REID ON MENDELIAN CHARACTERS 203 



He states that sexual characters are not alternative, but that 

 while one sex predominates, traces of the other are always 

 evident. The same takes place in the case of the dominant 

 and recessive Mendelian characters, recessive appearing 

 occasionally in lines of pure dominants, and vice versa. 



This theory appears to agree with the available evidence 

 more nearly in some ways than the purely Mendelian inter- 

 pretation, but it stops far short of the facts at our disposal. 

 It is quite true that, just as traces of the opposite Men- 

 delian character are found in extracted dominants or reces- 

 sives, traces of the male are found in the female and vice 

 versa. We also find gradations between hermaphroditism 

 and complete functional differentiation of the sexes. To 

 say, however, that there is no real alternative inheritance 

 seems to be playing with words. The alternativeness may 

 not be absolutely complete, but in the case of many organisms 

 the functions of the male and female are confined to separate 

 individuals. It is possible that the potentiality of develop- 

 ing into a male or a female individual may be present in all 

 the fertilised ova. If this be the case, then there must be 

 something controlling the appearance of the characters 

 belonging to one sex, and this something must be trans- 

 mitted in an alternative manner. The very fact that 

 even in an organism where the sexes are so definitely 

 separated as in man, hermaphrodites occasionally appear, 

 suggests that one set of characters is patent and the 

 other latent. This is also suggested by the fact that one 

 or two male characters appear occasionally in the female 

 and vice versa. While therefore it is evident that, as with 

 the Mendelian characters, the alternativeness is generally 

 not complete, still the characters are alternative, and only 

 one set appears fully in one individual. 



In the vast majority of cases there seems to be an 

 explanation which is quite compatible with all that is known 

 with regard to the inheritance of sex. In some unicellular 

 organisms where fertilisation has been shown to take place, 1 



1 See p. 205. 



