INBREEDING AND SELECTION IN DROSOPHILA AMPELOPHILA 151 
TABLE 13 
PER CENT | PER CENT 
OF FEMALE OF MALE 
INFLUENCE INFLUENCE 
Re 
Experiment 1-from broods selected for one { 212 214 92.7 Phew 
POMELRUIOUG 5. VA Wao nir: +f os eA ee | 214 212 65 85 
Experiment 2-from broods selected for 2 and 3f 252 255 78 | 22 
POMETA LIONS 2S i's. <1 Uday sche mplays fap ee meets | 255 252) 100 0 
Experiment 3-from broods selected for 4 and 5f{ 275 278 100 | 0 
PeMerablOnS:s 25.4 vases 4. eee oe \ 278 275] 
87 13 
This fact of the prevailing or exclusive influence of the female in 
determining the sex-ratio occurs in some other species of animals. 
Phylloxerans (Morgan’09) and Dinophilus apatris (Korschelt’82). 
On the other hand, Whitney (’09) seems to have shown that in 
rotifers certain eggs which will produce males if unfertilized 
are changed to females, if impregnated. In the case of Droso- 
phila, we can not be certain that the sex-ratio is established before 
fertilization since the experiments do not with certainty entirely 
exclude the male influence. 
5. Discussion of sex-ratio 
It is not the intention to enter into an elaborate discussion of 
the problem of sex control. The literature is certainly already 
sufficiently burdened with such. The writer wishes merely to 
point out briefly a few conclusions about sex in this species which 
his results seem to warrant. 
The property of sexuality possessed by this species expresses 
itself not in the equal production, numerically, of its two states, 
male and female, but in an unequal production. Studies in normal 
sex-ratios involving a sufficiently large number of individuals are 
not numerous. The unequal production of the two sexes in the 
human species is well established. Montgomery (’08) has given 
the data of a large number of individuals of Theridium and finds 
a marked inequality in the sexes. The general assumption seems 
to be that an equal sex-ratio is the rule. It is not improbable, 
