220 GENETICS 



Finally, when these newly made lacticolor males (3) 

 were crossed with heterozygous grossulariata females 

 (4) (Fig. 71), the proportion of sexes was approxi- 

 mately equal, as expected, that is, 145 males to 130 

 females, but all of the males were of the heterozygous 

 grossulariata type (2) and all of the females of the re- 

 cessive lacticolor type (5), showing a return to the sex- 

 limited condition. All of these curious results find a 

 satisfactory and complete explanation in the assump- 

 tion, first, that sex is a Mendelian character carrying 

 tw^o determiners for maleness and one for femaleness ; 

 and, second, that the determiner for the character of 

 grossulariata when present is always linked to the sex 

 determiner. 



This case is of particular interest, since it agrees 

 with the microscopical evidence already referred to 

 in connection with the chromosomes of Baltzer's sea- 

 urchins, in which the male was likewise homozygous 

 and the female heterozygous with respect to sex. 



The chromosomes of Abraxas present certain techni- 

 cal difficulties which at present have not been over- 

 come, so that we do not yet know whether the evi- 

 dence of the heterozygous character of one sex and the 

 homozygous character of the other, obtained from the 

 breeding experiments of Doncaster and Raynor, will 

 be confirmed upon a microscopic examination of the 

 chromosomes in the germ-cells. 



(3) The Behavior of Hermaphrodites in Heredity 



Certain plants occur in monoecious form, that is, as 

 hermaphrodites, and also in dioecious form, that is, with 



