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 Brace, — 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 ‘ Bibliothéque Universelle de Ge- 
néve,” “ De la Question sur 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. 
