T "/ ' r//< f : /03. LIBRARY OF The Brodie Club Toronto By 5 r t*/Krr T A om j r* % Date N'/**, /Ml, n i Digitized by the Internet Archive in 2018 with funding from University of Toronto https://archive.org/details/microscopyforbegOOstok MICROSCOPY FOR BEGINNERS OR COMMON OBJECTS FROM THE PONDS AND DITCHES F. J. WATSON. By ALFRED C. STOKES, M.D. ILLUSTRATED “The 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 HARFER & BROTHERS, FRANKLIN SQUARE /#8y Copyright, 1887, by Harper & Brothers. All rights reserved. CONTENTS PAG It INTRODUCTION.. . ix CHAPTER I. Tiie Microscope and its Parts . 1 CHAPTER II. Common Aquatic Plants useful to tiie Microscopist .... 47 CHAPTER 111. Desmids, Diatoms, and Fresh water Alg^e . . 04 CHAPTER IY. RmzoroDS . Ill CHAPTER V. Infusoria . 131 CHAPTER VI. Hydras . 155 CHAPTER VII. Some Aquatic Worms, Cii^etonotus, and Ciiironomus Larva . 1G3 IV CONTENTS. CHAPTER VIII. pAon 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. PAGE 1. A Pocket-lcns . 3 2. A Compound Microscope. . .* 9 3. A Growing-slide . 39 4. Air-bubbles . 40 6. Reflector for Drawing the Magnified Object . 42 6. Leaf of Ranunculus aquati- lis . 49 7. Peduncle of Nymphma odo- rata ; transverse section . . 50 8. Whorl of Myriophyllum Leaves . 52 9. A Leaf of Utricularia . 53 10. Quadrifid Process from Inner Surface of Utricle of Utri¬ cularia . 55 11. Whorl of Leaves of Cerato- phyllum . 66 12. Leinna polyrrhiza . 57 13. Lemna Minor . 58 14. Anacharis Canadensis . 59 15. Portion of Leaf of Sphagnum 61 16. Riccia fluitans . 62 17. Didymoprium Grevillii . 76 18. Sphgerozosma pulchra . 76 19. Ilyalotheca dissiliens . 76 20. Bambusina Brebissonii .... 76 21. Desmidium Swartzii . 77 22. Closterium lineatum . 78 FIG. PAGE 23. Closterium juncidum . 78 24. Closterium accrosum . 79 25. Closterium Lunula . 79 26. Closterium Ehrenbergii .... 79 27. Closterium acuminatum ... . 79 28. Closterium Diante . 79 29. Closterium Venus . 79 30. Closterium rostratum . 80 4 31. Closterium setaceum . 80 32. Micrasterias radiosa . 81 33. Micrasterias rotata . 81 34. Micrasterias truncata . 81 35. Micrasterias arcuata . 82 36. Micrasterias dichotoma .... 82 37. Micrasterias Kitchelii . 82 38. Micrasterias oscitans . 82 39. Micrasterias laticeps . 82 40. Euastrum crassum . 83 41. Euastrum didelta . 83 42. Euastrum ansatum . 83 43. Tetmemorus granulatus .... 84 44. Tetmemorus Brebissonii ... 84 45. Docidium Baculum . 84 46. Docidium crenulatum . 84 47. Cosmarium Ralfsii . 85 48. Cosmarium pyramidatum .. . 85 49. Cosmarium margaritiferum . 85 50. Cosmarium Brebissonii .... 85 51. Staurastrum punctulatum . . 86 VI ILLUSTRATIONS. FIG. PAGE 52. Staurastrum furcigerum. . . 86 53. Staurastrum gracile . 86 54. Staurastrum macrocerum . 86 55. Xanthidium armatum .... 87 56. Xanthidium antilopmum . . 87 57. Arthrodesmus incus . 87 58. Arthrodesmus convergens . 87 59. Spirotaenia condensata. . . . 87 60. Triploceras vertieiilatum . . 87 61. Penium Brebissonii . 88 62. Meridion circulare . 94 63. Diatom a vulgare . 94 64. Bacillaria . 95 65 and 65a. Fragelaria capucina 95 66. Ilimantidium pcctinale. . . . 96 67. Encyonema paradoxa . 96 68 and 68a. Cocconema lanceo- lata . 96 69. Gomphonema acuminata . . 97 70. Epithemia turgida . 97 71. Cocconeis pediculus . 97 72. Eunotia tetraodon . 97 73. Pleurosigma . . 98 74. Surirella splendida . 98 75. Navicula cuspidata . 99 76. Pinnularia major . 99 77. Pinnularia viridis . 99 78. Stauroneis phcenocenteron. 99 79. Scenedesmus quadricauda. 101 80. Pediastrum granulatum . . . 101 81. Hydrodictyon utriculatum . 102 82. Batracliospermum monili- forme . 104 83. Anabaena . 105 84. Oscillaria . 105 85. Spirogyra . 10G 8G. Spirogyra in conjugation ; with spores . 106 FIG. PAGE 87. Zygnema insigne . 107 88. Yaucheria . 108 89. Chtetophora elegans . 109 90. Draparnaldia glornerata. . 110 91. Bulbochaete . 110 92. Amoeba proteus . 118 93. Vampyrella lateritia . 118 94. Acanthocystis chaetophora 120 95. Actinophrys sol . 121 96. Actinosphserium Eich- hornii . 122 97. Difflugia pyriformis . 124 98. Difflugia corona . 125 99. Centropyxis aculeata .... 126 100. Arcella vulgaris . 127 101. Arcella dentata . 127 102. Trinema enchelys . 127 103. Euglypha alveolata . 129 104. Cyphoderia ampulla . 129 105. Clathrulina elegans ..... 130 106. Dendromonas . 140 107. Carcliesium . 141 108. Epistylis . 142 109. Yorticella . 143 110. Dinobryon . 144 111. Vaginicola . 145 112. Platycola . 146 113. Cothurnia . . . . . 146 114. Stentor polymorphus .. . 147 115. Stentor Barretti . 148 116. Stentor igneus . 14S 117. Astasia . 149 118. Euglena . 149 119. Chilomonas . 150 120. riiacus pleuronectes . 150 121. riiacus longicaudus . 150 122. Uvella . 151 123. Traehelocerca . 151 ILLUSTRATIONS. FIG. PAGE 124. Amphileptus . 152 125. Paramaecium . 152 126. Euplotes . 153 12V. Stylonychia . 153 128. Chilodon . 154 129. Loxodes . 154 130. Hydras adherent to Lenina rootlets . 156 130a. Hydra sting . 158 1306. Tricliodina pediculus — Parasite of Hydra . 160 131. Chironomus larva . 16V 132. Chaetonotus larus . 168 133. Anguillula . 184 134. Snout of a Pristina . 189 135. Posterior extremity of a Pristina . 189 136. Posterior extremity of a Pristina . 189 13V. Posterior extremity of a Dero . 192 138. Posterior extremity of an Auloplioriys . 193 139. Podal spines and bristles of Strephuris . 194 140. Nais . 198 141. Podal Spine of Nais . 199 142. Steplianoceros . 209 143. Floscularia ornata . 210 144. Actinurus . 211 145. Melicerta ringens . 213 146. Limnias ceratophylli . , . . . 214 14V. Hegalotrocha . 215 148. Rotifer vulgaris- . 216 vii FIG. PAGE 149. Stephanops . 21V 150. Pterodina . 218 151. Dinocharis . 218 152. I’olyarthra . 218 153. Brachionus . 219 154. Philodina . 220 155. Pectinatella magnifica . . . 229 155a. Statoblast of Pectinatella 230 156. Plumatella . 231 15V. Paludicella . 233 158. Urnatella . 235 159. Daphnia . 24V 160. Bosmina . 249 161. Cypris . 250 162. Camptocercus . 251 163. Chydorus . 251 164. Alonopsis . 251 165. Diaptomus . 252 166. Cantlioeamptus . 253 16V. Cyclops . 254 16Va. Young Cyclops . 254 168. Limnetis . 255 169. Artemia (a female) . 256 1V0. Branchipus (a male) . 258 1 VI. A Water-mite . 260 1V2. The Water-bear (Hacro- biotus) . 268 1V3. Coxm of Ilydrachna . 269 1V4. Coxa) of Eylais . 2V0 1V5. Coxa) of Arrenurus (fe¬ male) . 2V0 1V6. Coxa) of Arrenurus (male) 2 V 1 1VV. Coxa) of Atax . 2V2 1V8. Eye-plate of Limnocliares. 2V3 INTRODUCTION. To the beginner in the use 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. surrounding him. Such books, if correct and helpful, are 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. “ 1 do beseech you, what is your name?” is the oft- asked question, not only by the beginner in the use of the microscope, but by the more advanced student in other depart¬ ments as well. Emerton’s “Life on the Sea-shore,” and his “Structure and Habits of Spiders;” Hervey’s charming “Sea- mosses,” Gray’s “ IIow Plants Grow,” Romyn Hitchcock’s “Synopsis of the Fresli-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 are 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 Low 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 x\ssociation,” 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 arc 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 stories 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- INTRODUCTION1. • « XII most instinctively, goes first to the water for his microscopic objects, probably because he 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. Xlll 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 no 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.” — Watcli-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 Con- 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 Beflector. — Micrometer. — Measuring the Object. — To as¬ certain the Magnifying Power. — Collecting -bottles. — Books and Magazines for Reference. Microscopes arc 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 lie walks on, and in the green scum that floats on every sum- n J Fi£. 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 tlie 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 tlie 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 liigli- 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 the whole number is used at once, the working distance is usually so short that the observer’s head or liat-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 he held almost in contact with the object. Rot long ago a rather expensive instrument called the “ Craig Microscope ” was extensively advertised, and sold as a remarkable thins;. 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. Ro 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 MICROSCOrY FOR BEGINNERS. 6 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,” which 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 T1IE 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. IIow 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 FOR 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 FARTS. 9 word, as commonly used, refers to the entire combination of brass, with or without the magnifying-glasses. But Fig. 2. — A Compound 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, 1* It) 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 magnifying - 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 magnif ying 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 observers 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 12 MICROSCOPY FOR BEGINNERS. one-inch, often also called “ B ” or “ C,” will be added. Opticians also make -J, 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 a 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 TARTS. 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. lie 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 he 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 : “ IIow 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. lie 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. lie 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 Angers, 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 wTould expose it to if an attempt should be made to wipe the glass. If line 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 jialm 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 y 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 TARTS. 17 tive for some time, and liis 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 -J-, y1^, and even -g^- 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 J 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 ^ 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 he 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 J, and such a glass need not be expensive to be good 18 MICROSCOPY FOR 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 liis stomach with gravel-stones or powder¬ ed glass ; bnt 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 alivays 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. 2* 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 w7ill 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 liigh-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-incli 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 J or F- 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 eve 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 line 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 lingers directly, as it can be if supported on this movable glass stage. These linger 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 wTould 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 oj>enings 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 u MICROSCOPY FOR BEGINNERS. 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 TARTS. 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 and, 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 sy>end 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 2G MICROSCOPE 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 TIIE MICROSCOPE AND ITS PARTS. 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 foo 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 b}r 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 TBr to inch or thinner ; No. 2, about T~ ; and No. 3, from to TV incli. 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 TIIE MICROSCOPE AND ITS PARTS. 31 be thinned bv the addition of more. It should be thick k / enough to flow freely from a small camel’s-liair 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 Bubber 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. No 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 TIIE 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. lie 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 trails-* ferred to the slip, and as readily washed off by a sudden outward flow from a full tube. 36 MICROSCOPY FOR BEGINNERS. Until recently I supposed tliis 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. Ilis 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 Bunsen 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,’5 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 inches 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-liair 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. 39 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. lie may also wish to watch its growth and development. A reservoir for a water sup¬ ply is necessary ; an “ individual 11 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 BEGINNERS. 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 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 Fit?. 4. — Air-bubbles. 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 Yolvox — small green globes rolling about in the water. Yolvox 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 dowrn on a sheet of paper spread on the table just under the camera, but of course with a space of several inches be- t* 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 one end to pass around the upper part of 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 Fig. 5. — Reflector for Drawing the Magni¬ fied Object. THE MICROSCOPE AND ITS PARTS. 43 will still be an inch long, but one-eiglitli of an incli 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 to x-gVir 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. 44 MICROSCOPY FOR BEGINNERS. The beginner will not need one, but be 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 yjy inch apart, and draw them on the paper. Do the same with every objective, drawing the y-jnnr 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 -yiy inch micrometer spaces, the object will measure yly, or -fo inch in length ; if five spaces of your scale, then it will measure y^-y, or IT77 inch long ; if only one-half a space of your scale, then it will measure one-half of y^-y of an inch ; if one- fourth of your scale space, then its actual length will be yjy inch. If the ^ or ^ objective is used in making your scale from the y-Jg-y inch micrometer spaces, then each division on the paper will represent -t Q- inch, and if the drawing of the object measures two of these spaces on your scale, the real length of the object will be yo20 0- inch, or yj-y 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 yjy inch spaces measures, when drawn on the paper, y1^ 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-Jy inch microm¬ eter sj^ace measures T4y inch, the power will be forty diameters ; each, therefore, corresponds to ten times. If the yoVir inch micrometer spaces measure, when drawn, y1^ inch, then each tenth corresponds to a power of one hundred times ; therefore, if the yoVo- 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. By Dr. J. E. Smith. Chicago. “How to Work with the Microscope.’5 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. 