686 THE GENERATIVE ORGANS. 
he found the gonads in the embryo of Pieris Brassice as red 
dots in the dorsal region of the eighth segment of the body 
right and left of the dorsal vessel. Brandt’s description of 
these bodies in the embryo tallies with Herold’s description 
of them in the caterpillar. Brandt adds, ‘In this stage they 
are elliptical bodies consisting of embryonic cells, with amoeboid 
nuclei, and are either attached to their ducts by the side or 
the posterior end; in the former case they are testes, and in 
the latter, ovaries.’ 
Brandt gives figures representing the several stages of the 
development of the ovaries and testes from these bodies, which 
are quite convincing as to their origin. 
Ganin [848] says the sexual organs, in Platygaster, first 
appear as two rounded cellular masses on each side of the 
primitive band close to the termination of the digestive tube ; 
these two masses are united with each other, one elongates 
and becomes the duct, and the other becomes the gonad. 
Weismann concluded that the rudiments of the gonads 
make their appearance in the embryo in Musca and Sarcophaga, 
but he was unsuccessful in discovering them before the larvae 
had attained the length of a centimetre; he, however, saw and 
described them in the newly-hatched larva of Corethra, which, 
owing to its transparency, is a favourable object for the in- 
vestigation. 
I have sought for these bodies in both the embryo and 
larva of the Blow-fly, but have failed to find them either 
in the embryo or newly-hatched larva. The investigation 
is one of great difficulty, however, owing to their minute 
size and the fact that there is no means of recognising them 
and distinguishing them from other groups of embryonic 
cells. 
In the larva of about one centimetre in length I have found 
in sections one or occasionally two pairs of encapsulated groups 
of small embryonic cells, situated in the fifth abdominal segment 
imbedded in the fat bodies on either side of, and dorsally to, 
the alimentary canal, which correspond in general characters 
and position to rudimentary gonads. The difficulty in my 
