238 Mr. II. J. Carter on Fecundation 



consists of an ovoid green body, partially divided into the num- 

 ber of cells just mentioned, each of which is provided with a 

 pair of cilia which project through a thin gelatinous envelope that 

 surrounds the whole mass. It is now in its smallest size, about 

 5-5400ths of an inch long, that is, not more than the diameter 

 of the Chlamydococcus-cell, fig. 9. PI. VIII., and swims by means 

 of its cilia, with the small end foremost, and with a rotatory 

 motion on its longitudinal axis, as often from right to left as 

 from left to right. An eye-spot is also present in each of the 

 four anterior cells, but seldom visible in the rest at this period. 



As the development progresses and the Eudorina increases in 

 size, the division becomes complete, and each cell, in addition to 

 the granular mucus and chlorophyll which line its interior, may 

 now be seen to be provided internally with a spherical trans- 

 lucent utricle (which is the nucleus), an eye-spot situated peri- 

 pherically and midway between the cilia and the opposite end of 

 the cell, a contracting vesicle* at the base of the cilia, and the 

 pair of cilia themselves. Each pair of cilia passes out through a 

 single channel in the gelatinous cell or envelope, which has now 

 become much thickened — and thus their movements are limited 

 up to this point, — while a denned line internally marks the 

 boundary of the original cell-wall, through which, of course, the 

 cilia also pass (PI. VIII. figs. 1,2). 



During the second stage, each of the cells again undergoes 

 duplicative division (the nuclei having been doubled previously), 

 and the whole organism becoming larger, they are separated 

 from each other, and, being no longer subject to the compression 

 which, with the lines of fissiparation tending towards the 

 centre of the ellipse (see section, fig. 2), and their confined posi- 

 tion, induced a more or less conical and polygonal shape, now 

 become spherical and enclosed respectively within distinct trans- 

 parent capsules (fig. 3) . The Eudorina is now 30-5400ths of 

 an inch long, and contains thirty-two green cells, which are 

 evidently situated between two large, ovoid, colourless, trans- 

 parent cells, one of which bounds a similarly-shaped cavity in 

 the centre of the Eudorina (fig. 2 c), and the other is the original 

 cell-wall (a), round which again is the newly secreted envelope 

 (6), — while the green cells are further fixed in their respective 

 positions by the passage of their cilia through the two latter, 

 both original cell-wall and envelope (fig. 2 h and fig. 8 c). Thus 

 we see that the Eudorina is derived from a simple (daughter-) 

 cell, and that its green cells have resulted from a duplicative 

 subdivision of the green matter which lined the cavity of this 



* Gonium has two " contracting vesicles/' unless, as in Euglena, one is 

 a reservoir to the other. 



