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 environments, 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 comparatively few surviving lines of a great number of lines which have come down through long and various 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 practical 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 simplest 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 the “improvement” out of their sphere of these would leave, and the increased risks which complicated structure (in machines or beings) has to run, we shall not wonder that the simple still numerically predominate.
TO CHARLES DARWIN.
Cambridge, June 10, 1877.
My dear Mr. Darwin,—Except when you are to be aided in your work I decline to give letters of introduction to you, knowing how you are occupied and how infirm your health at any time may be. So please take this note to mean just this. The happy couple who bear it would be delighted to call some day, if you say so, and pay their respects to you, and I will tell you why I am disposed to promote their wishes.
Mr. Burgess[100] was a favorite pupil of mine, and is a young naturalist of much promise; not in my department, however, but in entomology. He takes particularly to the anatomy of insects, draws capitally, and shows talent for research, which we trust will bring forth good fruit. I cannot blame him if his modesty and caution have kept him back from publication as yet, but he has time before him, and even a sight of you will be a stimulus to his ambition as well as something to remember in after years. I need not say that he takes to Evolution; all young naturalists of any good do. He has just married the daughter of my dear old friend, the late Mr. Sullivant, who did for muscology in this country more than one man is likely ever to do again. The young lady is very dear to your good friend Mrs. Gray and to me; and, as you have more than once made a remark complimentary to American ladies, and as you are such an excellent judge, I must even give you the opportunity of extending your range of instances.
But please do not give our young friends the opportunity of calling upon you, unless it quite suits you.