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a bright red spot (fig. 2, e e e), which was called the eye ; and 
hollow spaces (fig. 2 , d d d), which were called stomachs ; but 
no aperture is perceptible which might have been mistaken 
for a mouth, and constant observation has failed hitherto to 
detect the entry of any extraneous body into the interior of 
the zoospore. The cavities or “ vacuoles ” do, however, 
possess a curious power of contracting at intervals of about 
forty seconds. This feature was first described by Mr. Busk. 
Had the earlier observers noticed it, they would have looked 
upon it as an additional evidence of the animal nature of 
Yolvox. But this peculiarity has been observed in other 
plants ; it is probably owing to certain chemical changes going 
on within, connected with the process of nutrition, &c. 
Those who have been accustomed to the examination of the 
Algas, and other of the lower tribes of plants, will easily re- 
cognize in the zoospore of the Yolvox, the strongest similarity 
to the ordinary zoospore, of which fig. 4 gives the common 
appearance. If one of the drop-shaped bodies of Yolvox were 
detached and set free, it would be precisely similar to them. 
The zoospore of the Algas is formed out of the contents of 
the cells, the outer wall of which after a time dissolves or 
bursts, and sets free the “ zoospore/"’ The latter now libe- 
rated, by the aid of two cilia, similar to those of the Yolvox, is 
vigorously impelled forward by a process something like that 
of the screw of a steam-ship. Hence we may describe Yolvox 
as a family of “ zoospores 33 which has a power different from 
others hitherto known, of continuing to reproduce itself for 
many generations. And this latter feature brings us to the 
consideration of an appearance which really is the most 
noticeable and striking of all. Upon the most casual obser- 
vations of Yolvox, round green balls (fig. 1, b b) of varying size 
may be seen within, either still attached to the inner surface 
of the outer membrane, or free in the interior, revolving there 
as if they were external. These are readily seen to be like the 
parent, only more green, and much smaller. These are the 
progeny — “ daughters,” as they have been called. Their 
number varies from two to ten ; six to eight being the more 
frequent. The darker colour is owing to the distance between 
the zoospores being less than in the parent at that time. 
However, as the young sphere enlarges, the distance is increased, 
and a greater transparency ensues. Now, each of these young 
Yolvoces originally springs from a zoospore. Nor is it so in- 
fantile but that it has already begun to rear “ granddaughters.” 
And it is in these latter that the process of development can 
be easily traced. Let us, therefore, for a moment, attend to 
the mode of growth. 
