roughish, but very hyaline, cucumber-shaped form; each " cucumber" at first crowned with a true vorticellan pitcher-mouth, mostly, however, closed and rounded over, occasionally gaping or as it were yawning spasmodically, at intervals only, and which finally "shut up" for good. The little glassy knobs-like so many trunk-nailsthat covered the surface, grow into soft jerking-bristles ;* the mouth into the well-known mustachioed slit of barbiform cilia; and the wan, limpid, empty and now entirely flattened, ligulate or sandalshaped body tears loose as a young fluttering, pallescent Oxytricha (Pelionella), or so-called "hackle-animalcule"; darting by the jerks of its stiffish marginal bristles, and by the constant "plying of the long-barbed, ciliate slit effecting its slower progress. It never revolves, but often crawls; both in contradistinction to the fleeced, revolving, and vacuole-propelled "Paramecium" form.

This is probably the "short-line" development of Oxytricha, directly from the germinal clouds or the parasite of Chlamydococcus through Vorticella. I have no good figures to refer to, since even the detailed ones of Ehrenberg, in Trans. Berlin Acad. Sc.,' 1833, tab. iii., figs. ii., iii., and iv., which belong here (as well as tab. xxiv. and xxv. of A. Pritchard's 'Hist. Inf.,' 1861), are too inaccurate to serve as a guide, or to be readily identifiable even by those acquainted with the real natural object-material itself.

At first the bristles of the (tongue-shaped, flat, and elongateelliptical) Oxytricha are fluttering and tremulous; but as it feeds and rapidly increases in bulk, all the well-known characters of the complete "Oxytricha," its stiffish darting-bristles, its grumose, obscured body, irregularly replete with granular yolks, and very frequently cross-dividing, become typified. When thus crossdivided (a process well known and abundantly figured) the front part alone retains the barbed mouth, which, from the apex, switches down like a mustachio on a longitudinal slit about a quarter of the whole length. The blunt rear-part, on the contrary, separates with an incurrent angle which soon contracts into a new mouth, whereby the rear animal takes a blunter shape (like the cotyledon of an almond, the flat side downward).

The Oxytricha is by no means, however, to be considered as an adult form, since it is never seen to exhibit a continuity as of a membrane, or of internal ducts or viscera. Neither is it seen to copulate" or adhere lengthwise, or in any other fashion to one another except in the process of self-division. Nor does it readily divide by longitudinal fission in this state. I have seen this only

66

In their onward development these softish bristles are indurated into "styles" (of specialists). The attentive reader will observe that on such alterations of growth alone a great many colloiding false genera and species have been formed. Sap. sat. We have naturally to reject all, of which the mode of development remains unknown, as indicating a false stand-point.

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once. Crawling and darting by an apparatus of marginal bristles, prolonged in front and particularly in the rear, it is destitute of the propulsive vacuoles," as found, e. g. in the large "Paramecium Aurelia;" but besides being studded, particularly in the rear portion, with a great number of larger and smaller granular pellets, its body exhibits near the middle a large, clear, and granular germinal speck" or nucleus, which is often observed to swell, protruding globularly over the surface, below and above, when seen crawling in profile.*

Occasionally it is seen to extrude suddenly that turgid germinal nucleus or yolk (vitellus), which, as in all these cases, is itself coatless, but hung around with divers jerking molecular fragments torn loose from the parental body, which is ruptured on the spot, but readily "re-cemented," as it were.

The larger of these coatless granular yolks (constituting the original pseudo-genus, and species "Zooglea Termo Dujard ") † mostly consist of two parts, viz. a general " albumen" of a granular and evidently trabecular texture, enclosing one or two distinctly coated, quite hyaline and perfectly globular vesicles. The latter resemble in shape a very clear white currant, as it were, by having a sharply-defined circlet inscribed near one side, that is caused by a local inversion of contents (somewhat like the air-vesicle within a hen's egg).

(To be continued.)

