Breeding experiments which show that hybridisation and mutation etc. 221 



an Fl containing both rubricalyx and rubrinervis, but no other types 

 or intermediates (1). It was, therefore, heterozygous in the ordinary 

 Mendelian sense, as is further demonstrated by the fact that the F2 

 ■offspring of Fj rubricalyx plants gave a simple 3 : i ratio of rubricalyx 

 and rubrinervis. This fact is of great importance, for it shows that 



Fig. 10. O. mut. rubricalyx, fuU-growTi plant. 



one unit change and one only was concerned in the appearance of 

 the original rubricalyx individual. It is all the more necessary to 

 insist upon this point, because Mendelians have introduced here a 

 fallacy in the interpretation of the polymorphic descendants of single 

 mutant individuals. I have already pointed out this fallacy (Gates 

 1913 b, p. 141), but it must be reiterated because it affects many of 



(1) It should also be emplasized that there were no intermediates between the 

 irubricalyx mutant and the rubrinervis population in which it appeared, a fact which 

 Heribert-Nilsson (1912) fails to take into account. See Gates (191: b). 



