Busk on Volvox glohator. 
43 
little if at all altered, from what I assume to be the normal 
form, and it will be seen that these little altered cells are 
mutually connected by the usual continuous filaments. In 
fig. 16 the zoospores are more expanded, and being in con- 
tact in many points, the connecting threads are absent ; 
fig. 17 shows a further degree of expansion, but more irregu- 
lar, and with irregular connecting filaments. In fig. 18 the 
enlargement is nearly as great as it can be, and numerous 
threads or processes of protoplasma extend from the central 
mass to the wall, just as they do in almost any vegetable cell 
from the nucleus to the primordial utricle, which utricle, in 
fact, is represented by the cell- wall in the case we are dis- 
cussing. In fig. 1 9, the dilatation is complete, and, owing to 
the greater age of the specimen from which this figure was 
taken, the protoplasma is much wasted, and all the filapientary 
processes completely gone. A faint granular appearance 
occupies the cavity of the primordial cell. It is a curious 
fact, as showing perhaps that all the vital action in the cell 
resides in or around the nuclear mass, that not unfrequently the 
central mass after considerable expansion of the cell, and the 
formation in that way of one wall, will begin to throw off 
a second. This condition is represented in a more highly 
magnified drawing in fig. 20. 
Although I have not myself seen any natural specimens in 
which this condition of the zoospores was present, except those 
for which I have been indebted to Mr. Williamson, still I 
have repeatedly observed a partial appearance of the same 
kind to take place, when a specimen of Volvox of the normal 
sort is kept for some hours under observation in the micro- 
scope. Figs. 21, 22, 23 show the series of changes that 
took place in a certain number of zoospores watched at 
intervals, and left undisturbed for about twenty-four hours. 
(Fig. 21, 10 A.M., Oct. 4. Fig. 22, 1 p.m., Oct. 4. Fig. 22, 
8 A.M., Oct. 5.) 
Now with respect to the other form of hexagonal areo- 
lation, for my knowledge of which, as I have stated, I am 
chiefly indebted to Professor Williamson, and which is 
represented in figs. 24, 25, I have already observed, that I 
regard it as quite distinct from that produced by the mutual 
pressure of contiguous dilated zoospores. Professor William- 
son appears, from what he has told me by letter, to consider 
that this appearance is invariably present, or at all events that 
it can be elicited in all cases by appropriate means. I must 
confess however, that I have not been successful in seeing it, 
or in producing it in very many instances, and that I believe it 
is occasionally impossible by any means to demonstrate its 
