788 The Theory of Sex and Sexual Genesis.  [August, 4 
Todd’s Cyclop., art. Generation). But experiments that have | 
been made on the larvæ of butterflies and maths furnish the mot 
conclusive evidence that has yet been obtained of the determina- 
tion of sex in animals by conditions of nutrition. 
In the Am. NATURALIST for March, 1873, an account is given 
by Mrs. Mary Treat of experiments on this point, both with but- 
terflies and moths. Larvæ that were shut up in paper boxes soon 
after the last molt and deprived of food, nearly all developed into 
males ; while larvæ of the same lot that were highly fed on good 
food as long as they would eat, nearly all developed into females. 
Similar experiments have been made by Gentry with moths, and 
with the same results; and he adds the following facts which 
came under his notice in the course of his observations and ex- 
periments: 1. That males are the invariable result when the 
larvæ are fed on diseased or innutritious food; 2. That in the 
fall, when the leaves have not their usual amount of sap, , 
are generally produced ; 3.. That more males are produced late in 
the season than females ; 4. That the sexes in early life cannot 
be distinguished, the change being brought about late in life by : 
the conditions of nutrition” (Abstract in Pop. Sct. Mon., April, 
1874, of a paper communicated to the Phil. Acad. of Sci.). In 
the case of the well-fed larve there is a greater accumula 
nutritive material to be reorganized in the metamorphosis than 
there is in the case of the ill-fed larve; while the other condi- 
tions of development, temperature and the supply of oxygen a 4 
the same for both. 
The effect which the time of the impregnation of the 
in determining sex has yet to be considered in its beari 
foregoing theory of sex. Girou found that if the female flowers 
of dicecious plants be fertilized as soon as they are 
the pollen, the seed resulting produced mainly female 
and that if the fertilization be deferred to as late period as 
ble, the seeds resulting produce mainly male plants. ‘da 
from this idea, and supposing that the complete ma ah 
ovum might be very favorable to the production of the si 
and inversely, M. Thury, of Geneva (1863), caused gait F 
impregnated, sometimes at the beginning, sometimes at 
of the rutting period. In the first case he obtaine 
in the second male calves. The experiment was 
Swiss agriculturalist, M. Cornaz, who twenty-nine 
EER I a A E ANT AS PEN EE N E E E E E 
lation of — 
ovum has : 
ngsonthe 
fit to receive , 
“Starting 
d female calves: q 
ated by? s 
times in wer 
SA Re EEEN Se eT ee 
