40 
Busk on Volvox glohator. 
inner surface of the wall of a spherical case, but forming by 
their aggregation, a discoid body, in which the separate fusi- 
form cells are connected together at one end, and at the 
other are free, and furnished each with a single cilium. In 
this stage these compound masses become free and swim 
about in the water, constituting, in fact, a species of the genus 
Uvella, or of Syncryi^ta of Ehrenberg. 
With respect to the chemical constitution of the above 
described parts, the following are the results at which I have 
arrived: — 1. By the use of iodine and sulphuric acid, tried 
repeatedly and in various ways, I have never succeeded satis- 
factorily in eliciting any tinge of blue in the wall of the mature 
Volvox. I therefore conclude that it contains no cellulose. It 
is invariably coloured, by the above re-agents, of a deep brown 
colour, and when thus coloured, this outer wall presents no 
trace whatever of structure ; it appears uniformly transparent 
and homogeneous. The ciliated zoospores, also, with the 
connecting filaments and cilia, are turned brown, but of a very 
deep brown, by the same re-.agents, excepting usually one or 
more particles in the interior of each, which are apparently 
turned blue. I am not satisfied as to the chemical re-action of 
the brown spot ; it appears to assume a blue colour, but from 
the intensity of its colour and consequent opacity I am not 
sure that this is the case. 
The embryo cell, when young, is turned a deep brown, 
but when older and fully formed, but before it has arrived at 
maturity, it will be found that it is only the green masses, or 
future ciliated zoospores, that are thus changed, the cell- wall 
acquiring scarcely any tinge of brown. But when a young 
cell thus tested with iodine and sulphuric acid is ruptured, I 
have occasionally noticed that the fi[uid contents contain an 
abundance of minute bluish flocculi — I use the word flocculi 
because the particles are light and flocculent, and not at all like 
any of the more ordinary and more solid forms of amylaceous 
matter. The quantity of this flocculent matter appears to be 
greater towards the periphery of the cell, and, in fact, it would 
seem that the green bodies are at this time imbedded as it were 
in an amylaceous matrix, which they not improbably assimilate, 
because in the mature cell nothing of the sort is apparent. 
In the embryonic bodies, however, or winter spores of 
V. aureus and stellatus, the presence of cellulose is rendered 
abundantly evident in the two coats forming the tunic of the 
spore by the blue colour produced in them by iodine and sul- 
phuric acid (fig. 11) ; nearly as distinctly, in fact, as it is in 
the tunic of Micrasterias and other Desmidiece. The appa- 
rently clear fluid between the two tunics is rendered brownish 
