220 Basis of Sex Determination 



lacuum, * is no longer so mysterious. This worm nor- 

 mally possesses in the segments near the head a pair of 

 ovaries and several pairs of testes. Janda found that if 

 the anterior parts containing the gonads of these worms 

 are cut off a complete regeneration takes place, includ- 

 ing both types of gonads, ovaries as well as testes. As 

 a rule, more than one pair of ovaries appear in the 

 regenerated piece. This important experiment shows 

 that in a hermaphrodite both types of sex organs 

 can be produced from body cells or from latent buds 

 resembling body cells. This phenomenon would be 

 intelligible on the assumption that in the body of a 

 hermaphrodite substances circulate which favour the 

 development of both types of sex organs, while in a 

 dicecian animal probably only one type of sex organ 

 would be developed; the formation of the other being 

 inhibited. 



Richard Goldschmidt has discovered in his breeding 

 experiments on the gipsy-moth (Lymantria dispar) 

 a phenomenon which will probably throw much light 

 on the physiology of sex determination. He found 

 that certain crosses between the Japanese and the 

 European gipsy-moth do not give pure sexes, males or 

 females, but mixtures of the sexual characters of both 

 sexes, and this mixture is a very definite one for defin- 

 ite crosses. These differences are such that it is 

 possible to grade the hybrids according to their mani- 



* Janda, V., Arch. f. Entwcklngsmech., 1912, xxxiii., 345; xxxiv., 557. 



