true tail of the Rotifer is usually a small affair, which the beginner must not mistake for the more im- portant foot, although it is placed on the foot, some- times quite near the body. It may be represented by a single short point, it may be in two parts and more con- spicuous, or it may be entirely absent. The uses of the foot seem to be to act as a rudder to guide the Rotifers when swimming, as they do in a hurried, headlong way, and also to anchor them when they desire to fish for food. The toes then adhere to the surface of the slide or of any other object, anchoring and holding the ani- mal against the propelling power of the ciliary disks. In some of the group, especially in the commonest of all — Rotifer vulgaris — the whole foot is arranged with joints that slide on each other like the joints of a spy- ROTIFERS. 203 glass. In this and similar forms the Rotifer can not only swim, but it can crawl by fixing the front of the body against the slide, drawing in the telescopic joints of the foot and clinging with the toes ; the front is then loosened, the foot extends and carries the whole body forward for a short distance, when the action is re- peated. A Rotifer can do this with surprising rapidity, and so travel over considerable distances in a short time. The mouth is usually placed between the two ciliary disks, when they are present, near the centre of the frontal portion of the body, or, in some forms, it is placed near the front, but on the lower surface of the animal. Those with the mouth in the last - mentioned position usually feed by gliding along with the front of the body in contact with the plant, tearing and biting off small particles as they go. These may be called the nibbling Rotifers. Following the mouth there is often a tubular passage leading to a pair of wonderful jaws inside of the body, which, with a low-power objective, can be seen in action through the transparent tissues of the Rotifer. These jaws are always present in these creatures, and are a great help to the beginner, for as soon as he observes them pounding and crunching away inside of a transparent, legless, microscopic animal, he may be sure that his specimen is a female Rotifer. The ciliary disk may be absent, or replaced by arms, hairs, or some other substitute, but if these internal jaws are present the specimen is a Rotifer, and can be nothing else. By some observers'these curious organs are called 10 204 MICROSCOPY FOR BEGINNERS. the gizzard, which they are not. The best word to ap- ply to them is mastax. The mastax is the most hard-working part of the creature's anatomy, except, perhaps, the cilia. "When the currents produced by the latter bring an acceptable morsel of food to the mouth, it is passed down to the mastax, where it is crushed and allowed to go on to the stomach. In some Rotifers this part is very compli- cated. In the simpler forms it consists of two appar- ently semicircular plates surrounded by a thick en- velope of powerful muscle, the flattened sides acting against each other and crushing the food between them. The surface of each plate very often bears several trans- verse parallel ridges, to be seen with a high power, each ridge projecting a short distance beyond the straight in- ternal edge, to form short teeth. These ridges, when the mastax is closed, are received in the depressions be- tween those on the opposite plate, thus making an ef- fectual crushing instrument. In other forms the mastax consists of three parts, one being immovable, and used as an anvil on which the other two pound the food as it passes by. In the nibbling Eotifers the entire mastax is protruded through the mouth, and bites, tears, and nibbles at acceptable food masses. If the beginner finds it difficult to make out the form and structure of the mastax, as he probably will when it is examined in action within the body, he may succeed by killing the Rotifer with a strong so- lution of caustic potassa allowed to run under the cover- ROTIFERS. 205 glass — a small drop at a time. This will dissolve the soft parts, and permit the hard, insoluble mastax to float out, when it can be examined with a high- power objective. The Rotifers are reproduced by eggs, which are some- times hatched within the parent's body, when they are said to be ovo-viviparous. This, however, is not com- mon. The eggs are usually semitransparent, ovoid bod- ies, very often to be seen on the slide among other matters, with the Rotifer partially developed, and the mastax grinding away inside of the unhatched body where it cannot possibly have anything to crush. The only parallel to this of which I know is Professor Agas- siz's statement that the jaws of the young snapping-tur- tle snap while the creature is still in the egg. The Ro- tifers may drop their eggs anywhere and leave them to the care of Nature, or they may prudently attach them to a leaf or some other aquatic object. Very often they are adherent to the posterior part of the parent, and are carried about until the young are hatched. In those permanently attached Rotifers that form a soft sheath this is a common occurrence, and several eggs may at almost any time be seen in the lower part of the lorica, or fastened to the animal's foot. In such instances, when the young are hatched they creep up between the parent's body and the side of the sheath and escape at the front. They swim about for a short time, and then secrete or build a sheath of their own, which they never voluntarily leave. The eggs are usually smooth ; some- 206 MICROSCOPY FOR BEGINNERS. times, however, they are covered with short spines or hairs. It is a curious fact that although there are male and female Eotifers, the males are seldom seen. In some species they have never been found, and are therefore entirely unknown. Those that have been discovered are much smaller than the females of the same species. They are always free-swimming, and are without a mas- tax and alimentary canal, or with the latter so imperfect that it is useless. Male Rotifers, therefore, never take food. It is not probable that the beginner will meet with them, or at least will recognize them as the males. This group of animals is almost as common and abun- dant as the Infusoria, and they are found in similar places. They are specially fond of hiding in masses of Ceratophyllum. Indeed, almost any pond or shallow body of still water may be examined with a certainty of finding them. They have even been sparingly ob- tained from the moss that grows between the bricks in damp pavements. Some species develop in vegetable infusions, but as a rule they prefer fresh water. The beginner will, of course, not expect that all the genera and species will be included in this little book. He will obtain very many whose names he cannot hope to learn. He can, however, know them to be Rotifers by the pres- ence of the mastax, which makes them one of the most easily recognizable groups of microscopic animals. They form an interesting class of creatures for microscopic ROTIFERS. 207 study. Very few of our American forms have been investigated, and there is no one book in the English, nor, so far as I know, in any other language, to which the beginner can be directed for help. The American " Wheel-bearers " form a large field which ought to be cultivated. There is room for many discoveries, and an opportunity to greatly add to the world's store of scientific information. In using the following Key, the beginner must re- member that the sheath of some of the Rotifers is very often colorless and rather difficult to see clearly, un- less it has particles of dirt or other matters adherent to it. At other times it may be conspicuous. The Key refers to only those forms included in this book. Key to some Genera of Rotifers. 1. In a gelatinous or other kind of sheath (a). 2. Not in a sheath, but growing in attached clusters. (<#). # Free-swimming (e). «. Clustered ; sheath soft, gelatinous, colorless. La- cinuldria, 1. a. Not clustered ; sheath gelatinous (5). a. Not clustered ; sheath not gelatinous (c). b. With five long, erect, ciliated arms on the front border. JStep/ianoceros, 2. £>. With five clusters of many long, fine, radiating hairs on the front border. Floscularia, 3. 5. With two ciliary disks ; sheath tubular, often branched. Actinurus, 4. 208 MICROSCOPY FOR BEGINNERS. c. Sheath formed of rounded brownish pellets. Meli- certa, 5. , c. Sheath membranous, brownish or colorless. Lim- nias, C. d. Ciliary disk horse-shoe shaped. Megalotrocha, 7. e. "With carapace (g). e. Without carapace ; ciliary disks two (/"). f. With ten or twelve short, scattered, recurved spines ; toes three. Philodina, 14. f. Without spines; foot with telescopic joints, toes two. Rotifer, 8. f. Without spines ; foot with telescopic joints, toes three, the middle one longest. Actinurus, 4. g. Carapace with a vizor - like projection in front. Stephanops, 9. g. Carapace circular ; foot long, cylindrical, retractile. Pterodina, 10. g. Carapace vase - shaped ; foot long, with two very long toes. Dinocharis, 11. g. Carapace with six long, narrow, movable fins on each side. Polydrthra, 12. g. Carapace with several tooth-like spines on the front border. Brachionus, 13. 1. LACDTDLARIA. The clusters contain numerous individuals secreting a common, soft, colorless, or pale yellowish short sheath without any special shape ; it surrounds only the poste- rior part of the colony and can serve as a very slight ROTIFERS. 209 protection, if any. The Eotifers are somewhat trumpet- shaped when extended, and to a certain extent resem- ble Megalotrocha (Fig. 147). The ciliary disk is single and horseshoe shaped. It is closed and drawn partly into the body when the Rotifers retire into their apol~ ogy for a sheath, as they often do, the whole colony continually waving and bobbing and bowing as the members retire, or ascend and expand themselves. The sheaths usually form a little mass of jelly-like sub- stance, from all parts of which the Rotifers project. The colonies are commonly adherent to Ceratophyllum or Myriophyllmn. 2. STEPHANOCEROS (Fig. 142). The body of this the most beautiful of all the Roti- fers is somewhat spindle-shaped. It ends in a long, flex- ible, tail-like foot which is attached to some submerged object, and has five long, slightly curved arms arranged in a row about the edge of the front border. These arms are held aloft and form a most effectual trap for wandering Infusoria, which are attracted or drawn into it by some means not easy to make out. The front of the body is like a deep open funnel leading down to the mouth, mastax, and stomach. The ordinary ciliary disk is absent, being re- placed by the arms, but around the inside border of the funnel -like front there seem to be many fine cilia which may produce the currents in the water. 210 MICROSCOPY FOR BEGINNERS. They are very difficult to see even with a high -power objective. The sheath is usually colorless and transparent, with considerable firmness. It often surrounds the body up to the origin of the arms. When a small animal once enters the cage formed by the arms it seldom escapes, but is gradually driven down into the funnel, when the Rotifer partially closes the front opening, and with a very perceptible gulp swallows and passes it on to the mastax. /Stephanoceros does not seem to be very common. The writer has found it sparingly on Myriophyllum as late as the middle of November. 3. FLOSCULARIA (Fig. 143). The front of the body is here also like an open fun- nel, the narrow part leading to the mastax. The ciliary disk is replaced by five little rounded elevations on the front margin, each bearing a thick clus- ter of long, fine, radiating hairs, which are flexible, and movable at the ani- mal's will, but which never vibrate like cilia. The long foot is attached to a sub- merged object, and is surrounded by a soft and transparent sheath. When the Rotifer retires into this protective cov- Fig. 143. ering, it folds the wide front part of the Floscularia orudta. body together, the clusters of long hairs seem to become much tangled into a single bunch, and ROTIFERS. 211 the creature slips back into the sheath. When she comes out, the bunch of hairs tremble in a very pretty way, reminding the observer of the quivering appearance of hot air often seen on a summer day. The front border opens, the clusters of hairs are spread apart, and the Rotifer is ready for something to eat. Any little ani- mal slipping in between the hairs seldom comes out again. The Floscularia gently contracts the frontal opening and directs the victim towards the mouth, where it is gulped down as in Stephanoceros, and the mastax finishes it. Several eggs are often seen at- tached to the foot. This splendid Eotifer is common, and where one is found others will usually be near by. 4. ACTINUKUS (Fig. 144). When a bottle of pond water and various plants is allowed to stand for a while undisturbed, there will of ten form on the sides very delicate, thread-like objects, frequently branching and otherwise resem- bling brownish Algse, waving and trembling as the bottle is stirred. They are so soft that they can hardly be removed with the dipping-tube without breaking them. They are the sheaths of a Rotifer. She makes them from a sticky secretion exuded by her body, and small particles of any matters that may be floating in the vicinity. The inside seems to be smooth, but the outside is rough and irreg- ular. The Rotifer projects from the open end, clinging 10* 212 MICROSCOPY FOR BEGINNERS. to one inside wall by the tips of her toes, and as the tube lengthens by the deposit of new material at the top, she takes a step forward so as to keep her expanded ciliary disks in the open water. If the student will al- low a mixture of fine indigo and water to run under the cover-glass, he will see the formation of the sheath. A blue ring of indigo will very soon appear at the top of the soft tube. In appearance the Eotifer resembles Rotifer vulgdms (Fig. 148), and when out of the tube, which she can leave at will, has similar actions. There are two ciliary disks, and usually two eye-spots. The foot is long, and can be drawn into the body by telescopic joints. It has three toes, the middle one being the longest. The eggs are hatched within the parent's body. The Rotifers oc- cupying the branches of the sheath are probably all members of the same family — mother, children, and grandchildren — the young forming the branches. There is a species of this genus which does not form a sheath. It may be known by its resemblance to Ro- tifer vulgaris, and by the three toes, the middle one being the longest. 5. MELICERTA (Fig. 145). The sheath of Melicerta resembles that of no other common Rotifer. It is built of pellets, which she makes and places in rows around her body, thus erecting a red- dish or yellowish-brown lorica that cannot be mistaken. The body itself is colorless, and is always attached by ROTIFERS. 