Busk on Volvox glohator. 
39 
other Algee — that it may, in fact, be termed the " winter 
spore" of Volvox^ destined, owing to its more persistent vi- 
tality, to continue the species, when its course of development 
in the usual way is interrupted by surrounding circumstances. 
Of that form of Volvox termed V. stellatus, I would only 
here observe that it seems to me merely a modification of the 
one last described, and that it appears to follow the same 
course of change and doubtless of future development. 
With respect to Sph(Erosira volvox, my observations have 
been very limited, and I by no means desire to express myself 
with certainty as to its relationship to the forms above de- 
scribed. I merely surmise that it may be found to represent 
a peculiar mode of development of one and the same species. 
In external aspect, except in the want of uniformity in the 
size of the ciliated zoospores, it appears to agree in all respects 
with V. glohator. It however contains no internal embryonic 
bodies, and it is therefore only to the ciliated cells that any 
reference need here be made. The smaller ones appear to 
me to resemble in all respects those of Volvox glohator, and 
each to possess two cilia, which is important if true, because 
the only distinction between Volvox and Sphcerosira in Ehren- 
berg's classification depends upon the circumstance, that in 
Sphcerosira there is only a single cilium to each zoospore, whilst 
there are two in Volvox. 
My supposition that Sphcerosira volvox and V. glohator are 
allied, is founded, it must be owned, not upon any direct ob- 
servation, but chiefly upon the fact, that in the water in which 
the specimens of Volvox I had under examination were con- 
tained, there was at first none of the Sphcerosira any more 
than of V. aureus observable, and that after some days both 
were very numerous. 
The difference I am about to describe in the after develop- 
ment of the ciliated zoospores, is not by any means a sufficient 
ground upon which they should be deemed distinct species, 
because much greater differences are known to exist in other 
of the lower Algae during their various forms of development 
without its being thence allowable to suppose that they are of 
different species. 
In Volvox sphcerosira then, as at all events it may be termed, 
the larger green granules are in fact the ciliated zoospores in a 
stage of further progressive development. In the same spe- 
cimen they will be seen in all stages of division or segmenta- 
tion (fig. 13) — first into two, then into four, and so on till, as 
in the case of the embryo Volvox, the ultimate result of the 
segmentation constitutes numerous minute ciliated cells or 
bodies (fig. 14) — not, however, as in that case, lining the 