47 CHAPTER II. COMMON AQUATIC PLANTS USEFUL TO TIIE MICROSCOPIST. Ranunculus. — Nymphaea. — Myriophyllum. — Utricularia. — Ccrato- phyllum. — Lemna. — Anacbaris. — Yallisneria. — 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 Leni¬ 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 MICR0SC0P1ST. 49 ance of the following forms, lie 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. G). A part of the stem and a single leaf of this plant are shown about natural size in the figure (Fig. G). 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 YIII.), Vorticellas (Chapter V.), and Stentors (Chapter Y.) are fond of attaching themselves. The leaves are placed above each Fig. e.-Leaf of Ranunculus other on opposite sides of aquatllls’ the rather brittle stem, and usually quite wide apart. 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. NYMPILEA ODORATA (White Water-lily, Fig. 1). 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 has charms known only to the microscopist. Cut 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. Y). Three-point¬ ed, four and five pointed, they Fig. 7. Peduncle of Nymphaea sparkle there like diamonds, yet odorata ; transverse section. x ^ 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. MYRIOPIIYLLUM (Fig. S). 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 Myriophyllura 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 tine, 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 mieroscopist 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 and largest. There is another rather common aquatic plant called Proserpindca , or u mermaid-weed/' which so closely re¬ sembles Myriophyllum wdien in the water that it has AQUATIC PLANTS USEFUL TO THE MICROSCOPIST. 53 often been mistaken for it. To make sncb 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 witli finely divided leaves, Utrieularia is probably the most interesting in itself, 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 TJtri- culdria vulgaris , a common species, is shown somewhat enlarged in Fig. 9, with the peculiar hollow bladders, or “ utricles,” that distinguish it from , .... . Fig- 9 — A Leaf of Utricn- all other plants, and give it one of its Mria. 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 the 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 plant. The whole inner surface of the fid Process from Inner Surface of utricles is lined by innumerable colorless utricle of u tri- 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. CERATOPHY LLUM 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 9 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, blit 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. ii.— whori of Leaves^of done in Myriophyllum. The leaves ceratophyllum. 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 Myriophyllum ; 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 wdiatever may be attached. Work with the microscope is delicate work, and the smaller the oR AQUATIC PLANTS USEFUL TO THE MICROSCOPIST. 57 ject, 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 POLYRRHIZA (Fig. 12) AND LEMNA MINOR (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 polyrrhiza, 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. Fig. 13. — Lemna Minor. mature. 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 this list. They all multiply by the growth of young fronds from the edges of the old and 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 polyrrluza, 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. 50 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, J ' Fig. 14 _ Ana- 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, 4 GO 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 Anacliaris 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 liigh-power objective. The one-incli glass wfill not show it. The plant is a fruitful source of supply for our two common species of Hydra (Chapter VI.), 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 IV.) 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 b (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 plant retains moisture for so long, and why it is so easily wetted. The second kind of cells, b, are found between the Fig. 15 _ Portion of Leaf of Sphagnum. 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. RICCIA FLUITANS (Fig. 16). ISTear the writer’s home this little floating plant (pro¬ nounced richsia) 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 Ceratopliyllum, or it floats on still waters in little patches 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 MICROSCOPIST. 63 whose ends are notched. The plant is green, and may be an inch 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 Alga3 (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 white surface. 64 MICROSCOPY FOR BEGINNERS. CHAPTER III. DESMIDS, DIATOMS, AND FRESH-WATER ALGiE. The desmids 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 Algae. DESMIDS, DIATOMS, AND FRESII-WATER ALG M. 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 cpiitc 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, 6G 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 Myriopliyllum. 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 frecpiently 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 ALGvE. 67 mids. And while 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 ofi; 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 desmid 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. F resh- 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 klature’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 cliloropliyl, there seems to be a nar¬ row space filled with colorless protoplasm, and it is here DESMIDS, DIATOMS, AND FRESII-WATER ALCEE. 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-fourtli 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 Algre, 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 Algge 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 Algae. The beginner need have no trouble to recognize them as Algae 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. lie then reads the second “ «” line : “ Color green, the plant not a hollow sphere,” which is of course right, as his plant is not a sphere. The (b) at the end refers to another line below headed by b. 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 ALGH2. 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, Ilydrodictyon , and refer¬ ring the student to the Algae, 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. Sce¬ ne! esmus (Algce, III.). 5. Plants forming a green net visible to the naked eye. Ilydrodictyon (Algce, III.). 72 MICROSCOPY FOR BEGINNERS. a . Color green, the plant a floating hollow sphere. Volvox ( Algce , ///.). g. Color green, the plant not a hollow sphere (5). g. Color golden-brown (c). b. Cell-wall smooth, rough, warty, or spine-bearing, also soft and flexible ; always floating freely, never growing on steins permanently attached to other objects ; a vacuole with swarming granules often present in each end. (. Desmids , I.) 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. DESMIDS. 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 Closterium in this profu- DESMIDS, DIATOMS, AND FRESH- WATER ALGyE. 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 Closterimn , 6 being the number of the paragraph fur- 74 MICROSCOPY FOR BEGINNERS. tlier 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 (b). a. Not in a jelly-like sheath ( 21.— Desimdinm 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. I). 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 (f). a. Back slightly convex, the whole cell slightly curved (b). a. Back strongly convex, ventrum nearly straight (c). a. Back strongly convex, ventrum strongly concave, with a central enlargement (d). a. Back strongly convex, ventrum without a central enlargement (e). b. Ventrum nearly straight; vacuoles close to the rounded ends ; fifteen or twenty chlorophyl glob¬ ules in a central longitudinal row in each semi¬ cell. C. linedtum , Fig. 22. Fig. 22. — Closterium linedtum. b. V entrum nearly straight ; body tapering towards the rounded, sometimes curved, ends ; vacuoles small, often scarcely visible. C.juncidum , Fig. 23. Fig. 23.— Closterium juncidnm. b. Ventrum and back equally curved; ends tapering; ten to fourteen chlorophyl globules in a central, longitudinal row in each semi-cell ; vacuoles very small. C. acerb sum, Fig. 2d. c. Ends rounded ; chlorophyl often arranged in nar- DESMIDS, DIATOMS, AND FRESH-WATER ALGJ3. 79 Fig. 24.— Closterium acerosum. row, longitudinal bands ; cliloropliyl globules nu¬ merous; vacuoles near the ends; cell very large. C. Lunula , Fig. 25. Fig. 25.— Closteriam Luunla. d. Ends rounded ; cliloropliyl often arranged in nar¬ row, longitudinal bands ; cliloropliyl globules of¬ ten numerous ; vacuoles close to the ends. C. Ehrenbergii , Fig. 2G. Fig. 2G. — Closteriam Ehrenbergii. Fig. 27. — Closterium acuminatum. e. Large, crescent - shaped ; centre broad, ends acute, vacuoles small. C. acuminatum , Fig. 27. e. Small, crescent-shaped, distance between the ends about ten times tlie central diameter; centre nar¬ row, vacuoles indistinct. C. Diana 3, Fig. 28. Fig. 28. — Closterium Di&nse. Fig. 29 Closterium Venus. e. Very small, crescent-sliaped, eight to twelve times as long as broad ; centre narrow, ends sharp, vacuoles distinct. G. Venus, Fig. 29. 80 MICROSCOPY FOR BEGINNERS. f. Each beak about as long as tlie green body, some¬ times shorter ; whole cell slightly curved, vacu¬ oles usually indistinct. O. rostrdtum , Fig. 30. Fig. 30. — Closterium rostratum. f. Each beak extremely tine, longer than the spindle- shaped green body, the tips alone curved. C. se- taceum , Fig. 31. Fig. 31. — Closterium setaceum. 7. Micrasterias (Figs. 32 to 39). Each Micrasterias is divided across the middle into two equal and similar halves, or semi-cells, by a deep slit, the sides of which may be either close together or somewhat separated. Both semi-cells are also very much slit and notched, but both in the same way, the description of one half, therefore, applying equally well to the other. There are forty-two species of the genus. The beginner must expect to find many forms not in¬ cluded in this list, which contains only some of the most common in the writer’s vicinity. Some Species of Micrasterias. 1. More or less circular in outline ( a ). 2. Not circular; divided into radiating arms (b). 3. Not circular; not divided into arms; central slit gaping 0). DESMIDS, DIATOMS, AND FRESH-WATER ALGJK. 81 a. Each semi-cell divided by four deep cuts into one end and four side lobes, each side-lobe divided by a short¬ er cut into two sec¬ tions, each section by a still shorter cut divided into two divisions, each division by a yet shorter cut divided into two parts, and each part with two teeth. Desmid very large. M. radiosa , Fig. 32. a . Each semi-cell divided by four cuts into one end and four side lobes, each side-lobe divided by a shorter cut into two parts, and each part with two teeth. M. rotdta , Fig. 33. Fig. 33.— Micrasterias rotAta. Fig. 34. — Micrasterias trunc&ta. a. Each semi-cell divided by two cuts into one end and two side-lobes, each side-lobe by a shorter cut divided into two parts, and each part with two 82 MICROSCOPY FOR BEGINNERS. teeth. End-lobes broad, often with two teeth oh eacli end. 31. truncdta , Fig. 34. b. Each semi -cell divided by deep rounded depres¬ sions into four tapering, slightly curved arms, the whole desmid having eight undivided arms. 31. arcudta , Fig. 35. Fig. 35 — Micras¬ terias arcudta. dichotoma. Fig. 37.— Micrasterias Kit- chelii. b. Each semi -cell divided by two acute depressions into one end and two side lobes, each side-lobe divided by an acute depression into two short parts, each part divided by an acute depression into two short arms, and each arm with two teeth ; arms of the end-lobes each with two teeth ; the wdiole desmid with twenty short arms. 31. dicho¬ tomy Fig. 36. Fig. 38.— Micrasterias oscitans. Fig. 39 — Micrasterias ldticcps. DESMIDS, DIATOMS, AND FRESH-WATER ALG.E. 83 c. Divided into one end and two side lobes (d). cl. Side -lobes divided by a shallow notch into two parts extending beyond the end-lobes, each part with two teeth on both ends. M. Kitchelii , Fig. 37. d. Side-lobes not divided into two parts, but extend¬ ing beyond the end-lobes. M. oscitans , Fig. 38. d. Side-lobes not divided into two parts, not extend¬ ing beyond the end-lobes. M. laticeps , Fig. 39. 8. Euastrum (Eigs. 40, 41, 42). Euastrum is divided into two halves by a central slit across the middle, but the cell is never circular as in Micrasterias, and the margins are wavy, never sharply toothed. The ends are usually notched. There are about forty species. 1. Each half oblong ; an end-lobe present in both halves, and formed by a short rounded cut on each side. E. cr.dssum , Fig. 40. Fig. 40. — Eu&strum cr&s- sum. Fig. 41. — Eu&strum didelta. Fig. 42. —Euastrum ansatum. 2. Each half somewhat triangular, without distinct end- lobes (a). 84 MICROSCOPY FOR BEGINNERS. a. Sides wavy, gradually expanding towards the cen¬ tral cut. E. didelta , Fig. 41. a. Sides hardly wavy, suddenly expanding towards the central cut. Small. E. ansatum , Fig. 42. 9. Tetmemorus (Figs. 43, 44). 1. Widest in the middle, the ends tapering. T. granu- latus , Fig. 43. Fig. 43. — Tetmemorus granulatus. Fig. 44. — Tetmemorus Brebissduii. 2. Not widest in the middle, the ends not tapering. T. Brebissonii , Fig. 44. 10. Docidium (Figs. 45, 46). 1. A rounded enlargement on each side of the central constriction. D. Baculum , Fig. 45. Fig. 45.— Docidium Baculum. Fig. 46. — Docidium crenulatum. . 2. Two or more small enlargements on each side of the central constriction, giving the edges a wavy ap¬ pearance. D. crenulatum , Fig. 46. 11. Cosmarium (Figs. 47, 48, 49, 50). The ends of Cosmarium are never notched nor in¬ cised. They may be, and often are, rough or warty, but the ends are always entire. There are about one hundred species. The following are common : 1. Surface smooth ; cell less than twice as long as broad, DESMIDS, DIATOMS, AND FRESH-WATER ALGHS. 85 tlie two semi -cells evenly rounded. C. Ralfsii , Fig. 47. 2. Surface smooth ; cell about twice as long as broad, the margins of each semi-cell slightly sloping tow¬ ards the flattened ends. C. piyramiddtum, Fig. 48. Fig. 47. — Cosma- rium R61fsii. Fig. 4S.— Cosma- rium pyrami- datum. Fig. 49. — Cosmd- riuni margari- tifernra. Fig. 50. — Cosma- rimn I’rebissd- nii. 3. Surface roughened by rounded, pearly elevations. C. margaritiferum , Fig. 49. 