213 the tip of the long foot to an aquatic object. The cil- iary disk consists of four parts or lobes of different shapes and sizes, and the little creature also has a very pe- culiar and rather complicated organ for making the pellets. The whole front part of the body can be folded together into a rounded mass when Melicerta is frightened and retires to her sheath. "When her fright is over, she slowly protrudes this rounded mass from the aperture, gradually spreads it open, sets the cilia at work, and proceeds to eat and build. The last she seems to do almost continuously. As her body grows, her house must be enlarged to re- ceive it. The ciliary disk of Melicerta will repay the most care- ful study. And careful observation will be needed to learn just how the three distinct currents that she makes in the water are produced. One current brings food particles to the mouth, where she selects the acceptable morsels and passes them on to the mastax ; a second current carries away the fragments for which she has no use ; and the third sets in towards the little organ that makes the pellets. This is a small cavity into which the building material is poured, and where it is turned about rapidly by the fine cilia which line it. A sticky secretion is exuded that causes the particles to adhere to each other, and the revolving motion gives the pellet the shape of a Minie-bullet. When the latter is formed to the Kotifer's liking, and all is ready for the final act, 214 MICROSCOPY FOR BEGINNERS. Melicerta turns herself in the tube, bends her body, and deposits the pellet on the top row, where she cements it in place with an invisible insoluble cement. The whole is done so quickly that the first time the observer sees it he is so surprised that he sees nothing. It is remark- able that, as a rule, she forms the pellet while standing on the side of the sheath opposite to the point where she means to place it. The pellets have often been de- scribed as round balls, but the student will see that they are conical, and that the pointed ends are on the out- side. Melicerta is quite common on Ceratophyllum. 6. LIMNIAS (Fig. 146). The sheath that this Rotifer forms is a rather stiff, membranous, nearly cylindrical tube, somewhat widest at the upper part. When young it is usually colorless and smooth, but it changes with age, becom- ing brown or blackish, and floating particles roughen it by adhering to the outside. The animal living within it is colorless, and has the ciliary disk divided into two lobes, which she folds together when frightened and forced to retire to the back part of the sheath for pro- tecti°n- The sheath is secreted from the body of the Rotifer ; it is not built of particles picked out of the currents from the ciliary disks. It is common on the leaflets of Ceratophyllum, and is prob- ably named Limnias cemtopliylli for that reason, al- though it is found almost as often on Myriophyllum. ROTIFERS. 215 There is another species of Limnias also quite com- mon in the writer's locality, which differs from Limnias ceratophylli in having the sheath apparently formed of narrow rings, so that the edges, as seen under the mi- croscope, seem finely waved or scalloped. By this it can be easily distinguished from the above. It is named Limnias annuldta. 1. MEQALOTBOCHA (Fig. 147). The clusters formed by Megalotrocha are sometimes so large that they are visible to the naked eye as whitish bodies clinging to Myriophyllum, which it seems to pre- fer. With a pocket-lens the individual Roti- fers may be seen rising and bobbing as they expand or contract, but a low power of the compound microscope is needed to appreciate their beauty. The expanded body is rather trumpet - shaped, very soft and flexible, and when young is colorless. As it grows old it becomes slightly yellowish. The eggs are FI&UT. Megalotrocha. often to be noticed adhering to the lower part of the parent. "When the young one is hatched it either remains in the old colony or it leaves and founds ,a new cluster, so that in favorite localities col- onies of almost any number of members may be ob- tained. The Eotifers of old colonies are often infested by an Infusorial parasite, which runs over the surface and apparently feeds on the mucous matters secreted by the Rotifers' skin. It is called Chilodon megalo- 216 MICROSCOPY FOR BEGINNERS. trochee, and somewhat resembles the Chilodon shown in Fig. 128. 8. ROTIFER VULGARIS (Fig. 148). This is the commonest of all the Rotifers. The body is spindle-shaped, tapering to both ends when the two ciliary disks are unfolded. The foot has two short toes, and can be drawn into the body by its telescopic joints. Between the two ciliary lobes is a cy- lindrical projection ciliated on the tip, and near- ly always bearing two little red eye-spots close together. It is called the proboscis. When hungry the Rotifer clings to the slide by her two toes, expands the ciliary disks, and sends a food-bearing current through the mouth to the mastax< When desirous of changing her place, she may either loosen her hold with the toes and be carried through the water by the action of the cilia, or she may fold the ciliary lobes together and go looping about by clinging with the tip of the proboscis while she draws up the foot, when, fastening it to a new point, she lets go with her proboscis, extends the body, takes a new hold with the foot, and thus moves about quite rapidly, somewhat after the manner of the " meas- uring-worms." 9. STEPHANOPS (Fig. 149). There are several species of these pretty little Roti- fers, all of which may be known as members of this ROTIFERS. 217 genus by the extension of the front of the carapace over the ciliary disk, like the visor of a boy's cap. A not uncommon species is shown by Fig. 149, in side view, so as to exhibit the long, movable bristle springing from the back, and the curved visor which, in the figure, looks like a line above the frontal cilia. The Rotifer is one of the nibblers. The mastax is protruded from the mouth, which is near the front of the lower flat- tened surface, and bites and tears the food it meets with. It is often to be seen gliding over aquatic plants, nibbling as it goes. The carapace is thin and quite flexible. It extends over the sides of the body, so as to give the Eotifer an ovate outline when seen from above or below. The bristle on the back is very mov- able and flexible. In one of the species the carapace is prolonged at the posterior border into two lateral teeth. In another this part is without teeth, and the dorsal bristle is also absent, as it is in all the known American species, except the one shown in Fig. 149. 10. PTEBODfNA (Fig. 150). The carapace is almost circular, much flattened, and perfectly transparent. The anterior border has a broad notch with rounded margins, over which extends a lip with a central rounded projection. The ciliary disks are two, and rather widely separated. In the figure they are shown retracted into the body. There are usually 218 MICROSCOPY FOR BEGINNERS. two eye-spots. The foot is long, tail-like, very flexible, and apparently formed of narrow rings. It can be withdrawn entirely into the carapace, and the Rotifer seems to take pleasure in doing so. It has no tail, but is terminated by a small sucker bordered by a circle of tine cilia. The Rotifer is often seen among Ceratophyllum leaflets. 11. DINOCHARIS (Fig. 151). The transparent, glassy carapace is rather squarely vase-shaped and somewhat flattened. It gen- erally has a tooth-like projection on each side of the posterior border. The Rotifer can al- ways be recognized by its two very long toes, in one common species one toe being very much longer than the other. The foot is formed of two joints slightly enlarged at the ends. 12. POLYARTHRA (Fig. 152). The form of the carapace is somewhat like an egg, with both ends cut squarely off. The character, how- ever, by which the Rotifer may always be known is the presence of the twelve long, serrated fins which project backward from the front part of the upper and lower sur- faces. They are arranged in clusters of three fins each, one cluster being on each side below, and one on each side above. By them the Fig. 151. Diu6charis. ROTIFERS. 219 Rotifer makes long, quick, very sudden leaps, often jumping so rapidly that it can hardly be seen ; it ap- pears to spread the fins and disappear. Occasionally it turns a complete somersault. The cilia are arranged in a row along the front border. There is no foot. The mastax is pear-shaped and large, but its structure is dif- ficult to make out. The Rotifer has only one eye, which is near the centre of the upper front surface. The little creature has been called by some writers the " sword-bearer," and is said to be quite common in some localities, but I have never been fortunate enough to find it. 13. BBACHIONUS (Fig. 153). There are several species of this genus, all of which may be known by the presence of a carapace with sev- eral tooth-like projections or spines at the front, and often also at the rear, by the two ciliary disks and the single eye-spot. The species whose empty carapace is shown in Fig. 153 is strict- ly American. It is very attractive in its glass- like transparency, active movements, and beau- tiful carapace. It was discovered by Mr. H. F. Atwood, of Rochester, and named Brach- ionus conium by him.* It is quite common, and may be easily recognized by the ten long teeth or spines on the front border — the central one on the upper side or back being largest, and bent at a right angle — and by * American Monthly Microscopical Journal, June, 1881. 220 MICROSCOPY FOR BEGINNERS. the four posterior ones. The foot is long and narrow, and has two toes. Eggs are occasionally to be noticed attached to the posterior part of the carapace. 14. PHILODINA (Fig. 154). This is readily distinguished from the common Roti- fer (Rotifer vulgaris) by the spines scattered over the back and sides of the hardened and minutely roughened body, by the three toes, and by the two eyes being some distance from the front border, while in Rotifer vulgaris they are close togeth- er on the proboscis. The species referred to is shown in the figure with the body partly con- Fig. 164. tracted, the ciliary disks and foot entirely so. The body is flexible, yet the skin is hardened and bears the conspicuous recurved spines, two of which are on the sides — one on each — and pointing forward. The tail is divided into two parts, which are shown in the figure, projecting beyond the body. The Rotifer is peculiar, and not uncommon. I have found it in sum- mer, and have taken it from under the ice in February. FRESH-WATER TOLYZOA. 221 CHAPTER IX. FKESH-WATER POLYZOA. THE reader now approaches a group of microscopic animals whose beauty is so exquisite, so delicate, so re- fined in its comeliness and grace, that no description could be too extravagant, no rhetoric too fervid when applied to the charming little creatures. Yet most of this fairness seems wasted so far as human appreciation is concerned, for how few among the millions of human beings in all the land know, or care to know, what the Polyzoa are, or how they look, or where they live, or whether they live at all ? Nature was never in bet- ter mood than when she began the development of the Polyzoa, so she fashioned them with care, and placed them most abundantly in all our slow streams and shal- low ponds, where they live and die and melt away in the shade of the lily-leaves, where no human eye sees their loveliness until a wondering lover of Nature spies them and is happy. The word Polyzoa is formed of two Greek words meaning " many animals," referring to their habit of living in colonies which sometimes reach an immense size. They are, with but one exception, always at- tached to some submerged object, except immediately after leaving the egg, when the young animal leads a 222 MICROSCOPY FOR BEGINNERS. short, free - swimming life. "When once attached they are adherent till death. The animals themselves are small, but often apparent to a trained eye ; they are al- ways visible under a good pocket-lens. The colonies, how- ever, of all the fresh-water forms need no magnifying; some of them are very conspicuous. These communi- ties are formed of the protective coverings or sheaths secreted by the animals. Some take the form of very narrow, brownish tubes, adherent to the lower surface of floating chips, boards, waterlogged sticks, or even occasionally to lily -leaves or the submerged stems of grasses. The little tubes branch like miniature trees, and spread over the surface as if the delicate tree had been flattened down and pressed so hard that it could never again rise up ; or they may be attached by the base only, the trunk and the branches then floating and waving in the water. The animals secreting these tubes live in them, projecting a part of the body beyond the orifice, and very quickly retreating when frightened. And they are usually very timid, retiring into the tubu- lar home at a slight disturbance of the water, needing a long time in which to recover and again look out at the entrance and spread their beautiful tentacles. In other forms the colony is surrounded by a thick, rather firm, jelly-like material, from which the animals protrude themselves, and into which they retreat. These jelly masses are usually colorless and semitransparent, or they may be tinged a pale red. They are to be found in the purest of still water, adherent to sticks, capping a FRESH-WATER POLYZOA. 223 submerged stump with a cushion of living jelly, cling- ing like crystalline globules to any projecting rootlet or water -soaked object beneath the surface, even to smooth stones. In bulk they may be like a boy's mar- ble, or a cart-wheel, with every intermediate size. They vary so much that to find a good comparison is not easy, and it is only right to say, lest some lover of these lovely creatures should be envious, that a colony the size of a cart-wheel has, in the writer's locality, been found but once, the foundation of this remarkable growth probably being the rim of an old wheel. When the tubular or the jelly-like colonies are re- moved to the collecting-bottle, they appear lifeless and unattractive. The jelly may excite wonder by its size, or curiosity to know what it can be, yet otherwise it will not be noticeable. But wait a while. Place the bottle in the shade and wait a few minutes ; then with a pocket-lens look at the surface of the jelly or the tips of the branching tubes. Treat them with care; move them gently. The little creatures are easily frightened, and like a flash leap back into their protective case. Perhaps while you gaze at the reddish jelly a pink little projection appears within the field of your lens, and slowly lengthens and broadens, retreating and reappearing it may be many times, but finally, after much hesitation, it suddenly seems to burst into bloom. A narrow body, so deeply red that it is often almost crimson, lifts above the jelly a crescentic disk orna- mented with two rows of long tentacles that seem as 224: MICROSCOPY FOR BEGINNERS. fine as hairs, and they glisten and sparkle like lines of crystal as they wave and float and twist the delicate threads beneath your wondering gaze. Then, while you scarcely breathe, for fear the lovely vision will fade, another and another spreads its disk and waves its sil- very tentacles, until the whole surface of that ugly jelly mass blooms like a garden in Paradise — blooms not with motionless perianths, but with living animals, the most exquisite that God has allowed to develop in our sweet waters. Perhaps you make an inarticulate cry to your companion, who is probably wondering why you are so still and what you are doing on the ground with the lens so close to the bottle, and as he too gets down and brings his lens to bear, maybe he jars the water, and the lovely Polyzoa flash their tentacles together and dart backward into the mass, leaving it as indescribably ugly as before. If he brings you to task, tell him to wait and look. And while he looks the little bodies again slip outward, the crescentic disks again spread wide open, the shining tentacles unfold and curl and lash the water until once more the ugly jelly mass be- comes a thing of indescribable beauty. This is Pecti- natella, well named the magnificent. The jelly is formed by the animals, and is in reality a collection of protective loricae, the huge masses often found being the result of the increase in the numbers of the Polyzoa inhabiting them ; or, as must frequently occur where they are very abundant, of the union of many contiguous growing colonies. A single animal FRESH-WATER POLYZOA. 