126 Rev. J. T. Gulick on the 



confining our attention to Mr, Wallace's very interesting and 

 suggestive volume on ' Darwinism ' we shall be better able to 

 judge of the possibility of producing a self-consistent theory 

 on this basis ; but we should bear in mind that the same view 

 is maintained by many naturalists, and that parallel statements 

 abound in their writings. Mr. Wallace^s volume not only 

 embodies the mature reflections of one of the joint autiiors of 

 the theory of natural selection, but it fairly represeuts that 

 phase of biological theory which considers diversity of natural 

 selection through exposure to different environments the only 

 cause of divergence. The following passage will show the 

 exclusive nature of his theory : — " A great body of facts on 

 the one hand and some weighty arguments on the other alike 

 prove that specific characters have been and could only have 

 been developed and fixed by natural selection because of their 

 utility. We may admit that among the great number of 

 variations and sports which continually arise many are alto- 

 gether useless without being hurtful ; but no cause or influ- 

 ence has been adduced adequate to render such characters 

 fixed and constant throughout the vast number of individuals 

 which constitute any of the more dominant species " (' Dar- 

 winism,' p. 142). This is in strong contrast with the follow- 

 ing passage from the close of the Introduction of the sixth 

 edition of the ' Origin of Species,' whicli is the last one that 

 received the revision of the autlior : — " I am fully convinced 

 that species are not inmiutable, but those belonging to what 

 are called the same genera are lineal descendants of some 

 other and generally extinct species, in the same manner as 

 the acknowledged varieties of any one species are the descen- 

 dants of that species. Furthermore 1 am convinced that 

 Natural Selection has been the most important, but not the 

 exclusive, means of modification." On page 421 of the same 

 edition Darwin calls attention to the fact that this passage 

 has " been placed in a most conspicuous position " in the 

 different editions of his work, and complains of the writers 

 who misrepresent his conclusions on this point. 



Facts that are neglected or denied. 

 Though Darwin maintains tliat besides the inherited effects 

 of use and disuse and the direct action of the external con- 

 ditions there arc other forms of variation loading to permanent 

 modifications of structure independently of natural selection 

 {'Origin of Species,' 6th London ed. p. 421), he does not 

 attempt to exjilain how these divergences arise. Neither 

 Darwin nor Walhice apjioars to have observed that, as in 

 domestication, the isolatctl breeding of otiier than average 



