OF THE PHTTOZOA. 161 



" ^Mien, however, the process of impregnation takes place, the division stops 

 at the second stage, — that is, when the Euclorina consists of thirty-two cells of 

 the largest kind, each of which is about 1 -1866th of an inch in diameter 

 within its capsule, which is therefore a little larger. The process is as follows : — 



'' At a certain period after the second stage has become fully developed, the 

 contents of the foiu' anterior cells respectively present hues of duplicative sub- 

 division which radiate from a point in the posterior part of the cell (and this 

 distinguishes this subdivision from that which took place in the original cell 

 from which the Eudorhia was derived, and that which takes place in the third 

 or last stage of development just described, where the lines of fissiparation 

 tend towards the centre of the ellipse or ovoid cell). These lines, which ulti- 

 mately divide the green contents of the cell into sixty-foiu- portions, where 

 the division stops, necessarily entail (from their radiating from a point and 

 terminating a little beyond the centre of the cell) a pyriform shape on the 

 segments, from whose extremities a mass of cilia may be observed waving in 

 the anterior part of the cell of the parent, while yet her o^vn pair of cilia are 

 in active motion, and her eye-spot still exists in situ on one side of her pro- 

 geny, — thus showing that the latter may be almost fully formed before the 

 parent perishes. At length, however, this takes place, and the progeny, which 

 we shall henceforth call ' spermatozoids,' separate from each other, and finding 

 an exit, probably by iTipture, through the effete parent-cell and her capsule, 

 soon become dispersed throughout the space between the two large ovoid cells 

 mentioned, where they thus freely come into contact with the capsules of the 

 twenty-eight remaining or female cells. 



" The form of the spermatozoid now varies at every instant, from the activity 

 of its movements and the almost semifluid state of its plasma ; and therefore, 

 if we had not seen it in the parent-cell, it would be very difficult to define 

 what this form really is. Its changes in shape, however, are confined to 

 elongation and contraction, like those of Euglena viridis, and not polymorphic 

 like those of Amoeba ; hence it is sometimes linear-fusiform or limular, at 

 others pyriform, short, or elongate. The centre of the body is tinged green 

 by the presence of a Kttle chlorophyll, while the extremities are colomiess ; 

 the anterior one bears a pair of cilia, and there is an eye-spot a little in front 

 of the middle of the body, also probably a nucleus. Thus we have a product 

 widely difterent from the common cell of Eudorina. It is about l-2700th of 

 an inch long, and 1- 10,800th of an inch broad. 



'' Once in the space mentioned, the spermatozoids soon find their way among 

 the female cells, to the capsules of which they apply themselves most vigor- 

 ously and pertinaciously, flattening, elongating, and changing themselves into 

 various forms as they glide over their surfaces, until they find a point of in- 

 gress, when they appear to slip in, and, coming in contact ^ith the female 

 cell, to sink into her substance as by amalgamation. I say ' appear,' because, 

 the female cells as well as the spermatozoids being so small, so numerous, and 

 so nearly grouped together, and there being no point like a micropyle that I 

 could discover, and the Eudorina continually undergoing more or less rotation, 

 I do not feel so certain of having seen the act of union take place as if there 

 had been only a female ceU present with a fixed point for the entrance of the 

 spermatozoids, as in the resting-spore of (Edogonium. But the act itself does 

 not require to be seen ; for the constancy of this form of Eudorina, the way 

 in which these little bodies are produced, their plastic natiu-e, and their be- 

 haviour towards the female cells are quite sufiicient to conrince those who 

 have given their attention practically to such subjects that they are spermato- 

 zoids, and that there can be no other object in their congregating about the 

 female cells than impregnation. If this be not sufficient, their number may 



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