460 LETTERS TO DARWIN AND OTHERS. [1862, 



But there is no " want of hybrids ; " there are plenty of 

 them, and they have mixed some few species (dogs, 

 for instance) ; but they play no important part in the 

 matters you are considering. 



" Want of connecting forms in living species," that 

 is to the purpose. Well, as a systematic botanist, I 

 wish there was a want. The connecting forms are 

 my great trouble every day. You would save me an 

 awful deal of trouble, time, and constant uncertainty, 

 if you would cause them to be wanting ! 



5. So you will not accept the motto " ex uno disce 



omnes.' 



If you admit the horse's evolution as proved, does 

 not that carry an implication of evolution in other 

 lines, of which similar, but fewer steps are known? 

 Or are all evolutions those of cavalry ? 



CAMBRIDGE, June 17, 1862. 



DEAR BKACE, Thanks for the " World." Who 

 wield its destinies ? 



It is, I suppose, your article on Darwin, a very good 

 one, for its purpose and space. 



Before you too confidently reject the evidence for 

 the existence of man in the diluvial period, just 

 turn over a very impartial and good article by Pic- 

 tet, a good judge of such matters, in the March 

 number of the " Bibliotheque Universelle de Ge- 

 neve," " De la Question sur 1'Homme Fossile." 



I presume it is in the Astor Library. If it is not, 

 you may tell Mr. Cogswell there might as well not be 

 any Astor Library. Ever thine, 



A. GRAY. 



