44 Evolution and Adaptation 



it was pointed out by Geoffroy Saint-Hilaire that, since the 

 conditions of the Egyptian climate are the same to-day as 

 they were two thousand years ago, there is no reason to 

 expect any change would have taken place. But waiving 

 this assumption, we should not forget that the theory of evo- 

 lution does not postulate that a change must take place 

 in the course of time, but only that it may take place 

 sometimes. 



The position that we have here taken in regard to the 

 lack of evidence as to the transformation of species is, per- 

 haps, extreme, for, as will be shown in some detail in later 

 chapters, there is abundant evidence proving that species 

 have been seen to change greatly when the conditions sur- 

 rounding them have been changed ; but never, as has been 

 stated, so far, or rather in such a way, that an actual new 

 species that is infertile with the original form has been pro- 

 duced. Whether, after all, these changes due to a change 

 in the environment are of the kind that makes new species, 

 is also a question to be discussed later. 



The experimental evidence, in favor of the transformation 

 of species, relates almost entirely to domesticated forms, and 

 in this case the conscious agency of man seems, in some cases, 

 to have played an important part ; but here, even with the 

 aid of the factor of isolation, it cannot be claimed that a 

 single new species has been produced, although great 

 changes in form have been effected. It is clear, therefore, 

 that we must, at present, rely on other data, less satisfac- 

 tory in all respects, to establish the probability of the theory 

 of transformation. 



MODERN CRITICISM OF THE THEORY OF EVOLUTION 



Throughout the whole of the nineteenth century a steady 

 fire of criticism was directed against the theory of evolution ; 

 the names of Cuvier and of Louis Agassiz stand out preemi- 



