200 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
its development until the following season ; that is, it becomes a “ winter 
egs.”” From such eggs there hatch invariably agamic females. 
These facts support the view already advanced, that in parthenogenetic 
animals a segregation of sex-characters takes place at the formation of the 
second polar cell. The female character passes into the second polar cell, 
leaving only the male character in the egg. Hence, if the egg which has 
formed two polar cells develops without fertilization, it must develop into 
a male. But if such an egg is fertilized, it invariably forms a parthenoge- 
netic female, 9 (@), that is, an individual in which the male character is 
recessive. Accordingly the functional spermatozodn must in such cases 
invariably bear the female character, and this is as invariably dominant 
over the male character when the two meet in fertilization. 
But we are now confronted with a serious difficulty. The egg, which 
has formed two polar cells, we have supposed, is purely male, yet the 
animal which develops from it by parthenogenesis produces only gametes 
purely female. 
The studies of Petrunkewitsch (:01) on the honey-bee give us a clue 
to the solution of this difficulty. The genital gland of the male bee 
probably develops, not from any part of the mature egg, but from the 
second polar cell, after the union of that body with one of the two prod- 
ucts of division of the first polar cell. But the second polar cell con- 
tains, according to our hypothesis, only the female character ; the same 
is probably true of one of the products of division of the first polar cell, 
perhaps of that one which fuses with the second polar cell. If so, the 
genital gland of the male bee will contain only the female character, and 
in the spermatogenesis of the bee, no segregation of sex-characters will 
be found to occur.. On the other hand, if the male character is borne by 
that derivative of the first polar cell which fuses with the second polar 
cell, the body formed by their union will contain both the male and 
female characters, and will be homologous with the cleavage nucleus of 
a fertilized egg. In that case we shall expect to find the occurrence of 
a normal process of spermatogenesis with segregation of sex-characters. 
If this is so, there doubtless are produced male as well as female sper- 
matozoa in the honey-bee, but the latter sort alone can be functional 
because the fecundable egg, as we have seen, invariably bears the male 
character. 
In support of the important observation of Petrunkewitsch may be 
cited the earlier observation of Henking (93). He finds that, as a rule, 
in insects generally no polar cells are formed at maturation, but merely 
polar nuclei which remain imbedded in the cytoplasm of the egg. The 