225 begins the colony; it becomes two by a process of bud- ding, the bud finally becoming another Polyzoon, se- creting more jelly, budding in its turn, so that the com- munity may in the end contain numberless members, and the mass may measure several feet in diameter. The color of the animals is usually a pale red or flesh tint, deepening to crimson about the mouth, which is placed near the centre of the crescentic or horseshoe- shaped disk of tentacles. In the largest, and therefore the oldest, colonies the jelly may exhibit many scat- tered white spots composed of carbonate of lime. There is another jelly-forming colony called Crista- tella, which the beginner may mistake for young Pecti- natella. It is to be distinguished by the absence of those great masses which characterize Pectinatella, by the general appearance of the colony, and by its motion. A community of Cristatella is usually long and narrow, often measuring several inches in length. One species is about eight inches long, one-fourth of an inch wide, and one-eighth thick. Young colonies are, of course, smaller, and are rounded. It has the power which no other fresh-water Polyzoon possesses — to travel from place to place. It moves very slowly, a colony about an inch in length moving an inch in twenty-four hours. All the fresh-water Polyzoa, of which there are sev- eral genera and species, have on the front part of the body a disk which bears the tentacles. It is named the lophophore, and is, in some forms, horseshoe-shaped, in others nearly circular. The tentacles are arranged on it 226 MICROSCOPY FOR BEGINNERS. as on a base, usually in a double row. The word is Greek, and means " wearing a crest." In those Polyzoa which secrete hardened, tubular, tree- like sheaths on the surface of submerged objects, the lophophore is protruded from the orifice in the end of the branch much as in Pectinatella, and there is only one animal to each limb and hollow twig. The protru- sion and expansion of the lophophore can be seen with a pocket-lens, as in Fig. 156 (from Professor Alpheus Hy- att's work on the Polyzoa), when it resembles in form that of Pectinatella. Those inhabiting the tubular sheaths seem much more timid than the gelatinous forms, retreating on slighter provocation, and remain- ing longer before they reappear and again spread the lophophore and tentacles. They are quite as graceful and attractive — perhaps they are more so, since they seem more delicate and less able to protect themselves. The tentacles are finely ciliated, as the microscope will show. The currents produced by the active vibra- tions of the cilia on the sixty to eighty tentacles of Pec- tinatella, or the eighteen to twenty in other members of the group, are quite powerful, and setting in towards the centre of the lophophore, they sweep the entrapped food to the mouth. The body of the Polyzoon is a transparent, membranous sack, with the lophophore and the mouth at the free end, most of the rest being im- mersed in the jelly or concealed in the brown opaque sheath. The mouth has on one border a short, tongue- like organ, which can close the opening and prevent the FRESH -WATER POLYZOA. 227 escape of the food. Extending from the mouth to the stomach is the food passage or oesophagus, the stomach itself being a widened tube, usually conspicuous on ac- count of its contents and the alternate narrow, reddish- brown and yellow bands traversing it lengthwise. It is suspended in the hollow body, and is bathed by a color- less fluid which fills the cavity and extends also into the hollow tentacles. The stomach is followed by the tubu- lar intestine, which curves forward, and generally opens below and on the outside of the lophophore. The ani- mals have no heart and no blood, unless the liquid in the space between the outer walls of the stomach and the walls of the body can be said to be blood. When the animal is frightened, the sides of the lo- phophore close together, the tentacles collect themselves into a bundle, and the front of the Polyzoon is drawn back into the body, and a muscle around the border closes that opening. The jelly of Pectinatella and the hardened tubes of the other forms are, therefore, the protectors of the body, while the body receives and en- closes the lophophore and tentacles, which are thus doubly protected. When the danger is past, the tips of the bundle of tentacles are very cautiously pushed out into the water, the lophophore follows, and if the creat- ure's confidence is restored, the crowns are spread open in all their indescribable grace and beauty. The favorite food consists of small Algae and Infuso- ria, which the ciliary currents sweep towards the mouth, the tentacles forming a cage from which the little ani- 11 228 MICROSCOPY FOR BEGINNERS. mals seldom escape unless the captor is willing. And not only are the tentacles used to capture the food, but " for a multitude of other offices. They are each capa- ble of independent motion, and may be twisted or turned in any direction ; bending inward, they take up and discard objectionable matter, or push down into the stomach and clear the oesophagus of food too small to be acted on by the parietal muscles." To examine the Polyzoa under the microscope de- mands a very deep cell to hold a large quantity of water and to prevent the cover-glass from pressing on the bodies. It is often better to place the microscope in an upright position and omit the thin cover. In this ar- rangement the water trembles easily, and not only inter- feres with the distinctness of the image, but terrifies the timid creatures on the slide. Thte observer must, there- fore, be careful not to touch the table, and to make his examination in a quiet room. They will ask a little at- tention and some gentle treatment, but what they will show with the help of a one-inch objective will amply repay the outlay of time and patience. The following Key to the genera will help the stu- dent to name the forms he may find. Key to Genera of Fresh-water Polyzoa. 1. In a jelly mass (a). 2. In adherent, branching cylindrical tubes (J). 3. In adherent, branching colonies formed of tubular, club-shaped cells (G). FRESH-WATER POLYZOA. 229 4. In adherent, pendent stems formed of urn - shaped cells (d). a. Jelly mass rounded, adherent, often very large. Pectinatella, 1. a. Jelly mass long, narrow, slowly travelling. Cris- tatella, 2. ft. Lophophore horse-shoe shaped. Plumatella, 3. b. Lophophore circular. Fredericella, 4. c. Lophophore circular, tentacles in a single row. Paludicella, 5. d. Lophophore circular or oval, tentacles in a single row. Urnatella, 6. 1. PECTINATELLA MAGNIFICA (Figs. 155, 155a). The appearance to the naked eye of the colorless jelly-like substance siwroimding the bodies, and of the animals themselves, has already been referred to. Pectinatella is not sensitive to sound, but a jar or shock to the water sends the an- imals into their contracted state very suddenly. The colonies are numerous throughout the summer and until October. They are most frequently found in the shade, al- though they may live in the sun if below the water. Exposure to air Fig. iss—pectinattiia mag- and sunlight together is speedily fatal. Therefore transfer the jelly to the collecting- bottle as soon as possible, otherwise you will have, on 230 MICROSCOPY FOR BEGINNERS. your return home, nothing but a softening, slimy mass that will soon force you to throw it away. If suspended in a large vessel of water kept very fresh by frequent change, Pectinatella will live for some time in captivity. In Fig. 155 (after Hyatt) is shown a small colony with the lophophores and tentacles expanded and enlarged, as they appear with a good pocket-lens. The absence of color and motion, however, makes a great difference in their beauty. In old colonies, especially late in the season, there are often to be seen very many small, rounded, brown bodies, which, as the animals die, float to the surface of the water. These are the winter eggs or statoblasts. They are formed within the body, and escape only when the Polyzoon dies and melts away, when they float out and remain unchanged until the*warmth of spring de- velops them. Under the microscope the stat- oblasts of Pectinatella are seen to be encircled by a row of double hooks, as shown in Fig. 155«- l liave collected them late in the fall, of Pectu an(j? keeping them in a small aquarium in a warm room, have had them hatch out in No- vember. The young fastened themselves to the sides of the glass bowl, where they appeared like delicate grains of translucent pearl. There was no jelly at this early stage, and each little Pectinatella stood alone, con- sequently all the internal organs were even more dis- tinctly visible than usual through their hyaline bodies. I hoped to see them develop into colonies, but the sur- FRESH-WATER POLYZOA. 231 roundings were not quite favorable, perhaps the proper food was not attainable, so they died. 2. CRISTATELLA. The form and movements of Cristatella have already been referred to on page 225. The young colonies are rounded, and are found in the same localities with Pec- tinatella. The statoblasts are circular and have two rows of double hooks, one row around the border, the other nearer the centre. In both, the hooks are not sim- ple as in Pectinatella, but have several branches at the top of the stern, and the tips are forked. According to the writer's experience, Cristatella is not common. 3. PLUMATELLA (Fig. 156). The tubes containing the animals may be attached only at the base, or the whole colony may be adherent to the submerged surface on which it grows. It is to be found in shallow water, usually near the shore. To see the lophophore and ex- panded tentacles, if the col- ony is small, it may be re- moved by slicing the wood to which it is attached, the Fig. 156.-Humatella. slice to be placed in a watch- glass of water on the microscope stage, which must, of course, be in a horizontal position. The mirror may then be swung above the stage, and Phimatella viewed 232 MICROSCOPY FOR BEGINNERS. by reflected light as an opaque object. It is exquisitely beautiful in this position, as is Pectinatella or any of the Polyzoa ; but the animals are very timid. To see the expanded tentacles will therefore demand much time and patience. Plumatella is almost as common as Pectinatella. A board or log that has been floating undisturbed in the pond will, during the summer, be quite sure to afford a rich harvest of Plumatella if its under-surface be examined. 4. FBEDEBICELLA. The colonies of this Polyzoon are found in the shadiest places and near the shores of shallow ponds, growing like Plumatella, and often in company with it, on the lower surfaces of floating or submerged objects. The whole colony may be adherent, or only the base, the stem and branches then floating. A single animal in- habits each hollow branch, and resembles Plumatella in appearance and structure. It may be distinguished from Plumatella, however, by the oval or nearly circu- lar lophophore, that of Plumatella being horseshoe- shaped. The colonies are usually small, covering a small space. The tentacles are never more than twenty-four in number. The statoblasts are more or less circular, and are without spines or hooks. 5. PALUDICELLA (Fig. 157). These colonies may always be known from all other tube-making Polyzoa by their jointed appearance, each FRESH -WATER POLYZOA. 233 joint or cell being club-shaped. The colonies are irreg- ularly branched, and are built up of a single row of cells placed end to end, the narrow end or the handle of the club being attached to the broad end of the cell immediately behind it. The opening through which the animal pro- trudes its Circular lo- Fig. W.-Palndicella. phophore is at one side of the broad end of each cell near the top. The base alone may be attached, or the stem may be adherent and some of the branches free, as in the figure. 6. URNATELLA (Fig. 158). The form and appearance of this Polyzoon are so characteristic that it need never be mistaken ; but while the other members of the group are usually rather con- spicuous objects to the eye of a microscopist, Urnatella, must be especially searched for. The colonies, or stem- like growths which it forms, are composed of urn-shaped cells or segments united end to end, and attached by a single disk-like enlargement to the supporting object from which they hang suspended. The lower surface of stones, beneath which the water constantly flows, seems to be Urnatella's favorite haunt. The stem-like colonies of urns are usually found two together pendent from the same disk of attachment, and appearing some- 234 MICROSCOPY FOR BEGINNERS. what like a string of beads — this being due chiefly to the alternate bands of brownish-white and black sur- rounding the urns. In length the stems vary from one- eighth to one -sixth of an inch, rarely reaching one- fourth. To be seen on a wet stone with the unaided vision, therefore, demands a trained eye. The cells or urns are joined end to end, the enlarged central portion of each being light-colored, while both the narrowed ends are dark or black. A single colony is seldom formed of more than a dozen urns, the stems thus built up being either quite straight or somewhat curved, or even on occasion loosely coiled. At times the stem is branched, the secondary stem originating near the point of attachment of one cell with the pre- ceding, but soon falling off or voluntarily breaking away. On each side of every segment of the mature stems is a small, cup-shaped projection, the two appear- ing almost like handles to the urns. These are sup- posed to be the remains of the branches or of those segments which have fallen away and gone to begin new colonies in another place. Each urn, therefore, has at some time two urns attached to it, one on each side, and occasionally a specimen will be found with one or more branches still adherent. The central enlarged portion of the urns is translu- cent, light-colored, and often with many transverse wrin- kles and transverse brown lines. It is. also brown spot- ted, and has many little tubercles of the same color. The necks of the urns where they are joined together FRESH-WATER POLYZOA. 