JST. 52.] TO A. DE CANDOLLE. 497 



species, and origin. Well, he has got on about as 

 far towards you as I have. It is clear enough that, 

 as I thought at first, derivation of species is to be 

 the word, and natural selection admitted. The only 

 question is, whether this is enough. 



Ever your attached friend, 



A. GRAY. 



TO A. DE CANDOLLE. 



CAMBRIDGE, February 16, 1863. 



I am disposed to join issue with you on the question 

 of Linnaeus' definition of species. I have long pon- 

 dered your discussion of the subject in " Geographic 

 Botanique," and still think, on the supposition of 

 the fixity of species (which Linna3us of course had 

 in view), that between " community of descent " and 

 " likeness," the former and not the latter is the fun- 

 damental conception in the idea of species. We may 

 test this by inquiring whether of the two can be de- 

 rived from the other. The likeness, I suppose, is the 

 consequence of the community of descent. But, then, 

 as the likeness is a thing of degrees, and, according 

 to present probabilities, species may have only a rela- 

 tive and temporary fixity, your view will after all 

 have the advantage ; and the question of species will 

 come to be metaphysical or logical, rather than nat- 

 ural-historical. The worst of all is that there will 

 remain no objective basis or standard; and species 

 will be what each naturalist thinks best so to con- 

 sider ! 



I am pleased to know that the view of my article 

 on the " Memoirs " 1 is well received by you. Read- 



1 " Memoirs of Augustin Pyramus De Candolle," Am. Jour. Sci., 

 xxxv. 1-10. 



