134 CYCLIC CHANGES IV 



§ 4. THE SEXUAL CYCLE OF BUFO BUFO $ AND ? 



Among Amphibia, as second group of Anamnia, Bufo bufo 

 interested us, especially because of the organ of BIDDER, 

 v/hich, in the adult animal is present in both sexes, and takes 

 an active part in the sexual cycle. The statistical histological 

 investigation made by BRETSCHNEIDER extends to the 5th 

 year of life in this species of toad, and relates to both males 

 and females. So far the following parts of the genital appar- 

 atus have been examined. 



a. The fat-body lies in front of the gonad, and its 

 behaviour during the reproductive cycle is similar to that of 

 other organs associated with metabolism. The only signifi- 

 cant fact is that the boundary between the fat-body and the 

 organ of BIDDER is variable. 



b. The organ of BIDDER lies behind the fat-body and may 

 be regarded, in both sexes, as a rudimentary ovary which, 

 however, shows certain cyclic variations. In both sexes the 

 germinal tissue produces oocytes which, together with their 

 follicular wall, form genuine corpora lutea, whose secretion 

 acts upon the oviduct. The formation of corpora lutea does 

 not differ in any respect from that in Rhodeus, but is limited 

 to fairly young oocytes, which remain undeveloped. Those 

 exceptions in which a few BiDDER-oocytes continue to grow 

 to considerable size show the ovarian nature of this organ, 

 2nd support the supposition that it actually is a rudimentary 

 ovary. 



c. The ovary lies behind the organ of BIDDER. It forms 

 oocytes, some of which change into corpora lutea while 

 others mature and ovulate, the ruptured follicle remaining 

 behind as calyx simplex. 



Oogenesis and corpus luteum formation in the ovary were 

 examined cytologically, and compared with similar processes 

 occurring in the organ of BIDDER. 



d. The testis arises from the genital tract. Its development, 

 spermatogenesis and the intcrstitium were examined cyto- 



