Sex-limited inheritance in 

 Lychnis dioica L. 



By George Harrison Shull, 



Station for Experimental Evolution, Cold Spring Harbor, Long Island. 

 (Eingegangen am 12. Marz 1914.) 



The hereditary distribution of sex-limited characters has been by 

 far the most fruitful source of experimental evidence concerning the 

 inheritance of sex, though crosses between hermaphroditic and dioecious 

 organisms have also given important data supporting the same conclusions. 

 It was in fact a cross of the latter sort between Bryonia alba and 

 B. dioica which led CORRENS (1907) to the clear formulation of the genetic 

 relationship between the sexes which has now been generally adopted, 

 the one sex being recognized as homozygous, the other heterozygous, with 

 respect to a sex-determiner which is inherited as a Mendelian gene. 

 The first statement of this hypothesis seems to have been made by 

 GEOFFREY SMITH (1906) as a deduction from the effects of parasitic 

 castration of the crab, Inachus, together with the discoveries of the cyto- 

 logists that the sexes are in many cases characterized by chromosome 

 differences which lead necessarily to the inference that, in these cases at 

 least, the one sex is homogametic, the other heterogametic. SMITH laid 

 no special stress upon this hypothesis as a generally applicable Mendelian 

 interpretation of the sexes, and as his statement was not based upon 

 genetic experiments, it has been generally overlooked by geneticists. 



The greater value of sex-limited characters for the genetic study 

 of the sexes, is due solely to the fact that such characters are relatively 

 common, while the occurrence of hermaphrodites in sufficiently near 

 relationship to dioecious species that crosses between them yield fertile 

 offspring, is very rare. The fact that the Fi hybrids between Bryonia 

 dioica and B. alba are sterile, makes it impossible to go beyond the 

 simple demonstration that when the cross is executed in the one di- 

 rection a uniform progeny results, while a cross in the opposite direction 



Induktive Abstammungs- und Vererbungslehre. XII. 19 



