SEX DETERMINATION IN THE WHITE-FLY 293 
The fact that development in the frog can be induced arti- 
ficially has been known for some time (Guyer, ’07; Bataillon, ’11; 
Loeb and Bancroft, 713 and others). Without entering into the 
question as to the nature of such a stimulus, it might be noted 
that Loeb (’18) reports that he has raised two females and seven 
males to maturity from such eggs. One of the males examined 
showed that the number of chromosomes is very probably diploid 
and certainly not haploid. On this basis Loeb offers as one of 
several hypotheses that the male is homozygous for sex, while 
the female is heterozygous, possibly being haploid. This would 
not explain the production of both sexes, although chromosomal 
irregularities accentuated by the abnormal method of develop- 
ment may possibly account for this also. But such a hypothesis 
disregards Swingle’s (’17) counts of chromosomes in Rana pipiens, 
which seem to show that the female has twenty-six chromosomes 
while the males have twenty-five.’ 
The maturation phenomena in the egg of Trialeurodes vapor- 
ariorum as it occurs in America probably belong to the group of 
which the bee is a typical representative, but unlike the latter, 
does not present complications due to the formation of multiple 
chromosomes. Conditions shown by the English form, involv- 
ing the parthenogenetic production of females, very probably 
resemble the cases mentioned in this discussion, where the dip- 
loid number is retained through a reunion of polar body and 
nucleus or secondary doubling in soma or germ cells. Regarding 
the spermatogenesis, the entire elimination of the reduction divi- 
sion is not found in any other animal so far investigated, although 
very often paralleled in the maturation of eggs. 
That the two extreme types of chromosomal behavior during 
maturation should be found within a single order, and even in 
such closely related families as the Aphidiidae and Aleyrodidae, 
lends force to the argument that the two types of maturation are 
not in reality as different as appearances indicate. In the bee 
type, the diploid female complex naturally has 2 X, while the 
’ Loeb has since then raised more frogs that were parthenogenetically pro- 
duced, and C. L. Parmenter, Jour. Gen. Physiol., vol. 2, who has investigated 
their cytology, finds that the chromosome number is clearly diploid. 
