Tin 



THE AMEBIC AN NATURALIST [Vol. L 



they are expected to appear when |ff] is comparatively 

 high in potency and MM comparatively low. There are 

 two possibilities for this event. (1) If we revert to our 

 original example of a cross between weak European and 

 strong Japanese races, we have in one direction : 

 Eu. $ X Jap. c? 

 |FF Mm X [FF] MM. 



80 60 TOO 80 80 

 As (FF) is inherited maternally, any generation of this 

 cross will have the weak set [FFl = 80. There is no com- 

 bination of two M's possible which is not at least 20 units 

 higher than FF, therefore no intersexual males can oc- 

 cur. Now take the reciprocal cross: 



Jap. ? X _ Eu. <$ 



@MmX \ff\ MM - 



100 80 80 60 60 



The F x males are |FF] MM and therefore normal, as 

 100 80 60 



e = — 40. F 2 from this cross has again the maternal 

 and grandmaternal set [FF] = 100. The Mendelian 

 factors MM are recombined and we get the combinations : 

 MM and MM. 



The latter males are therefore : 



|ff] mm. 



100 60 60 



This means that e has just the limiting value — 20. It 

 follows, that if we have two races, in which the relative 

 values differ only slightly from this example to the dis- 

 advantage of the weaker M, say M = 59 instead of 60, 

 male intersexuality is to be expected in the F 2 generation 

 of a cross, where the mother belongs to the stronger race. 

 This is indeed one of the actual facts. 



According to the above derived formulae these inter- 

 sexual males ought to number exactly one half of the 



