176 ZOOLOGY. 
‘“*HMerold* it was, says Weismann, in his great work on the 
‘Development of the Diptera,’ who first showed as regards the 
Lepidoptera that even in the egg, the germ of 
the sexual glands was formed, and when indeed 
the difference between the sexes is easily per- 
ceived. In the flies the same holds good, 
though indeed the differences between the 
germs of the female and male sexual we 
are less striking to the eye. .... t the 
sexual glands are formed in the egg wef: 
from their position in the midst of the fatty 
body, when they are cut off from any connec- 
tion with parts to which they could owe their 
origin. The youngest larva in which I saw 
them was a centimetre (about four-tenths of an 
inch) long, and about five days old. With 
much expense of time it would be plainly pos- 
sible to discover them even in the larva freshly 
excluded fromthe egg.” (Die Entwicklung der 
Dipteren, p. 133.) 
We may also cite the case of the larva of 
Polynema figured by Ganin (see this journal, vol. v. pp. 47, 48). 
As seen in the adjoining cut (Fig. 33) the rudiments (imaginal 
disks, t) of the ovipositor of the female are indicated at the same 
time as those of the legs (/) and wings( f) of the adult ichneu- 
mon fly. 
In Platygaster, Ganin says, ‘“the earliest indication of the sex- 
ual glands appears, as we shall see below, during the time when 
the first larval form passes into the second. With the first indi- 
cation of the ovary that of the seminal glands agrees in all its 
relations. Both appear as small roundish structures arising out of 
the embryonal cells. For a long time (in the course of all the 
larval stages) these germs of the sexual organs remain in an unor- 
ganized state.” It should be remembered, however, that the first 
larval stage of this egg-parasite which lives in the body of the 
 larve of all gall flies (Cecidomyia). is not a true larva in the usual 
sense of the word, like that of the fly; it is an embryo set loose 
Fig. 33, 
from the egg with organs not homologous with those of the fully 
*Entwicklungsgeschichte der Schmetterlinge, 1815. 