235 to form the stems, are opaque and black. The first or foundation segment of the growth is larger than the others, and its base expands into a broad disk, which adheres to the stone and supports the entire stem. Through the centre of the whole -collection of urns passes a cylindrical cord, whose purpose would seem to be to strengthen the fragile pile and to give it the great flexibility which it has. The two segments near the free end of the stem are smaller than the others and rather different in shape. They are also nearly transparent and colorless. They seem to be urns in the process of growth, while those below are matured and hardened. It is only the terminal segments that contain the living animal, the urns forming the stem below them being filled with a soft, trans- lucent, granular substance packed into the cavity around the central cord. The animal that produces this beautiful series of brown urns Fig. 153.— Urnat611a. lives at the free end of the pile solitary and alone with the exception of the temporary companionship of those short branches which sprout out near it, as shown in Fig. 158. It is these short growths that are supposed to drop off and leave the cup-shaped 11* 236 MICROSCOPY FOR BEGINNERS. scars on eacli side. Barely are there more than two of these projecting scars on each urn. The animal itself, which terminates the main stem and its branches, when in active condition, appears, Dr. Leidy, its discoverer, says, as a bell-shaped body with a widely expanded oval or nearly circular mouth, directed obliquely to one side or ventrally. The mouth of the bell is bordered by a broad waving band or collar, from the inside of which springs a circle of tentacles. Of these there are usual- ly sixteen, though sometimes from twelve to fourteen. They are cylindrical, and reflected from the mouth of the bell. They are invested with an epithelium fur- nished with moderately long, active cilia.* Like most of these beautiful creatures, Urnatella is very timid and sensitive. At the slightest disturbance the tentacles are folded together and drawn into the mouth of the bell, which closes around them, and the entire stem suddenly bows itself down to the ground, or, when long, rolls itself into a loose coil. No eggs nor statoblasts have been observed. During the winter the urns do not seem to become separated. "Perhaps, as reproductive bodies, after the polyp-bells perish, they remain in conjunction securely anchored through the first of the series, and are preserved during the cold of winter until, under the favorable condition of spring, they put forth buds and branches, which, by * "Urnatella gracilis : A Fresh-water Polyzoon." By Professor Joseph Leidy. Journal of the Academy of Natural Sciences of Phil- adelpldu, vol. ix. FRESH -WATER POLYZOA. 237 separation and settlement elsewhere, become the foun- dation of new colonies." Thus far I have not been fortunate enough to find a specimen of Urnatella, although it is probably not rare among stones in running water. A sight of its beau- tiful and curious collection of urns tipped by its grace- ful bell and swaying tentacles is worth many a long tramp, and careful scrutiny of many a wet stone. My account of this Polyzoon, because of my want of ac- quaintanceship with it, is gleaned from a paper, already referred to, by Dr. Leidy, who discovered and named it Urnatella grdcilis. And those who desire to be fully informed as to the anatomy of the charming creatures which form the group of the fresh- water Polyzoa, and to distinguish the several species, are referred to Professor Alpheus Hy- att's work on " The Polyzoa," published by the Essex Institute, Salem, Mass., and to Professor Joseph Leidy's papers on the subject in the Journal of the Academy of Natural Sciences of Philadelphia. 238 MICROSCOPY FOR BEGINNERS. CHAPTER X. ENTOMOSTKACA AND PHYLLOPODA. THE reader is familiar with the crayfish, lobster, and crab as members of that great group of animals called the Crustacea, because they are covered by a hard, shelly coating ; but, with the exception of the crayfish, he may associate them all with salt water, while in reality our fresh-water ponds are densely peopled with minute crus- tacean creatures. The little fresh -water animals are often enclosed in a bivalve shell, which some of them have the power to open and shut ; or the back of the body may be simply hardened, but without a distinct shell. The feet, or legs, are usually numerous, and very hairy or bristly, and in one section of those re- ferred to in this chapter are flattened, and each one bears near the body a flattened plate; consequently, since these parts are somewhat leaf-like, the animals have, as a class, been called the leaf-footed or the Phyl- lopoda, which is putting the words into Greek. Yery many others, to be found much more abundantly and frequently than the Phyllopoda, are without these plates, although the feet are as numerous and, in some, almost as flat, and the shells or the shelly back as well marked. These have been, by naturalists, grouped together under the name of the Entomostraca, meaning little animals ENTOMOSTRACA AND PHYLLOPODA. 239 in a shell, but the translation of the word has no dis- tinctive signification, since members of both groups have shells. The Entomostraca are more abundant in fresh water than the Phyllopoda, and are remarkably active. They are usually visible to the unaided eye as little specks, skipping, flirting, or jerking themselves through the water, although probably few will measure more than one-tenth of an inch in length. Under the microscope some are, as already stated, seen to be enclosed in a bivalve shell, and others are entirely free from so dis- tinct a covering. The feet are arranged in pairs, and may be very numerous. They serve, in the shell-bear- ing forms, not only as swimming organs, but as gills or similar contrivances for the absorption of air from the water for the aeration of the little animals' blood. This is probably one reason why they are kept in such inces- sant motion. Even when the shell - bearing Entomos- traca come to rest, to feed, or for some other purpose, certain of the feet keep up a ceaseless beating of the water, as can be readily seen through their transparent case. The mouth parts are complicated, much patience and microscopical skill being needed to investigate and un- derstand them. On each side of the head, however, and usually near the mouth, are two thread-like but jointed organs called the antennae, and these the beginner must recognize, as they often become important aids in learn- ing the animal's name. They vary in length, one on 240 MICROSCOPY FOR BEGINNERS. each side often being quite short and difficult to see distinctly, while the other two are usually long and con- spicuous. They are all formed of short and well- marked joints, the number varying greatly in the dif- ferent genera, and sometimes in different species of the same genus. One or more black or dark red eye-spots are com- monly present. In some the eye is single, and in the centre of the forehead. It may also be slightly movable at the will of its possessor. The young animal, as not rarely happens, may have two distinct eyes, which, as it grows older, become joined into one and covered by the shell. The heart is very frequently visible, especially in the shell-bearing forms, being there placed at the back of the body and near the head. It beats rapidly, and ap- parently sends the colorless blood quickly through the system. They all increase and multiply through the formation of eggs, which may remain within the shell and there be hatched, or they may be attached to the parents' body in external clusters. In the shell-bearing forms they are passed into a brood cavity at the back between the body and the shell, where they are kept until the young are hatched, when the latter make their escape into the water, and care for themselves. In those without shells the eggs are passed out of the body into one or two small, pear-shaped sacks called external ovaries, where they remain until hatched. In these cases, however, the ENTOMOSTRACA AND PHYLLOPODA. 241 egg masses are carried about by the parent, and are con- spicuous objects. It is a common occurrence to find the little animals apparently loaded with the burden of eggs, and not uncommon to see the young escape. The " common Cyclops" is an instance. No member of the Entomostraca is so frequently seen and so abundant as the Cyclops, and hardly any other affords so good an example of this method of depositing and caring for the eggs in external ovaries, Cyclops having two of the latter, while some other almost equally common forms have but one. The external ovaries are usually long, pear-shaped bodies attached to the rear of the animal, near where it diminishes to form its tail -like portion. The eggs are round, unless they are made polygonal by pressure, almost black, and entirely opaque. In Cantho- camptus there is but one external ovary. Both kinds are shown in Figs. 166 and 167. The young, when first hatched, bear so slight a re- semblance to the parent that some of them have been described and named as entirely different animals ; and it was not until they were seen leaving the egg while still attached, or in the external ovary, that their true character was discovered. This is especially true of Cyclops. The young animal is shown in Figure 1670. It changes its skin several times before it begins to re- semble its mother, a similar peculiarity being noticeable in many of the Entomostraca. These little crustaceans are found in almost every body of still water. Some prefer the surface, where, on 242 MICROSCOPY FOR BEGINNERS. a sunshiny day, they are occasionally seen in immense numbers, sinking when a cloud shades them, and rising again to the sunlight. Others are to be taken only in deep water, while still others can be obtained only at night. Very many, however, are collected in every gathering of aquatic plants. They abound at all sea- sons of the year, even in midwinter. Their movements are rapid and characteristic. An Entomostracan can be readily recognized as such by the unaided sight, on ac- count of the peculiar leaping, or short, jerking motions with which it travels through the water. They are not only interesting little creatures to the microscopist, but they are extremely useful as well. They play a very important part in the food supply of fishes, forming the chief article of diet of some of our best fresh- water fishes. And they are almost as impor- tant as scavengers. Their favorite food is dead and decaying Algae and animal niatter, which, if allowed to remain in the great abundance in which it exists, our ponds ancl slow streams would before long become pu- trid and unbearable. But these numerous little creat- ures, by eating this refuse matter, transform it into an innocent and innocuous material, and confer a benefit both on themselves and us. Mr. C. L. Herrick, writing on this subject, says, " Their importance depends large- ly on their minute size and unparalleled numbers. The majority of non-carnivorous crustaceans are so consti- tuted that their diet is nearly confined to such floating particles of matter as are present in the water in a state ENTOMOSTBACA AND PHYLLOPODA. 243 of more or less fine comminution ; for, nearly without prehensile organs, these animals, by means of a valvular or, at most, ladle-like labrum, dip from the current of water kept flowing by the constant motion of the bran- chial feet, such fragments as the snail and scavenger- fish have disdained : bits of decaying Algae, or the broken fragments of a disintegrated mosquito, all alike acceptable and unhesitatingly assimilated. The amount of such material that they will dispose of in a short period of time is truly astonishing." When the shallow ponds are dried by the summer heat, the Entomostracans bury themselves in the mud, and there remain quiescent, but alive, so long as any moisture is present. When the mud is completely dried they die, but the eggs have the ability to endure heat and dryness without injury, and to develop and mature as the pools again become filled by the rain, or by the melting snow of early spring. The Phyllopoda may also often be recognized without a microscopical examination, by their large size and al- most universal habit of swimming on the back. Bran- ckipus, sometimes called the fairy shrimp, and Artemia, or the brine shrimp, are nearly an inch in length. As in the Entomostraca, their bodies may be incased in a bivalve shell or not. The broad, flattened feet are numerous, but the branchial or breathing-plates already referred to may be small and inconspicuous, and there- fore difficult to be observed by the beginner. They are especially well-marked in Artemia (Fig. 169), and in 244 MICROSCOPY FOR BEGINNERS. Brancliipus (Fig. 170). Eyes are usually present, and large. In some forms they are elevated on stalks, thus reminding the observer of the stalked eyes of lobsters. The eggs of the bivalve Phyllopoda are kept within a brood cavity, somewhat as in similarly incased Ento- mostraca, while in the shell-less forms they are carried about in a bottle-shaped sack at the end of the body, near the origin of the long, narrow, tail-like portion. In both kinds the young bear scarcely the remotest resem- blance to the adults. In the fresh and brackish waters of the eastern part of the country there are but few genera of the Phyl- lopoda represented, and none have yet been found in the ocean ; while on the western plains and among the Kocky Mountains they abound. These latter forms are, however, not included in those referred to in the fol- lowing list. All these little crustaceans should be examined in a deep cell, to prevent the weight of the cover-glass from crushing their bodies. The shells and the shelly coat- ing give them the appearance of hardness, but they are delicate and easily injured. The large Phyllopoda will need an especially deep and extensive cell. The following Key will lead to the common genera of both divisions of these attractive animals. The only trouble the beginner may meet with in using at will probably be in determining whether the specimen is a Phyllopod or an Entomostracan ; but as the former are large, and swim on the back, they may usually be deter- ESTOMOSTRACA AND PHYLLOPODA. 245 mined by these appearances, and the name learned by the Key, in connection with a pocket-lens. The two Entomostracans, Diaptomus, and Canthocamptus, are separated in the Key by the number of the joints in their long antennae. This seems to be a very minute character to use in so artificial a table, but it need not be an annoyance to the beginner, since the antennae of these two common little crustaceans differ so conspicu- ously in size and length that the joints need not be actually counted ; a glance will show which is Cantho- camptus, with its short and rather inconspicuous an- tennae. The beak referred to is the front part of the shell extended in a long, usually curved and pointed prolon- gation, containing the eye and portions of the animal's head. Key to Genera of Entomdstraca and Phyllopoda, 1. Legs with flat plates near the body ; animal swim- ming on the back (A). 2. Legs without flat plates (a). a. Body enclosed in a bivalve shell (b). a. Body not enclosed in a shell (g). I. Shell with a sharp posterior spine or a tooth on or near the upper posterior angle (c). b. Shell without a posterior spine, or with one to four small teeth on the lower posterior angle (d). c. Smooth ; spine on the upper angle, or near the middle of the border. Ddphnia, 1. 