conceive the latter as a separate branch of physics and mechanics. But we shall postpone the analysis of these endeavors, hoping that some opportunity may soon be offered to come to some more definite ideas out of the conflicting theories of the present moment. IV. WHEN Schwann, closely following upon Robert Brown's and Schleiden's work, published in 1839 his famous "Microscopical Researches," and came to the conclusion that all possible tissues of both animals and plants consist of cells, or of materials derived from cells, it seemed that the primary units the molecules, so to say-of which all living beings are built up, had finally been discovered. A small piece of structureless, granulated, jelly-like substance- the sarcode in animals and the protoplasm in plants-surrounded or not by a thin membrane, and containing a nucleus, this was the primary unit, giving origin to all the most complex and varied tissues. of this work, and the recent researches of Strasburger, Flemming, Guignard, and Fol, while fully confirming the broad gen. eralizations laid at the foundation of modern biology, revealed a wide series of new facts having a direct bearing upon the question of heredity, which is so much debated now in connection with Weissmann's views.* It appeared, first, from the above-mentioned researches, that protoplasm itself consists of, at least, two different substances; one of them being a minute network of very delicate fibrils, while the other is an apparently homogeneous substance filling up the interstices between the network. Then it became evident that the nucleus which makes a necessary constituent part of cells, has a still more complicated structure, and that it plays a most prominent part in all the phenomena of subdivision of the cells and those of reproduction. It consists of a nuclear plasm, surrounded by a very thin membrane; it contains very often a still smaller nucleolus; and within the nuclear This conception evidently gave a for-plasm the microscope discovers extremely midable impulse to science and to scientific thin threads, or fibres, consisting in their philosophy altogether, the more so as it turn of extremely thin minute granules, or was soon followed by a most important spherules - the whole appearing as a ball discovery which established the close re- of thread coiled up somewhat roughly.† semblance existing between the subdivi. This being the usual aspect of the nucleus, sion of cells and the phenomena of sexual a series of modifications begin within it, reproduction in plants and animals. Twen- when the moment comes for a cell to sub. ty-two years later, another still more divide. The nucleolus disappears; the important step was made in the same beaded threads, or fibres, shorten and bedirection, when Max Schultz published come thicker. They take the shape of his memoir, "Das Protoplasm," and minute hooks, and these hooks join toproved that the granular, jelly-like sub-gether (by the tops of the bendings) in one stance of the cells is identical in both the animal and vegetable kingdoms; that it is the very seat of all physiological activity, as it is capable of movement, of nutrition, of growth, of reproduction, and even of sensibility, or, at least, of irritability. Many must certainly remember the effect produced by the broad generalizations based upon Max Schultz's ideas by Haeckel in Germany and Mr. Huxley in this country, in his well-known lay sermon, "The Physical Basis of Life." However, if protoplasm were the seat of physiological activity; if it could move, grow, reproduce itself, and display irritability, was it still to be considered as a "structureless, granulated jelly or slime"? It was a world in itself, and the microscope had to be directed towards the further study of this world. So it was, by Lionel Beale, Schultze himself, Strasburger, and most histologists of renown. Discovery upon discovery was the reward point, the pole. By the same time the membrane of the nucleus is reabsorbed, and the surrounding protoplasm of the cell penetrates within the nucleus, thus mixing up together with the nuclear plasm. Thereupon a most important change fol Strasburger, Ueber Kern und Zell Theilung im botanique de France, 1890, t. 36, and Comptes Rendus, Pflanzenreiche, Jena, 1888; Guignard, in Bull. Soc. 1891, t. 112, pp. 539, 1074, and 1320; t. 113. p. 917 1891, Bd. 37, P. 249, and Anatomischer Anzeiger, W. Flemming in Archiv für mikrosk. Anatomie, 1891, p. 78. An immense literature has suddenly grown up upon this subject. Excellent résumés of the whole question have been given in English, up to 1888, by Prof. McKendrick in Proceed. Glasgow Philos. Soc., vol. xix. ; and to the end of 1890 by Sir William Turner, in an address, "The Cell Theory, Past and Present," delivered in October, 1890, before the Scottish Microscopical Society (Nature, vol. xliii., p. 11 and sq.) The albuminous matter of which these threads consist received the name of "nuclein," and the threads themselves were named "chromatin fibres," owing to their affinity to coloring matter. The transformations in the nucleus which have just been described received the general name of "karyokinesis," or nuclear movement." The names, as seen, are simply descrip tive. lows. Each of the thickened nuclein | is now formed by both coalesced nuclei, fibres, or threads, splits in its length, and surrounded by a radiation of the fibrils of the number of the threads being thus protoplasm. Then begins what Fol names doubled, one-half of them is attracted" the quadrille of the centres." Each