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 hsema- 

 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 



FIG. 100. A section through the ovary of a pupa about four days old. f, fat-cells ; 

 /, mesoblastic ligament continuous with the fat bodies ; ;;/, mesoblastic stroma ; 

 y, 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 Brassicse. 



b. On the supposed Origin of the Rudimentary Gonads in the 

 Embryo from the Polar Cells of Weismann. 



The investigations of Metschnikow [341] and Leuckart 

 [342] on the development of the ovaries in the viviparous larvae 

 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 



