160 GERM-CELL CYCLE IN ANIMALS 
without the disintegration of the migrating chroma- 
tin. In plants also Gates (1911) has shown that 
chromatin may migrate from one pollen mother-cell 
of Cnothera gigas into a neighboring mother-cell 
where it remains visible for some time before be- 
coming incorporated with the surrounding cyto- 
plasm. Many more cases of cellular fusion might be 
mentioned, but in no instance so far as I am aware 
has the union of two well-developed odcytes to form 
one egg been reported. It is true that in Copido- 
soma the chromatin in one (the proximal) odcyte 
(the keimbahn-chromatin) finally disintegrates and 
disappears in the cytoplasm, and thus the condition 
here may be compared with that in the cases men- 
tioned above, but the stage of fusion in Copidosoma 
is extremely late in the growth period, and the 
chromatin material remains visible for a remarkably 
long interval of the germ-cell cycle. 
According to Silvestri the first cleavage cell of 
Copidosoma consists of the egg nucleus surrounded 
by only a small portion of the substance in the pos- 
terior end of the egg in which is embedded the keim- 
bahn-chromatin. If the two materials within the 
odcytes do not become intimately fused, it is obvious 
therefore that the cells of the embryo which are 
descended from the first cleavage cell are derived 
from the nucleus of the anterior of the two fused 
odcytes and cytoplasm from the posterior odcyte 
with the addition of the keimbahn-chromatin. 
The history of the germ cells after their segrega- 
tion is not known for any polyembryonic animal. 
