DEVELOPMENT OF THE GENERATIVE ORGANS. 689 
neck, which is continuous with the genital cord, and with a 
number of diverging finger-like processes, the rudimentary 
egg-stocks, which radiate towards the convex surface of the 
ovary. These consist of cells precisely similar to those of 
the neck of the ovary. The egg-stocks are enclosed in a thick 
capsule of mesoblastic cells, which sends processes between 
them, separating them from each other. Like the capsule of 
the testis, this tissue stains much more deeply with hema- 
toxylon than the epithelial elements (egg-stocks) which it 
surrounds. 
The rudimentary gonads and the genital cords in both sexes 
are surrounded by, and attached to, the remains of the larval 
fat-bodies, and the mesoblastic tissue of the ovary forms a 
Fic. 100,—A section through the ovary of a pupa about four days old. f fat-cells ; 
7, mesoblastic ligament continuous with the fat bodies ; 7, mesoblastic stroma ; 
J yelk-stocks. 
kind of broad ligament connecting it with the hypodermis in 
the region from which the oviducts are formed (Fig. 100). 
The above description of the gonads in the Blow-fly pupa 
agrees in all essential particulars with Brandt’s description of 
the rudimentary gonads in the larva of Pieris Brassicz. 
b. On the supposed Origin of the Rudimentary Gonads in the 
Embryo from the Polar Cells of Weismann. 
The investigations of Metschnikow [841] and Leuckart 
[842] on the development of the ovaries in the viviparous larvee 
of Cecidomyia have led many authorities to regard the polar 
cells of Weismann as the origin of the gonads. According to 
the above-named observers, the four polar cells are formed by 
the proliferation of a single cell, which is separated from the 