4. Surface roughened by minute sharp points. C. Bre- bissonii , Fig. 50. 12. Staurastrum (Figs. 51, 52, 53, 54). In front view, or in the position in which the desmids usually lie naturally, Staurastrum resembles Cosmarium, but in end view it is always angular. It is sometimes rather troublesome to get Staurastrum, or indeed any other desmid, tilted up on end so that it can be exam¬ ined in that situation, but in a moderately deep cell, with considerable water and a low-power objective, it can usually be turned over by gently tapping and press¬ ing the cover-glass with a needle. Staurastrum is a large genus, containing about one hundred and twenty species. 1. Cell dumb-bell shaped ; without arms ; surface rough- 86 MICROSCOPY FOR BEGINNERS. enecl by small elevations. St. punctuldtum , Fig. 51. 2. Cell not dumb-bell shaped ; with arms (a). a. Cell triangular in end view, the angles toothed ; arms in a cluster of about three on the end of the cell, their ends toothed. St.furcigerum , Fig. Fig. 51 _ Staurfi- Fig. 52.— Staura- Fig. 53. — Stanrfi- Fig. 54.— Stanrastrum strum puuctula- strum furcige- strum gracile. macrocerum. turn. rum. a. Cell triangular in end view, the angles prolonged as narrow arms, the ends of which are three¬ toothed ; surface roughened. St. gracile , Fig. 53. a. Cell with six or seven radiating arms, their ends tliree-toothed. St. macrocerum , Fig. 54. 13. Xantiiidium (Figs. 55, 56). The cells bear near both ends a prominence or tuber¬ cle that may be rounded and smooth, truncate, or appar¬ ently encircled by small beads. 1. Cell about twice as long as broad ; spines short, their ends irregularly toothed ; tubercles circular, beaded. This is the only species with toothed spines. X. armatum , Fig. 55. 2. Cell not twice as long as wide, each half somewhat kidney-shaped ; spines in four or six pairs on each DESMIDS, DIATOMS, AND FRESII-W ATER ALGJ3. 87 semi-cell, not divided nor toothed, but often curved ; tubercle a curved row of bead-like elevations. X. antilopmim , Fig. 56. Fig. 55. — Xantbidium nrmatum. Fig. 56. — Xanthidium antilopaum. 14. Artiirodesmus (Figs. 57, 58). 1. Spines on the same side curving or spreading from each other ; surface smooth. A. incus , Fig. 57. 2. Spines on the same side curving towards each other ; surface smooth. A. convergens , Fig. 58. Fig. 57.— Arthrodesmus Fig. 58.— Arthrodesmus Fig. 59.— Spirotoenia con- incus. convergens. densata. 15. Spirotoenia. Ends rounded ; spiral band closely wound. S. con- densdta , Fig. 59. 16. Triploceras. Surface roughened by small projections arranged in rows around the cell, their tips notched or finely toothed ; cell twelve to twenty times as long as broad. T. verti- cillatum , Fig. 60. Fig. 60.— Triploceras verticillatum. 88 MICROSCOrY FOR BEGINNERS. 17. Penium. Cylindrical ; ends rounded, surface smooth. P. Ere - bissonii , Fig. 61. If it is desired to preserve any of the desmids or Alg?e, the following solution will be found to be an ex¬ cellent medium. In it the plants retain their green color, and the cell contents have less tendency to shrink from the cell-wall than with any other of the many media often recommended. Any druggist can make the solution. It is composed as follows : Camphorated water and distilled water, of each 50 grammes; glacial acetic acid, 0.5 gramme; crystallized chloride of copper and crystallized nitrate of copper, of each 2 grammes ; dissolve and filter. The plants should be placed in a cell made of shellac, a few drops of this preservative copper-solntion added, and the cover fastened down with shellac. If any other cement, except perhaps Brown’s rubber cement, is used with this solution it will inevitably run under and ruin the preparation. If the beginner should find the desmids so attractive that he desires to study them rather than to learn the names and appearance of a few of the commonest, he should refer to the Kev. Francis Wolle’s excellent book entitled “The Desmids of the United States.” DESMIDS, DIATOMS, AND FRESII-WATER ALG.E. 89 II. DIATOMS. For a long time there was much discussion as to the animal or vegetable nature of the diatoms, but that they are plants is now the general belief. Their peculiar motion was one great reason for classing them among the animals, although some undoubted plants have even a more rapid movement. N o class of microscopic objects, except, perhaps, the Infusoria, is so abundant. No ditch or pond is with¬ out them. No pool is too small to harbor them ; even a depression made by a cow’s hoof in a wet meadow soon becomes a home for them. They will probably form some of the first things to attract the attention of the beginner in the use of the microscope. Their shape is as varied as their number is great, and their hard and glass-like surface is most beautifully lined and dotted, and sculptured in delicate tracery. Most plants are comparatively soft, but the diatoms are noteworthy for the hard case enclosing the semi-fluid, yellowish-brown contents, a case that is indestructible. It may be heated to redness, it may be boiled in strong acids and alkalies, and at the end be as it was before, as gracefully formed and as beautifully marked. Indeed, to properly study the diatoms they should be treated by some method to destroy the coloring matter often obscuring the surface markings for which they are chiefly valued. For the beginner, however, who desires only to recognize a diatom when he meets with one 90 MICROSCOPY FOR BEGINNERS. iii the field of his microscope, and to learn its name, if possible, such preparation is unnecessary. Diatoms are also peculiar in their structure. In this they have often been compared to a pill-box. The dia¬ tom is formed of two parts called valves, one of which may be likened to the pill-box proper, and the other to the lid, since it slips over the edge of the lower valve. The entire box-like diatom is called the frustule ; the surfaces of the upper and lower valves are usually marked and shaped alike, and are called the sides. But when the frustule happens to be turned so that the nar¬ rowest part, or that part corresponding to the thickness of the pill-box, and called the front, is towards the ob¬ server, then the shape is so different from that of the valves as to puzzle the beginner. If in doubt about the position, gently tap the cover-glass with a needle, when the frustule will generally roll over on its broad side. This seems somewhat bewildering at first, but there is no difficulty if it is borne in mind that the thickness of the pill-box corresponds to the front of the frustule, and the broad surfaces of the lid and bot¬ tom to the sides of the valves. In addition to the ordinary markings on the valves — that is, the transverse lines which are sometimes so coarse that they are called ribs — each valve frequently bears a line or narrow smooth band down the middle, while at each end and at the centre there is often a small rounded spot resembling a circular space, but being in reality an elevation; called a nodule. DESMIDS, DIATOMS, AND FKESII-WATER ALG/E. 91 Iii remote ages diatoms existed in even greater num¬ bers than at present. Immense beds of fossil frustules are found in many parts of the world, especially in our own country. In Maryland and in New Jersey diato- maceous earth is obtained containing exquisite forms. In Virginia a certain deposit is especially renowned, since it is eighteen feet thick and underlies the city of Richmond. This has afforded the student some of the rarest and most valued frustules, or valves, for the frus- tule, before it can be properly studied, must be sepa¬ rated into its two valves. To have produced such a mass they must have existed in incalculable numbers in a great body of water where, dying, and sinking to the bottom year after year, their skeletons accumulated as others continued to fall. To appreciate the probable length of time, as well as the number of diatoms, need¬ ed to make such a deposit, it is only necessary to know that a single frustule is seldom thicker than the one ten-thousandth of an inch. At the present day living diatoms are often found in large numbers forming a yellowish-brown film on the mud in shallow water. In such cases it is no trouble to skim them up and so gather them. Usually, however, the beginner will first see them floating freely about his slide, or attached to various plants. But few are visi¬ ble to the naked eye except when collected in great masses, and only then as brownish patches ; the indi¬ vidual valves are seldom seen without the microscope, and then only to the most acute and best educated eye. 5* 92 MICROSCOPY FOR BEGINNERS. They are difficult to study and to name. To prop¬ erly examine them demands the highest power object¬ ives of the best construction, and a skill in the use of the microscope and accessary optical apparatus not at the beginner’s command. Much has been written about them, but the literature of the subject is so widely scat¬ tered through the scientific magazines that only those who make a special study of the diatoms can hope to have it in their libraries. But the beginner need not despair. With ease he can learn to recognize a diatom whenever seen, and to know the names of the com¬ monest forms, and this is all he will care to learn at first. Yet he will find it a satisfaction to be able to say to a friend, u That is a diatom,” and to explain its box-like structure. The following Key has been made to assist the be¬ ginner in ascertaining the names of a few of the com¬ monest fresli-water forms. It is impossible to include even a tithe of the plants, and the beginner will surely find many not mentioned in the succeeding list, but from the brownish color, the movements common to so many, and the hard, dotted, lined, and sculptured valves, he can readily know them as members of the Diatoma- cece after he has seen and recognized one. More than this he can scarcely hope to do. The brown coloring matter will often be seen con¬ tracted to a narrow strip or to a spot at each end, and very frequently the frustule will be entirely colorless. Diatoms are the favorite food of many microscopic ani- DESMIDS, DIATOMS, AND FRESII- WATER ALGJS. 03 male, which absorb the cell contents, often leaving the hard and indigestible valves colorless, but otherwise un¬ changed. Key to Genera of Diatoms. 1. Growing in bands or ribbons (a). 2. Growing on colorless steins or in a jelly-tube (c). 3. Growing with their concave sides attached to other plants (e). 4. Free-swimming [f). a. Band curved or coiled. Meridion , 1. a. Band zigzag ; frustules attached together by the corners. Didtomci , 2. a. Band uneven, frustules long, narrow, rapidly slid¬ ing on each other. Bacillar ia, 3. a. Band straight, or nearly so, edges even, frustules motionless (b). b. Each frustule six times as long as broad. Frage- luria , 4. b. Each frustule twice as long as broad. Ilimanti- dium , 5. c. In a narrow jelly-tube ; valves boat-shaped. En- cyonema , G. c. On the ends of colorless stems ( d ). d. Valves boat-shaped. Cocconema , 7. d. Valves wedge-shaped. Gomjphonema , 8. e. Valve six to seven times as long as broad. Epi- themia , 9. e. Valve oval, nearly as long as broad. Cocco7ieis, 10. 94 MICROSCOPY FOR BEGINNERS. f. Yalve not curved nor S-shaped (g). f. Yalve in side view arched, the convex edges scal¬ loped. Eunotia , 11. f. Yalve long S-shaped. Pleurosigma , 12. f. Yalve boat - shaped, the ribs conspicuous. Suri- rella , 13. f. Yalve boat-shaped, ribs none. Namcula , 14. g. Yalve strongly ribbed ; a nodule at each end and in the centre. Pinnularia , 15. g. Yalve not ribbed ; with a central longitudinal, and a transverse smooth band. Stauroneis , 16. 1. Meridion circulare (Fig. 62). Yalves wedge-shaped, transverse lines indistinct, bands spiral, often broken into small curved sections (Fig. 62). Fig. 62.— Meridion circulare. Fig. 63.— Diatoma vnlgdre. 2. Diatoma vulgare (Fig. 63). Frustules oblong, the four angles right-angles, band often attached to aquatic plants, easily separable into its component frustules (Fig. 63). % 3. Bacillaria (Fig. 64). Frustules long and narrow, united laterally, freely DESMIDS, DIATOMS, AND FRESH-WATER ALG.E. 95 and rapidly sliding backward and forward over each other ; free-swimming (Fig. 64). This is probably one of the most interesting of the common fresli-water diatoms, on account of its strange movements. When quiet, as it prob¬ ably will be immediately after being t=d~Erj£=rJ' placed on the slide, the band will ' Fig. 04.— Bacill&ria. somewhat resemble a row of fence pickets lying closely side by side. Suddenly each picket shoots forward until they are all nearly end to end, the band becoming a long irregular line, and quite as suddenly closing together again. This alternate back¬ ward and forward gliding is continued until the diatoms become apparently exhausted, or the oxygen in the wa¬ ter is consumed. What prevents one frustnle from slipping off the end of the other is not known ; indeed the cause of the entire performance can only be guessed at. All the species of the genus Bacillaria are said to live in salt water. The form which I have ventured to identify as a sweet- water variety of B. paradoxa is not uncommon in fresh-water ponds. 4. Fragelakia capucina (Figs. 6o and Goa). Frustules very narrow, never wedge-shaped, band long. Fig. 65 shows the band of united frustules ; Fig. Goa the ap¬ pearance of a single valve more highly magnified. The ends of the Figs. G5 and 65a. — Fragela- valves are somewhat wedge-shaped. ria enpneina. 9G MICROSCOPY FOR BEGINNERS. 5. Himantidium pectinale (Fig. 66). Frustules mucli wider than the preceding, transverse lines distinct on both sides of a narrow central smooth space (Fig. 66). Fig. 60. — Himantidium pectinale. Fig. 67. — Encyonema paradoxa. 6. Encyonema paradoxa (Fig. 67). The jelly- tubes are usually very slightly, if at all, branched, the frustules commonly arranged in longi¬ tudinal lines within the tubes, which are attached to other plants (Fig. 67). 7. Cocconema lanceolata (Figs. 68 and 68a). Stems often much branched, attached to acpiatic plants and other submerged objects, frustules on the ends of the branches, in side view (valves) slightly curved with a median longitudinal line, a nodule at each end and in the centre (Fig. 68). The frustules are often found sepa¬ rated from the stems and floating freely, when they are usually seen in side view. Fig. 68^ shows a single valve highly mag¬ nified. 8. Gompiionema acuminata (Fig. 69). Stems often much branched, but fre- Fig os and os«. quently found unbranclied ; attached to — Cocconema lanceolata. other plants ; frustules slightly swollen in DESMIDS, DIATOMS, AND FRESH-WATEIl ALG^E. 97 the centre, the narrowest end of the wedge attached to the stem (Fig. GO). 9. Epithemia TDTtGIDA (Fig. 70). Valves curved or bent, transverse lines coarse and conspicuous (Fig. 70). 10. Cocconeis pediculus (Fig. 71). Valves oval, with a line down the cen- F]s- 69.— Gompho- ueina acuminata. tre and a small nodule in the middle ; at¬ tached by one valve to aquatic plants, especially to the leaves of Andcharis (Fig. 71). Fig. 70.— Epithemia tur- Fig. 71.— Cocconeis Fig. 72.