Evidences of Physiological Selection. 89 



tions were not guided by the results of a verification 

 which had already been supplied. These anticipations 

 were deduced exclusively from the theory itself, as 

 representing what ought to be the case if the theory 

 were true ; and, I must confess, if I had then been 

 told that they had already been realized — that it 

 had actually been found to be a general rule that 

 endemic species present constant and hereditary 

 varieties, intimately commingled on common areas, 

 morphologically almost indistinguishable, but physio- 

 logically isolated by selective fertility — I should 

 have felt that the theory had been verified in 

 advance. For there are only two alternatives: 

 either these things are due to physiological selection, 

 or else they are due — as M. Jordan himself believes 

 — to special creation. Which is equivalent to say- 

 ing that, for evolutionists, the facts must be held 

 to verify the former theory in as complete a manner 

 as it is logically possible for the theory to be 

 verified. 



Evidence from Prepotency. 



We have now to consider the bearing of what is 

 called " prepotency '* on the theory of physiological 

 selection. 



Speaking of the vast number of species of Com- 

 positae, Darwin says : — 



There can be no doubt that if the pollen of all these species 

 could be simultaneously or successively placed on the stigma of 

 any one species, this one would elect with unerring certainty its 

 own pollen. This elective capacity is all the more wonderful, as 

 it must have been acquired since the many species of this great 

 group of plants branched off from a common progenitor. 



