LYMANTRIA DISPAR 4I 



determining genes, very strong (F 70) in the Japanese 

 variety and weak (F 24) in the European; that all the 

 autosomes carry sex-determining genes, some male- and 

 some female-determining, and that in the Japanese variety 

 the autosomal female-determining genes are strong (F 20) 

 and weak in the European (F 4). 



By the use of these assumptions, which are exactly like 

 those made by Goldschmidt himself elsewhere, all reference 

 to the c\1;oplasm can be avoided and the facts of sex- 

 determination in Lymantria can be brought into line with 

 the rest. 



Baltzer (1937), who for many years had been studying 

 problems of sex-determination and of intersexuality in 

 Bonellia viridis, found himself unable to accept Gold- 

 schmidt's notion of the turning point or switch-over. 



This marine worm in its larval form floats on the surface 

 of the sea. When it settles on or near the proboscis of an 

 adult female it thereafter pursues a male differentiation. 

 If, on the other hand, chance leaves it far removed from an 

 adult female, it becomes a female. If the young individual, 

 having begun to differentiate as a male, is removed to a 

 distance from the adult female its differentiation switches 

 to the female pattern and an intersexual form results. It has 

 been shown that there is a chemical substance in the female's 

 proboscis which dominates the sexual differentiation of the 

 young individual. 



These events relate to the physiology of sex-differentia- 

 tion and not to the phenomenon of sex-determination. 

 There may or may not be a chromosomal, genetic, sex- 

 determining mechanism in Bonellia. If there is it is over- 

 ridden by an external chemical influence. 



Baltzer is satisfied that in the intersex of Bonellia there is 

 no purely male development period followed by a female de- 

 velopment period but that the intersexual organs are inter- 

 sexual from the beginning. 