246 MICROSCOPY FOR BEGINNERS. c. Smooth, brown ; spine on the lower angle. Sca- pholeberis, 2. c. Reticulated; spine on the lower angle; antennae large, cylindrical. Bosmina, 3. c. Reticulated ; spine or tooth on the upper angle ; an- tennae long, witli two branches. Ceriodaphnia, 4. d. Beaked in front (e). d. Not beaked, oval, both ends rounded ; smooth or hairy. Cypris, 5. e. Posterior border with one to four small teeth. Camptocercus, 6. e. Posterior border without teeth (f). f. Shell nearly spherical ; posterior border truncate. Chydorus, 7. f. Shell not spherical ; posterior border convex ; an- tennas small. Alonopsis, 8. f. Shell not spherical; posterior border truncate; antennae large, long, and branched. Sida, 9. g. Body long and narrow ; antennae long, twenty-five jointed. Didptomus, 10. g. Body long and narrow ; antennae short, four to ten jointed. Canthocamptus, 11. g. Body racket (battledoor) shaped, with two external ovaries. Cyclops, 12. h. Body enclosed in a bivalve shell (£). A. Body not enclosed in a shell (/). i. Shell nearly spherical, smooth. Limnetis, 13. *'. Shell oval or oblong, flattened, amber-colored, with longitudinal lines. Estheria, 14. ENTOMOSTRACA AND PHYLLOPODA. 247 j. In brine pools and salt lakes ; eyes black, on stalks. Artemia, 15. j. In fresh water ; males with large frontal append- ages ; females without frontal appendages, but with an external, posterior, broad, short, and bot- tle-shaped egg-sack (&). k. Frontal appendages much twisted and coiled ; body slender. Chirocephalus, 16. k. Frontal appendages not twisted nor coiled ; body stout, granchipus, 17. ENTOMOSTRACA. 1. DAPHNIA (Fig. 159). There are several species of Ddphnia, all of which may be known by the presence on the posterior border of a sharp spine, which is never on the lower angle. It varies in length in the different species, sometimes being nearly as long as the shell, and extending oblique- ly upward. It also varies in length and in position on the same indi- vidual, being longest in the young, and becoming quite short with age. In the species figured (Ddph- nia pulex) it is usually on the upper angle, but not rarely as shown in the cut. In very old specimens it may be entirely absent, but it is 248 MICROSCOPY FOR BEGINNERS. always present at some time of the animal's life. The shell is oval and slightly flattened. The antennae are prominent, and are usually divided into two parts at the free end, each division bearing several feathery bristles. The feet are flattened, and generally in rapid motion, so as to bring food to the mouth, and oxygen to the blood. The heart is noticeable as a small color- less organ under the shell of the back near the head. It pulsates rapidly. The eye is large and conspicuous. The eggs are placed in a brood cavity, as shown in the figure, and there hatched, the young being very different in appearance from the parent. Daphnia is common in the spring. 2. SCAPHOLEBEUIS. The shell is somewhat beaked and usually dark brown. The surface may be indistinctly reticulated or entirely smooth. From jBosmina, for which the beginner may be inclined to mistake it, the absence of the curved, cylindrical antennae common to that species will distin- guish it. The posterior spines are short. The eye is large and conspicuous. The egg is carried in the brood cavity. It is said that but one egg is present at a time. This Entomostracan is common. 3. BOSMIKA (Fig. 160). The student will not have any trouble to recognize £6smina, on account of the long, large, cylindrical an- tennae, each one curving downward from the side of ENTOHOSTRACA AND PHYLLOPODA. 249 the head like the trunk of a microscopic elephant. The shell is oval, colorless, and the posterior border has a spine at its lower angle, never at any other point. The net-work of lines on the surface may extend over the entire shell or be restricted to some one part. The eye is large. The eggs are hatched in a brood cavity on the back beneath the shell. The heart is visible near the centre of the back. Bosmina is not so common as Daphnia. 4. CEKIODAPHNIA. The shell is oval, oblong, or somewhat four-sided, and always beautifully, if coarsely and conspicuously, reticu- lated, the meshes being hexagonal and comparatively large. The head is separated from the body by a de- pression in the shell, and just behind the rather small eye -like spot it has a slight elevation. The eye is usually near the rounded lower margin or tip of the beak-like head. The antennae resemble those of Daph- nia, being long, and divided into two three - jointed branches of equal length. The angle or tooth on the upper corner of the posterior border is usually sharp and conspicuous. This Entomostracan is abundant in the writer's lo- cality. It is visible to the naked eye, being about one twenty -fifth of an inch long. In the aquarium its movements are almost distinctive. It seems to prefer the centre of the vessel, where it darts upward for a 250 MICROSCOPY FOR BEGINNERS. short distance with a jerk, only to allow itself to float back to the starting-point. A glass jar well stocked with these pretty creatures leaping up and down ir- regularly and incessantly is an interesting sight. Un- der the one-inch objective the little animal is more than interesting. 5. CYPRIS (Fig. 161). The shell entirely surrounds the animal, so that the little creature, when danger threatens, shuts itself in as completely as a clam or a mussel, and allows itself to fall to the bottom. The form varies from an oval to a kid- ney shape, according to the species, and the color may be green or brown, or whitish and marked with several dusky bands. It may be smooth, or entirely covered °r . IClCypris ders may be fringed. The shell is never opened wide, but the legs and feathery antennae project from a narrow cleft between the valves, the lit- tle animal swimming rapidly by their aid, or creeping about the slide or over the aquatic vegetation. Cypris is reproduced by eggs, but " the mass of eggs, including about twenty-four, is attached by the female to water- plants with the aid of a glutinous secretion, an opera- tion which lasts about twelve hours." 6. CAMPTOCERCTJS (Fig. 162). The shell is elongated, somewhat quadrangular, trans- parent, and marked by lines traversing the surface ENTOMOSTRACA AND PHYLLOPODA. 251 lengthwise. The beak is blunt, and usually curved downward, or it may extend slightly away from the body. The head is strongly arched. The teeth on the posterior border (not shown in the figure) are small, and vary from one to four. The eye is small. The eggs are carried in a brood cavity. The animal occurs chiefly in lakes and large ponds. 7. CHYDORUS (Fig. 163). The surface of this nearly spherical shell is usually reticulated. The beak is long, curved, and pointed, being sharp in the female. The posterior border is truncate in young specimens, becoming more rounded in the old. The eye is present and single. The eggs are hatched in the brood cavity. The animal occurs Fig. 163.-Chydoms. abundantly yerj ear]y in the gprmg) usu. ally near the bottom, living chiefly on vegetable mat-, ters. The motion is rolling and somewhat unsteady, and uncertain in appearance. 8. ALONOPSIS (Fig. 164). The lower or free edge of the shell is fringed with bristles, which are longest in front. The beak is long, pointed, and separat- ed by some distance from the body of the shell. Eye large. One of the feet (the third) has a long spine fringed with "pig. icL-Aionopsis. 12 252 MICROSCOPY FOR BEGINNERS. short hairs on the edges, and often reaching to the pos- terior margin of the shell. The surface is usually marked by a few conspicuous diagonal lines. The ani- mal's movements are slow. 9. SIDA. The shell is long and narrow, with the head separated from the body by a depression. The posterior margin is nearly straight, and has no spine or tooth. The antennae are large, and somewhat resemble those of Daphnia, although in Sida they are rather stouter, and are divided into two unequal branches. There is but one species — Sida crystallma. It is quite common in some localities. 10. DIAPTOMUS (Fig. 165). Diaptomus may be recognized by the very long an- tennse, which are often as long as the body. The latter, including the head, is formed of six joints, and the pos- terior narrower part or abdomen of five, although in the female two of the latter may be united, thus giving it a three-jointed appearance. The animal is among the largest of the Entomostraca, Fig. 1C5 — Di&ptomus. often measuring one-tenth of an inch in length. The color is often brilliant, varying in the different species, and even in the different parts of the -body of the same individual. It may be deep ENTOMOSTRACA AND PHYLLOPODA. 253 red, brilliant purple, bluish with purple-tipped antennae, whitish, or colorless. The animals may be found in shallow pools in the fall and early spring, and occasion- ally in slowly flowing streams. The external ovary is single. 11. CANTHOCAMPTUS (Fig. 166). After Cyclops and Daphnia this is the commonest fresh-water Entomostracan in the writer's vicinity. A gathering of aquatic plants can seldom be made in this neighborhood without obtaining many of the graceful little Canthocampti. They are visible to the unaided eye as small, flesh-colored, or pinkish lines darting through the water in short jerks, after the manner of most En- tomostraca. Like all minute animals, they will collect on the best lighted side of the bottle, where they may be easily captured with the dipping-tube. The eye is single. The antennae are short and quite hairy. The body is long, narrow, and sub- cylindrical, being widest and thickest in front. There is no distinct heart. The external Fig.166._Canthoc,mptus. ovary is single. It is attached to the parent by the thinnest and apparently most deli- cate part, although considerable force is necessary to separate it from the body. The eggs are round and opaque. The young differ greatly from their mature aspect. Canthocamptus is found in almost any shallow body of still water, and all the year through, even occa- sionally in midwinter. It is shown in side view in the 254: MICROSCOPY FOR BEGINNERS. figure, so as to exhibit the single external ovary so characteristic of it. 12. CYCLOPS (Figs. 167, 167a). This commonest of all fresh-water Entomostraca has a single eye in the middle of the forehead, like the giants of ancient story, a bifid tail adapted for swim- ming, and two external ovaries, one on each side. These ovaries are long, pear-shaped sacks filled with dark, opaque eggs, and at- tached to the body by the narrow or stem end of the pear. The young (Fig. 16 70) pass through Fig. 1<>7.— Cyclops. , . . . several stages before they begin to resemble the parent. It lias been said that the eggs are carried in the external ovaries only until they are ready to hatch, when they are deposited before the young make their escape. This is a mistake, as the student will probably soon observe. The young leave the eggs while they are still attached to the parent. They break the egg membrane very suddenly and unex- .j, i , , , •. Young Cyclops. pectedly, although the observer may have been for some time watching the little creatures rest- lessly moving about inside. As they escape they often dart half-way across the field of a low-power objective. • If Cyclops had no enemies the waters would soon become filled with them in numbers almost beyond im- ENTOMOSTRACA AND PHYLLOPODA. 255 agining. One female Cyclops has been seen to lay ten times in succession ; but, to be within bounds, the ob- server who made the calculation supposes a single one to lay eight times only, and forty eggs at each time. " At the end of one year this female would have been the progenitor of 4, 442,189,120 young- — :that is, near four and a half thousands of millions." There are about thirty species of Cyclops, and in all of them there are four antennas, two being long and conspicuous, the other two small, and often carried so that they are invisible unless the Cyclops is turned on its back. PHYLLOPODA. 13. LIMNETIS (Fig. 168). The oval or nearly spherical, smooth shell has a well- marked beak, which in some of the species is enor- mous, while in others it is less conspicuous. "When the valves are closed they measure about one-sixth of an inch in length, and have often been mistaken for small fresh-water mollusks of the genus Pi- Fig. 16S.-Limn6tis. sidium. The eyes are two, but so close together that they often appear to be united ; they are black. The animals swim on the back, as do so many of the Phyllopoda. In the males the two front legs are flattened, and have on the end of each a compli- cated organ called the hand, although it bears the most remote resemblance to the human hand. The eggs are 256 MICROSCOPY FOR BEGINNERS. carried on the back under the shell. The animals are flesh color. 14. ESTHEIUA. The shell is smooth and shining, and marked with dis- tinct lines running almost parallel with the front, or free edge, of the valves. It is very thin, flat, and large, measuring about two-thirds of an inch in length. The males have two pairs of hands, or one on each of the four front legs. The shell of the several species varies from oval to oblong with the upper margin very much flattened, or it may be somewhat globose. Most of the species are confined to the waters west of the Missis- sippi River, one, however (Estheria Mexicdna\ being found near Cincinnati. Many of them are in appear- ance not unlike a small clam, or the little fresh-water mollusk, Pisidium, so common almost everywhere. 15 ARTEMIA (Fig. 169). Artemia occurs only in brine or the water of salt lakes. It is not rarely found in the hogs- heads of water on railroad bridges or tres- tles, where the water is made salt to pre- vent freezing. The bodies are slender and pale red, flesh -color, or sometimes greenish. The feet are eleven pairs, beau- tifully fringed with many long hairs, and P5 169— Artomia Bearing the flattened branchial or breath- (a female). ing-plates. When the creature swims on its back, as it habitually does, these feathery feet beat ENTOMOSTRACA AND PHYLLOPODA. 257 the water in rapid succession, as if a wave of motion were rapidly passing above them. It is a beautiful creat- ure, and one sure to attract attention, not only by its graceful motions and preference for salt water, but by its size, being half an inch or more in length. The eyes are black, and placed on the ends of stalks projecting from each side of the rather small head. The antennae are short, but conspicuous. The eggs are yellowish- white. The young are very active, and differ much in appearance from the parent. They are blood red, with one bluish eye. 16. CHIROCKPHALUS. This curious creature has eleven pairs of swimming feet, as has Branch'ipus, but there need be no difficulty in distinguishing it from Branchipus (for which it may be mistaken) provided the male is obtained. If the fe- male alone is captured some trouble may be experienced by the beginner in determining one from the other. The female of Chirocephalus, however, is slender, while that of Branchipus is stout ; but such a distinction is valueless until both have been seen, or the two sexes have been taken from the same pond. In the latter case the male may be known by the two remarkable ap- pendages hanging down from the sides of the head. These are about one-fourth of an inch long when ex- tended, and are curved and coiled and twisted in a way that defies description. Each one is broad near the up- per or attached ends, and diminishes to a long, curved point covered with minute spines, while in its entire 258 . MICROSCOPY FOR BEGINNERS. length it is curiously lobed. The egg-sack of the fe- male is short and small, and the attached end is length- ened, somewhat like the neck of a bottle. The eggs are very large, and about twelve in number. The body of each sex is about two-thirds of an inch long. Chiro- cephalus is often found in company with Branchipus, usually in the spring, as early as the middle of March. 