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 $ sX s 



sXs spotless c? 



sXS spotted g 



SXs spotted (J 



SXS spotted (J 



FIG. 78. Diagram to show inheritance of spot when E. rariplarius (?) 

 is mated to E. servus (cT). 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 F 2 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 y 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. 



