No. 530] 



CONCEPTION OF PURE LINES 



71 



These formulae have certain advantages over those 

 now in vogue, first, because the male gene is not ignored 

 as a factor in sex determination; second, that its pres- 

 ence, both in males and females, explains how under cer- 

 tain conditions the male or the female may assume some 

 of the characters of the opposite sex; third, that the 

 paradox of the female being the heterozygous form in 

 one class and the male in the other class is, in part at 

 least, resolved; fourth, that the ease with which species 

 pass from the hermaphrodite condition to that of sexual 

 dimorphism and the reverse is understandable; fifth, 

 that the production of males by parthenogenetic females 

 can be accounted for by the loss of one of the female 

 genes in the polar body; and lastly, we see how there 

 may be two kinds of eggs, as in Dinoplillus apatris, both 

 of which can be fertilized; for, in such cases the sperma- 

 tozoa should be all alike. 



I do not wish to urge this view too positively, for I am 

 acutely aware that we are only at the beginning of our 

 understanding of the problem of sex determination, but 

 I believe that the difficulties of the current hypotheses 

 must be clearly understood and met if possible. 4 



The Inheritance of Secondary Sexual Characters 

 From the point of view reached in the preceding dis- 

 cussion let us now examine the problem of the inherit- 

 ance of secondary sexual characters. 



Males arc distinguished from females not only by the 

 presence of sperm in place of eggs, but by the presence 



in general. That view I have entirely abandoned. In the present hypoth- 

 esis the relation of the determining elements is stated in the same form as 

 in other Mendelian formulae, with the possible exception that here one gene 

 is represented as larger or smaller than its allelomorphs, and the scale is 

 turned by the mass relation between these female genes and those of the 



* I have not discussed here the possibility of selective fertilization, 

 because if we can explain the facts without this problematical assumption 

 we simplify the problem greatly. Moreover, the evidence brought forward 

 by Payne, Brown and myself, while admittedly insufficient, stands definitely 



