No. 574] 



INHERITANCE 



ewe (or else more developed in the ram than in the ewe) ; 

 the color of butterflies like Papilio Mcmnon, with three 

 types of females ; and the dark spot on the abdomen of the 

 male of the bug Euchistus variolarius. These characters 

 can not be transferred through the gametes to the female 

 of their own race by any known combination. 



Whether one likes or does not like the particular terms 

 used to denote these two classes of cases, the fact remains 

 that there are two such categories, and to ignore their 

 existence is only to make obscure a distinction that is per- 

 fectly plain. 



Concerning the mechanism involved there is something 

 more that may be said. It has been sufficiently shown in 

 the case of sex-linked inheritance that the sex-linked char- 

 acter follows the known distribution of the sex chromo- 

 somes. It is unnecessary to repeat here the abundant 

 evidence jn support of this statement. The simplest inter- 

 pretation of this known relation is that the character is 

 dependent for its realization on the sex chromosomes. I 

 do not mean, of course, that the sex chromosomes alone 

 produce the character but that something in these chromo- 

 somes, some "factor," acting in conjunction with the rest 

 of the cell, conditions the character. 



On the other hand, in the case of sex-limited characters 

 the facts can not be explained on the assumption that the 

 characters follow the sex chromosomes. It is clear that 

 they do not do so. But we can give a consistent interpre- 

 tation of the facts if we assume that sex-limited characters 

 follow the distribution of the ordinary chromosomes. 



Since this relation has recently been not understood 

 and misinterpreted I may be pardoned, I hope, for taking 

 up the question once more. 



Wood crossed horned Dorset sheep with hornless Suf- 

 folk*. The sons had horns, the daughters lacked them. 

 Inbred these gave in the F 2 generation— horned 3; 

 hornless J, 1; horned 9. 1; hornless $, 3. Bateson and 

 Punnett have shown that the results are explicable on the 

 basis that one factor for horns in the male produces 