*The transformation of the "rear-part" of Oxytricha, as given by J. Haime in ‘Ann. Sci. Nat.,' Ser. 3, tom. xix., p. 109 (and represented in Carp. ‘Micr.,' pp. 447 and 448), I have not been able to verify myself; it must not, however, by any means be confounded with the encystments (1) of Vorticella, producing waferlike molecules; (2) of the non-pulsating, tear-shaped "Paramecium kolpoda" grub, producing free Oxytricha; nor (3) with that of the " "oyster" or 'portemonnaie" grub, producing paramecium-like bodies, Gregarina-fashion; nor either (4), with some large Oxytricha "currants," containing the revolving "crucible." † As represented by Cohn in Nov. Act. Nat. Curios,' 1854, vol. i., tab. xv., fig. ix. In Klob's Microscopic Researches on Cholera' the term is misapplied to engorged joints of dissected corruptive fibrils (or "Oidium lactis ") replete with bacterial daughter-cells. ̧

PROGRESS OF MICROSCOPICAL SCIENCE.

"On

Difficulty of Experiments on Spontaneous Generation. Mr. CraceCalvert, F.R.S., cites the following experiment in his first paper Protoplasmic Life," read before the Royal Society (received May 8):Although he was prepared, by the perusal of the papers of many workers in this field, to experience difficulties in prosecuting the study, he confesses he did not calculate on encountering so many as he met, and especially those arising from the rapid development of germ-life, and of which he had hitherto seen no notice in any papers which had come under his observation. Thus, if the white of a new-laid egg be mixed with water (free from life), and exposed to the atmosphere for only fifteen minutes, in the months of August or September, it will show life in abundance. From this cause he was misled in many of his earlier experiments, not having been sufficiently careful to avoid even momentary exposure of the fluids to the atmosphere. To the want of the knowledge of this fact may be traced the erroneous conclusions arrived at by several gentlemen who had devoted their attention to the subject of spontaneous generation.

Regeneration of the Corneal Epithelium.-Dr. Hjalmar Heiberg, of Copenhagen, has written a very valuable paper on the above subject which is reproduced in the Lancet.' A paper recently appeared in Virchow's Archiv,' by Julius Arnold, on the same subject, who came to the conclusion that the new cells which replaced the old, when these had been detached, were derived from a finely granular blastema that changes into protoplasm, and that in this protoplasm the new cells arise by a process of free cell-formation. The correctness of this conclusion is contested by Dr. Heiberg, who maintains the view that young cells are developed from the old, in which certain changes have taken place. His mode of procedure was to scratch the surface of the cornea with a cataract needle in animals (frogs, birds, rats), and, after the lapse of from eighteen to forty hours, to remove the eye andlexamine the cornea both by means of fresh sections and after careful preparation in solutions of chloride of gold (maceration for from three to five minutes in a one-half per cent. solution of the salt). In certain preliminary experiments it was found that the injured part immediately after the injury presented sharply-defined irregular borders; after six hours the margins were considerably flattened, so that the boundary of the abrasion was much less distinct. After eighteen hours it was difficult to tell the seat of the injury with the naked eye, and its diameter had become reduced to one-half or one-third; and after forty hours recovery was complete. He convinced himself by microscopic investigation that the process of regeneration of the epithelium proceeds from the margins of the abrasion, the layers of cells immediately bounding the seat of injury becoming elongated, and, as it were, sending forth processes towards its centre; so that the margins are rendered very oblique, whilst at the same time the exposed surface of the cornea is raised considerably above the level of that which is still covered by the cells. Sometimes the cell-processes become detached and contract

into glassy, clear, rounded masses; but he has never noticed the free formation of cells in a blastema, and does not believe that the white corpuscles of the blood or "migrating cells" play any part in the regeneration of the cells, though he has occasionally met with them between the epithelial cells and in the substance of the cornea in the vicinity of the injury. In no single instance has he observed any appearance leading him to think that they undergo conversion into epithelial cells. The processes thrust forth by the cells, as above mentioned, were found, from observations extending over many hours, during which the cornea was placed in a current of serum, to undergo slow changes of form and size, the movements however being in no way comparable in activity to those of amoeboid cells. The cells situated at a greater distance from the injured part often became granular, and their margins more distinct. In rats both the upper flattened and the deeper, more columnar cells seemed alike to thrust forth the processes destined to cover the floor of the injured part. Dr. Heiberg expressly remarks that he has not satisfactorily followed the separation of the cell-processes to form new cells, which again push out new outgrowths, to be again detached, though he obviously thinks this is what really occurs. Dr. Heiberg gives several drawings to illustrate the points mentioned in his paper, which is in every respect a most valuable contribution.

