266 



THE THEORY OF THE GENE 



The Transformation of Bidder's Organ of the 

 Male Toad into an Ovary. 



The anterior part of the testis of the male toad is com- 

 posed of rounded cells that resemble young egg-cells 



Fig. 147. 



Bidder's organ at the anterior end of the testis of a half -grown 

 male of a California species of Bufo. The lobes of the fat bodies 

 lie at the sides, the kidney beneath. The testes are indicated by the 

 branching blood vessels in their walls, the Bidder's organs lie in 

 front of the testes each consisting of several lobes. 



(Fig. 147). It is conspicuous in the young toad even be- 

 fore the germ-cells in the more posterior part or testis 

 proper have differentiated. The anterior part is called 

 Bidder's organ and has for many years excited the inter- 



