§ 4 



SEXUAL CYCLE OF BUFO BUFO $ AND $ 



139 



Reciprocally with this loss, there is an intensive activity in 

 the germinativc tissue, resulting in the formation of sperma- 

 togonia and oogonia (Fig. 96 A, B). The organ of BIDDER 

 is no exception, for there, too, restitution is greatest in the 

 summer months following the breeding period (Fig. 96 C). 



The size of this organ diminishes in winter with the for- 

 mation of corpora lutea, and increases again in summer. It is 

 probable that the gametogenesis is prompted by a gonado- 

 trophic stimulus from the hypophysis (Fig. 96). It is also 

 evident from the atrophy of the organ of BIDDER, and the 

 gonads after hypophysectomy (HoUSSAY, 1929) that this 

 potential ovary is subject to a similar gonadotrophic influence 

 from the hypophysis. 



Experiments on mammals with gonadotrophic hormones 

 such as Ambinon (anterior pituitary extract "Organon") and 

 Pregnyl (chorionic gonadotrophin "Organon") showed two 

 different effects in the male. Ambinon caused, through some 

 luteinisation factor, a marked increase of corpora lutea in 



A. ° 

 lutein, fact. 



Ambinon 

 Pregnyl 



VpTt't'' ""<■"'• 



ovid. 



characterist. 



org. Bidder. ovary 



sexual- endocrine 

 System of Bufo bufo O and O 



Fig. 96. The pituitary influence on the sexual endocrine organization in 



Bufo bufo. 