of towards a radiated spindle-figure in one them divides into two half-centres, and all part of the cell, while the other half ar- four move, so that each half-centre of the ranges in the same way in its opposite male cell meets and coalesces with one part. The two radiated figures thus sep-half-centre of the female cell, and the two arate, and only then (if the nucleus sub-newly formed centres become the poles of divides in giving origin to two new cells) a attraction for the spindles of the nucleus. membrane, or parts of a membrane, grow The act of fecundation is thus not a simple between the two. After the separation, coalescence of two nuclei, originated from the fibres either coalesce with their ends, two separate individuals, as was supposed or return in the shape of a ball of thread. before; it also consists of the union of each two of the four half-centres originated in the protoplasm. It is a whole world undergoing a whole cycle of modifications. And yet this is not all. It appears from Strasburger's work that all the cells are not quite similar, but that the number of nuclein fibres varies from eight to twelve and to sixteen in various families of plants, the individuality of the types thus seemingly depending upon their number; while Guignard found that with several plants the cells which will be destined, after the division of the mother cell, to become the reproductive organs will always have but one-half of the normal number of fibres (say twelve), while those which are destined to become the vegetative organs will have the full number say, twenty-four. The former will acquire the full number of fibres only after fecundation. Are, then, the cells differentiated from the first moment of their bi-partition? And what part does the number of chromatin fibres play in that differentiation? Further complications are discovered through the study of the protoplasm itself. It was known some time ago that there are, in the animal cells, two peculiar spots, surrounded by rays of sarcode, which were named spheres of attraction, or directing spheres, or centrosomata, or simply "centres." The same minute centres have now been found by Strasburger and Guignard in vegetable cells also, and it appears that these bodies, essentially belonging to the protoplasm not to the nucleus -take a leading part in the phenomena of reproduction. Professor Fol, who carried on his researches with eggs of sea-urchins, saw that when the elements of the male cell have entered the female cell, the centre of the former separates from the top of its nucleus and joins the centre of the latter. Both lie close to one another; then they become elongated and take positions on the opposite sides of the nucleus, which Report upon which the Prix Bordin was awarded to Guignard, in Comptes Rendus, December 21, 1891, P. 917. The interest attached to these minute changes is great, on account of their consequences as regards the theory of heredity. The observations of Fol, and the quite analogous observations of Guignard as regards plants, would only confirm the doubts expressed by Sir William Turner in his address before the Microscopical Society, as to the germ plasm being "so isolated from the cells of the body generally as to be uninfluenced by them, and to be unaffected by its surroundings;" and they would give further weight to its restrictions as regards Weissmann's theory of heredity. However, the questions at issue are so complicated and so delicate, that further research is wanted, and eagerly expected by specialists. But what is protoplasm itself? What is this jelly-like matter which exhibits all phenomena of life? Science has not yet given a positive answer to this great question. On the one side, we have the germs of an opinion, shared by some biologists who are inclined to see in protoplasm an aggregation of lower organisms. Thus R. Altmann † and I. Straus consider that the granulations of protoplasm are the essential and fundamental elements of the organic being. As to the cell, it is not, in Altmann's view, an elementary organism, but a colony of elementary organisms which group together according to certain rules of colonization. They constitute the protoplasm as well as the nuclear plasm, and they are the morphological units of all living matter. These granules, he maintains, are identical with microbes; their shape, their chemical reactions, their movements, and their secretory functions are similar; but the granules of the pro toplasm differ from bacteria in not being | origin. The compound eye consists, as capable of a separate existence. They known, of hundreds and thousands of can only live in cells. It is absolutely impossible to say, at the present time, how far this view may find support in ulterior research, though it must be mentioned that it is derived from elaborate investigations into the cells of various glands and their secretions, and that it finds support in facts accumulated by many well-known anatomists. It must also be added that some biologists namely, J. C. Vogt-go a step further and maintain that all micro-organisms, and all cells of more complicated organisms, are structures of a fourth or higher order; they are colonies of "polyplasts," which themselves consist of "monoplasts," or those granules which are distinguished in the protoplasm and the nuclear plasm. But, on the other side, we also have the other extreme view, supported by the authority of Professor O. Bütschli, who sees in protoplasm nothing but a foam, quite similar to the foams which may be