Life-cycle of the Lower Crustaceans 345 
development of the parthenogenetic and the ‘‘winter” egg that 
have a bearing on the present question. The wall of the ovary 
swells up, and its cells become filled with a fluid when the par- 
thenogenetic egg is about to develop. The egg seems to get its 
nourishment from these cells. On the other hand, when the 
winter egg develops the walls of the ovary do not enlarge, but the 
egg develops at the expense of the surrounding cells that afford 
the nourishment for its growth. The conditions in the ovary 
itself would seem, therefore, to be determinative as to which 
kind of egg will develop. It should be observed, however, that 
we do not know whether it is the same cell that becomes in one 
case a winter egg and in the other a parthenogenetic egg. In 
fact, Weismann has stated that the two kinds of eggs come from 
different parts of the ovary. The special conditions that lead 
to formation of the male egg are unknown. 
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