§ 4 SEXUAL CYCLE OF BUFO BUFO $ AND $ 137 



which it drops again. In comparison to the size of the animal 

 as indicating its age, we may say that the significance of the 

 organ of BIDDER is inversely proportional to the age of the 

 animal. If we compare the development of the oviduct up 

 to the first oviposition with the production of corpora lutea 

 from both the potential and the genuine ovary (Fig. 94 B) , 

 we see that growth and shrinkage of the oviduct run parallel 

 with the frequency of corpora lutea. In the young animal 

 in the summer, there are a great number of corpora lutea, 

 and the oviduct is large; but in winter it is small. While 

 the organ of BIDDER is active, in pro-estrus, the oviduct 

 expands strongly and at estrus numerous large ovarian cor- 

 pora lutea appear. The decreasing hormone content of the 

 involuting organ of BIDDER is compensated by the enormous- 

 ly increasing hormone content of the ovary. jDuring the 

 inter-estrus which follows, the ovarian corpora lutea regulate 

 the size of the oviduct and prevent its atrophy, which would 

 set in on castration (Fig. 94 B). During the period of 

 growth and differentiation the oviduct is influenced by the 

 corpora lutea of the organ of BIDDER, whose incretion pre- 

 pares it for the subsequent functional period. It hyper- 

 trophies during the pro-estrus under the influence of the 

 corpora lutea in the organ of BIDDER and the ovary, and is 

 maintained, during inter-estrus, at a sufficient degree of 

 development by the corpora lutea of the ovary to prevent 

 atrophy. 



g. The significance of the organ of BIDDER in the male. 



The possession of a potential ovary and oviduct suggests 

 that the male Bufo is hermaphrodite. Whereas, in many 

 amphibia, the rudimentary oviduct atrophies, in Bufo bufo 

 it remains quiescent. It is largest in size simultaneously with 

 a maximum production of corpora lutea in the organ of 

 Bidder, and smallest in the inter-estrus (Fig. 95), as in the 

 female. Neither our own histological analysis nor the experi- 

 mental investigations of other writers were able to prove 

 convincingly the existence of any other function of the organ 

 of Bidder in the male. We can explain the significance of 