artificially produced, and who maintains that all phenomena observed in living protoplasm are simply physical and chemical processes. The great question as to what protoplasm is, evidently will not be solved soon. But the above-mentioned researches will give an idea of the problems which at this moment absorb the attention of biologists. One important step has certainly been made the complicated structure of protoplasm has been recognized, and the exploration of the vital processes in "living matter" now stands on a firm footing. v. IT is known that Darwin, when he be gan thinking about the possible origin of the eye, used to feel a kind of shudder in consequence of the difficulties standing in the way. An important step towards smoothing these difficulties has now been made by Professor S. Exner, who has brought out an elaborate and richly illustrated work on the eyes of crustaceans and insects, and by Mr. Watase, who has studied the question as to their possible The author names Gianuzzi, Ranvier, Renaut, and partly Henri Martin. Das Empfindungsprinzip und das Protoplasma, auf Grund eines einheitlichen Substanzbegriffes, Leipzig, 1891; Journal of the Microscopical Society, February, 1892. Prof. R. Greef's exploration of the motor-fibrils of the A maba terricola (Biologisches Centralblatt, November, 1891, pp. 599 and 633) may be mentioned as an illustration of such researches. Die Physiologie der facetten Augen von Krebsen und Insecten, Leipzig, 1891. separate conical, almost cylindrical, parts, All stages of evolution of the eye may be studied among the insects and the Arachnides. Thus, beginning with the eye of the Limulus, Mr. Watase shows how it may have originated from a simple minute cavity in the epithelium. The sensitive cells lie in direct continuity with those of the epithelium, or hypodermis; and a cavity, with a pigment cell therein, and covered by epithelium, may represent the first rudiment of the eye. Later on the cavity deepens, and the roughly con "On the Morphology of the Compound Eye of the Anthropodes," in "Studies from the Biological Laboratory, Johns Hopkins University," vol. iv. (Bal timore). ical thickening of the epidermis which | exhausted, while the dark lines under her fills it becomes the "lens cylinder." A succession of drawings made by Mr. Watase upon the simplest forms of the ocellæ of larvæ and some millepeds perfectly well illustrate the various possible phases of evolution of the eye, from the minute cavities, or ocellæ, which appear in great numbers, closely packed together, to the more complicated eyes described by Exner. We thus have in Mr. Watase's work, confirmed by another work, by M. Kishinouye, a most valuable contribution to the solution of one of the complicated problems of the doctrine of evolution. We can only mention several very interesting works on the origin of the prickles in various plants, on the effects of high altitudes upon animals, on the compound structure of the higher plants and the effects of atavism, and so onall resulting from the modern endeavors of many biologists at explaining the origin and development of variations in animals and plants under the effects of their surroundings. A good deal of attention being paid now to the chapter of "direct adaptation" in the theory of the evolution of species, many interesting facts are continually brought to light by the work of the modern followers of Lamarck. IT was about half past five, on a March afternoon some few years ago, when Gertrude Hurst, worn out with a long morning of teaching, and a long afternoon of correcting books, let her pen slip from her hand, and leaned back in her armchair, just for a few moment's laziness. "I will not even shut my eyes," she said, as though in excuse to herself for this unwonted indulgence. But Nature inexorably claims her own, and before many minutes had passed, this tired London high-school teacher had fallen fast asleep. Her arms rested listlessly on each side of the chair, and her head was pressed against its cane back. There was a worried look on her thin face; and indeed her whole strength seemed eyes told a story of study protracted late into the night. She was dressed in some kind of loose-fitting gown, of a style free and unfashionable; her dark-brown hair was cut short, in the way that many girls now choose for comfort and convenience; not any of her features were beautiful, but there was the beauty of thoughtfulness about her face. Her table was strewn with exercise and lesson books, and a few set apart were obviously for her own private work, being several volumes of biology, inorganic chemistry, and physics, and Salmon's "Conic Sections," and Smith's " Analytical Conics," and two or three frowning treatises on trigonometry. Her little sitting-room, rather comfortless in its poverty, had for ornaments two or three photographs of pictures from the National Gallery, and a photograph of Watts's beautiful picture of "Hope." This picture faced Gertrude Hurst's writing-table, so that every time she raised her eyes from her work, they fell naturally there. The other ornaments of the room were a few books, held together by a home-made book-shelf. On the fire the kettle was boiling merrily, waiting impatiently until it should please the lady to fill the little black teapot which was reposing in a corner of the fender. A shabby white cat was sitting upright on the hearth, contemplating with learned gravity some loose sheets, which had fallen to the ground, and which were covered with figures and signs having something