360 



THE AMERICAN NATUEALIST [Vol. LII 



Fg FemoJe Gametes 



c Sf O O O O 



ol 



.© 



AABB 



AAS* 







e 





© 



© 



AO.B-&- 









© 



e 



© 





e 



© 



© 



F z Zygotes Pftenotypic Ratio j 



//to^«a£/Ve Experiment:-^ " 



But practically 5 instead of 9 somatic types were actually 

 found because gene "A" and gene "B" are so nearly equal in 

 value that it is not possible in a given individual, simply by 

 measuring the skin-color pigment, to determine whether gene 

 "A" or gene "B" is responsible for the quantity of melanin 

 possessed. Thus in the 5 classes the two 54 per cent, cases 

 (AABb) and the two 55 per cent, cases (AaBB) constitute the 

 three quarters blacks or "sambos," the two 21 per cent (Aabb) 

 cases and the two 23 per cent. (aaBb) eases constitute the one 

 quarter blacks or "quadroons," while the one 36 per cent. 

 ' AAbb) case and the one 40 per cent. (aaBB) case are so nearly 

 like the four 38 per cent. (i. e., the "mulatto" AaBb) that they 

 constitute a single class of six individuals. Hence the contracted 

 ratio 1:4:6:4:1. 