— Eundtia gida. pediculus. tetraodon. 11. Eunotia tetraodon (Fig. 72). Valves curved, a small nodule at each end of the concave margin ; the convex border apparently scal¬ loped, but in reality bearing four or more rounded ridges (Fig. 72). 12. Pleurosigma (Fig. 73). Valves long S-sliaped, widest in the middle and ta¬ pering to both ends, one of which curves towards the 98 MICROSCOPY FOR BEGINNERS. riglit-hand side, the other towards the left-hand (Fig. 73). A narrow S-shaped line extends down the centre of the valve, with a nodule in the middle. There are a large number of species of this genus, all of which may be known by this peculiar and beautiful curvature of the sides, the word Pleurosigma meaning S-shaped sides. The valves are very finely striated, Fig. 73.— pieu- the lines being remarkably close together, and demanding a comparatively high-power objective of excellent construction to see them. The valves are therefore often used to test the good quali¬ ties of certain objectives. To the beginner, however, all the Pleurosigmas will probably appear to be smooth. The species most frequently used as a test is P. angu- latum , a salt-water form. 13. SlURIKELLA SPLENDIDA (Fig. 74). The ribs are large and conspicuous, the spaces be¬ tween them seeming to be lower than the edges of the valves, thus giving the latter the appearance of having a narrow wing around the margin (Fig. 74). The mem¬ bers of this genus are also used as test- objects, the one most commonly employed Fig. 74.— surirei- being a marine species. la splendida. 14. Navicula cuspid at a (Fig. 75). Yalves widest in the centre, tapering with straight DESMIDS, DIATOMS, AND FRESH- W ATER ALGyE. 99 margins to each end ; a straight line down the middle with a central nodule (Fig. 75). 15. Pinnularia (Figs. 76 and 77). 1. Sides of the valves parallel, the ends and centre somewhat swollen ; trails- cuspuidta. verse ribs large and conspicuous; a line down the middle, with a nodule at each end and at the cen¬ tre ; frustule large. Common. P. major , Fig. 76. mug Fig. 76.— Piunnldria major. Fig. 77.— Piuuularia viridi?. 2. Sides of the valves slightly convex, the ends and the centre not swollen ; ribs large and conspicuous ; a line down the middle, with a nodule at each end and one in the centre ; frustule smaller than the preceding. It is named green iviri- dis ), probably because it is always brown. P. viridis , Fig. 77. 16. Stauroneis piicenocenteron (Fig. 78). Valves widest in the middle, tapering with curved sides to both ends ; central and transverse bands smooth and conspicuous. Common (Fig. 78). lieis phcenocen- III. FRESH-WATER ALGiE. The Algae often collect together and form green clouds in the water or a scum-like growth on the sur- O 100 MICROSCOPY FOR BEGINNERS. face. Frequently, however, the student will find iso¬ lated filaments under his microscope, and not know how they were placed there, or he will find single threads adherent to other objects which he may be examining. The color of the visible masses is usually bright green ; it may be brownish if the plants are in fruit, or the nat¬ ural tint of the individual alga may be brownish or purplish. Many species are coated with a mucous or slimy material that makes them very slippery and diffi¬ cult to handle, or to remove from the water unless a dipper or spoon be used. They are seldom found in any abundance in deep water. They seem to prefer shallow ponds and slowly flowing streams, where they may have plenty of warmth and light. Few of the species are free - swimming. Most kinds are adherent to leaves, stones, or sticks in the water ; some form feathery clusters of branching fil¬ aments, others surround themselves by little balls of translucent jelly often attached to leaves of grass or to other submerged objects. The following have been partially described in the Key on page 71. 1. Scenedesmus (Fig. 79). The cells are usually four, attached together by their long sides. The spines on the narrow ends of the two terminal cells are curved towards each other, and a spine sometimes grows from the centre of one of the middle cells. The plant is quite common. /S. quadricduda, Fig. 79. DESMIDS, DIATOMS, AND FRESII- WATER ALCEE. 101 2. Pediastrum (Fig. 80). The green cells are usually so arranged as to leave narrow colorless bands between them, and occasionally, in those species formed of a great number of adherent Fig. 79.— Scened6smus quadricauda. Fig. 80.— Pedi&strnm grauukitum. cells, several apparently empty colorless spaces are scat¬ tered about the disk. In the latter cases the colorless marginal teeth are often very numerous, but they are usually more or less conspicuously arranged in twos. In the species here figured the marginal teeth are gener¬ ally twelve in number. P. granuUitum , Fig. 80. 3. Volvox. A small sphere continually in movement, rolling through the water in a very graceful manner, its sur¬ face studded with green points. Under a low power it seems like a hollow globe, and the cause of the mo¬ tion is a mystery ; but the \ inch objective, when the Yolvox moves slowly or rests, shows that each green point bears two fine cilia or little hairs continually vi¬ brating and lashing the water. It is from their vibra¬ tions that the Yolvox receives its rolling motion. The deep green balls often seen within the globe are young plants in different stages of development. When ma¬ tured the mother-globe is broken and the young plants 102 MICROSCOPY FOR BEGINNERS. iloat out and roll away through the water, revolving as they are often seen to do even before leaving the parent. The water in some localities is, in June, so filled with these rolling globes that it is colored green by them, and when the collecting-bottle is held against the light they become visible to a sharp eye as small pale-green spheres. The diameter of a full-grown plant is about one-fiftieth of an inch. V. globdtor. 4. IIydrodictyon (Fig. 81). A yellowish-green scum is sometimes seen on the wa¬ ter, which, when spread out over the fingers, proves to be a net of delicate green meshes. It may grow to ten or twelve inches in length, and form floating masses several inches in thickness. The nets are composed of narrow short cylindrical cells. Under a low power they are re¬ markably beautiful. The Fig. 81. — IIydrodictyon utriculatum. figure shows a part of a net. II. utriculatum , Fig. 81. The masses which the Algm form are usually com¬ posed of great numbers of long threads, commonly called filaments, and matted together, probably by their rapid growth, among other causes. Each filament is DESMIDS, DIATOMS, AND FRESH- WATER ALG.E. 103 built up of many cells attached to each other by their narrow ends, the single filament being considered a sin¬ gle and entire plant. They have no roots, although they may fasten themselves by one end to submerged objects. Some are simple, straight, or curved cellular threads ; some give off branches which generally resem¬ ble the main plant or stem. Their color is usually some shade of green, although a few purplish and brownish ones are known. The following is a key to those genera referred to in this book. Key to Genera of Fresh-water Alycc. 1. Color brownish-green, bluish, or olive (a). 2. Color pure green (cl). a. Filaments branched (b). a. Filaments not branched (o). 1). Branches with many, whorled, moniliform threads ; plant slippery. Batrachospermum , 1. c. Moniliform, with larger scattered spherical cells. Anabama , 2. c. Not moniliform ; bluish green ; twisting, bending, gliding. Oscillaria , 3. d. Green color in one or more spiral bands in each cell. Spirogyra , 4. cl. Green color in two star-shaped masses in each cell. Zygnema , 5. cl. Green color not in patterns (e). e. Terminal cells with a colorless, hair-like bristle (f). e. Terminal cells without a bristle. Vaucheria , G. 104 MICROSCOPY FOR BEGINNERS. f. Forming small green, visible, jelly-like masses. ChcBtophora , 7. f. Not forming jelly-like masses (g). g. Cells of the branches green, those of the stem larger, with a transverse green band. Brapar - ndldia , 8. g. Cells of branches and stem green ; bristles with a swollen base. Bulbochcete , 9. 1. Batraciiospeemum (Fig. 82). The plant often grows abundantly, attached to sub¬ merged objects, in springs, ditches, and ponds. It varies in length from an inch or less to one or two feet, and in color it may be bluisli-green, brownish, or purplish. It is covered with a mucous substance that makes it very slip¬ pery and difficult to handle. It is much branched, and the branches bear many short threads in whorls, each thread plentifully beaded. The whorls are often so close together that the entire plant as it floats beneath the water seems to be a string of little balls. Under the microscope each mo- niliform thread is often seen to be ter¬ minated by a colorless liair-like bristle. Fig. 82.— Batracho- . spermum moniii- Inis, however, is not always present. forme- With a high power the ends of the beaded filaments seem to run down the main stem in long, narrow, almost colorless cells. B. monUiforme , Fig. 82. DESM1DS, DIATOMS, AND FRESH- WATER ALGvE. 105 2. Anabusna (Fig. 83). Filaments moniliform, freely floating, tlie cells spheri¬ cal, the larger scattered ones globular, yellowish. The -/'Tjtn filaments are often curved, and sur- rounded by a delicate mucous mate- Fig. S3.— Anabsena. rial. There are several 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- fciliLL iii1 A Fig. 84.— Oscillaria. 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. 4. SriROGYRA (Figs. 85, 86). The Spirogyrce 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 Fig. 85. — Spirogy'ra. cell -wall, the num¬ ber helping to de¬ termine the species, of which there are many. The plants usually grow in 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 Algee have a similar method. The cells of two filaments lying side by side begin, usually at the same time, to throw out from those2 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- Fig. 86. — Spiro- gyra in con¬ jugation ; with spores. DESMIDS, DIATOMS, AND FRESII-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 green in color. The formation of the spores re- Fig. S7.— Zygnema insigne.. sembles that of Spirogyra. It is found in conjugation in April. Z. insigne , Fig. 87. C. 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 he 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- 6 108 MICROSCOPY FOR BEGINNERS. ament like tlie 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. Fisr. SS.— Vatichcria. 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 Vauclieria. 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. CmETOPiiORA. (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 Chmtojihora 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 ALGAE. 109 their ends bearing a fine, colorless hair or bristle. Un¬ der a low -power objective the plant, if carefully flat- / tened out, is very beautiful. It is justly named u ele¬ gant.” Ch. elegans , Fig. 89. 8. Drapaknaldia (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. glomerata , Fig. 90. 110 MICROSCOPY FOR BEGINNERS. Fig. 90. — Draparnuldia glomerata. 9. Bulbocieete (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. — Bulbochrete. . RHIZOPODS. Ill CHAPTER IV. RlflZOrODS. The Rhizopods 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 Amoeba, 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, Difflio- 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 Khizopods 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.), Rotifers (Chapter YIII.), 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 Algse, especially on the lower surface of water-lily leaves, and among Myriophyllum and Ceratopliyllum. 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 ; Rliiz- 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 (c). b. Body colorless, very changeable in shape. Am<& ba , 1. c. Body orange or brick -red, with pin -like rays. Varnpyrella , 2. c. Body colorless or greenish (d). d. Rays stiff, forked at the ends ; body often green. Acanthocystis , 3. 6* 116 MICROSCOPY FOR BEGINNERS. d. Hays flexible, not forked. Actinophrys , 4, or Actinosphceriinn , 5. Shell formed apparently of sand-grains (f). e. Shell not formed of sand-grains (g). e. Shell a latticed globe on a long stem. Clathru- Una , 12. f. Not inclined ; pear-shaped, or globular with spines at the summit. Eifflugia, 6. f. Inclined ; circular or oblong, thicker and with spines at the rear. Centropyxis , 7. g. Shell brown (ft). g. Shell colorless, ovoid, not curved (i). g. Shell often yellowish, ovoid, curved (retort shaped), mouth circular. Gyphoderia , 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 psendopodia from some 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. Amoeba 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 pro¬ portion of the body with a vil- teus* lous or velvet -like patch of very short, colorless pseudopodia. A. villosa. 2. Vampyrella lateritia (Fig. 93). A red or orange colored, Amoeba-like creature wdtli 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, 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 Fig. 93.— Vampyrella lateritia. 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 Spirogyrae. 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. Acantiiocystis cii^etopiiora (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 liigh-power objective, as they are small, but 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 Bhizopod 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 Fig. 94.— Acauthocystis gp0k This may happen at any part chaetophora. 1 J 1 1 J 1 of the surface. Acauthocystis 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. Actinopiirys 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 RHIZOPODS. 121 that it lias received the name of the “ sun animalcule.” The rajs are seldom entirely with¬ drawn. It feeds on smaller animals and the spores of Alg®. When an animalcule comes in contact with the rays it seems to lose some of its power of motion. It appears to 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. Fig. 95. — Actiuophrys sol. 5. Actinosph.erium Eiciiiiornii (Fig. 96). At first the beginner will confound this Rhizopod with Actiuophrys 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 Actinoplirys 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 Actinoplirys, 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 Rhizopod is Actinosphaerium. But there is another and more impor¬ tant difference, which the be¬ ginner will not observe un¬ less he searches for it with a liigh-power (J or |) object¬ ive. Each ray has a thread Fig. 96 — Actiiioephcerimn 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 wTitli Actinoplirys, among Lemna and other aquatic plants. It feeds on other animals as vTell 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 wTitli the long rays seems, as with Actinophr37s, to become in¬ capable of escape ; it is then slowdy 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 Ithizopods. 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- Fig. 97.— Difflugia orless, thick, blunt. It is almost as pyrifdrmis. , 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, hut 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 Rhizopod 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. acuminata. Fig. 9S.