17. BRANCHIPUS (Fig. 170). The flesh-colored or pale red body is stout and large, often measuring an inch in length. The head is large, and the frontal appendages of the male are long and broad, as shown enlarged In Fig. 170. These hang down on each ' side of the head, and are formed of two quite dissimilar parts. The upper half is broad and thick, and Fig. m-Branchipus about one- fifth of an inch (a male). long. It ends in a stiff, bristle-like prolongation of nearly equal length, with a short, bristle-like tooth at the inner side at the point of junction of the two parts. There are eleven pairs of swimming feet, and the animal swims on the back. The eyes are two, black, and elevated on the ends of short stalks. The body of the female is as large and as stout as that of the male. The egg-sack is noticeable near the point of union between the posterior narrow portion of the body and the broader front. It is a curious fact that Branchipus is killed by even ENTOMOSTRACA AND PHYLLOPODA. 259 the heat of early summer or late spring. Dr. Packard, describing a visit to a pond where these creatures had been found on May 2d, but from which they had all disappeared by May 13th, says, " It seems from this quite evident that the animal probably dies off at the approach of warm weather, and does not reappear until after cool weather sets in late in the autumn, being rep- resented in the summer by the eggs alone; and thus the appearance and disappearance of this Phyllopod is apparently determined mainly by the temperature." A vessel full of water in which Branchipus is floating on its back is a strangely beautiful and interesting sight. The pale reddish or flesh-colored bodies rising and fall- ing in long curves, with their numerous broad feet waving together rhythmically, make a living picture long to be pleasantly remembered. Those readers who desire to pursue the subject, es- pecially in respect to the anatomy and development of these crustaceans, are referred to Mr. C. L. Herrick's " Crustacea of Minnesota," published in the twelfth an- nual report of the State Geologist, and to Prof. A. S. Packard's " Monograph of the Phyllopod Crustacea of North America," issued in the twelfth annual report of the United States Geological and Geographical Sur- vey of the Territories, Dr. F. V. Hayden in charge. 12* 260 MICROSCOPY FOR BEGINNERS. CHAPTER XL WATER-MITES AND THE WATER-BEAK. THE Water-mites (Fig. 171) are sometimes called wa- ter-spiders, probably because they bear some resemblance to small spiders, and have eight legs. Naturalists have seen the resemblance and have placed them in a family group near to the spiders. Water-spider, however, is not a good name for them, as we have some true spiders that are semi-aquatic in their habits and have therefore a better title to such a name. The water-mites are usually very active little animals, swimming freely and rapidly through the water, or forcing themselves among the leaflets of aquatic plants, probably in search of food. They may generally be obtained in some abundance by collecting water -weeds in the way previously recommended, namely, by sinking the bottle and floating the plants into it without removing them from .,./*, m, Fig. 171.— A Water-mite. their native element. They are all quite visible to the unaided eye, and may for the most part be studied with a comparatively low-power objective. Their bodies are plump and oval, or nearly spherical. WATER-MITES AND THE WATER-BEAR. 261 The skin of most of the forms is soft and easily broken, but in the members of a single genus, Arrenurus, the surface is firm and comparatively hard. They are all brightly, even brilliantly, colored. They may be of one uniform tint, with a few blackish or brownish spots on the posterior region, or the single individual may be variously tinged in different parts of the body. The colors are of almost every imaginable shade of crimson, azure blue, yellow, green, brown, gray, or purple. The eight long legs also share in the general brilliancy, and often present a coloration entirely different from that of the body. The eyes are usually on the upper surface near the front border. They are small, and may be either round or crescentic in shape, red, black, or carmine in color, and two or four in number. They are usually placed close together, and when four in number, are arranged in two distinct pairs. The upper part or the back of the little animals may be entirely smooth, densely clothed with short hairs, or with a few scattered, fine bristles. It may also present no markings when magnified, or, as in a single genus, Arrenurus, it may be beautifully ornamented with a net-work of narrow meshes in a hexagonal pattern. In all, or nearly all, of the mites the upper surface bears two or more black, dark brown, or reddish spots quite distinct from the general coloring of the body. These are caused by nearness to the surface of the intestine or other internal viscera, the dark contents of which show 262 . MICROSCOPY FOR BEGINNERS. their color through the skin. In some these dark spots become large, occupying much of the upper surface, and so arranged and shaped that they leave between them in the middle line of the body a Y-shaped space which may be white, yellow, or other color. These spots are called cosca or the ccecal markings, the word being the plural of ccecum, meaning a certain part of the intestinal canal. They are useful to the student in identifying the species. The lower or ventral surface is the most important part to the observer who desires to ascertain the name of his specimen, or to the student who wishes to make a more serious study of the animals, for on this surface are the parts most used by the naturalist in classifying the mites. The beginner must therefore seek to have the little creature arranged on its back before it is placed under the microscope, so that the ventral surface shall be presented to the objective. This is sometimes a difficult operation to accomplish without injuring the delicate body. The writer has used for the purpose a little home-made contrivance that answers well and can be made by any one. A hole about half an inch in di- ameter is drilled through a glass slip, and into one side is cemented with shellac a thin glass circular cover a little smaller than the hole, so that the thin cover may not be flush with the surface of the slip. It is not very difficult to grind a hole through a thin glass slip if the file or other grinding tool is kept wet with tur- pentine. The aperture may not be a perfect circle; it WATER-MITES AND THE WATER-BEAR. 263 will probably be very irregular — I know mine is — but it will answer every purpose. The mite is placed in this cell, and a thin cover applied to the opposite side, thus forming a glass box that can be turned over for the ex- amination of both surfaces of the animal, and is deep enough not to injure the soft body, yet shallow enough to restrain its movements. The mouth of the mite is usually a complicated affair, and is sometimes surrounded by a circular elevation or ring called a hood, and always having short, jointed palpi, or feelers. At some distance back of the mouth, in some forms quite near to the posterior border, but always in the median line, will be seen in the female mites a small dark spot or narrow line which is really an opening. In some this orifice, which may be called the ventral opening, is covered and concealed by a large plate, called the ventral plate ; or there may be two plates, curved, oval, or other shape, one on each side of the ventral opening. They are useful to the naturalist as one means by which the mites may be classified, and they should be carefully searched for by the beginner who desires to learn the name of his specimen. They are not present in the males. The reader will therefore perceive that to identify his captive the specimen must be a female. The two sexes, however, differ so con- spicuously in appearance that they are easily recognized. The female always has the posterior border of the body more or less evenly rounded, while the male frequently possesses a peculiar little tail -like process projecting 264 MICROSCOPY FOR BEGINNERS. from the middle of the rear margin. One form of this curious projection is shown in Fig. 176, a female by Fig. 171, the projection varying in shape and size in the different species. The males seem much less abun- dant than the females ; they are, at least, less frequently captured by the microscopical fisherman. On the ventral surface, behind or before, or on both sides of the ventral plates, will be observed one or more very small dark spots never bordered by a plate. These are the external openings of the tracheae or air-tubes, which extend through the body and supply it with oxy- gen. As the mites are not known to come to the sur- face for a supply of air, as so many aquatic animals do, the tracheae are supposed to be able to absorb it directly from the water. The tracheal openings are not an im- portant aid in ascertaining the name of the creature, but the beginner must not mistake them for the aperture bordered or covered by the ventral plates. In some mites they are not well marked, and may be overlooked, and there is still another dark spot usually present near the posterior part of the ventral surface which must not be confounded with the ventral opening since it is in the median line. This is the external opening of the intestine. It is never bordered by plates, and is always behind the ventral orifice, but it is not always con- spicuous. Equally important to the student are certain eleva- tions of the ventral surface which appear to cover the attached ends of the legs. These are called the coxa, WATER-MITES AND THE WATER-BEAR. 265 the plural of coxa, a Latin word meaning the thigh. They are variously shaped and arranged, one coxa seem- ing to cover the end of each leg, or appearing to be the thigh belonging to that leg. They are motionless, how- ever, and are really only elevations of the skin, beneath which the muscles of the legs may be seen in action. In some mites the coxae on each side of the body are arranged in groups of two each, the borders of the two which form the group being in contact either by their whole length, as in Figs. 175, 176, and 177, or only at some single point, as in the posterior group shown in Fig. 174. In Figs. 174, 175, 176, and 177 there are four groups, formed of two coxae each ; in Fig. 173 there are six groups, the anterior alone being formed of two, the two posterior groups on each side being of but one coxa each and separated. Their shape differs widely even in the species of one genus ; their arrangement, however, is constant and important. The eight legs are long and jointed, the last joint ending in one or two short claws. The hairs fringing their margins are long and numerous, and are used as aids in swimming. They add a good deal to the beauty of the animal. Mites are found in salt as well as in fresh water, but with the marine forms this little book has nothing to do. The fresh-water ones are propagated by means of eggs, which are often seen attached to the stems of aquatic plants or to the lower surface of floating leaves, where the writer has obtained them and had them to ,266 MICROSCOPY FOR BEGINNERS. hatch in captivity. They are small, brownish, jelly masses, which might easily be overlooked or passed by as snails' eggs, often to be found in the same localities. The newly-hatched young often bear but a slight re- semblance to the parents, those of some genera having but six legs, those of one species being said to have but three. Many of these immature forms are parasitic on aquatic insects, becoming free-swimming and independ- ent when they attain adult growth and age. Some of the mature mites are also parasitic in the gills of the fresh- water mussel (Unio}. On account of these pecu- liarities the study of their life history is a difficult one. The Entomostraca and Infusoria are said to form their favorite food. There may seem to be but little connection between the water-mites and the water-bear, and still less resem- blance, yet naturalists have classified them near together. The water -bear (Fig. 172) is a common and curious aquatic animal, so closely and so comically resembling a transparent eight-legged microscopic bear that the be- ginner will know it the first time he sees it ; further ref- erence to it is therefore reserved for another page (p. 267). Key to Genera of the Water-mites (Hydrachnidce). 1. Body colorless, cylindrical, elongated, and transpa- rent ; legs eight, short, with claws ; the animal walks slowly and is bear -like in appearance. Wa- ter-bear (Macrobi6tus\ 1. WATER-MITES AND THE WATER-BEAR. 267 2. Body brightly colored, oval, or spherical ; legs eight, long ; animal swimming actively (a). 3. Body brightly colored, oval, or spherical ; legs eight, long ; animal walking, never swimming (e). a. Ventral plate single, cordate, the apex pointing for- ward. Diplodontus., 2. a. Ventral plate single, cordate, the apex rounded, pointing backward (5). a. Yentral plate double (c). b. Posterior coxae on the same side not in contact. Hydrdchna, 3. c. Posterior coxae on the same side in contact by their whole length (d). c. Posterior coxae on the same side in contact only by their internal ends, their outer extremities di- verging. Eyldis, 4. d. Yentral plates oval, with an oval plate on each side ; mouth round, with a circular hood. Arrenu- rus, 5. d. Yentral plates narrow, curved, each with two or three translucent tubercles. Atax, 6. e. Eyes four, on a lanceolate plate; coxae in four groups. Limnochares, 7. 