HORMONES AND REPRODUCTION 



57 



such substances as androsterone which are biologically 

 less active. 



6. THE OVARY 



The vertebrate ovary is a solid organ encased in 

 connective tissue and covered by a thin sheet of cells. 

 These cells form the germinal epithelium, which is 



Germinal 

 epithelium 



Oogonium 



Oocyte 



Interstitial 

 tissue 





Fig. 6. — The structure of the ovary of a star- 

 ling, showing a j'^olk-^fiUed primary oocyte. 



continuous with the peritoneum, and they are highly 

 important since from them the ovary is replenished with 

 eggs. The centre of the organ is filled with a matrix of 

 fibrous connective tissue through which run blood 

 vessels and lymph spaces, and in which are embedded 

 the growing eggs. Each egg is enclosed in a group of 