— Difllugia corona. 126 MICROSCOPY FOR BEGINNERS. 7. Centropyxis aculeata (Fig. 99). The shell of this Rhizopod is usually formed of sand- grains, aud 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¬ pears 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 Fig. 99. — Centro¬ pyxis aculeata. RIIIZOPODS. 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 vulgaris , 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 wTide facets. Not rare. A. mitrdta. Fig. 100. — Arcella vulgaris. la dent&ta. Fig. 102. — Triuema euchelys. 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 month 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 tine, thread-like, and few in number. The Uhizopod 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. Euglypiia (Fig. 103). The shell of Euglypiia 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 Euglyphse 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 RmzoroDS. 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 ./\ » < \ /• /*. v VVbV, yi the ooze of ponds. Euglypha dive- Fig. m-Eugiypha olata, Fig. 103. "lTeol"“- 2. Shell with a cluster of spreading spines springing from the centre of the summit. Common in Sphagnum. E. cristdta. 3. Shell with the summit and sides fringed with bris¬ tles. Common in Sphagnum. E. cilidta. 11. C YPKODEllIA 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* Fig^oT— cypho- ing, the mouth of the shell is in contact dena ampulla, with the object over which the 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. Clath¬ rulina 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 L history very little is known. They Fi". 105. — clathrulina eie- form a department in which there gans. . , . . . . is room lor 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. INFUSORIA. Tiie 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 VIII.). 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. Xo collec¬ tion of Algae, 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 otf 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 Algm, 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 otf 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 loricre 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 loricse building animals are almost as perma¬ nently fastened to their loricre 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 loricae, 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 a flagellum (plu¬ ral, 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 Rotifers 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 liigh-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-incli 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 he 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 teaspoonful) 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 j^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 Vorticella 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 Inf usoria. 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 (b). a. Stem much branched, neither it nor the animals contractile. Dendromonas , 1. a. Stem much branched, both it and the animals con¬ tractile. Carchesium , 2. a. Stem much branched, only the animals contrac¬ tile. Epistylis, 3. a. Stem not branched, contracting into spirals. Vor¬ ticella. , 4. b. Loricre vase-shaped, transparent ( c ). b. Loricse soft, granular, brownish ie). c. Attached to each other to form colonies. Dmo- bryon , 5. INFUSORIA. 139 c. Not attached to each other (d). d. Lorica without a stem, adherent by the narrow base. Vaginicola , G. 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. y. With one or more flagella at the front (y). f. Without flagella, but with cilia (A). g. Body very changeable in shape, colorless. Asta¬ sia , 10. g. Body very changeable in shape, green or red. Puglena , 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. Phdcus , 13. g. Body not changeable in shape, green, united in a revolving colony. TJvella , Id. h. Cilia on the entire surface (i). h. Cilia confined to the lower or flat surface (7r). i. Neck long, very elastic and extensile. Trachelo- cerca , 15. i. Neck long, flattened, not extensile. Amphileptus , 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. Si ten- tor, 9. 140 MICROSCOPY FOR BEGINNERS. k. Cilia large, few, scattered (l). h. Cilia fine, numerous ( m ). l. Body more or less circular in outline. Euplotes 5 18. l. Body more or less oblong in outline. Stylonychia , 19. 77i. Mouth followed by a conical tube of rods. Cld - loclon , 20. m. Mouth followed by a brown, sickle-shaped mem¬ brane. Loxodes , 21. 1. Dendromonas (Fig. 106). The stem is manv 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 Fig. 106.— Den- dromouas. 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¬ 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 POR BEGINNERS. brandies and tlie stem will distinguish it from all other tree-like Infusoria. 3. Epistylis (Fig. 108). 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-sliaped, their widest part being the free end which closes when the body contracts. The front border is encircled by a row of «/ T 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 F'S styiiT1 1 ' 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. Yorticella (Fig. 109). The unbranched stem of Yorticella 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 Vorticellm 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-sliaped, 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 F>s- 109-— Vor- & . . ticeiia. 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 Algie then found so abundantly in the shallow pools, colonies of very small, vase-shaped loricas 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 loricse 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 higli-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. Fig. 110.— Di- nobryou. 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-m-— 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. Vaginicola 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 y 146 MICROSCOPY FOR BEGINNERS. view with the 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. ° 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. Cothurnia (Fig. 113). The beginner may mistake this for a small Vaginicola, as the loricm 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 for. 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. ii3. the enclosed Infusorium is not colored. In its cothurma. ac^ong ^ resembles Vaginicola 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 ( b ). 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. 'polymorplius , Fig. 114. Fig. 114.— Sten¬ tor polymor¬ phic. 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 higli-power (-J- 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 is never found in company with others of the same species. It is Barretti. r not uncommon on Ceratophyllum. S. Barretti , Fig. 115. b. 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 shallow ponds in early spring. The green color then always entirely con¬ ceals the red. S. igneus , Fig. 116. 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. coer (ileus. b. Body dark brown, almost black. This also resem¬ bles Fig. 116. Common. S. niger. Fig. 115. — Stentor 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. — AstAsia. Fig. US. — 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 with 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. CniLOMONAS (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 lmncli -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. — Child- Fig. 120. — Ph&cns Fig. 121. — Ph&cus monas. pleurondctes. lougicaudus. 13. Phacus (Figs. 120, 121). The body of Phacus is flattened, thin, and rather like a small leaf. It is widest in front, usually rounded, and tapering from the centre to the short, pointed, colorless tail-like prolongation ; at the broad end it has one long flagellum, often difficult to see. There are several spe¬ cies in our ponds, all of which are green. 1. Body not twisted at the rear, tail short, curved. Pli. pleuronectes , Fig. 120. 2. Body twisted or not at the rear, tail long, straight. Ph. lougicaudus , Fig. 121. 14. Uvella (Fig. 122). The little animals forming these rapidly swimming and revolving colonies are united by their narrow ends into almost spherical microscopic masses, varying in INFUSORIA. 151 number from two or three up to forty or fifty or more. Each Infusorium has a narrow, yellowish - green band down each side of the somewhat egg-shaped body, and two long, fine flagella at the broader front end. The colonies are common in early spring in shallow pools with Alga3. Fig. 122.— Uvella. Fig. 123.— Traclielocerca. 15. Traciielocerca (Fig. 123). This will probably be a greater surprise to the begin¬ ner the first time he sees it than any other common In¬ fusorium, on account of the remarkable neck, which can be stretched out to five or six times the length of the body, and drawn back until it almost entirely disap¬ pears. The body, without the neck, is somewhat spin¬ dle-shaped, and occasionally ends in a short, tail-like part. The Infusorium may often be concealed in a mass of fragments or a heap of dirt, while only that wonderful neck is visible, stretching and bending and writhing like a colorless snake, as it searches the slide for food. The end of the neck is rather pointed, and bears the mouth at the tip. The whole Infusorium is covered with fine cilia. It is quite common. 16. Amphileptus (Fig. 124). This is one of the largest of the Infusoria, sometimes 152 MICROSCOPY FOR BEGINNERS. measuring ^ inch in length. The neck is not extensile as in Trachelocerca, although it is the longest part of the whole animal. The body, without the neck, is some¬ what spindle-shaped, taper¬ ing more rapidly towards Fig. 124. — Amphileptns. the rear than towards the front. The latter or neck¬ like part is flexible, and is turned and twisted about in a way that often suggests the movements of an ele¬ phant’s trunk. The whole body is covered with fine cilia. 17. Paramvecium (Fig. 125). This is often called the “ slipper animalcule ” from its shape. It is frequently found in the ponds, but is espe¬ cially abundant in vegetable infusions. The hollow place resembling the opening in the slipper for the foot, is the part leading to the mouth near the centre of the lower surface. The whole body is cov¬ ered with fine cilia, and sometimes a clus¬ ter of longer, coarser cilia is noticeable on Fig. i25.-Para- . . T msecium. the posterior tip o± the body. In the writer’s locality this cluster of cilia is present on all the specimens ; I have never seen a Paramcecium without it. This Infusorium increases rapidly by dividing into two parts across the middle. Its movements are rapid. 18. Euplotes (Fig. 126). This is one of the walking Infusoria, the cilia on the flat lower surface being very large and strong. The INFUSORIA. 153 animal uses them for swimming, or it walks about the slide or climbs among aquatic plants by resting part of its weight on their tips as if they were legs. When the creature happens to be turned on its back, these large cilia can be seen pattering irregularly against the cover- glass. They vary in number from ten to twelve. The front border has a row of finer but still large cilia extending down the side of the Hat surface to the mouth near the centre of the body. Four straight, stiff hairs Fig. 120.— Eu- project from the posterior margin, two of plotes’ them often being divided into fine branches. The back of the Infusorium has no cilia, but is a hard surface, al¬ most like a shell. The animal is very active. There are several species common among Ceratophyllum and Myriopliyllum. 19. Stylonyciiia (Fig. 127). To the beginner the members of this genus will quite closely resemble Euplotes, as all the cilia are confined to the frontal border, the part about the mouth, and irregularly distributed over one side of the flat lower surface as walking or¬ gans. It can easily be distinguished from Euplotes by its shape, being much more ob- Fig. 127.— sty- long. Sometimes it is quite long and nar- lonychia. -. .-. -r-, -i , • -i i row, while Euplotes is always more or less circular. It has no cilia on the back, which is usually hard and shell-like. The species are several, being espe¬ cially common in vegetable infusions. 154 MICROSCOPY FOR BEGINNERS. 20. CnfLODON (Fig. 128). The body is oval and flattened, the lower or flat sur¬ face alone being ciliated. The front border is convex, and rather sharply pointed at one corner, and the side of the body extending from this corner to the rounded posterior margin is nearly straight, while the opposite side is convex. The back is smooth and naked. From the pointed corner a curved line of cilia extends back over the flat surface to the mouth, Fig. i2s. which opens into a cone-shaped bundle of fine Chilodon. rods visible under a high power. The ends of these rods can be seen with a moderately low power, en¬ circling the mouth like beads. The Infusorium lives upon smaller Infusoria and diatoms, which it appears to seize with this peculiar throat, the rods separating as the food is slowly swallowed. Chilodon is common in still waters. 21. Loxodes (Fig. 129). The body is quite long and narrow, the frontal border being convex, with one corner rather pointed ; but on one side, just below the pointed corner, is a concave space con¬ taining a brown, sickle-shaped body lining the hollow which is part of the Infusorium’s throat. The upper portion, or blade of the sickle, seems only to stiffen that part of the cavity, the true mouth being at the beginning of the short handle Fig. 129. of the sickle. The cilia are fine, and are on the low- Loxodes' er flat surface only. The body is flexible, often bending on itself. The Infusorium is quite common in some localities. HYDRAS. 155 CHAPTER VI. HYDRAS. When Hercules was going about doing those wonder¬ ful things of which we have all heard, it was suggested that he should turn his attention in the direction of Lake Lerna, near Argos, where a monster with a hun¬ dred heads was making itself unpleasantly active. lie visited the place and interviewed the creature, but when he had cut off one of the heads, lie must have been sur¬ prised to see two new ones sprout out of the bleeding surface. It was discouraging, but the hero began to have the best of the contest when he began to burn the fresh cuts with a hot iron. The monster was the Hy¬ dra of mythology. Science has preserved its memory by giving the name to a common and curious creature inhabiting all our ponds and ditches. The fresh-water Ilydra (there are no salt-water Hydras) has a soft and elastic body attached by the tip of one end to an aquat¬ ic plant or other submerged object, and eight or ten long fine arms arranged around a mouth at the op¬ posite end. There are two species, the green (II. viridis) and the brown (Ilfusca), both being very common. The whole animal is elastic, and when extended may be an inch long and easily visible to the naked eye ; when com 8 156 MICROSCOPY FOR BEGINNERS. tracted it resembles a minute globule of green or brown jelly, with the shortened arms at the summit like very small drops or projections. It is very active so far as the arms are concerned, for the body is always adherent to some submerged object. The arms or tentacles are usually stretched out to their fullest extent, then often exceeding the body in length, waving and twisting about in search of prey. The figure (Fig. 130) shows several Fig. 130.