152 W. J. MOENKHAUS 
however, that, as careful determinations upon different species 
multiply, the condition of unequal ratios will be found increasingly 
common. Any theory of sex must take into consideration this 
normal inequality in the sex-ratios. 
Sex-ratio like color, size etc., is a character belonging to a 
species. Sexuality of course is not, for it is common to all species 
reproducing by the sexual method. The particular form of sexu- 
ality, however, the proportion of the two sexual persons to which 
it gives expression in the process of differentiation, this is specific. 
For Drosophila ampelophila, the ratio of one male to 1.126 females 
is a specific character. This is not a ratio of merely the present 
generations but has been transmitted from generations remote. 
It is inherited. It is the expression of the physiological condition 
to which the species has been developed by its environmental 
demands. 
Like other specific characters this ratio should be subject to 
modification, but this should not be more easily done or by other 
methods, in general, than those used in the modification of other 
characters. From this view point it should not be expected that 
the sex-ratio in an animal could be materially changed by such 
agents as food, temperature,etc. A change in the proportion of the 
sexes involves a much more fundamental modification than simple 
starvation or the reverse is likely to induce. In regard to other 
characters, we have long ago ceased to regard them as modifiable 
by such methods, but in the case of sex, it is only recently that 
their futility is being entertained. The most potent factor and 
the one most generally used to modify a character is selection. 
If the experiments herein recorded prove what they are held to 
prove, this process of selection is a potent factor in the modifica- 
tion of the sex-ratio also. It would be interesting to try to line 
this fact up with the chromosomal conception of sex. However, 
the writer regards this as the task of those who are engaged in 
these interesting and important investigations. 
