CASTLE: THE HEREDITY OF SEX. 201 
first of these polar nuclei commonly divides about at the time of forma- 
tion of the second polar nucleus. There are thus formed three polar 
nuclei (or cells), which all lie imbedded in the cytoplasm of the 
egg. There regularly takes place a fusion of the inner derivative 
of the first polar cell with the second polar cell, exactly as observed 
by Petrunkewitsch in the case of the honey-bee. Further develop- 
ment of this body was not observed in most of the cases studied by 
Henking, though he mentions certain apparently abortive “ attempts” at 
division by this body. The outer product of division of the first polar 
cell was observed regularly to undergo disintegration without further 
change, except in a few cases, such as that of the parthenogenetic gall- 
wasp, Rhodites rosae, in which all three polar nuclei fuse into a single 
body. Henking seems to regard ultimate disintegration as the normal 
fate of all the polar nuclei, whether or not conjugation has occurred 
among them. This is precisely what the observations of Petrunke- 
witsch would lead us to expect in the case of all fertilized eggs, as well 
as of parthenogenetic eggs which form but one polar cell. We have no 
reason to suppose that Henking ever studied the development of a male 
parthenogenetic egg, in which sort alone (in addition possibly to Rhodites) 
we should expect to find the genital gland of the embryo developing out 
of the conjugated polar nuclei. 
If, contrary to the opinion of Petrunkewitsch, it shall be found that in 
the male honey-bee the testis develops, not from polar cells, but from a 
blastomere, we may well look for evidence of segregation of the testis fund- 
ament early in cleavage. For, if our assumption be correct, that in par- 
thenogenetic animals the female character is uniformly dominant over the 
male, it will be impossible for the male character to find expression in 
the soma of the individual, until the female character has been elimi- 
nated from it. 
(6) Speceal Cases. 
The explanations offered of sex-heredity in the honey-bee and rotifer 
are applicable to all cases known to the writer of normally parthenogenetic 
animals, except two. These are the gall-wasp Rhodites rosae, and the 
rotifer Hydatina senta. 
A. RHODITES ROSAE 
In Rhodites males are very rare, and parthenogenesis is the normal 
method of reproduction. According to Henking, the unfertilized egg in 
this species undergoes two maturation divisions, yet the offspring devel- 
