THE GENITAL GLANDS AND DUCTS INDIFFERENT STAGE 



217 



ens over the ventro-median surface of the fold, becomes many-layered and bulges 

 into the ccelom ventrally, producing the longitudinal genital fold. The genital 

 fold thus lies mesial and parallel to the mesonephric fold. At 10 to 12 mm. the 

 genital epithelium shows no sexual differentiation (Fig. 214). There is a super- 

 ficial epithelial layer and an inner epithelial mass of somewhat open structure. 



Owing to the great development of the suprarenal glands and metanephroi, 

 the cranial portions of the urogenital folds, at first parallel and close together, are 

 separated. This produces a double bend in the fold and in 20 to 25 mm. embryos 

 the fold shows a cranial longitudinal portion, a transverse middle portion between 

 the bends, and a longitudinal caudal portion. In the last named, the mesonephric 



Lot. body 



Post, cardinal V -2. 



Suprarenal 

 gLand. 

 Glonierulus 



Mesonephrit 



Inner epithet, mass 

 ofqenifaL yiand. 



Epithelium of 



qen'itaL y{atid 



Mesentery 



FIG. 214. Transverse section through the mesonephros, genital gland and suprarenal gland of the right 

 side; from a 12 mm. human embryo. X 165. 



ducts course to the cloaca and here the right and left folds fuse, producing the 

 genital cord (Fig. 225). As the genital glands increase in size they become con- 

 stricted from the mesonephric fold by lateral and ventral grooves until the origi- 

 nally broad base of the genital fold is converted into a stalk (Fig. 220). This 

 stalk-like attachment extends lengthwise and forms in the male the mesorchium, 

 in the female the mesovarium. The urogenital fold is, at the same time, constricted 

 from the dorsal body wall until it is attached only by a narrow mesentery which 

 eventually forms either the lig. testis or lig. ovarii. 



The Indifferent Stage of the Genital Ducts. The mesonephric ducts, with 

 the degeneration of the mesonephroi, become the male genital ducts. In both 



