Sex Determination in Phylloxerans and Aphids 333 
that the egg cell of dioica fertilized by pollen from a male plant of 
the same species produces two kinds of offspring. Combining this 
result with the first experiment (1) it is certain that the egg cells 
have a definite sex-tendency, but that the product of their fertiliza- 
tion is not necessarily of the same sex; otherwise all the offspring 
in both experiments "must have been female. 
3 When Bryonia alba ¢ was crossed with B. dioica & half 
of the offspring were male and half female. Again it is evident 
that the moneecious condition (males and females on the same 
individual) is recessive to the dicecious condition. It follows that 
the decision in regard to sex rests with the male cells. “The male 
germ cells of B. dioica cannot be all of the same sex, for the off- 
spring would then be of one sex only, because it 1s certain that 
the female germ cells of B. alba are all alike. 
Correns’ scheme may be summed up by saying that the male 
is heterozygous, i. €., it contains both the male and the female 
tendencies; when the spermatozoa are produced there is a separa- 
tion of the sex characters and spermatozoa with male and female 
tendencies result; the female is homozygous and all of her eggs have 
the female tendency; when a female egg is fertilized by a female 
sperm a homozygous female results; when a female egg is fertilized 
by a male sperm a heterozygous male results owing to the domi- 
nance of the male character. 
Correns’ conclusion agrees with that in the insects in so far as 
two kinds of sperm are assumed that determine the sex of the off- 
spring, but the results are not in harmony with the facts for the 
phylloxerans, aphids, hydatina, daphnians and some other par- 
thenogenetic forms, because here the fertilized egg produces a 
female which must therefore be dominant since from it both males 
and females are produced later. Appreciating the difficulty in the 
case of the bee, Correns tried to escape from the position to which 
his view leads him if applied here by assuming that there are two 
kinds of eggs—male (parthenogenetic), afid female (sexual) eggs. 
Even if it be granted that Dzierzon’s theory for the bee is not 
conclusively proven, yet the facts seem almost oe hee in 
favor of that 1 interpretation. 
In connection with Mendelism and sex, Bateson, Punnett, 
