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figs. 6, 7) resembling that of the original cell before subdivision 
commenced. Here and there we find ‘cilia* (the little loco- 
motive fibres already described) protruding through the outer 
gelatinous coat; and these cilia, which belong to some of the 
divided cells, cause the whole mass to revolve by their simul- 
taneous movements. They do not, however, make then- 
appearance until growth has considerably advanced. 
When the process of segmentation is complete, and as many 
of the young cells (which are called ‘zoospores/* or ‘ gonidia*) are 
present in the mulberry mass as are afterwards found upon 
the mature Yolvox, then the transparent enveloping mem- 
brane begins to expand, and the green gonidia spread wider and 
wider apart, but remain connected together by thread-like fila- 
ments, which become thinner and thinner as the distance between 
the cells increases, until at length they are hardly traceable even 
under a high microscopic power; and then the Yolvox presents 
the appearance of a beautiful crystal globe studded all over with 
ciliated cells or gonidia (pi. v.). 
You may easily understand this mode of development if you 
picture to yourself one of those hollow india-rubber balls pro- 
tected by a network, that are used as toys by children; and 
suppose the network on one of these balls to be elastic, and so 
completely covered with green beads that the ball is rendered 
invisible. How, imagine the ball to be gradually distended with 
air, and the beads thus stretched farther and farther apart, and 
until the network is lost to view, and only the beads are per- 
ceptible, studded all over the thin distended globe. This will 
enable you to understand the circumstances under which Yolvox 
is developed, and assumes its beautiful appearance. 
To revert to our living Yolvox, however, the gonidia, or green 
cells, which appear to be upon its surface, are inreahty imbedded 
in the gelatinous membrane that forms the globe, the cilia alone 
protruding through the latter (pi. vi. fig. 9) ; and it is these 
gonidia that undergo subdivision or segmentation in the manner 
described, forming the smaller globes (the young Yolvoces, in 
fact) that roll about within the larger one ; for they grow inwards 
(pi. vi. fig. 8), and as soon as they have attained a certain growth, 
they become detached and fall into the cavity (pi. v. larger globe). 
The number of the smaller globes is usually eight ; and as 
these soon become too large for the parent to hold them, the 
latter bursts and sets them free, after which they move about 
in the watery element, and in like manner give birth to similar 
forms. But what is most remarkable, is that even whilst the 
lesser globes are still within the parent, they sometimes produce 
a third series, so that a parent Yolvox often carries about with 
it two generations one within the other. 
* Very inappropriately, for the word signifies “animal germs.” 