— Hydras adherent to Lemna rootlets. Hydras nearly the natural size adherent to Lemna root¬ lets. The body is like a narrow bag, the hollow part of the little sack being the stomach, and communicating directly with the external water, in which the Ilydra lives, by means of the mouth, around which are arranged the arms or tentacles. These tentacles are themselves hollow, and communicate with the hollow of the stomach. HYDRAS. 157 The food consists of small worms, water-fleas, or other Entomostraca (Chapter X.), or even little pieces of raw beef, if the observer chooses to feed them. They seize the victim as it is swimming past, by twining a tentacle around it and drawing the struggling creature down to the mouth, through which it is thrust into the stomach. The act of seizure takes place so rapidly that the eye can seldom follow it. The observer can usually only know that the prey is caught and is slowly approach¬ ing the mouth. Often when the captured object is too large or strong for one arm to hold, several tentacles bend over and twine around it. A creature once caught rarely escapes. When a quantity of aquatic plants is brought home, the Hydras soon make their way to the lightest side of the -aquarium or bottle and attach them¬ selves to the glass. At such times I have often amused myself, and doubtless pleased the Hydras, by feeding them with small larvae or aquatic worms. Take with the forceps a small aquatic worm by one end, and pre¬ sent the wriggling thing to a Hydra’s arm. No second invitation is needed. The worm is embraced as quick as a flash, and, if too long to be swallowed all at once, part of it will hang out of the mouth until the other end is partially digested, but the tentacles will not cease to fish for more. It is said that if the Ilydra and the worm are placed in a very deep cell under the micro¬ scope, the performance can be watched through a low- power objective. I have never succeeded in doing this, but there is no trouble in feeding them in an aquarium. 158 MICROSCOPY FOR BEGINNERS. They never eat any but animal food, and they are al¬ ways hungry. The body and tentacles of Ilydra viridis are rough¬ ened by little elevations or warty prominences. The brown species {H. fused) is not so much roughened. These warts contain what are called the stings. These are small oval or vase-shaped hollow bodies, with a fine thread coiled in the interior, and four minute spines near the summit. When the Ilydra is irri¬ tated by the pressure of the cover-glass these stings are thrown out violently, and the long stifT thread can be well seen. When in the animal’s body they cannot be easily examined. One is shown much magnified in Fig. 130a. Fig. i30a. They are often found on the slide when no Hydra is to be seen, and they are sometimes noticeable sticking in the body of some worm or larva that has escaped a fatal embrace. I have more than once found a Chironomus larva (Chapter VII.) in a dying condition and ornamented by a spiral band of these stings in its skin, it having evidently had a tussle with a Ilydra and escaped. The Hydra increases in numbers rapidly by a process of budding. A little protuberance appears on one side of the body, enlarging and growing, and finally, while still attached to the parent, developing tentacles, then resembling the mature animal in everything except size. And it is not unusual to see one or more still younger Hydras sprouting from these before they are free from HYDRAS. 159 tlie parent, so that the old Hydra is often a grandmoth¬ er before she is a mother. The young one is hollow, and communicates with the hollow of the parent. It captures food like the parent, and it is said to be no un¬ common sight to see the old and the young both seize the same worm. In such cases the strongest wins, un¬ less the worm breaks in the unfilial struggle, when the parts go into the one common stomach. Very often two young Hydras may be noticed growing from the sides of a single older one, instances of which are shown in Fig. 130. The budded young finally separate from the parent, then leading an independent life, and soon producing young Hydras from their own sides, if they have not already done so. The creatures are very hardy. They may endure much harsh treatment, and seem to thrive under it. They have been made the victims of many apparently cruel experiments, but they are probably not very sen¬ sitive to a feeling of pain. The sensation of hunger, and a touch delicate enough to know when a desirable morsel or an obnoxious object comes in contact with the tentacles, are probably the extent of their feelings. Trembley, a Dutch naturalist who studied the Hydra as long ago as 1739, first called attention to the harsh treatment they would endure and live. In a rather quaint, old-fashioned translation it is said that, “If one of them be cut in two, the fore part, which contains the head and moutli and arms, lengthens itself, creeps, and eats on the same day. The tail part forms a head and 160 MICROSCOPY FOR BEGINNERS. month at the wounded end, and shoots forth arms more or less speedily as the heat is favorable. If the polype be cut the long way through the head, stomach, and body, each part is half a pipe, with half a head, half a mouth, and some of the arms at one of its ends. The edges of these half pipes gradually round themselves and unite, beginning at the tail end ; the half mouth and half stomach of each becomes complete. A polype has been cut lengthwise at seven in the morning, and in eight hours afterwards each part has devoured a worm as long as itself.” He also sliced them across, and found that each piece developed a cluster of tentacles, and he finally turned them inside out, and in a few days the maltreated creature swallowed food, although its old skin was now lining its stomach, and its old stomach mem¬ brane had now become its skin. There is a peculiar parasitic Infusorium (Fig. 130J) often seen in considerable numbers gliding rapidly over the body and arms of the Ilydra, especially of H. vi- ridis. They do not seem to be objectionable guests, as the Hydra never appears to notice them. It is said that they infest sick or weakly victims only, but that is not according to the writer’s experience, if the condition of pediculus— x Parasite of the Hydra may be judged by appearance, ac¬ tivity, and appetite. One of these parasites is shown in side view (Fig. 130&). It is shaped like a short dice-box, with a circle of fine cilia at each end, but none on the rest of the body. It glides along Fig. 1306. Trichodina HYDRAS. 161 rapidly on tlie ends of the dice-box, running out to the tips of the tentacles and skirting fearlessly around the edges of the mouth. It is the Trichodma pediculus. The Hydra also occasionally has another form of In¬ fusorial parasite running over its skin. This is some¬ what kidney-shaped, and has cilia only on one surface of the body. It is called Kerona polyporum. It does not seem so common as Trichodina. If the observer desires to preserve the Hydra as a per¬ manently mounted object for the microscope, he may be easily gratified, thanks to Mr. A. II. Breckenfeld,* of San Francisco, who has devised an admirable method which the writer has tried and recommends. Transfer the Hydras to a slip in a large drop of water, where they can be seen if the slide is held over white paper. When their tentacles are fully extended, “ quickly move the lamp directly under the drop, with the top of the chimney about an inch beneath the slide, and hold it in that position for about three to five seconds, the exact time depending principally upon the intensity of the heat. Then quickly remove the slide and place it upon a slab of marble or metal. When cool, pour the drop containing the zoophytes into the prepared cell on the slide which has been held in readiness ; add a drop or two of a suitable preservative fluid, arrange the little animals if necessary by means of a needle or camel’s- liair brush (using very great care, however, as the ten- * American Monthly Microscopical Journal, March, 1884, p. 49. 162 MICROSCOPY FOR BEGINNERS. tacles will be destroyed by the least rough handling), cover with thin glass, and finish as in the case of any fluid mount.” I have not found it necessary to use two slips of glass. If a deep shellac cell that has been made for some time and is perfectly dry and hard is used, the Hydras may he placed in it and there cooked and al¬ lowed to remain. When cold, arrange the arms if neces¬ sary, add a drop of weak glycerine and water, and ce¬ ment the cover -glass with shellac. The Ilydras thus prepared can he kept indefinitely, and at any time shown to admiring friends. Both the green and the brown species are abundant duiing the summer among Anacharis and Lemna. SOME AQUATIC WORMS, ETC. 163 CHAPTER VII. SOME AQUATIC WORMS, CII^ETONOTUS, AND CniRONOMUS LARVA. The collector of microscopical objects from the ponds and slow streams is doubtless familiar with the appear¬ ance of tlie bristle-bearing worms (Fig. 140), on account of their general resemblance to those long-suffering creatures which he in his youth impaled on a hook and with them sought the nearest water. The extensive bristles of the aquatic worms are an addition which greatly lessen their resemblance to the common earth¬ worm, and their transparency is another characteristic that may temporarily mislead the observer, but their elongated bodies and general worm-like aspect tell the story. In addition to the bristles which most members of this class possess, there are usually two or more rows of long, curved spines (Fig. 141) on the ventral or lower surface. These can be protruded or withdrawn into the body at the possessor’s will, and when pro¬ truded are used to assist the worm to crawl. They are therefore called the podal or foot spines. They may not .be noticed when retracted unless specially searched for. Having observed them and the bristles in a row on each side above them, the student need have no trou¬ ble in knowing where to class the worms ; but with an- 8* 164 MICROSCOPY FOR BEGINNERS. other division of the group the beginner may not fare so well. These have flattened, usually almost opaque bodies, with the entire surface densely clothed by fine cilia, and, probably on account of the stir and disturbance which the cilia make in the water, naturalists have classed the worms together under the name of the Tur- bellaria , from a Latin word meaning a stir or bustle. Their motions are rapid, and apparently without effort. They glide smoothly and swiftly over submerged objects, or swim back downward on the surface of the water. There is still another group of common aquatic worms, but to recognize them will give even the begin¬ ner very little trouble. They are often rather sluggish in their movements. They have a perfectly transparent, smooth, thread-like body, which is apparently truncate in front, and is prolonged posteriorly in a sharpened, point-like tail. They have no bristles nor cilia, and they rather closely resemble a microscopic eel ; indeed the scientific name, Anguillula means a little eel. Many members of all these classes are found in the superficial sediment of shallow ponds, in the crevices of wet and water -soaked logs, under submerged stones, among the leaflets of Myriophyllum, Sphagnum, and other water-plants. Sphagnum seems a favorite place for several kinds. I have obtained members of five genera, JVdis, Pristina «, Dero , Chcetogaster , and yPolo- soma, by placing a little piece of the moss in a watch- glass with a small quantity of water, and gently tearing SOME AQUATIC WORMS, ETC. 1G5 away the leaves with needles, when the concealed worms hurried out and ’were readily captured with the dip¬ ping-tube. If the watch-crystal stands on black paper the wrork is facilitated, as the translucent worms then appear to the naked eye as minute, writhing, silvery threads. In this chapter the reader will also find descriptions of two very common microscopic aquatic animals, one of which is certainly not a worm, the proper position of the other being rather doubtful. They are Chcetonotas and Chironomus larva (Figs. 131, 132), both having some¬ what worm-like bodies. They are here referred to for the convenience of both reader and writer. The begin¬ ner will be quite sure to at first mistake Chironomus larva for a worm. The bodies of all the worms are very soft and easily injured. It is best, therefore, in studying them to use a cell shallow enough to somewhat restrain their move¬ ments, when the cover-glass is added, but deep enough to avoid undue pressure, or they will rapidly go to pieces. The following Key will assist the beginner in deter¬ mining to which class his worm may belong, leading to the names of the groups under which some of their generic titles may be found : 1. Body with four leg-like appendages bearing hooked bristles ; eyes distinct ; head large, brownish - red. Chironomus larva , I. 2. Body without leg-like appendages (a). a. Tail forked ; mouth small, circular, on the front 166 MICROSCOPY FOR BEGINNERS. part of the lower or ventral flat surface ; back convex, usually bearing spines, prickles, or scales. Chcetonotus , II. a. Tail not forked, but often bearing finger-like ap¬ pendages (b). b. Body entirely and finely ciliated, usually flattened. Turbelldria , III. b. Body smooth, without cilia, bristles, or spines ; tail pointed. Anguillula , IV. b. Body with bristles, podal spines, or both. Oligo- chceta , V. I. Chironomus larva (Fig. 131). Chironomus larva has a worm -like, more or less jointed, colorless body, eight or nine times as long as wide, a large head, the mouth parts usually being dis¬ tinctly apparent. The four short rudimentary leg-like appendages are in pairs on each end of the long body, the brownish hooks or strong curved bristles on their extremities being more or less retractile, while two clus¬ ters of long bristles spring from the upper surface near the posterior border of the animal. The perfect in¬ sect into which this larva will develop is a two-winged fly resembling a mosquito. These are often seen in great numbers above the ponds and marshes. The spe¬ cies are very numerous, and have never been studied by American entomologists. The eggs are very common on sticks, floating chips, or other objects in the water. They are deposited in a SOME AQUATIC WORMS, ETC. 167 mass of jelly, liuge in bulk when compared with the size of the insect, the eggs appearing as distinct but minute, often brownish, specks, arranged in beauti- fully regular rows. Fig. 131 — Chironomus larva. It is always interesting as well as important for the collector to take home all the little jelly-like egg masses which he may find attached to submerged objects. If placed in a watch-glass or an “individual” butter-dish, and the water kept fresh and pure, they will usually hatch, and thus give the observer valuable information often not otherwise obtainable. Chironomus eggs can hardly be described so that the beginner shall recognize them at first glance, but if once hatched at home they will afterwards always be known. The first little mass of jelly experimented with may prove to be snails’ eggs, but they will be none the less interesting. They may also prove to be the eggs of water-mites (Chapter XI.). The beginner will, of course, not mistake the green jelly globules of Chsetophora for insect eggs. II. CmETONOTUs (Fig. 132). There are several species of these lithe and graceful little creatures in our fresh waters, and they so closely resemble each other in external form that they can be distinguished only by the cuticular appendages, or the coat-of-mail by which most of them are protected. 