to do with parabolæ and tangents, asymptotes and other mathematical mysteries. The room was evidently that of a solitary student, and yet the slight figure of the girl yonder seemed so childlike, that at first sight she might well have been taken for a child; only on closer inspection one could see that she had lived through years of toil and of sorrow, and had learned things which time alone can teach. Gertrude Hurst must have been sleeping for more than half an hour, when some one knocked at the door. Receiving no answer, the person asking for admittance refused to be kept waiting any longer, and opened the door for himself and looked into the room. Then, seeing the sleeper in the armchair, he stood hesitating what to do. "Poor tired child!" he whispered; "she is worn out with work." He went gently up to her side and bent over her, and stooping down, picked up the pen which had fallen from her hand, and replaced it on the inkstaud. He lin gered by the fireplace as though he were | before his time; but the enemy, consump reluctant to go away. "I suppose I ought to go," he said to himself; "for she thinks I am still in Australia, and I should startle her on her first awakening." And again he murmured to himself: "Poor child! she is worn out. I am glad I have come home to help her." Perhaps he would have really gone; but at that moment the black kettle boiled over, and Elkin Annerley bent down to rescue it from the indignant fire, whilst the shabby cat looked calmly on, as though it understood all about the proceedings, and did not intend to ruffle itself on ac count of an agitated kettle. The kettle was placed in safety on the hob; and Elkin Annerley was just turning towards the door, when he suddenly caught sight of those papers lying under the armchair. And a few well-known hieroglyphics arrested his attention, everything that was mathematical in him arose in excitement. He took up the loose sheet as though it were some precious gem, and began to examine it; then he frowned and shook his head, and mechanically drawing a pencil out of his pocket, he made some few corrections. "The whole thing is wrong," he said impatiently; "waste of time and waste of paper. She ought to be ashamed of herself, after all my teaching, too." He snatched from the shelf a large book on which to fix the paper, and he settled himself in a low chair near the fire, and rested his feet against the fender. He was soon lost in the interesting and absorbing nature of his work; and to judge from the far-away look on his face, he had probably forgotten everything save the one important fact that here was a most intricate problem badly worked out, in defiance, too, of some of the most elementary mathematical rules and formulæ. "This is just the sort of carelessness to irritate me," he said. "Perhaps it is a good thing for my pupils that I am not now teaching mathematics." His face cleared, though, when he turned over the page and found some other problems cleverly worked out. "Come, come," he said, "this problem redeems the other." And with the old instinct of a master, he put V. G. at the end of it, and signed his initials E. A., smiling somewhat mournfully as he did so. He was a man of about thirty years of age, very frail, and of medium height. He had the appearance of being worn out tion, had not been able to rob him of everything, and there was still a pleasing sort of defiance in the way in which he carried his head a head which had not submitted itself to the doubtful mercies of the conventional barber. His eyes seemed fixed on distant objects, as though they were trying to penetrate into that Infinite which is the pleasure-ground of all mathematicians. For a mind bent on tangents and parabolæ and hyperbolæ, on sines and cosines, and the resultant of forces, and the properties of cones, is allowed on all hands to be hopeless, so far as the plain and matter-of-fact things of the outer world are concerned. And Elkin Annerley, the young mathematical master, whose bad health had obliged him to give up all his work and his prospects, seemed quite to have lost himself, as he sat there working out problems, probably suggested by these others which he had just been correcting. His hand moved over the paper quickly, and then as quickly crossed out all the working, the writer shaking his head in vexation. "That was not the shortest way of doing it," he said. "Ah! this is far neater and prettier. It would be a good rider to set for an examination paper. I shall make a note of it." Whilst he was thus busily engaged, Gertrude Hurst awoke, and, turning round, saw her visitor. She rose, and stood waiting until he should look up. At last he did look up, and she said: "Why, I thought you were in Australia, Mr. Annerley. I have been wondering all the time how you were getting on there." That was all she said, but there was a glad smile on her frank face, which told how pleased she was to welcome him back from Australia. He had thrown aside his papers, and stood beside her. "Do you know," he said, "you look very tired? And you cannot disguise from me that you have fallen asleep over your work." She pushed the hair off her face, and laughed. "Is that all you have to say, after your long voyage to Australia?" she said. "I should have thought you would have had some remarks to make about the climate, or your fellow-passengers, or the steamer." "That may come later," he answered, as he watched her busying herself about making the tea. "Perhaps you'll clear the table?" she said to him, "and get the cups and sau |