1. THE WATER-BEAR: Macrobibtus (Fig. 172). The body -is soft, colorless, and transparent. The legs are very short, and have on the end of each several sharp claws, the legs being arranged three on each side of the body and two at or near the posterior, extremity. The 268 MICROSCOPY FOR BEGINNERS. mouth is a small opening at the front of the part repre- senting the head. It is followed internally by two short, somewhat curved and diverging rods, said to be used to wound the prey. The so-called gizzard, at a short dis- tance from the mouth, is plainly visible through the transparent body. It has no motion. Two small eyes are usually present, one on each side of the head. The animal's movements are very slow and awk- ward, the creature appearing to work hard, with but little result so far as progress is concerned. Macrobiotus is produced by eggs, which water-bear are deposited in an interesting way. When (Mncrobi6tus). they are suinciently matured, the water-bear sheds its skin and leaves the eggs in the empty and cast- off case. It is no unusual occurrence to find the empty skin of Macrobiotus with the empty eggs inside, the young having escaped. The young resemble the par- ent, it is said, in all except size. This strange, bear-like creature is to be found quite often at the bottom of shallow ponds ; or, if an aquari- um is kept, it will be almost sure to make the bottom its home. It is entirely invisible to the naked eye, meas- uring rather less than one-sixtieth of an inch in length. On account of their slow movements, the water-bears are often called Tardigrades. The scientific name of the common American form is Macrobiotus Ameri- ctinus. WATER-MITES AND THE WATER-BEAR. 269 2. DlPLODONTUS. This mite may be recognized by the form of the ven- tral plate as given in the Key, and by the fact that the plate is roughened by minute granules. The eyes in one species are two in number, very small, and wide apart. They are placed on the edge of the front border. In another species they are four, and are placed so far forward on the front margin that they are best' seen when the animal is on its back, and thus examined from beneath. The coxae are in four separate groups. The body of the two-eyed species has the front part black, spotted with red, and the posterior half red, with a central longitudinal black band. The one with four eyes has the body bright red. 3. HYDRACHNA (Fig. 173). The anterior coxae on the same side form a single group, being in contact by their whole length; the mid- dle one is entirely disconnected from the others ; the most posterior is the largest, and is also entirely separate. In one species the body is spherical and black, with yellow dots, the legs being shorter Fig. ITS.— coxse of than the body, and black, with red ends. In another the body is red, with two pairs of dark red eyes, and long legs. The young are said to have but three legs. 4. EYLAIS (Fig. 174). The two anterior coxse are in contact by their entire length, and form one group on each side. The two 270 MICROSCOPY FOR BEGINNERS. posterior coxse are in contact only as described in the Key. They are all moderately narrow. The mouth is round, ciliated, and with a kind of hood which the be- ginner may have some trouble to recognize. The ventral plates are curved, almost cres- centic, and narrow, one being on each side of the ventral opening, and just behind them are two small tracheal apertures. The in- Fi mon plants. When searching for these crystals a small fragment of the plant should be crushed with a penknife, and exam- ined in water with a moderately high power, as most of the crystals are small. The cuticle should also be stripped off. This may be done in the onion bulb and Richweed (P'dea). 21. CRYSTALS. — If the student has a polariscope he will especially appreciate the beauty of crystals as ex- emplified in color ; if he has none he can study and ad- mire the beauty of their forms. Almost any soluble salt COMMON OBJECTS WORTH EXAMINING. 291 may be made to crystallize by preparing a strong solu- tion and allowing it to slowly evaporate, and the forma- tion of the crystals may be watched with the micro- scope. A small drop is placed on the slip and allowed to evaporate while on the stage. Sugar crystals can be prepared in this way. Common salt is very easily made to crystallize, and scarcely anything can be more beau- tiful than salt crystals viewed as opaque objects with a strong light reflected on and from them. The follow- ing are also noteworthy :* Tartaric Acid. — Make a strong solution and place a large drop on the slide. Evaporate with a gentle heat by holding the slide several inches above the top of the lamp chimney. Gallic Acid.— A. small drop of a strong solution in al- cohol should be allowed to evaporate very slowly. Pyrogallic Acid. — A strong cold solution in water forms long needle-shaped crystals, " but if a very minute shower of some insoluble foreign substance be allowed to fall upon the solution when on the slide the effect is grand — each minute speck forming a nucleus around which the needle-shaped crystals gather, forming, if ex- amined with a selenite slide, so resplendent an object that no words of mine can adequately describe it." * Chlorate of Potash. — Make a strong solution in hot water and allow a small drop to spread evenly over the cell and evaporate slowly. To form dendritic or tree- * American Monthly Microscopical Journal, August, 1883. 292 MICROSCOPY FOK BEGINNERS. like crystals of this salt, heat a drop over the lamp. As soon as the crystals begin to form at any point, tilt the slide so that the liquor may ran off, then continue the crystallization by gentle warmth. There are many other salts which produce beautiful crystals when treated in the above or a similar manner, but the student would doubtless prefer to experiment for himself, rather than to have a bare list set down be- fore him. And there are innumerable other common objects easily to be procured and worthy of study. It is not possible to enumerate a millionth part of them. Examine for yourself. Try and see what a good thing a microscope is. And the writer wishes the reader ev- ery success in the use of the delightful instrument. GLOSSARY. Acute : sharp or pointed. Alimentary : pertaining to food. Antenna (plural antenna) : a jointed, movable tentacle or feeler on the head of certain Crustacea and insects. Anterior : front, going before. Aquatic : living or growing in water. Assimilated: turned to its own substance by digestion. Beak : the lengthened end or front. Bi: in compound words, meaning two. Bifid: two-parted. Bosses : knobs, protuberances, usually rounded. Branchial : relating to gills or branchiae. Carapace : the firm shell of some Infusoria, Rotifers, etc. Carnivorous : flesh-eating. Caudal : pertaining to the tail. Cellular : formed of or possessing cells. Chlorophyl : the green coloring matter of plants. Cilium (plural cilia) : a short, fine, vibrating hair. Caecum (plural caeca) : a part of the intestinal tube. Colony : a cluster of several or many. Comminution: the act of pulverizing or grinding. Component : composing ; an elementary part. Concave : hollow like a bowl. Conical : cone-shaped. Conjunction : union, association. Constricted: suddenly narrowed or contracted. Contractile : capable of being shortened or drawn together. Cordate : heart-shaped. 294: GLOSSARY. Cornea : the transparent membrane forming the front of the eye. Corpuscles : particles of matter. Crenate : scalloped, or with rounded teeth. Crescent : shaped like the new moon. Crystalline : resembling crystal ; clear ; transparent. Cuticle : the thin membrane covering the surface of plants ; the outermost layer of the skin. Cyclosis : the movement of protoplasm within a closed cell. Cylindrical : like a cylinder or long, circular body. Dentate: toothed. . Denticulate : with small, pointed teeth. Diagonal : extending obliquely. Diffused : spread out, extended. Disintegrated : reduced to minute parts. Distal : the furthest part. Diverging : spreading from a central point. Dorsal : pertaining to the back. Dorsum : the back. Ejected: thrown out. Elliptical: oval. Emarginate : notched. Epithelium : the membrane lining various internal cavities and free surfaces of animals. Expansile : capable of being expanded or widened. Extensile : capable of being lengthened or extended. Facet : a little surface or face. Fascicle : a cluster. Filament : a thread, or resembling a thread. Fission : division or cleaving. Flagellum (plural flagella) : a little lash. Flexible : capable of being bent. Frond : a leaf of fern ; the entire plant of Lemna. Frontal : pertaining to the front. Frustule : the entire diatom, consisting of two valves and the hoop. Furcate: forked. GLOSSARY. 295 Gelatinous : like jelly or gelatine. Globule : a small round particle. Granular : formed of or resembling small grains. Granules: small grains. Hemisplierical : half a sphere. Hexagon : a figure with six sides and angles. Hispid: rough, with short, stiff hairs. Homogeneous : of the same kind throughout. Hyaline : glass-like, transparent. Illoricate : without a lorica. Imbricated : overlapping like shingles on a roof. Invested : clothed, covered. Labrum : a part of the mouth of Crustacea and insects. Lanceolate : lance-shaped. Larva (plural larvae) : an insect in its first stage after leaving the egg. Laterally : by the sides. Lophopliore : the disk supporting the tentacles in the Polyzoa. Lorica, (plural loricoe) : the sheath or dwelling of certain microscopic animals. Loricate : with a lorica. Mastax : the internal jaws of the Rotifers. Median: middle. Membranous : formed of a thin skin. Moniliform : like a string of beads. Monograph : a treatise on a single subject. Nodule : a small, rounded elevation. Oblong : longer than broad. Obtuse: blunt. (Esophagus: the tubular passage extending from the pharynx or throat to the stomach. Opaque : not transparent. Ovoid : egg-shaped or oval. 296 GLOSSARY. Papilla (plural papittce) : a small rounded protuberance. Parasite : a hanger on ; as one animal or plant living at the expense of another. Parietal: pertaining to the wall or side. Pellet: a little ball or mass. Pellucid : translucent or transparent. Pendent: hanging. Perianth : the leaves of a flower that cannot be distinguished into a calyx and corolla. Pigment : coloring matter. Podal : pertaining to, or used as, feet. Polyp : a radiate animal, without locomotive organs, with retractile tentacles around the mouth, and a hollow body in which are sus- pended the digestive and other organs. Posterior : the rear end. Prehensile : adapted for grasping or seizing. Process : a part prolonged or projecting beyond other parts connect- ed with it. Protoplasm : the semi-fluid, jelly-like contents of cells. Protrusible : capable of being thrust forward. Pulsating : throbbing, beating. Recurved : directed backward. Refracting : bending from a direct course. Reticulated : with the form of a net. Retort : a chemical glass vessel. Retractile : capable of being drawn back or into the body. Rudimental : imperfectly developed or formed ; immature. Segment : one of the rings or component parts of a worm or other body. Semi: in compound words, meaning half. Serrate : toothed like a saw. Shaft : the stem or straight part between the ends. Silicious : resembling or formed of silica. Spherical : round like a ball. Spinous : bearing spines. Spiral : winding like a screw. Spore: the minute seed of flowerless plants. GLOSSARY. Statoblast : the winter egg of the Polyzoa. Striated : finely streaked. Sub : in compound words, meaning under, or less than. Submerged : under water. Saltation : a groove. Tortuous: winding, twisting. Translucent: semitransparent. Truncate : as if cut off square. Tubercle : a small, knob-like elevation. Tubular : resembling or formed of a tube. Utricle : a little sack or bladder. Ventral: pertaining to the lower surface; opposed to dorsal. Ventrum: the concave side of Closterium (as here used). Viscera : the intestines, or abdominal contents. Visor : the fore-piece of a cap. Whorl : several leaves in a circle around the stem. Zoophyte : a word applied to certain plant-like animals. INDEX. Acanthocystis, 1 1 5, 1 19. — chcetopkora, 119. Adinopkrys, 116, 120. — so/, 120. Actinonphrerium, 116, 121. — Eichhornii, 121. Actlnurus. 207, 208, 211. Adapter, 12. Adjustment, the coarse, 18. — the fine, 20. jftolosoma, 164, 188, 194. Agassiz Association, the, xi. — Prof. Louis, 205. Air-bubbles, 40. • AlgEe, fresh-water, 63, 64, 69, 72, 73, 99, 102. Algae, fresh-water, key to genera of, 103. Algae, fresh-water, to preserve, 88. Alonopsis, 246, 251. American Monthly Microscopical Journal, 161, 219, 291. Amceba, 111, 114-118. — proteins, 117. — radiosa, 118. — villosa, 118. Ampetopsis quinquefolia, raphides in, 289. Amphileptus, 139, 151. Anabeena, 103, 105. Anacharis Canad&isis, 58, 162. —. cyclosis in, 59. Anguillula, 164, 166, 183. — aceti, 184. — glutinis, 184. Animalcule, 131. Animals, microscopic, to collect, 45, 47. H Anthrenus larva, hairs of, 283. — mitseorum, 283. — scrophidarice, 283. Apgar, Prof. A. C., oa Bunsen-bum- er, 36. Arcella, 112, 116, 126, 127. — dentata, 127. — milrata-, 127. — vulffarix, 127. Arm of microscope stand, 10. Arrenurus, 261, 267, 270. Artcmia, 243, 247, 256. Arthrodesmus, 75, 87. — convergens, 87. — incus, 87. Astasia, 139, 149. Asters, crystal prisms in, 290. Atax, 267, 271. Atwood, H. F., on Brachionm, 219. Aulopfionts, 183, 193. B. Bacillaria, 93-95. — paradoxa, 95. Bambusina, 74, 76. — Brebissonii, 76. Batrachospermum, 103, 104. — moniliforme, 104. Beetles, gizzard of, 282. Body of microscope stand, 10. Books to assist in mounting objects, 46. JSosmina, 246, 248. Bottles for collecting, 45. Bouncing Bet, 289. Brachionus, 208, 219. — conium, 219 Branchipw, 243, 247, 258. Breckenfeld, A. II., on preserving Hydra, 161. 300 INDEX. Brewster, Sir David, the inventor of the Coddington lens, 7. Bubbles, air, 40. BulbocluEte, 104/1 10. Bull's-eye condensing lens, 23. Bunsen-burner, Apgar's, 36. to make, 37. Butterfly, scales from, 278, 279. C. Camera lucida, 42. Camptocerais, 246, 250. Canada balsam, 25. Canthocamptus, 241, 245, 246, 253. Carchesium, 138, 140. Cardinal flower, 287. Carrot, seeds of, 287- Caterpillars, feet of, 279. Cells, cement, 30, 31. — device for centring, 31. — paper, 32. — plant, 59. Cement, Brown's rubber, 83. — shellac, 30. Centropyxis, 116, 126. — aculcata, 126. Ceratophyllum demersum, 48, 55. Ceriodaphnia, 246, 249. Chcetogaster, 164, 188, 190. Cluetonotus, 163, 165-167. — acaHt/iodes, 172, 177. — acanlhophoms, 172, 179. — caudal appendages and glands, 169. Cluctonotm, classification of, 170. — concinnits, 171, 173. — dorsal appendages, 168. — eggs of, 170. — enormis, 172,179. — food of, 168. — head, 168. — key to species of, 171. — larus, 171, 175. — longispinosus, 172, 176. — loricatus, 171, 173. — mazimus, 171, 175. — mouth of, 168. — octonarius, 172, 176. — oesophagus of, 1 69. — podura, 171,172. CJuetonotus rhomboidcs, 171, 172 — gpinifer, 172, 177. — spinosuhis, 172, 176. — sulcatus, 171, 173. — to collect, 168. Chcetophora, 104, 108, 167. — elegcms, 108. Chilodon, 140, 154, 215. — meffalotrochce, 215. C/iilomonas, 139, 149. Chirocephalus, 247, 257. Ckironomus, eggs of, 1 66. — larva, 163, 165, 166. Chlorophyl, 59, 62. Chydorm, 246, 251. Cilia of Infusoria, 135. — of Turbellaria, 180. Circles, thin glass, 29. Cirsiwn, crystal prisms in, 290. Clathrulina, 112, 116, 130. — deffftns, 130. Closterium, 72-74, 77-80. — acerosnm, 78. — acuminatum, 79. — Diana, 79. — Ehrenbergii, 79. — jnncidum, 78. — key to species, 78. — lineaium, 78. — Lumda, 79. — rostralum, 80. — sctaceum, 80. — Vemu,l9. Clover, crystal prisms in, 290. Coal, 275. Cocconeis, 93, 97. — pedicuhts, 97. Cocconema, 93, 96. — lanceolata, 96. Coddington lens, 7. Collecting-bottle, 45. Collomia, seeds of, 287. Condensing-lens, bull's-eye, 23. Conjugation of Spiroffyra, 106. Copper solution for preservin, raids and Algae, 88. Cosmariwn, 75, 84, 85. — Hrebissonii, 85. — mtuyarttiferwn, 85. — pyramidatum, 85. — SalfsU, 85. IXDEX. 