168 MICROSCOPY FOR BEGINNERS. They are readily to be found by fishing for them with a dipper, as recommended for Rhizopods, as they are fond of edidino; over the soft ooze at the bottom of shal- low ponds. If the collector will also sweep his dipper under the lily leaves and among the submerged stems of Nuphar, he will not be disappointed. The animal consists of a free-swimming, flexible, and elongated body, the anterior extremity usually enlarged to form what may be called the head, a slight constric¬ tion behind this part constituting the neck ; the central portion of the body is formed with convex Fig. 132. _ chsetonotns larus. lateral borders and a more or less strongly convex back or dorsum, this region being variously appendaged with spines or scales, and suddenly narrowed to produce the posterior ex¬ tremity, which is forked, and bears two conspicuous tail¬ like prolongations. The lower or ventral surface is a flat and nearly level plane extending the entire length of the body. It bears one longitudinal band of cilia near each lateral border, seldom more. The head is usually some¬ what triangular, and formed of three or five rounded lobes. It has two tufts of vibratile hairs on each side. The mouth is on the ventral surface of the head, and under a moderate amplification seems to be a circular opening, but with an objective of high power it will be found to be somewhat complicated. The whole upper surface of the body is, in the differ¬ ent species, covered with rounded papillae, scales, spines, SOME AQUATIC WORMS, ETC. 169 or prickles, or with, both scales and spines at the same time. In the latter kinds the scales cover the back and sides, and the spines spring from these appendages, arch¬ ing back towards the forked tail. And in all cases these little scales are imbricated, or overlapping like the shin¬ gles on a roof, only they have the curious habit of lap¬ ping in what seems to be the wrong way, that is, their free margins point towards the animal’s head, or in a direction just opposite to that of the scales on a fish. They are usually minute, and require high powers to see them properly. The two caudal prolongations are movable and flexi¬ ble. Their chief use seems to be to anchor the animal to the glass slide or cover, or to some object in the wa¬ ter, clinging with the tips, and apparently assisted by a secretion that is supposed to exude from them, this sticky fluid passing from two ovate glands usually visi¬ ble in the upper or anterior part of each. The mouth opens into a very muscular oesophagus, which itself opens into the intestine, a tapering, tubular passage lined with nucleated cells and passing in almost a straight course along the median line, terminating be¬ tween the two caudal prolongations. If the observer can get the animal in such a position that he can focus down on the front of the head, he will see that the cav¬ ity of the oesophagus is triangular. It is not very diffi¬ cult to do this, since the little creatures are exceeding¬ ly restless; they are continually turning and writhing about, and lifting the head in various directions. It can 170 MICROSCOPY FOR BEGINNERS. often be seen in tlie animal while still in the egg, for even there, when almost ready to escape, it is also very restless. The eggs are often found on the slide, with the young Chsetonotus doubled up within. The eggs by which Chsetonotus is reproduced are formed in an ovary placed in the median line of the body immediately above the intestine. Usually only one egg is formed at a time, but it is not rare to see two or more in various stages of ovarian development. Upon the absence or presence of an egg in the ovary depends, to a great extent, the degree of convexity of the back. The eggs are dropped anywhere in the water, and left to the care of nature. The food consists of the minute particles of decayed animal and vegetable matters so abundant in the soft surface of the mud at the bottom of our shallow ponds. These particles are taken in with a peculiar and a sud¬ den snapping movement of the cavity of the oesophagus, easily to be seen but difficult to describe. Diatoms are rarely swallowed. So far as their classification is concerned, these attract¬ ive little animals have given naturalists a good deal of trouble. Some have said that they belong with the Rotifers ; others have placed them among the Infuso¬ ria; others have called them low wTorms, putting them among the Turbellaria ;• and still others think, and they are doubtless correct, that Chgetonotus should stand in a group by itself, among the worms, and not very far from the Rotifers. SOME AQUATIC WORMS, ETC. 171 They are all rapid swimmers, and on that account are rather difficult to study, but by following one for a little while, it will usually settle down and begin to seek food, and that is the observer’s opportunity, un¬ less he desires to kill the specimen, and study it after death. The following Key leads to some of our common forms : Key to Species of Ckcctonotus. 1. Upper surface with neither spines, prickles, nor scales (a). 2. Upper surface bearing scales only ( b ). 3. Upper surface bearing spines or prickles only ( c ). 4. Upper surface bearing both spines and scales ( f ). 5. Upper surface bearing posterior spines and anterior prickles (y). a. Back smooth and naked, not furrowed, poclura, 1. a. Back transversely furrowed, sulcdtus , 2. a. Back covered with small hemispherical elevations, concinnus, 3. b. "Caudal branches of moderate length, scales round¬ ed, loricdtus , 4. b. Caudal branches very long and jointed ; scales very small, rhombic, rhomboides , 5. c. Spines covering the entire upper surface ( d ). c. Spines not covering the entire upper surface ( e ).% d. Spines long, mouth beaded, mdximus , 6. d. Spines short, mouth not beaded, larus, 7. e. Spines eight, in two longitudinal rows of three 172 MICROSCOPY FOR BEGINNERS. each, with one anterior and one posterior central spine, octondrius, 8. e. Spines in two transverse rows, not projecting be¬ yond the ends of the caudal branches, spino- sulus , 9. e. Spines in two transverse, highly - arching rows, the posterior longest and projecting beyond the ends of the caudal branches, longispinosus , 10. f. Each with a subcentral, transverse hedge of large spines, scales double, acanthodes , 11. f. Back without a distinct spinous hedge, scales not double, spinifer , 12. g. Spines in four transverse rows, five spines in each, acanth6pho7'us , 13. g. Spines in transverse rows, less than five spines in each, enormis , Id. 1. ClEETONOTUS PODURA. Chcetonotus , or bristle-back, is rather a misnomer for a species with a perfectly smooth dorsum, yet such a one is not uncommon. The spines and other dorsal ap¬ pendages are here represented by two hairs standing al¬ most vertically on the neck, and two on the rear part of the back. These are usually seen with difficulty, but they are present on all the species, even the scaly and the spinous ones. The egg of this species is also smooth. Ehrenberg called this Icthydium po - dura. SOME AQUATIC WORMS, ETC. 173 2. ClEETONOTUS SULCATUS. The characteristic of this form is in the deep trans¬ verse furrows conspicuously developed on the back and sides. The body is transparent, and unusually soft and flexible. The posterior region between the arch of the back and the caudal furcation is narrowed, and much longer than in other species. The oesophagus is short, being not more than one-sixth the length of the body. 3. ClLETONoTUS COfiCJNNUS. The back and sides, which are more nearly parallel than in most species, are closely covered by small hemi¬ spherical elevations arranged in oblique lines and giving the animal a peculiarly neat and attractive appearance. The two caudal glands are unusually large and conspic¬ uous. 4. CmETONOTtTS LORICATUS. The scales on the back and sides are arranged in im¬ bricated rows, the convex free margins being directed for¬ ward. Although so completely covered, the body is very flexible, the scales freely sliding over each other when the animal curves to one side. The mouth is obliquely placed, as may be seen when the Chaetonotus is viewed in profile, and its internal margin is strongly beaded. The eggs are armed by hollow papillae, or by short hol¬ low spines whose summits are bifid or emarginate. 5. ClEETONOTUS RIIOMBOIDES. This is easily recognizable by the peculiar head, the 174 MICROSCOPY FOR BEGINNERS. minute rhombic scales covering the hack and sides, and by the remarkably long and jointed caudal branches, each of the latter forming from one-third to one-fourth of the entire length of the body. The animal is the largest yet discovered, measuring -g1^ inch long. The caudal branches are composed of about twenty sections or joints, each of which is slightly constricted. The head is broadly rounded, and formed of three lobes, one front¬ al and two lateral, the former terminating on each side in a single, acuminate, hook-like process, habitually in close apposition with the anterior region of the lateral lobes, of which the posterior extremities also terminate each in a single hook-like continuation, rather more con¬ spicuous than those at the front. The mouth is beaded, and has immediately behind it on the ventral surface a deep, narrow, transverse, and slit-like depression, rather less than one-lialf as long as the diameter of that part of ' _ the head. This is the only known Chsetonotus with this problematical feature. The back and sides are completely clothed by minute, imbricated, rhombic scales, their front, pointed margins being directed towards the head. They are not more than -g-oVo inch in length, and when examined with a high power (one thousand diameters) they present a beautiful appearance. The lateral margins then seem to be thickened, and the posterior border of each scale appears to bear a minute supplementary scale. in the shape of a triangle. Although the beginner may not be able to distinctly SOME AQUATIC WORMS, ETC. 175 see these scales, the very long caudal branches with their joints, and the sulcation behind the mouth, will be sufficient to identify the specimen. 6. ClUETONOTUS MAXIMUS. The back and sides are covered with spines which are often rather longer on the posterior region than else¬ where. They are arranged in longitudinal parallel rows, yet they often seem to be irregularly scattered, so that the animal presents an untidy, dishevelled, and disrep¬ utable appearance. The spines are minutely forked near the free ends. The branching is very uneven and is easily overlooked, one branch being very small, often scarcely more than a minute linear projection. The ventral cilia are in two longitudinal lateral bands, and the space between is clothed with short, hispid, re¬ curved hairs, two or more long fine bristles projecting from the same part beyond the posterior border, be¬ tween the two caudal branches. 7. Celetonotus larus (Fig. 132). The whole upper surface is clothed with short, conical spines in longitudinal rows, these appendages being re¬ curved and not branched. They are often largest pos¬ teriorly. The mouth is not beaded. The ventral cilia are in two broad longitudinal bands near the lateral mar¬ gins, and the intervening space often bears two addi¬ tional parallel lines of cilia, which may be absent from some specimens. These cilia, as in all the species, sub- 176 MICROSCOPY FOR BEGINNERS. serve locomotion. The egg is smooth, or hispid with short hairs. 8. ClUETONOTUS OCTONAltIUS. This is a small, active form, readily recognizable by the arrangement of the recurved dorsal spines. These are unequally branched, and placed in two lateral lon¬ gitudinal rows of three spines each, with one anterior and one posterior central thorn. It seems to be the least common of the species. 9. ClI/ETONOTUS SPINOSULUS. The back usually bears seven unequally furcate spines in two transverse rows — four spines in the anterior series, three in the posterior. Occasionally the lateral thorns in the posterior row are suppressed, and in some indi¬ viduals the front series contains but three. The lateral body-margins are bordered by short, conical setrn, which are constant in all the specimens thus far observed. The rest of the upper surface is without appendages of any kind, except the four tactile vertical bristles present in all species. The egg is hispid with short hairs. 10. ClI.-ETONOTUS LONGISPINOSUS. The spines vary from four to eight, the latter being the usual complement. They are nearly one-half the length of the body, and curve upward and backward in a wide arch from the centre of the back. In front of the anterior row the surface is setose with stiff, recurved bristles, and the body- margins are fringed by coarse, SOME AQUATIC WORMS, ETC. 177 rigid setae. The dorsal spines are always in two trans¬ verse rows, but the number varies from four in each to three in one and five in the other. They are unequally furcate. 11. ClEETONOTUS ACANTnODES. The upper surface of this form is wondrously well protected. It possesses both spines and scales, the lat¬ ter imbricated, and their somewhat pointed free margins directed forward, each one bearing a small supplement¬ ary scale or scale-like thickening on its posterior part, from which springs a recurved, unequally furcate spine. Near the body-centre the dorsal surface is traversed by a series of large stout spines rising obliquely upward and backward, and forming a kind of spinous hedge, the surface behind these appendages bearing few small conical thorns or none. The body margins are fringed by short spines. The central space on the ventral as¬ pect between the two longitudinal, lateral bands of cilia, is beset with short, fine, recurved prickles, and five or more long bristles project from the same surface beyond the border of the posterior bifurcation, while on each side of the body near the posterior extremity there are two large recurved spines. The animal is usually found among Sphagnum. 