326 M. D;) Hid: 
the original eight chromosomes is a single complete structure ; 
and if the process were like what occurs in Styelopsis, the 
nucleus of the ovocyte I.would contain thirty-two chromo- 
somes. Owing to its extremely small size this is a mechanical 
impossibility, and hence there is no such precocious splitting 
to form eight “‘ Vierergruppen.” 
Hence it seems to follow that those who would see in this 
precocious splitting a process especially brought about in 
order to ensure a more varied combination of ancestral units, 
are obliged to recognise that it may take place in one species 
of the same group and not in another. In Phallusia at no 
one stage of maturation\there /are \thirty-two chromosomes 
“to choose from,’ so to speak, but the division takes place 
exactly as in normal cell-division, except that the chromo- 
somes divide transversely and not longitudinally (? in second 
polar body). On the contrary, the two cases of Phallusia and 
Styelopsis seem to point towards the phenomena of matura- 
tion being nothing more than normal cell-division. Whereas 
in the former case the large number of chromosomes prevents 
precocious division, in the latter the small number allows it, 
and it is possible that some good to the organism may be 
gained thereby. The point to be found out is at what stage 
does the reduction from sixteen to eight chromosomes in the 
development of the sexual cells of Phallusia take place, which 
is the only real ‘ reducing division” of the kind. 
The fact that the process of maturation of the egg of Phal- 
lusia resembles what has been described for the egg of certain 
vertebrates, may be an additional point of evidence for a 
phylogenetic connection between them and the Ascidians. 
Narites; March, 1895. 
