ON THE VOLVOX GLO BATOR. 
141 
In the youngest “ daughter/* you will find that some of the 
“ zoospores ** are larger than the others (fig. 5). It is from 
these that the future offspring arises. The changes are as 
follows : — first, generally the cell is divided by a septum 
(fig. 6) into two parts by the process known to botanists as 
“ binary ** cell- division, or segmentation ; or it may commence 
by the separation of the whole mass at once into as many as ten 
smaller portions (fig. 7), each of which becomes a cell by the 
process of “ free cell- division/* as it is called. Or this latter 
mode may occur after the division. In any case, after the 
division has proceeded thus far, the secondary cells again 
divide so as to form a round ball (fig. 9), containing, after the 
final division, as many green cells (figs. 10-11) as there are 
zoospores in the future Yolvox. At this time the cells become 
possessed of cilia (figs. 10-11), which, in this state, are very 
close together, and very readily perceptible by their waving. At 
this time the whole is inclosed in a delicate layer of colourless 
mucus (figs. 10-11, a a), which, before long, becomes dis- 
solved. Up to this time the young Yolvox is still attached to 
the interior surface, without causing any bulging of the parent 
wall, of which we may consider it as a “ gemma,** or bud. It 
continues to grow, and after a time becomes detached from 
the wall, proceeding to move about in the interior of the old 
Yolvox in the same manner as the latter does in the vessel. 
It is ultimately released from within by the dissolution of the 
parent, when it becomes completely independent ; but by that 
time the same changes have been going on within it, so that 
the third generation can be already detected. This, then, is 
the mode of growth in the typical Yolvox, and these pheno- 
mena may be repeated in the same way, for an indefinite 
period throughout the summer. 
But there are some other appearances which may be ob- 
served in this plant not unfrequently towards the end of 
summer, which are to physiologists of a highly interesting 
character, although they are at present unable to determine 
their entire value. 
The first is that described by Cohn, where the segmentation, 
or division of the spores, instead of going on to the formation 
of a Yolvox like its parent, divides into small spindle-shaped 
ciliated bodies, disposed in a disc-shaped group (fig. 14, a a a). 
These he looks upon as equivalent to the antherozoids of the 
Algae and most flowerless plants, which are the analogue 
of the pollen in the flowering plants. Indeed, he says 
he has observed that they become diffused through the in- 
terior of the Yolvox, and then coming in contact with some of 
the cells which are larger than the rest, and which he calls the 