301 Cotkurnia, 139, 146. Craig microscope, 5. Cricket, gizzard of, 281. Cristalella, 225, 229, 231. Crystals, plant, 289. — polariscope, 290. Cyclops, 241, 246,254. Cyclosis in Auacharis, 59. — in Closterium, 77. — in desmids, 68. — in Vallisneria, 60. Cynthia Virginica, crystal prisms in, 290. Cyphoderia, 116, 129. — ampulla, 129. Cypris, 246, 250. D. Dandelion, 287. Daphnia, 245, 247. Davies, Thomas, on preparation and mounting of microscopic objects, 46. Dendroccelum lacieum, 183. Dcndromonas, 188, 140. Dero, 164, 188, 192. Desmidinm, 74, 77. — Swartzii, 77. Desmids, 61, 64,72. — key to genera of, 66. — to preserve, 88. — vacuoles of, 68. Deutzia scabra, 285. Diaphragm of microscope stand, 22. Diaptonuts, 245, 246, 252. Diatoma, 93, 94. — mdgare, 94. Diatoms, 61, 64, 72, 89, 92. — as food for microscopic animals, 92. Diatoms, fossil, 91. — key to genera of, 93. — literature, 92. — movements, 66. — structure, 90. — surface markings, 67, 89. — to study, 92. Didymoprium, 74, 76. — ' GremUii, 76. Difflugia, 112, 116, 123. — acuminata, 125. Difflugia corona, 125. — globulosa, 125. — pyriformix, 125. Dinobri/on, 138,144. Dinocharis, 208, 218. Diplodontus, 267, 269, 273. Dipper, tin, a useful collecting tool, 48. Dipping-tube, 34. — to make, 36. — to use, 35. Docidium, 75, 84. — Baculum, 84. — crenulatum, 84. Draparnaldia, 104, 108. — glomerata, 108. Drawing the object, 41. — camera lucida for, 42. — reflector for, 42. Draw-tube, microscope, 11. Dry object?, to examine, 26. to mount, 33. Duckmeat (Lemna), 48, 57. Eggs of Chironomm, 167. — of Eidomostraca, 240. — of insects, 281. — of Rotifers, 205. — of snails, 167. — of mapping-turtle, 205. — of Tubifex, 198. — of Turbdlaria, 181. — of water-mites, 167. Elytra, 279. Ernertoii's " Life on the Sea-shore," x. — "Structure and Habits of Spi- ders," x. Enchytrans, 188, 189. — social^, 190. — vermindaris, 190. Encyonema, 93, 96. — paradoxa, 96. Entomostraca and Phyllopoda, 238. key to genera of, 245. — antennae, 239. — beak, 239. — effect of heat on, 243. — eggs of, 240. — eyes of, 240. 302 INDEX. Entomostraca, habitats of, 241. — heart, 240. — Herrick, C. L., on, 242. — literature, 259. — reproduction, 240. — usefulness of, 242. .Epidermis of leaves, 284. Epistylis, 138, 142. Epit hernia, 93, 97. — turgida, 97. Equuetum spores, 288. Eriyeron, sphaeraphides in, 289. Estkeria, 246, 256. Euastrum, 74, 83. — ansatum, 84. — crassum, 83. -- didelta, 84. Euglena, 139, 149. Euglyplia, 116,128. — alveolata, 129. — ciliata, 129. — cristata, 129. Eunolia, 94, 97. — tetraodon, 97. Euplotes, 140, 152. Evaporation from beneath cover- glass, 37. Excelsior microscope, 5. Eye-pieces, construction of, 11. — different powers of, 12. — eye-glass of, 11. — field-glass of, 11. — why so named, 10. Eyes of insects, 279. — of spiders, 280. Eylais, 267, 269. F. Feet of insects, 279. Field of view, 18. Fish, scales of, 282. — small, captured by Utricularia, 55. Flagella of infusoria, 135. Fleabane, 289. Floscularia, 200, 207, 210. Flower-de-luce, 290. Focus, objects out of, 20. — of compound objective, 19. — of pocket-lens, 4, 5, 8. Foot of microscope stand, 10. Fragelaria, 93, 95. — capucina, 95. Fredericella, 229, 232. G. Gallic acid crystals, 291. Geranium, seeds of, 287. — sphjeraphides in, 289. Gizzard of insects, 281. Gladiolus, crystal prisms in, 290. Glass, thin cover, 27, 28. — thickness of the three kinds of thin cover, 29. Glass, to clean thin cover, 29. Gnats, scales from, 278. Golden-club, 289. Gomphonema, 93, 96. — acuminata, 96. Gray's " How Plants Grow," x. Growing-slide, a simple, 38, 39. H. Hairs, animal, 282. — Anthrenus larva, 283. — plant, 286. — stellate, in stems of water-lilv, 50. Hairs, stellate, in stems of Nuphar, 51. Hawkweed, 290. Herrick, C. L., on Eniomostraca, 242, 259. Hervey's " Sea-mosses," x. Hibiscus, sphffiraphides in, 289. Hieratium, crystal prisms in, 290. Himantidium, 93, 96. — peciinalc, 96. Hitchcock's " Synopsis of the Rhizo- pods," x., 130. Hollyhock, 287. " How to See with the Microscope," by J. E. Smith, 46. "How to Use the Microscope," by J. Phinn, 46. " How to Work with the Microscope," by Dr. L. S. Bcale, 46. Ifyalotheca, 74, 76. — dissilims, 76. Hyatt, Prof. Alphens, on Polyzoa, 226, 237. Hydra, 60, 155. INDEX. 303 Hydra, apparent harsh treatment of, 159. Hydra, food of, 157. — fusca, 155, 158. — 'parasitic infusoria on, 160, Ifil. — reproduction of, 158. — stings of, 158. — tentacles, 156. — to permanently preserve, 161. — translation from Trembley on the, 159. Hydra viridis, 155, 158. Hydrachna, 267, 269. Hydrachnidce, 266. I. Ickthydium podura, 172. Impatiens fnlva, raphides in, 289. Infusoria, 61, 131. — colors of, 135. — free-swimming, means of move- ment, 135. Infusoria, illoricate, 134. — in infusion of hay, 134. — key to genera of, 138. — loricate, 133,134. — parasitic on Hi/dm, 160, 161. — parasitic on Megalotrocha, 215. — permanently adherent, 134. — preservation of, 137. — structure of, 133. — to collect, 131. — to kill, for examination, 137. — to study, 136. — water colored red or green by, 149. Insects, eggs of, 281. — eyes, 279. — feet, 279. — from the cellar, 274. — gizzard of, 281. — probosces, 280. — to examine, 281. Iodine mixture for killing infusoria, 137. Iris versicolor, crystal prisms in, 290. Iron, pcrchloride, for killing infu- soria, 137. J. Jordan's " Manual of the Verte- brates," x. Journal of the Academy of Natural Sciences of Philadelphia, 199, 236, 237. Katydid, gizzard of, 282. Kerona polyporum, 161. Key to desmids, diatoms, and fresh- water algae, 71. Key to genera of fresh-water algae, 103. Key to genera of desmids, 74. — to genera of diatoms, 93. — to genera of Eutomostraca and Phyllopoda, 245. Key to genera of Infusoria, 138. — to genera of Oligochaeta, 187. — to genera of Polyzoa, 228. — to genera of Rhizopods, 115. — to genera of Rotifers, 207. — to genera of Water-mites, 266. — to species of Chcetonotits, 171. — to species of Closterium, 78. — to species of Micraxlerias, 80. — to species of Stentor, 147. Keys, analytical, how to use, 70. — to Chironomnx, C/uetonotns, and classes of worms, 165. L. Ladnularia, 207, 208. JLeauminosce, crystal prisms in, 290. Leidy, Dr. J., 61, 193, 194, 199, 236, 237, 277. Leidy, Dr. J., on Rhizopods of North America, 130. Zemwa,48, 57,162. — flower of, 58. — minor, 57. — polyrrhiza, 57. — raphides in, 289. — rootlets of, useful to the micros- copist, 58. Lens, Coddington, 7. — pocket, combination, 4. employment for the, 3, 234. 304 INDEX. Lens, pocket, simple, 2. — — simple, with long focus de- sirable, 4, 5. Lens, pocket, simple, to focus, 8. — watchmaker's, 6. Lepisma saccharina. scales from, 269. Lichens, 274. Light, importance of modifying the, 22. Lily, the white water, 50. Limnetis, 246, 255. Limnms, 208, 214. — annul ata, 215. ZtmnocAara, 267, 270. Linden, 290. Lingual ribbons of mollusks, 283. Lobelia cardinalis, seeds of, 287. Lorica of infusoria, 133, 134. Loxodcs, 140, 154. Lumbriculus, 188, 191. M. Macrobiolm, 266, 267. — Americanm, 268. Magazines, American Microscopical, 46. Mallow, common, 289. Malva rotund/folia, sphseraphides in, 289. "Manual of Microscopic Mounting," Martin's, 46. " Manual of the Vertebrates," Jor- dan's, x. Maple, 290. Measuring the object, 43. Megalotrocha, 208, 215. Afc/teerto, 208, 212. Meridian, 93, 94. — circulare, 94. Mermaid weed, 52. Micrasterias, 74, 80. — areuata, 82. — dichotoma, 82. — key to species of, 80. — KUduttii, 83. — latictps, 83. — oscilans, 83. — radiosa, 81. — truncata, 82. Micrometer, stage, 43. — to ascertain magnifying power by use of, 44. Micrometer, to use, 44. Microscope, books relating to optical construction of, 46. Microscope, boy's vertical, 18. — compound, 2, 8. — Craig, 5. — Excelsior, 5. " Microscope, How to See with the," by J. E. Smith, 46. " Microscope, How to Use the," by J. Phinn, 46. " Microscope, How to Work with the," by Dr. L. S. Beale," 46. Microscope, parts of the, 1. — simple, 1. action of, 2. "Microscope, the, and its Revela- tions," by Dr. W. B. Carpenter, 46. Microscope, to adjust for use, 24. — use of, not injurious to eye- _sight, 23. Microscope, vertical, 18. Microscopical Society of London, The Royal, 12. Mimulus ringens. crvstal prisms in, 290. Mirror of microscope stand, 23, 24. Mollusks, lingual ribbon of, 283. Monkey flower, crystal prisms in, 290. Mosquito, scales from, 278. Moth, common clothes, scales from, 278. Mounting, microscopical, 25, 33. books relating to, 46. Myriophyllum, 48, 51. Nais, 164, 188, 198. Names of specimens, the desire to know, ix. Natural history, pleasure of study- ing, 277. Navicula, 94, 98. — cuspidata, 98. Needles, dissecting, 33. Nerium Oleander, stomata of, 285. sphseraphides in, 286. Note-book, importance of, 41. INDEX. 305 Note-book, extract from a boy's, 41. Nupliar, 51. Nymphcea odorata, 50. 0. Objectives, American, 13, 14. — care of, 15. — field of, 276. — French triplet, 13. — modern American, 14. — one-fifth preferred to one-fourth, 17. Objectives, students' series, 16. — to be selected by the beginner, 16. Objectives, to focus, 19. — why so named, 10. Objects, opaque, 276. — to mount microscopical, 25. — to prepare microscope for ex- amination of, 24. Objects, transparent, 276. . — worth examining, some common, 274. Ocnerodrilm, 187, 188, 195. Odontophore of mollusks, 283. (Enothera, raphides in, 289. Oleander, spha:raphides in, 286, 289. — stomata of, 285. Oliffochceta, 166, 184. — beneath decaying bark, 189. — blood of, 186. — bristles, 184, 185. — fluid in body cavity, 1SG. — food, 187. — key to genera of, 187. — mouth and alimentary canal, 186. — podul spines, 184, 185. — reproduction, 1 87. Onion, crystal prisms in, 290. Optical construction of microscope, books relating to the, 46. Orontium aquaticum, raphides in, 289. Oscillaria, 103, 105. Oxalis, sphan-aphides in, 289. Packard, Dr. A. S., on Branchipus, 259. Packard, Dr. A. S., on Phyllopod Crustacea, 259. Palludicella, 229, 232. Paramcecium, 139, 152. Passion-flower, 287. Paste eels, 184. Pedinatella, 224, 229. | — statoblasts, 230. ' Pediastrvm, 71, 101. I — ffrannlatnm, 101. i Penium, 75, 88. ! — Brebissonii, 88. P/iacus, 139, 150. I — longicaudus, 150. j — plcuronectes, 150. Philodiim, 208, 220. Phyllopoda, 243, 245. — branchial plates of, 243. — eggs, 244. — Entomostraca and, 238. — eyes, 244. — literature, 259. — to examine, 244. — western, 244. Pilea pumila. crystals in epidermis of, 290. Pinnularia, 94, 99. — major, 99. — viridis, 99. Pisidium, 253. Planaria torva, 183. Plants, common aquatic, to identify, 49. Plants, common aquatic, useful to the microscopist, 47. Plants, common aquatic, without English names, 48. Platycola, 139, 145. Pleuros/fftna, 94, 97. — angulatum, 98. Plumatella, 229, 231. Pocket-lens, combination, 4. — employment for, 3, 274. — simple, 2. Pollen, 286. Polyarthra, 208, 218. Polyzoa, blood of, 227. — external structure, 222. — food, 227. — fresh-water, 221. — habitats, 222. 306 INDEX. Poljzoa, habits, 222. — key to genera of, 228. — jelly-like loricse, 224. — literature, 228. — lophophore, 225. — mouth, 225, 226. — reproduction, 225. — retraction and expansion, 227. — stomach, 227. — tentacles, 226. — to examine, 228. — tubular loricae of, 226- Poppy, seeds of, 287. Porlulaca, seeds of, 287. — sphaeraphides, 289. Potash crystals, chlorate of, 291. Primrose,"289. Prisms, long crystal, 290. — short crystal, 290. Pristina, 164, 187, 188. Probosces of insects, 280. Proserpinaca, 52. Pseudopodia of Bhizopods, 111. — pin-like of Vampyrella, 118. Plerodina, 208, 217. Pyrogallic acid crystals, 291. R. Eabbit's foot (Tn folium arvense\ 290. Ranunculus aquatilis, 49. Raphides, 289. Reflector for drawing the object, 42, Rhizopods, 61,62, 111. — books relating to the, x., 130. — favorite haunts of, 114. — food of and its capture by, 113. — habitats, 114. — illoricate, 112. — key to genera of, 115. — loricate, 112. — permanently adherent, 1 30. — pseudopodia, 111. — structure, 111, 113. — to gather, 114. Riccia fluitcms, 62. Richwced, 290. Rotifers, 200. — eggs, 205. — eyes, 200. — foot, 202. Rotifers, habitats, 206. — key to genera of, 207. — literature, 207. — loricse, 201. — male, 206. — mastax, 204, 206. — moutli, 203. — nibbling, 204. — reproduction, 205. — tail of, 202. Rotifer vidgaris, 202, 208, 216. Rubber cement, Brown's, S3. S. S;ilt, crystals of, 291. Saponaria officinalis, sphaeraphides in, 289. Scales, fish, 282. — from insects' wings, 278. — to mount, 279. Scapholeberis, 246, 248. Scenedesmus, 71, 100. — guadricauda, 100. Science News and Boston Journal of Chemistry, 36. Screw, the Society, 12. Sea-mosses, Hervey on the, x. Seeds of wild plants, 27, 287. Shellac cement, 30. Sida, 246, 252. Slide, a simple life, 38, 39. Slips and slides, distinction between, 25. Slips, proper size of, 27. Snails, lingual ribbon of, 283. Spatterdock (Nuphar), 51. Sphaeraphides, 286, 289. Sphcerozosma, 74, 76. — pulchra, 76. Sphagnum, 60, 1 64. Spiders, eyes of, 280. — feet of, 279. Spiderwort (Tradescantid), 289. Spiroffyra,103, 106. — as food of Difflugia, 124. — as food of Vampyrella, 119. Spirotcema, 75, 87. — condensata, 87. Spores of Eqnisetum, 288. Spring-clips, 22. Squares, thin glass, 29. IXDEX. 307 Stage, microscope, 21. Stand, the microscope, 9. Statoblasts of Cristatella, 231. — of Fredericella, 232. — of Pectinalella, 230. — of Urnatella, 236. Staurastrum, 75, 76, 85. — fnrcigerum, 86. — gracile, 86. — macrocerum, 86. — punctulatum, 86. Stauroneis, 94, 99. — phcenocenteron, 99. Slentor, 139, 146. — Barretti, 148. — cceruleus, 148. — igneus, 148. — key to some species of, 147. — niffer, 148. — polymorphic, 148. Stephanoceros, 200, 207, 209. Stephana)*, 208,216. Strephuris, 188, 193. Stylonychia, 140, 153. Sugar crystals, 275, 291. Surirella, 94, 98. — splendida, 98. Sword-bearer, 219. T. Tardigrade, 268. Tartaric acid crystals, 291. Tetmemorus, 75,' 84. — Hrebissonii, 84. — granulahts, 84. 7'Ae Microscope (magazine), 46. Thistles, 290. Touch-me-not (Impaliens fulva), 289 Trachelocerca, 139,151. Tradescantia, raphides in, 289. Trembley on the Hydra, 159. Trichodina pedicidus, 1 60. TrifvUum, crystal prisms in, 290. Trinema, 116", 127. — enchelt/s, 127. Triplocerax, 75, 87. — vertidllatum, 87. Tube, glass-dipping, 34-36. Tublfex, 187, 188, 196. . 14* Turbellaria, 164, 166, 179. — American naturalists on 181 — cilia of, 180. — eves, 180. — food, 181. — mouth, 180. — propagation, 181. Turn-table, 31. U. Uiiio, 266. Urnalella, 229, 233. — reproduction of, 236. Utricles of Utricularia, quadrifid processes within the, 55. Utricles of Utricularia, structure of 54, Utricularia vulgaris, 53. its method of capturing ani- mal food, 54. Uvella, 139, 150. V. Vaginicola, 139, 144. Vallimeria, 60. — cyclosis in, 60. Vampyrella, 115, 118. — lateritia, 1 1 8. Vaucheria, 103,107. "inegar eel, 184. Virginia creeper (Ampclopsis), 289 Volvox, 72, 101. — qlobator, 101. '^orticella, 135, 138,142. Tater colored by Infusoria, 149. — lost by evaporation from be- neath the thin cover, to supply, 37. fater, to examine objects in, 27. rater»bear (Macrobiotics), 266, 267. fater-lily, white (A'l/mpfuea), 50. fater-mitcs, 260, 263. — cffica of, 262. — coxa of, 264. — eggs, 265. 308 IXDEX. Water-mites, eyes, 261. — food of, 266. — intestinal opening, 264. — legs of, 265. — literature, 273. — markings of, 261. — mouth of, 263. — parasitic, 266. — preserving and mounting, 273. — propagation, 265. — sexes, external differences of the, 263. Water-mites, tracheal openings, 264. — to examine, 262. — ventral plates, 263. X. 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