THE EFFECTS OF CASTRATION 



153 



panying diagram (Fig. 78) . The analysis rests on the 

 assumption that neither one, nor two doses of S in the 

 female is able to produce a spot, while in the male one 

 dose of S suffices. 



E. variolarius ? SX ~ SX 

 E. servus S sX — s 



<^ 



%\CA 



F, 



<. 



Gametes 



of /^l 



sXSX spotless 9 /<:S' cP^"^ ^<^^ 



sXS spotted S /^- -^ '*^'3^-^> ^<^ ' ^ 



I Eggs sX — SX ' ' ^ 



i— U' 



i Sperm sZ — SX — s — S 



■^•^ '>}) -^, 



F, 



sXsX 



sXSX 



SXsX 



SXSX 



sXs 



sXS 

 SXs 



SXS 



<^yN^. 



> 



^ 



K 



/ 





spotless ? 



spotless (? 



spotted (J 



spotted (J 



spotted cJ 



Fig. 78. — Diagram to show inheritance of spot when E. variolarius (?) 

 is mated to E. servus (d). S ^ spot. s= no spot. X = sex chromosome, 

 that does not carry the factor S for spot. 



It is very important to understand just what is meant 

 by this ; for otherwise it may seem only like a restate- 

 ment of the facts. In the F2 female with the formulae 

 SXSX, with two doses of the S factor, no spot is as- 

 sumed to appear (nor in the hybrid female >SXsX). At 

 first sight it seems that a female having the formula 

 SXSX is only double the male with sXS, especially if 

 small s is interpreted to mean absence of spots. But 

 this view, in fact, involves a misconception of what the 

 factorial hypothesis is intended to mean. 



