208 GERM-CELL CYCLE IN ANIMALS 
a posterior region which becomes an ovary or testis. 
Bidder’s Organ persists in the adult of males, where 
it lies just anterior to the testis, but in the females 
of Bufo variabilis, B. cinereus, B. clamita, and B. 
lentiginosus it disappears at the end of the second 
year. Bufo vulgaris seems to differ from the other 
species since here Bidder’s Organ persists, becom- 
ing small and shrunken during the winter (Ognew, 
1906) and regenerating during the summer months 
(Knappe, 1886). At first the cells in both the 
anterior and posterior portions of the genital ridge 
are similar, all possessing a polymorphic nucleus, 
and dividing mitotically, but later those of Bidder’s 
Organ begin to divide amitotically and assume the 
characteristics of young odcytes with rounded nuclei. 
Knappe (1886) claims that these cells never become 
functional ova because they are unable to form yolk. 
King (1908), however, does not consider this prob- 
able, but traces their differentiation to irregularities 
in the synizesis stage. 
By most investigators Bidder’s Organ is regarded 
as a rudimentary ovary. Others believe that the 
AMPHIBIA were derived from hermaphroditic ances- 
tors and that in the male it is a rudimentary ovary 
and in the female a rudimentary testis. This seems 
more probable than Marshall’s suggestion that this 
organ is the result of degenerative processes proceed- 
ing backward from the anterior end of the genital 
ridge, or than that it represents the remains of a 
sex gland possessed by the larve of ancestral toads 
when they were pedogenetic, as Axolotl is at the 
