328 Wager. — On the Structure and 
thus formed, and each nucleus divides karyokinetically into 
two. The apical portions of these projections, each with 
a single nucleus, are then cut off by a partition-wall, and 
these two nuclei then degenerate and disappear. The par- 
tition-wall between the two contiguous cells is then resorbed, 
and the two masses of protoplasm, each with its nucleus, fuse 
together to form the zygospore. Chmielewsky (’89) was able to 
observe the ultimate fusion of the nuclei into one egg-nucleus. 
The fusion of the nuclei takes place very slowly, but in zygo- 
spores four weeks old they are always found fused together. 
The author makes the extremely interesting observation that 
quite ripe zygospores with fused nuclei would not germinate, 
but that unripe zygospores with the nuclei as yet not fused 
would germinate very easily when placed under suitable 
conditions. He explains the fact that the ripe uninucleate 
zygospores would not germinate because, obviously, they 
require a longer resting period. 
This division of the sexual nuclei previously to fusion is 
exactly similar to what occurs in Peronospora and Cystopus , 
and according to Trow in Saprolegnia also. It would be 
interesting to know if it takes place in Pythium . The readiest 
explanation of the phenomenon would of course be that it 
is a reducing division, but this does not appear probable in 
the light of recent investigations on the reduction of the 
chromosomes in plants and animals, and also from the fact 
that, so far as I was able to observe in Cystopus , the number 
of chromosomes in the dividing nuclei in the oogonium is less 
than the number in the dividing nuclei of the fully formed 
oospore, as will be seen later. Moreover the explanation of 
this phenomenon, whatever it may be, is probably bound up 
with the explanation of the post-sexual process of reduction 
described by Klebahn (’88) in Cosmaruim and Closterium , 
and by Chmielewsky in Spirogyra. 
That 4 we can only regard the nuclear divisions in oogonium 
and antheridium as phylogenetic reminiscences of the forma- 
tion of gametes by cell division/ as suggested by Hartog 
(’91), is possible, but it seems to me that more facts are 
