532 Colonel R. Meinertzhagon on [Ibis, 



only cases of mutational variation which I can call to mind 

 in nature are dimorphic forms, and it is by no means proved 

 that such are mutational. 



The mutationist will argue that whenever a domesticated 

 variety resumes a wild life, the original wild stock being 

 dominant to the recessive domesticated variety, such variety 

 must revert, and that such a process is in strict accord with 

 Mendel's theory. 



But under natural conditions^ constant variations, which 

 unaided Nature has produced and which natural selection 

 has perpetuated^ do not revert. This still farther convinces 

 me that it is dangerous to apply to wild life the results of 

 evolutional experiments on domestic animals and plants. 

 Both the experiments of Mendel and of more recent investi- 

 gators have been conducted under conditions which do not 

 exist in wild nature. 



I would further mention that there is no artificial mutation 

 wdiich resembles any known variation separating natural 

 species one from the other. Whether we take the domestic 

 pigeon, fowl, or canary, it is remarkable that no single 

 artificial variety has ever, so far as we know, occurred in a 

 wild state. 



I would also mention that natural selection^ where environ- 

 ment remains unchanged, has no effect on evolution, except 

 in those few cases of dimorphism which may or may not be 

 mutational. But such an exception is pure theory. 



I do, however, agree that in some cases natural selection 

 may have allowed dimorphism, which is possibly mutational, 

 to initiate a species. Such cases exist among the genus 

 (Enantlie, in the Jackdaws {Colceus dauricus and neglectus) , 

 in the Skuas, and in many others. It appears that such 

 mutants niight establish themselves as good species, which 

 would result in two species, separated by slight superficial 

 differences, inhabiting the same area. Such a state at present 

 exists among the Tree-creepers, Dippers, Eock-Nuthatches, 

 the Whooper [C. c}/gnus) and Bewick's Swan (C,'. heimrli), 

 and others. 



But I cannot call to mind any geographical race which 



