Origin of Different Kinds of Adaptations 369 



it so often is in Darwin's writings, when the theory of natural 

 selection fails to give a sufficient explanation. 



On the other hand, this is one of the cases that seem to 

 fit in excellently with the mutation theory, for if these two 

 forms of the primrose should appear, as mutations, and if, as 

 is the case, they do not blend when crossed, but are equally 

 inherited, they would both continue to exist as we find them 

 to-day. Whether the similar forms were infertile with each 

 other would be determined at the outset by the nature of 

 the individual variation, and if, despite this obvious disadvan- 

 tage, the forms could still continue to propagate themselves, 

 the new dimorphic form would remain in existence. Darwin 

 cannot explain the origin of dimorphic forms and trimorphic 

 forms unless he can show that there is some advantage in 

 having two forms, and as we have seen, he fails completely 

 to show that there is an advantage. On the other hand, the 

 result might have been reached on the mutation theory, even 

 if the dimorphic and trimorphic forms were placed at a 

 greater disadvantage than were the parent forms. In such 

 a case fewer individuals might appear, or find a foothold ; but 

 as long as the race could be kept up the new forms would 

 remain in existence. Thus, while no attempt is made to ex- 

 plain what has always been, and may possibly long remain, 

 inexplicable to us, namely, the origin of the new form itself, 

 yet granting that such new forms may sometimes appear 

 spontaneously, they may be able to establish themselves, re- 

 gardless of whether they are a little more or a little less well 

 adapted to the environment than were their parent forms. 

 If it should appear that the question is begged by the as- 

 sumption that mutations such as these may appear (at one 

 step or by a series of steps is immaterial), it should not be 

 forgotten that the whole Darwinian theory itself also rests 

 on the spontaneous appearance of fluctuating variations, 

 whose origin it does not pretend to explain. In this re- 

 spect both theories are on the same footing, but where the 



