Williamson oji Volvox globator. 
47 
eluded that, in the earlier stages of the process of segmentation 
and development of the germ, each protoplasmic segment 
would be invested by a similar external cell-membrane, as is 
the case with HcBmatococcus^ Palmella^ &c. I could not ascer- 
tain what became of these outer cells, as successive subdi- 
visions of their contained protoplasms multiplied their number, 
but hazarded the surmise, that the earlier cells might either 
have been re-absorbed, or that they still existed in the form of 
thin membranes, consolidated with and investing the newer 
cells which I supposed had been developed within their in- 
terior. It is now obvious that none of the protoplasmic seg- 
ments have secreted their external cell-membrane, until the 
entire number destined to compose the matured organism has 
been completed. This interpretation accounts for many ano- 
malous circumstances. It explains the very close contact in 
which we find the green protoplasms of the immature germ. 
No transparent spaces intervene ; these only appear when the 
young germ is matured and furnished with cilia. It also 
explains my want of success in searching for the layers of 
cellulose, the residue of the supposed earlier-formed cells, 
which must have existed had the organism been developed in 
exactly the same way as a Palmella or an Hcematococcus. In 
these latter objects, each segmentation of the protoplasm is 
followed by the secretion of a true cell, which invests each 
segment. 
The point now to be demonstrated is the existence of two mem- 
branes surrounding each mass of protoplasm. First an inner 
one, very thin, and in the living state, closely embracing the gra- 
nular protoplasm, and corresponding with the inner cell-mem- 
brane of the ordinary Confer vae ; second, an outer cell-mem- 
brane secreted from the exterior of the first. To facilitate 
describing, we may term the former of these the protoplasmic 
membrane, and the latter the cell-membrane. 
The protoplasmic membrane is easily shown to exist. Fig, 
6, PI. VI. represents a very young gemma, or budding germ, 
which consisted of but few segments, as it appeared when sub- 
jected to pressure under water. Some of the protoplasmic seg- 
ments glided through an aperture made in the common vesicle, 
without becoming ruptured. They accommodated themselves 
to the size and form of the aperture, and, on escaping, regained 
their spherical form. On increasing the pressure, each seg- 
ment burst, all the granular and mucilaginous contents flowing 
out and mingling with the water (6Z>'). As they did so the 
protoplasmic membranes (6 c) were distinctly seen as thin 
hyaline spheres. In the subsequent development of Volvox 
this membrane always continues in existence. Its appearance 
VOL. I. e 
