Busk on Vohox globator. 
41 
and turbid at the same time (figs. 11, 12), and the solid con- 
tents of the interior are shown to consist, for the most part, of 
amylaceous grains of the peculiar botryoidal form above 
noticed. (Fig. 9.) The yellow oil-like fluid in the ripe 
spore acquires a green tint under the action of the same 
re-agents. (Fig. 9.) 
Appendix. — {October, 1852.) 
The above are the observations read at the Microscopical 
Society. I am now satisfied that they afford an account of 
but one of the multiform varieties under which Volvox occurs 
at different times and places. I must own also, that at the 
time my observations there detailed were made, I was unable 
to reconcile much of what I saw with some of the statements 
and figures in my friend Professor Williamson's ingenious 
paper on the same subject. Subsequent investigation, how- 
ever, and some correspondence with him, have satisfied me that 
I was hasty in drawing conclusions from one form only of a 
very protean object. I freely confess, that in much, in respect 
to which I had conceived Professor Williamson had fallen into 
some error of observation, he has been quite right, though at 
the same time I must say that his explanations of the appear- 
ances described and figured by him, do not exactly accord with 
my notions respecting them. I still maintain that the structure 
of the wall of Volvox — upon which alone I think we are dis- 
agreed — is essentially such as I have described it, viz., that it 
is formed by a continuous, external tunic, lined by the ciliated 
zoospores. Professor Williamson, on the other hand, as I 
understand him, conceives the globe to be "a hollow vesicle, 
the walls of which consist of numerous angular cells filled with 
green endochrome, &c., the intercellular spaces being more or 
less transparent." The ciliated zoospore, therefore, according 
to him, is not a mass of vegetable protoplasm, without dis- 
tinct wall, and precisely analogous to a Euglena, or other 
naked zoospores, but represents the endochrome of a cell hav- 
ing two walls, an external and an internal, which latter is " a 
ductile cell-membrane, lining the interior of each cell and sur- 
rounding the cell-contents," and which " inner membrane be- 
comes separated from the outer cell-wall excepting at a few 
points, where it is retained in contact." And he thus explains 
the mode of formation of the connecting filaments. In this 
case, therefore, these filaments would never pass directly from 
one green mass to another, but would of course be interrupted 
in their course by the walls of two contiguous cells. That this, 
