154 VOLVOX. 



If, now, we magnify it very highly, and get a profile view of it, 

 we shall see that it is a hollow sphere whose crust is a thin trans- 

 parent gelatinous substance, (fig. 93, c 1 ,) of equal depth through- 

 out, and that it very closely resembles the cell-wall of the snow- 

 plant (fig. 76, c). This it does, too, in other respects, as we 

 shall see presently. The emerald spots which I spoke of just 

 now turn out to be a colony of oval bodies (fig. 93, g~, g l ) almost 

 identical in character with the spores of the snow-plant, (figs. 76 

 to 79, #,) but with this difference, that, instead of being loose in 

 the cavity of the cell, their points are all fixed in the thickness of 

 the gelatinous shell, (fig. 93, c 1 ,) and the double lashes (I) vibrate 

 on its outside. By the combined action of these vibratory cilia, 

 the sphere is kept in motion, revolving from place to place with a 

 never-ceasing meaningless aim. The threads (ft, n } ) of the net- 

 work connect the spores (g, g l ) with one another by attaching 

 themselves to the sides of the latter, and in fact they seem to 

 be portions of the substance, or cell-wall, of these spores drawn 

 out into fine threads. 



There is also additional evidence of the relation of Volvox to 

 the snow-plant in the mode of reproduction. As in the latter 

 the zoospore of Volvox is covered by a gelatinous layer (w, iv } ) 

 which corresponds to a cell-wall. Now, when new individuals 

 are formed, the first step taken is a self-division of the green con- 

 tents of a zoospore into two masses. This being done, the once 

 single zoospore is in the condition of the like body of the snow- 

 plant after undergoing a similar process, (fig. 74,) and in fact it 

 is not always possible to distinguish the one from the other at 

 this stage. When the division has occurred again, it resembles 

 the cell of the snow-plant with four young zoospores, (fig. 75,) 

 even to the position of the pointed ends (e, e 1 ) which lie next 

 the cell-wall. And so the self-division goes on until a large 

 number of zoospores are produced, (fig. 93, g- 2 ,) whilst the original 

 wall of the primarily dividing zoospore enlarges (fig. 93, c) to 

 accommodate the increasing colony, at the same time adhering 

 to the wall of the parent stock (c 1 ) by a sort of neck (c 2 ) until 

 a certain period, when the young Volvox escapes by breaking 