12. Ch^etonotus spi'nifer. Among Riccia and Lemna in shallow ponds this wTell-armored form is not rare. The upper surface is covered by rounded imbricated scales, the free margins 178 MICROSCOPY FOR BEGINNERS. directed forward. From each scale there arises a stout, recurved, unequally and minutely furcate spine, whose base is enlarged and thickened. These spines do not commonly originate from the centre of the scales, but near the posterior part, and between the margins of those laterally contiguous. The spines are largest and stoutest on the back proper, decreasing gradually over the neck and head, and rapidly over the posterior parts, while across the dorsal surface immediately in front of the caudal bifurcation there extends a supplementary series of four thorns, longer and stouter than those on any other part of the body. The posterior region of the space between the longitudinal ventral bands of cilia bears five bristles, arranged to form a long triangle, the apex pointing forward. The eggs vary considerably in external ornamenta¬ tion, showing three patterns. In one, the ends and one side bear low, stout, hollow processes, whose apices are truncate, and four or live parted when viewed from above. In another, the appendages are long, hollow, conical spines, whose distal ends are trifid or quadrifid, the branches in profile appearing very fine and delicate, but when viewed from above are seen to taper to the ends, where each terminates in a widely spreading fur¬ cation. In the third form, one side and both ends are covered by an irregular net -work of raised lines, the meshes being four or five angled, while the opposite side is rugose with fine, minutely sinuous lines. SOME AQUATIC WORMS, ETC. 179 13. ClEETONOTUS ACANTIIOPIIOIIUS. The superior surface of the head aud neck and the lateral body-margins are clothed with recurved prickles or short spines, while the dorsal region proper bears four rows of long thorns, each row curved towards the head, and each formed of five unequally furcate spines, with an additional one on both sides near the posterior extremity. The spines rise from an enlarged base, so that the animal is almost completely clothed in an armor composed of these basal enlargements. 14. ClI/ETONOTUS enokmis. The upper and lateral surfaces of the head and neck are clothed with short, recurved prickles, which also ex¬ tend along the ventro-lateral margins. The central and posterior parts of the back bear thirteen posteriorly di¬ rected, but only slightly curved, spines arranged in transverse rows, with three in the first row, four in the next following, two widely separated in the third, three in the fourth, while the fifth series consists of a single centrally located one. On each side near the posterior margin are two long, conspicuous, and recurved thorns, apparently belonging to the series of small spines fring¬ ing the lateral body-margins. III. turbellAria. The ciliated or Turbellarian worms seem to prefer the bottom of shallow ponds, probably because the food- supply there is better and more easily obtained. They 9 180 MICROSCOPY FOR BEGINNERS. are soft and flexible, and some are quite changeable in shape, having the power to lengthen themselves, to ex¬ tend the posterior border into a short projection, or to narrow the front into an apology for a head. Some, however, have the front part naturally prolonged into a short snout. They are usually brownish and almost opaque, the opacity being increased by the large amount of food commonly present in the stomach. The cilia clothing the entire surface are visible only under a high power. The result of their motion, how¬ ever, can be seen with the one -inch objective, as they produce currents in the water that sweep small objects quite rapidly away. Two or more small black or reddish eye -spots are often present near the front border, and in some of these worms may be quite complicated in structure, having a covering that may not inappropriately be called a cornea, a refracting body corresponding to a crystalline lens, pigmentary or coloring matter, and a nerve. The position of the mouth varies widely in the differ¬ ent families. It may be at or near the front border, at some point nearer the centre of the body, or even close to the posterior margin. It is usually large and expan¬ sile, and is often followed by a large and very muscular organ called the pharynx, which some of the worms can protrude, and with it snap up their living prey. The lining of the pharynx may be finely ciliated. The stomach occupies the largest portion of the body, SOME AQUATIC WORMS, ETC. 181 usually extending from the pliarynx to the posterior border. In some it is simply a great sack, receiving all that the mouth and pharynx turn into it ; in others it divides into many branches whose terminations may be seen near both sides of the body. The stomach seldom has a posterior opening, for, as a rule, there is no intes¬ tine. After the nutriment has been digested from the food, the insoluble remains must be ejected through the mouth. It is no unusual sight to see one of these ciliat¬ ed worms vomit up a mass of indigestible and empty Bhizopod shells, Botifer carapaces, with many unrecog¬ nizable particles and fragments. They seem to prefer animal food, usually selecting Bhizopods and Botifers, but they are as fond of Infusoria, which must be as nourishing and more easily digested. 1 have more than once lost an interesting specimen of Infusorium because one of these Turbellarian worms had been included un¬ der the cover-glass : there were a worm and an Infuso¬ rium ; a pause, a single snap, and only the worm re¬ mains. They are propagated in two ways — by eggs and by transverse fission ; that is, one worm divides across the middle and so makes two, each of these again dividing. And often before the division has been accomplished both halves are also partly divided, so that the single body seems to be formed of several incomplete worms. The eggs of the commonest species are brownish egg- shaped bodies, dropped anywhere in the mud or water, or they may have a stem which attaches them to sub- d d 182 MICROSCOPY FOR BEGINNERS. merged objects, and from which they are easily broken. The latter kinds are readily recognized, being formed of a yellowish brown, transparent membrane, egg-shaped, and with the stem almost equalling their own length. If the observer be fortunate he may see the worm es¬ cape by pushing oil the top of the egg, which falls awTay like a round cover, leaving an empty case shaped like a deep cup. These empty vases are often found at the bottom of long-standing collections of plants. The Turbellarian worms are very common, but the beginner can scarcely hope to learn the generic name of each one that he may find. He will be safe, however, if he refers to them all as Turbellarians, or Turbellarian worms. The subject has not been studied very exten¬ sively by American naturalists, and there is, consequent¬ ly, nothing in the language to which the beginner can be referred for help. The worms are often visible to the naked eye as minute whitish or flesh - colored floating bodies, or as small bits of white thread. There are two forms fre¬ quently met with which are huge when compared with most of these ciliated creatures, needing no microscope to identify them. Both are found on the lower sur¬ faces of submerged stones or sticks, or gliding over the sides of the collecting-bottle. The body of one of these may be about half an inch in length and about five times as long as broad. It is opaque and almost black. Hear the anterior border are two black eyes, which are conspicuous on account of the SOME AQUATIC WORMS, ETC. 183 oblong white space in front of each. The mouth is near the centre of the body, opening on the lower or ventral surface. The worm glides smoothly and quite rapidly over a submerged surface. Naturalists have named it Planaria torva. The second one referred to somewhat resembles Pla¬ naria torva , but is usually smaller, and has the head end more nearly triangular. It is similar in its movements and in the presence of two black eyes near the front border, each at the inner margin of a white space, thus giving the worm a cross-eyed appearance. The body is nearly white, and has a dark line passing lengthwise through the centre and giving off on both sides many short branches which are themselves often branched, these dark lines on the white body giving the latter a very pretty appearance. They are not for ornament, however, but are the branching stomach. The mouth is near the centre of the lower surface. The body may measure half an inch in length. It has been named urn lacteum. The entire surface of both these worms is finely and closely ciliated. The color of the body will at once in¬ form the observer which one he has captured. IV. ANGU1LLULA (Fig. 133) The body is thread-like, perfectly transparent and colorless, about fifteen times as long as broad, rather widest in the middle, whence it slightly tapers towards both ends. The frontal border is rounded, but with a 1S4 MICROSCOPY FOR BEGINNERS. low power appears as if truncated. The round mouth is at the centre of this end, and leads into an oblong pharynx or throat. The tail is usually long and sharply pointed. The worm’s movements are generally slow and deliberate, but oc¬ casionally it has a lively spell. They Fig. 133. — AnguUlula, are reproduced by eggs, one or more often being visible within the transparent body. Anguillulse are common in wet moss, among the leaflets of aquatic plants, and in the ooze of the ponds. The well-known “ vinegar-eel ” is an Anguillnla (An- guillula aceti ); and the paste-worm (A. glutinis) be¬ longs to the same genus. Some naturalists regard these as the same species. V. OLIGOCELETA. The fresh-water bristle-bearing worms whose bodies are never ciliated, show more or less distinctly that they are formed of segments or rings. Each segment often has on both sides near the back one or more long, fine, liair-like bristles extending into the water, and together forming a row along each side of the worm. On the lower surface there are two or more rows of thicker, inflexible, and gracefully curved spines, the rows being formed of clusters which have two or more spines in each, the free end of every one being usually divided by a deep notch, so that it appears like a double hook, the parts being unequal in size and degree of curvature. They are used to assist the worm to crawl, and are SOME AQUATIC WORMS, ETC. 185 therefore called podal or foot spines. They can be protruded from the body, or partially withdrawn into it, at the animal’s will. The long bristles are used to assist in swimming. In some of these worms both the bristles and the podal spines are present, in others one or the other set of organs may be absent. The spines, which with but few exceptions are pres¬ ent, are each gracefully curved like a long italic S, their shape resembling the line which artists have called the line of beauty. The free end, or the one projecting into the water, is forked in a way already described (Fig. 111). The body or shaft of the spine has, at some point of its length, a globular enlargement or a shoul¬ der, below which the spine is often much narrowed. These organs are used by being protruded and forced against the surface over which the worm is travelling. They are arranged in a row on each side of the ventral surface, each row being composed of many clusters, and each cluster of from two to ten podal spines. The worm can protrude several clusters at once, or two on the op¬ posite sides of the same segment or body-ring, but it seems unable to extend them irregularly. The bristles are very flexible, and are arranged in two rows on the sides, near the upper surface, one row on each side. They are usually much longer than the width of the body, and may be so arranged that there are several or only one on each lateral margin of the segment. They are sometimes accompanied by a straight spine much shorter than the bristle, and pro- 186 MICROSCOPY FOR BEGINNERS. jecting beside it. The free ends of these rudimentary spines are occasionally finely forked. The bristles are absent in some genera. The worms are usually visible to the naked eye as very fine whitish or yellowish threads, sometimes an inch or more in length when extended. They are found abundantly among aquatic plants, and in the mud of shallow ponds. When allowed to remain in the col¬ lecting-bottle they will often make their way to the lighted side, where some will form sheaths or protect¬ ive cases from various floating fragments or particles. The mouth may be close to the front end, or sonio distance back, since in a few worms the front border is extended as a long, flexible snout. The posterior border is rounded in many forms, while in others it is expanded into a broad, funnel-like region, with several finger-like prominences surrounding it. In such worms these parts are ciliated on the inside, the currents thus pro¬ duced being supposed to bring at least a portion of the oxygen needed for respiration. The alimentary canal extends through the centre of the entire body, and is usually crowded with the brownish remains of undi¬ gested food. The whole cavity of the body outside of the alimentary canal is filled with a colorless fluid visi¬ ble only by means of the movements of the corpuscles seen floating to and fro as the worm moves under the cover-glass. The beginner must not mistake this fluid for the blood, which in many of the bristle-bearing forms is red SOME AQUATIC WORMS, ETC. 187 and contained in two distinct vessels, one extending lengthwise above, the other below the intestine. These vessels unite at both ends of the body, so as to form a long, closed tube, with branches springing from the front part, or from the upper or dorsal tube as it passes through each segment, where they then appear as pul¬ sating loops. Usually the blood is impelled by the ir¬ regular pulsations of the dorsal vessel, a wave-like con¬ traction passing along and driving the blood before it. In two genera ( Tubifex and Ocnerodrilus) there are little pulsating hearts attached to the dorsal vessel in the neighborhood of the frontal border. Reproduction is by eggs or by tranverse fission, the latter being most frequently observed. Most of these worms live upon animal food, seeming to prefer Rhizopods and Rotifers to almost anything else ; a few are vegetarians. Key to Genera of Microscopic , chiefly Fresh-water , Worms ( Oligochceta). 1. Body with both bristles and podal spines (a). 2. Body with podal spines only ( h ). 3. Body with bristles only (f). a. Anterior extremity with a flexible, finger-like pro¬ longation. Pristina , 1. a. Anterior extremity without a finger-like prolon¬ gation ( d ). h. Podal spines forked ; worms aquatic (c). h. Podal spines not forked ; worms aquatic (g). 9* 188 MICROSCOPY FOR BEGINNERS. b. Podal spines not forked ; worms living beneath decaying bark of dead trees. Enchytrceus , 2. c. Podal spines, six to ten in each cluster, the clusters in two rows. Chcatogaster , 3. c. Podal spines, two only in each cluster, the clusters in four rows. Lumbriculus , 4. d. Posterior extremity without finger -like append¬ ages (. Lophophore circular. Fredericella , 4. tion only.) LOSSING’S FIELD-BOOK OF THE REVOLUTION. Pictorial Field-Book of the Revolution ; or, Illustrations by Pen and Pencil of the History, Biography, Scenery, Relics, and Traditions of the War for Independence. By Benson J. Lossing. 2 vols., 8vo, Cloth, $14 00; Sheep or Roan, $15 00; Half Calf, $18 00. LOSSING’S FIELD-BOOK OF THE WAR OF 1812. 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