The Psychic Life of Micro-organisms: A Study in Experimental Psychology

The subjoined cuts, explanatory of the conjugation of Micro-organisms, refer respectively to the descriptions on pages 67, 67 and 68, 68, 69 and 70, 71 and 72. Fig. 7 a. — Positions preliminary to conjugation among the Paramcecium aurelia. (Balbiani.) Fig. 7 b. — Several pairs of Stentor c(E-rideus fixed upon a conferva filament, enlarged fifteen diameters (after Balbiani). Fig. 7 c. Position preliminary to the copulation of the Stylonychia mytilus. The two animals are superimposed upon each other by their ventral faces (Balbiani).

Fig. 7 d. — Gemmiform conjugation of the Vorticellinae (Carchesium polyfa'num). A, first stage: the microgonidium mi has fastened itself by a filament upon the peduncle of the macrogonidium. B, a more advanced stage: the microgonidium has fastened itself directly upon the body of the macrogonidium, and its substance begins to penetrate into the latter. In both individuals the nucleus has separated into small rounded fragments, and in the microgonidium are seen the two striated segments resulting from the division of its nucleolus. C, last stage of the conjugation. The microgonidium, completely void of its contents, remains attached to the body of the macrogonidium under the form of a minute hollow tube, which in the end drops away, — ma, macrogonidium; mi, microgonidium; n, nucleus; nu, nucleolus; v. c., contractile vesicle. (Figures from M. Balbiani.)

In the Chilodon cucullulus the following is the series of phenomena presented (the row of figures given opposite, have been procured through the kindness of M. Balbiani, and will serve to illustrate our description): The figure A shows the beginning of conjugation; each animal is shown with its mouth (<£), its multiple contractile vesicles (v. c.}, its nucleus (n), and its nucleolus (mi}; the nucleolus will become the main seat of the modifications effected in fecundation. In the figure B the principal change pertains to the nucleolus; in each of the two animals, the nucleolus has moved away from the nucleus and has begun to break apart into two segments; the nucleus commences to show signs of regression. Between the figure j?and the figure C phenomena take place lljl J gl* of the highest importance, but - which are still the subject of dispute. The following appears from present investigations to " ^§ « Q be the most probable: the °-|2 two animals in conjuga- o § ti°n exchange with each

other one of the capsules produced by the division of the nucleolus, so that when we come to the phase of the process represented in figure C, we find an animal which contains, besides its nucleus, two nucleolar segments in immediate proximity (mf «#'); it was the same in figure B; each animal already possessed two nucleolar segments, but these segments were obtained from the division of the nucleolus properly belonging to the animal itself, while in figure C, in consequence of an exchange effected, one of the nucleolar segments belongs originally to each animal and the other comes from its mate.

M. Balbiani, who made the first observations upon these phenomena of a nature so delicate and complex, originally supposed that the two adjacent nucleolar segments, which have been represented in the figure C, were produced by the longitudinal division of the nucleolus exchanged between the two animals in conjugation. M. Maupas has recently proposed a different explanation, which seems to be further corroborated by the very figure given twenty years previously by M. Balbiani. According to M. Maupas the segment exchanged proceeds to fuse with the segment not exchanged, in order to form a compound segment; the two contiguous segments, seen in figure C, would not, therefore, be the result of the division of one segment solely, but the first stage of the conjugation of two elements having different origins. A fact which apparently argues in favor of this opinion, is the aspect presented by the two segments; if they proceed from a division, we would find there certain phenomena of caryokinesis, which were furthermore completely unknown at the time when M. Balbiani made his first observations.

However this may be, it is seen by figure C that the regression of the old nucleus (n) is sharply marked. In the figure D, the two nucleolar segments have fused together and have formed a compound segment, which segmentates in its own turn; the two new products of that segmentation grow to unequal sizes; the largest capsule attains a size of forty thousandths of a mm. ; it is this that forms the new nucleus of the Chilodon. The second capsule shrinks and becomes compressed, it takes its place beside the first one and becomes the new nucleolus.

The figure E represents the last stage of the phenomenon; the animal is in possession of its new nucleus and its new nucleolus; the old nucleus is reduced to a small pale and rumpled mass and will shortly disappear. To recapitulate, then, if the opinion of M. Maupas (who did not study this species, but like ones) be accepted, the nucleolus divides into two capsules: the one, playing the part of a male element, is exchanged between the two animals in conjugation, and proceeds to fuse with one of the capsules derived from the division of the nucleolus of the other animal; the other capsule, which acts the part of a female element fuses in the same way with the male element coming from the other animal. The result of that fusion is a compound capsule which, undergoing a process of division, produces the new nucleus and the new nucleolus of the animal fecundated.

Page i, line 16. The doctrine of unicellularity in regard to the Infusoria has been upheld by Sibold and Kolliker; the majority of naturalists have conceded it. Page 12, line 29, et seq., vide Arbeiten aus dent zoolog. Institut in Wurzburg, herausgegeben von Prof. C. Semper, Vol. I. p. Page 19, line 28, vide Balbiani, Lecons sur les Sporozoaires. Page 20, line 6. By protoplasm in this connection is understood the entire cellular body; the distinction of function between the protoplasm properly so called, and the nucleus, is established later on in the essay.

Page 58, lines 30 and 31, vide Henneguy, Sur la reproduction du Volvox dioique. Acad. des Sciences, July 24, 1876. Books not returned on time are subject to a fine of 50c per volume after the third day overdue, increasing to $1.00 per volume after the sixth day. Books not in demand may be renewed if application is made before expiration of loan period.