Mendelism 



261 



which it appears to be so. The fundamental fact in Men- 

 delian inheritance then is segregation, not dominance. 



In the cases just cited segregation is perfectly evident in the 

 second generation, but there are cases in which it is not. 

 There is a breed of domestic rabbit known as the " lop- 

 eared" rabbit in which the ears are very long and pendant. 

 When such a rabbit is paired with the ordinary kind, the 

 ears of the hybrid are intermediate in length, and this condi- 

 tion persists in succeeding generations. Is this not a true 



INHERITANCE IN GUINEA PIGS 



Figs. A and B, the parents; C, the first generation, the second gener- 

 tion containing animals of all four types, A, B, C and D. From Castle, 

 ' ' Genetics and Eugenics. ' ' 



By permission of Harvard University Press. 



" blend" between different degrees of ear length? The mu- 

 latto is another example of an apparent blending of charac- 

 ters in inheritance. Is a different interpretation possible? 



There are certain varieties of corn with yellow kernels, 

 which when crossed with white corn give yellow offspring. 

 These latter, when mated with each other, give, instead of 

 the usual Mendelian ratio of 3 :1, fifteen yellows to one white. 

 This is exactly what we should expect if there were two char- 

 acters involved in producing the color of the yellow variety, 

 for when two pairs of factors are involved in a cross i.e., 

 tall, red peas x dwarf whites ; long-winged, gray fruit flies x 

 black, dwarf -winged ; black, rough ("rosette") haired guinea 



