130 A Defence of Mendel's 



cross individuals ? Here again, generally speaking, when 

 thoroughly green cotyledons are crossed with thoroughly 

 yellow cotyledons, the first-cross seeds will have yellow 

 cotyledons ; when fully round peas are crossed with fully 

 wrinkled the first result will generally speaking be round, 

 often with slight pitting as Mendel has stated. This has 

 been the usual experience of Correns, Tschermak, Mendel, 

 and myself* and, as we shall see, the amount of clear 

 and substantial evidence to the contrary is still exceed- 

 ingly small. But as any experienced naturalist would 

 venture to predict, there is no universal rule in the 

 matter. As Professor Weldon himself declares, had there 

 been such a universal rule it would surely have been 

 notorious. He might further have reflected that in 

 Mendel's day, when hybridisation was not the terra 

 incognita it has since become, the assertion of such uni- 

 versal propositions would have been peculiarly foolish. 

 Mendel does not make it ; but Professor Weldon perceiving 

 the inherent improbability of the assertion conceives at 

 once that Mendel must have made it, and if Mendel 

 doesn't say so in words then he must have implied it. 

 As a matter of fact Mendel never treats dominance as 

 more than an incident in his results, merely using it as 

 a means to an end, and I see no reason to suppose he 

 troubled to consider to what extent the phenomenon is or 

 is not universal a matter with which he had no concern. 



* The varieties used were Express, Laxton's Alpha, Fillbasket, 

 McLean's Blue Peter, Serpette nain blanc, British Queen, tres nain 

 de Bretagne., Sabre, mange-tout Debarbieux, and a large "grey" 

 sugar-pea, pois sans parchemin geant a tres large cosse. Not counting 

 the last two, five are round and three are wrinkled. As to cotyledons, 

 six have yellow and four have green. In about 80 crosses I saw no 

 exception to dominance of yellow ; but one apparently clear case of 

 dominance of wrinkled and some doubtful ones. 



