CHAPTER XVII.

INFLUENCE OF DARWIN UPON HOOKER AND ASA GRAY--NATURAL SELECTION AND DESIGN IN NATURE (1860–68).

Hooker wrote on November 21st, speaking of the “glorious book” in the warmest terms. Later on in the year he wrote again in the same spirit, but speaking of the difficulty he found in assimilating the immense mass of details: “It is the very hardest book to read, to full profits, that I ever tried--it is so cram-full of matter and reasoning.” Hooker must, however, have been familiar with the arguments and proofs, and for this reason did not attempt any detailed discussion. It is unnecessary to say more of Hooker’s reception of the “Origin.” During their long friendship Darwin had discussed the difficulties and the evidences of his theory more fully with him than with any other man; and, as “a man sharpeneth the countenance of his friend,” the influence of Hooker was one of the most potent forces under which Darwin produced the greatest work of his life.

Many years later, when Hooker was awarded, in 1887, the Copley Medal of the Royal Society, reviewing his past experiences and work in his speech at the anniversary dinner, he concluded by telling us that his long and intimate friendship with Charles Darwin was the great event of his scientific career.

[Sidenote: ASA GRAY.]

In sending a copy to Asa Gray, he wrote (November 11th):--

“I fully admit that there are very many difficulties not satisfactorily explained by my theory of descent with modification, but I cannot possibly believe that a false theory would explain so many classes of facts as I think it certainly does explain. On these grounds I drop my anchor, and believe that the difficulties will slowly disappear.”

Asa Gray’s reply was contained in a letter to Hooker, written January 5th, 1860, four days after reading the “Origin.” He asks that Darwin may be told of what he had written. He says that the book “is done in a _masterly manner_. It might well have taken twenty years to produce it.” He expressed the intention of reviewing the book, and seeing that Darwin and Hooker had fair play in America. A little later (January 23rd) he wrote to Darwin about the American reprint, etc., and spoke of the work itself in somewhat greater detail:--

“The _best part_, I think, is the _whole_, _i.e._ its _plan_ and _treatment_, the vast amount of facts and acute inferences handled as if you had a perfect mastery of them.... Then your candour is worth everything to your cause. It is refreshing to find a person with a new theory who frankly confesses that he finds difficulties.... The moment I understood your premisses, I felt sure you had a real foundation to hold on.... I am free to say that I never learnt so much from one book as I have from yours.”

He considered that the attempt to account for the formation of organs such as eyes by natural selection, was the weakest point in the book. This view is to be explained by his strong teleological convictions.

Although Asa Gray was the great exponent of the “Origin” in America, he could not agree with Darwin on one important point--viz. on the exclusion of the ordinary conceptions of design in nature by the principle of natural selection. He believed that the two conceptions could be reconciled, and that design in some way worked in and through natural selection. By design is here meant what Huxley called “the commoner and coarser form of teleology,” and which he believed to be now refuted--“the teleology which supposes that the eye, such as we see it in man or one of the higher vertebrata, was made with the precise structure it exhibits for the purpose of enabling the animal which possesses it to see, has undoubtedly received its death-blow.” Huxley goes on to point out that there is a “wider teleology, which ... is actually based upon the fundamental proposition of evolution ... that the whole world ... is the result of the mutual interaction, according to definite laws, of the forces possessed by the molecules of which the primitive nebulosity of the universe was composed.” Therefore, “a sufficient intelligence could, from a knowledge of the properties of the molecules of that vapour, have predicted, say, the state of the fauna of Britain in 1869, with as much certainty as one can say what will happen to the vapour of the breath on a cold winter’s day.” (“Genealogy of Animals,” _The Academy_, 1869, reprinted in “Critiques and Addresses,” and quoted in his chapter “On the Reception of the ‘Origin of Species’” in the “Life and Letters,” Vol. II.)

But at the time of the appearance of the “Origin,” many who sympathised with the general drift of the argument were not yet prepared for the “wider teleology.” Of these Asa Gray may be taken as the representative; and it will be of interest to follow the controversy between him and Darwin as regards design and natural selection. The recently published “Letters of Asa Gray to Charles Darwin” (Macmillan) enable us to follow the correspondence from the side of the great American evolutionist.

Writing November 26th, 1860, Darwin refers to one of Asa Gray’s articles on the “Origin”:--

“I grieve to say that I cannot honestly go as far as you do about Design. I am conscious that I am in an utterly hopeless muddle. I cannot think that the world, as we see it, is the result of chance; and yet I cannot look at each separate thing as the result of Design. To take a crucial example, you lead me to infer--that you believe ‘that variation has been led along certain beneficial lines.’ I cannot believe this; and I think you would have to believe, that the tail of the Fantail was led to vary in the number and direction of its feathers in order to gratify the caprice of a few men. Yet if the Fantail had been a wild bird, and had used its abnormal tail for some special end, as to sail before the wind, unlike other birds, everyone would have said, ‘What a beautiful and designed adaptation.’ Again, I say I am, and shall ever remain, in a hopeless muddle.”

