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. 



Fig. 78. — Diagram showing a possible interpretation of the heredity 

 of spot of male when E. servus is crossed with E. variolarius. S = spot; 

 s = no 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 formula 

 SX SX, i.e. two doses of the S factor, no spot is assumed 

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

 first sight it seems that a female having the formula SX 

 SX 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. 



