No. 580] INFERTILITY OF DROSOPHILA 



249 



double fertilization has actually brought about the par- 

 ticular results that that case shows. 



Incidentally this sex mosaic (gynandromorph) and others 

 of its kind confirm the conclusions drawn from grafting 

 experiments in insects, namely, those in which the testes 

 were grafted into the female and the ovary into the male 

 without influence on the secondary sexual characters that 

 developed later. These characters in the insects must be 

 determined by the chromosomal composition of the cells, 

 and not be affected by the sex " glands" as such. In 

 contrast to this situation in the insects we find in birds 

 that the sex ''glands" of the female play an important 

 role in the suppressing in the female of some of the sec- 

 ondary sexual characters— characters that appear only in 

 the males or in castrated females. Gynandromorphs are 

 exceedingly rare in birds, but there are a few well-authen- 

 ticated cases. It is difficult to explain their occurrence 

 under the conditions named above. It is just possible, how- 

 ever, that their occurrence may be accounted for in the fol- 

 lowing way. If a mosaic condition of the chromosomal 

 complex shouldarise the secondary sexual characters would 

 still all be like those of the female, owing to the presence 

 of the ovarian secretion, but, if, in such a case, the ovary 

 should become infected, or degenerate through senile 

 changes, the true male parts might sooner develop the 

 characteristics of the male than do the true female parts, 

 i. e., those parts of the body that have the female sex com- 

 plex. This suggestion has no value unless it may lead 

 some one to examine the condition of the ovary, when such 



An examination of the ovaries of many rudimentary 

 females was made. In the majority of cases the ovaries 

 become nearly as large as those in the normal female, and 

 while they may contain full-sized eggs most of the eggs 

 remain immature. Examination of the food shows that 

 very few eggs are laid ; in fact, most females lay no eggs. 

 Of those laid some at least hatch. From these observa- 

 tions, and from the experiments, it seems clear that the 



