Principles of Heredity 183 



Magenta Lavender White 



red faiutly tinged 



1901 1st batch 19 27 14 

 2nd 9 20 9 



1902 1st 12 23 11 

 2nd 14 26 11 



54 96 45 



The numbers 54 : 96 : 45 approach the ratio 1:2:1 

 so nearly that there can be no doubt we have here a simple 

 case of Mendelian laws, operating without definite domi- 

 nance, but rather with blending. 



When Laxton speaks of the "remarkably fine but 

 unfixable pea Evolution " we now know for the first time 

 exactly what the phenomenon meant. It, like the " Giant 

 Lavender," was a "mule" form, not represented by germ- 

 cells, and in each year arose by " self-crossing." 



This is only one case among many similar ones seen in 

 the Chinese Primrose. In others there is no doubt that 

 more complex factors are at work, the subdivision of 

 compound characters, and so on. The history of the 

 "Giant Lavender" goes back many years and is not 

 known with sufficient precision for our purposes, but 

 like all these forms it originated from crossings among 

 the old simple colour varieties of sinensis. 



VI. THE ARGUMENT BUILT ON EXCEPTIONS. 



So much for the enormous advance that the Mendelian 

 principles already permit us to make. But what does 

 Professor Weldon offer to substitute for all this ? Nothing. 



Professor Weldon suggests that a study of ancestry 

 will help us. Having recited Tschermak's exceptions and 



