SEX DETERMINATION IN THE WHITE-FLY 281 
Schreiner’s description of the origin of cytoplasmic granules in 
case of Myxine finds one curious parallel in these cells. Very 
often a cell will show three or more nucleoli, which, judging from 
their size, have originated from the normal single nucleolus. In 
many cells the nucleolus is seen dividing, and in -others-a sort 
of budding is observable. In the latter case, smaller masses of 
nucleolar material are visible in the nucleus, some just forming 
from the parent body, others separated from it by variable dis- 
tances, but still connected with it through a-faint but definite 
thread, and still others near the periphery of the nucleus and 
entirely independent of the nucleolus. I was unable to find such 
bodies still connected with the nucleolus, but outside of the nu- 
clear membrane. In every instance where such an interpreta- 
tion might have been made, the alternative of incorrect focusing 
or confusion with cytoplasmic inclusions of a different nature 
could be held. To eliminate the latter possibility, I tried the 
expedient of destaining very strongly. Since the nucleolar mate- 
rial retains the hematoxylin after the other cell constituents 
have become decolorized, its presence outside of the nucleus could 
then be determined with more certainty. But although the nu- 
cleolar material appeared perfectly sharp and distinct inside: of 
the nucleus in such cases, none of it could ever be found definitely 
~ outside. : 
DISCUSSION 
Without attempting to give here any general review of the 
great literature relating to parthenogenesis, I will briefly indicate 
certain difficult and still obscure points which seem to call for 
further investigation. It must be remembered throughout that 
parthenogenetic eggs belong to either of two -groups~—one in 
which they are incapable of fertilization and development ‘is 
asexual in the true sense; the other inf which the eggs may be fer- 
tilized or not, development proceeding in either case. Usually 
the unfertilized eggs of this last group then develop with the hap- 
loid number of chromosomes. 
The researches of Schleip (’08), Nachtsheim (’13), and others 
have now well established the fact that in the majority of Hymen- 