The Microscopic Structure of Cotton-seeds.-This is a paper, published in the Neues Jahrbuch für Pharmacie,'* by Dr. F. Flückiger. It is a long paper, and contains, in the first place, a succinctly-written botanical description of the several kinds of shrubs and trees from which cotton is obtained; next, we meet with a histological and morphological minute description of the microscopical structure of the cotton-seeds, illustrated by coloured lithographs. The latter portion of this essay is devoted to a well-condensed and very complete review of all that has been done in various parts of the world in reference to the scientific, as well as industrial, researches on cotton-seeds, and the oil it yields. According to the author, the quantity of cotton-sced annually gathered amounts to 1,000,000,000 of kilos., which, under the least favourable conditions, would yield 150,000,000 kilos. of oil.

Discovery of the Animal of the Spongiada confirmed.—Mr. H. J. Carter, F.R.S., sends a line to 'Silliman's American Journal' (July), "just to tell you what you will be glad to learn, viz. that I have confirmed all that Professor James Clark, of Boston, has stated about the sponge-cell, and much more too. It is after all only what was published and illustrated in the Annals' in 1857. Indeed I am astonished now at the accuracy and detail of that paper,† now all confirmed by an examination of a marine calcareous sponge. I have not only fed the sponge with indigo, and examined all at the moment, but the sponge so fed was put into spirit directly afterward, and now shows all the cells (monociliated) with the cilium attached and the indigo still in the cells. This, I think, will break down Häckel's hypothesis, which is as imaginative and incorrect as it is beautiful. His "Magosphæra" too is figured in the Annals' (1856), and de* Double number, May and June, 1871. Ultimate Structure of Spongilla," &c.

scribed in extenso as the amoeboid cell which inhabits the mucus of the cells or internodes of the Bombay great Nitella. But there are no people in England, if on the Continent, who seem to be able to show this, if even they be cognizant of it. Ex oriente lux used to be the old phrase; the light is now being reflected back from America. It is from there that we must expect novelties now."

The Anatomy of the Graafian Follicles in Man.-These have been very fully explained by Dr. Kronid Slavjansky in Virchow's Archiv,'* and are well abstracted by the 'Lancet' in a late leader. The author's observations have been made on subjects of all ages brought to the Anatomical and Pathological Institute of the Medico-Chirurgical Academy of St. Petersburgh. The preparations were macerated immediately after removal from the body (which was usually effected in from three to eight hours after death) for a week or a fortnight in Muller's fluid, then placed in a 70 per cent. solution of spirits of wine, and then in a 90 per cent., after which fine sections were made. In the examination of the ovaries of children he recognizes three forms of follicles -(1) primordial follicles, which are the youngest; (2) a transitional form to the mature follicles; and (3) more or less developed mature Graafian follicles.

The primordial follicles are of roundish or elliptic form. They consist of the primordial egg, with the yelk, the germinal vesicle, and germinal spot surrounded by a series of small round cells in contact with one another, and without any intermediate substance. In very young follicles a spot can always be found where these cell-series are interrupted, and where the egg apparently is in direct contact with the wall of the follicle. This is the follicle-pole of Pflüger. At a subsequent period this spot is covered by a layer of cells. The wall of the follicle presents no characters distinguishing it from other parts of the ordinary stroma of the ovary. On its inner surface, however, he admits the presence of a lustrous layer, similar to that found in acinous glands, in which sometimes a few fusiform cells may be discovered, and thus differs from Waldeyer, who in his description of the structure of the primordial follicles states that they are destitute of a membrana propria, and that the stroma tissue lies in immediate contact with the contents of the follicle, the fibres being arranged circularly around it. Thus it appears that in the very youngest follicles the egg is surrounded by a series of epithelial cells representing the future membrana granulosa. The delicacy and instability of these cells explain the circumstance of their being denied by Klebs, Schron, and Florinsky. Such follicles as those that have just been described may be seen in certain parts of the ovary, at every age from the eleventh week of intra-uterine life to the grand climacteric. In embryos they are usually found between the cortical and medullary layers; in newborn children they are found in all parts; in adults they are met with only in the most superficial layers of the cortex, where they are closely packed, and when badly prepared, in consequence of the destruction of the epithelium, look like rows of large cells from which, near the centre of the ovary, the follicles appear to develop. Slavjansky accepts and corroborates Waldeyer's description of the origin

* Band 51, Heft. 4.