DEVELOPMENT OF THE GENERATIVE ORGANS. 687 
mind is to account for the occurrence of more than a single 
pair of these rudimentary organs. Ganin’s observations on 
Platygaster, however, appear to be in favour of the existence 
of two pairs of such rudiments. These groups of cells re- 
semble the imaginal discs, and are solid ovoid masses of small 
epithelioid cells measuring ‘2 mm. in their long diameter. I 
have no absolute evidence as to their true nature. 
The earliest stage in which I have been able to identify the 
gonads with certainty is the first day of the pupa state, when 
they are occasionally seen in sections as ovoid groups of small 
epithelial cells enclosed ina cellular mesoblastic capsule, which 
stains more readily than the cells enclosed within it. The 
long diameter of the capsule is ‘2 mm. 
Fic, 98.—The ovary and testis on the third day of the pupa stage ; from dissections. 
z, testis ; d, duct of the testis ; 0, ovary; gc, genital cord ; 4, hypodermis. Seen 
with an inch objective. 
On the third day of the pupa I have succeeded in dissecting 
out both the ovaries and testes, which are now very distinct, 
and in sections exhibit a marked differentiation of structure. 
The Testis on the third day of the pupa isa glistening white 
reniform body *4 mm. in diameter. The genital cord is 
attached to it laterally at the hilus; this is a slender cellular 
cord invested bya distinct peritoneal membrane which extends 
backwards towards the apex of the abdomen; it subsequently 
becomes the vas efferens. Its length isabout 1 mm.; it unites 
with its fellow at an acute angle, and forms the rudiment of 
the vas deferens, which is attached to the hypodermis a little 
in front of the position of the future anus. 
45 
