CHROMIDIA AND THE BINUCLEARITY HYPOTHESES. 305 
I will consider this last case in more detail, as it is the 
basis of much theorizing. 
Whatever theoretical value we may give to the chromatin 
itself, it cannot be denied that chromidia represent an inter- 
mediate stage in the simultaneous formation of a number of 
nuclei from a single nucleus. The reason why we find this 
method of multiple division so frequently occurring in 
gametogenesis is, to my mind, quite obvious. It is an 
adaptation to ensure the formation of a number of 
gametes at the same time. From the very nature of 
the life-conditions of many Protozoa it is absolutely neces- 
sary for a large number of gametes to be formed at once ; 
for a large number must usually, like the sperms of Metazoa, 
fail to fulfil their duty. 
There are few accurate accounts of other methods of 
multiple nuclear division, but it has been studied carefully in 
at least one protozoon—Calcituba (Schaudinn, 795). Except 
for the fact that all the events take place inside the nuclear 
membrane, it is exactly comparable with the method by 
chromidia formation as seen in Aggregata, etc. 
In Thalamophora, Radiolaria and Rhizomastigina, where 
the chromidium remains for some time as a permanent orga- 
nella during the vegetative life of the cell, we see merely a 
device by which, through the independent growth of the 
chromidia, a larger brood of gametes can be eventually pro- 
duced than by the sudden multiple division of a single nucleus. 
The multiple nuclear division in Opalina is cloaked by 
the fact that the cell is originally multinucleate. This applies 
also to Pelomyxa. And here, apparently, nuclear reduction 
and multiple division occur at the same time, so that they 
obscure one another. 
There is one other interesting conclusion which may be 
drawn from the facts regarding chromidia. It is that an 
actual cell death exists in the “immortal” Protozoa. Con- 
sider the following instances. In many of the rhizopods the 
primary nucleus and the remains of the cytoplasm are left 