Elsewhere Darwin suggested that the pouter pigeon, if it occurred wild, and used its inflated crop as a float, would be considered as a striking example of design.

This controversy between them continued for many years. We find Asa Gray referring to the argument of the pigeons three years later. Thus he wrote (September 1st, 1863):--

“I will consider about fantastic variation of pigeons. I see afar trouble enough ahead quoad design in nature, but have managed to keep off the chilliness by giving the knotty questions a rather wide berth. If I rather avoid, I cannot ignore the difficulties ahead. But if I adopt your view boldly, can you promise me any less difficulties?”

Writing the concluding paragraphs of the “Variations of Animals and Plants under Domestication,” Darwin evidently bore in mind his controversies on the subject with Asa Gray and Lyell, and the attacks of the Duke of Argyll and others. Sending advanced sheets to Asa Gray, he wrote on October 16th, 1867:--

“I finish my book with a semi-theological paragraph, in which I quote and differ from you; what you will think of it, I know not.”

In relation to this interesting controversy, I think it well to quote, almost in full, the metaphor by which Darwin enforced his argument that the origin of species by natural selection precluded a belief in design in nature as it was ordinarily conceived at the time.

This metaphor forms an important part of the conclusion of the work in question (“Variation of Animals and Plants,” etc.):

“The long-continued accumulation of beneficial variations will infallibly have led to structures as diversified, as beautifully adapted for various purposes and as excellently co-ordinated, as we see in the animals and plants around us. Hence I have spoken of selection as the paramount power, whether applied by man to the formation of domestic breeds, or by nature to the production of species. I may recur to the metaphor given in a former chapter: if an architect were to rear a noble and commodious edifice, without the use of cut stone, by selecting from the fragments at the base of a precipice wedged-formed stones for his arches, elongated stones for his lintels, and flat stones for his roof, we should admire his skill and regard him as the paramount power. Now, the fragments of stone, though indispensable to the architect, bear to the edifice built by him the same relation which the fluctuating variations of organic beings bear to the varied and admirable structures ultimately acquired by their modified descendants.

“Some authors have declared that natural selection explains nothing, unless the precise cause of each slight individual difference be made clear. If it were explained to a savage utterly ignorant of the art of building, how the edifice had been raised stone upon stone, and why wedge-formed fragments were used for the arches, flat stones for the roof, &c.; and if the use of each part and of the whole building were pointed out, it would be unreasonable if he declared that nothing had been made clear to him, because the precise cause of the shape of each fragment could not be told. But this is a nearly parallel case with the objection that selection explains nothing, because we know not the cause of each individual difference in the structure of each being.”

* * * * *

“The shape of the fragments of stone at the base of our precipice may be called accidental, but this is not strictly correct; for the shape of each depends on a long sequence of events, all obeying natural laws.... But in regard to the use to which the fragments may be put, their shape may be strictly said to be accidental....”

In his article in the _Nation_ (March 19th, 1868), Asa Gray criticised the metaphor as follows:--

“But in Mr. Darwin’s parallel, to meet the case of nature according to his own view of it, not only the fragments of rock (answering to variation) should fall, but the edifice (answering to natural selection) should rise, irrespective of will or choice!”

This passage is quoted in the “Life and Letters” (Vol. III., p. 84), and Francis Darwin makes the convincing reply:--

“But my father’s parallel demands that natural selection shall be the architect, not the edifice--the question of design only comes in with regard to the form of the building materials.”

Darwin’s reply was contained in his letter to Asa Gray dated May 8th, 1868:--

“You give a good slap at my concluding metaphor: undoubtedly I ought to have brought in and contrasted natural and artificial selection; but it seemed so obvious to me that natural selection depended on contingencies even more complex than those which must have determined the shape of each fragment at the base of my precipice. What I wanted to show was that, in reference to pre-ordainment, whatever holds good in the formation of an English pouter-pigeon holds good in the formation of a natural species of pigeon. I cannot see that this is false. If the right variations occurred, and no others, natural selection would be superfluous.”

To this, Asa Gray replied in his letter of May 25th:--

“As to close of my article, to match close of your book,--you see plainly I was put on the defence by your reference to an old hazardous remark of mine. I found your stone-house argument unanswerable in substance (for the notion of design must after all rest mostly on faith, and on accumulation of adaptations, &c.); so all I could do was to find a vulnerable spot in the shaping of it, fire my little shot, and run away in the smoke.

“Of course I understand your argument perfectly, and feel the might of it.”

From this last letter I think we may conclude that Asa Gray’s feelings on this subject rested, as he says, “on faith,” and that, intellectually, he saw no way of meeting Darwin’s arguments.