7.66.) TO G. FREDERICK WRIGHT. 667 
how Kingsley caught at my essay, which was reprinted 
in England long ago; see his memoirs 
1877. 
I would say to President Fairchild something like 
this : 
Where only one individual out of a thousand or 
a million can survive to maturity and propagation, 
clearly only the very best adapted to the environment 
will so survive; and in somewhat different environ- 
ments, only those best adapted respectively to the 
two, three, or more different environments. The 
intermediates, i. e., those least particularly adapted to 
the two or three different emergencies, surely have 
least chance. 
Now our species of plants and animals are the com- 
paratively few surviving lines of a great number of 
lines which have come down through long and vari- 
ous periods of great tribulation, in the literal sense 
of the word; they have been ground over and over, 
first on this trial, then on that, leaving, as it seems 
to me, no chance of the survival, side by side, of all 
sorts and shades of intermediate forms. Hence, 
under this, and the general law of heredity, the prac- 
tical distinction of species and genera appears to be a 
natural result. 
That low, and even the lowest, forms of life should 
survive and abound all down the ages, and be the 
most widely diffused over the earth, seems also the 
most natural result, being simple adaptations to sim- 
plest conditions of air and water, so nearly the same 
the world over. These are still far most numerous in 
individuals, and have, so to say, the surest hold on 
life. When we think of the vast void below which 
