might have come about, both in the animal and vegetable kingdoms.  As soon as this reason was provided them, they turned to the store of facts within their own knowledge, and rapidly arranged the evidence which had been lurking only partly visible in favour of the fact of evolution.  It cannot be disputed that here and there earlier writers than Darwin and Wallace had suggested the possibility of natural selection acting upon existing variations so as to cause survival of the fittest.  MacGillivray, the Scots naturalist, and the father of Huxley’s companion on the Rattlesnake, had published suggestions which came exceedingly near to Darwin’s theory.  In 1831 Mr. Patrick Matthew had published a work on Naval Architecture and Timber, and in it had stated the essential principle of the Darwinian doctrine of struggle and survival.  Still earlier, in 1813, a Dr. W.C.  Wells, in a paper to the Royal Society on “A White Female, Part of whose Skin Resembles that of a Negro,” had, as Darwin himself freely admitted, distinctly recognised the principle of natural selection—­but applied it only to the races of man, and to certain characters alone.  Finally, long before either of these, Aristotle himself had written, in Physics, ii., 8:  “Why are not the things which seem the result of design, merely spontaneous variations, which, being useful, have been preserved, while others are continually eliminated as unsuitable?” None of these foreshadowings were supported by lengthy evidence, nor worked out into an elaborate theory; and it was not until Darwin had done this that we can say the birth of natural selection really took place.  Huxley writes: 

“The suggestion that new species may result from the selective action of external conditions upon the variations from their specific type which individuals present,—­and which we call ‘spontaneous,’ because we are ignorant of their causation,—­is as wholly unknown to the historian of scientific ideas as it was to biological specialists before 1858.”

But that suggestion is the central idea of the origin of species, and contains the quintessence of Darwinism.

Some weeks before the Origin was published, Darwin wrote to Huxley, sending him a copy of the work, and asking him for the names of eminent foreigners to whom it should be sent.  In the course of his letter he wrote:  “I shall be intensely curious to hear what effect the book produces on you,” and it was clear that he had no very confident expectation of a favourable opinion.  Huxley replied the day before the Origin was published, saying that he had finished the volume, and stating that it had completely convinced him of the fact of evolution, and that he fully accepted natural selection as a “true cause for the production of species.”  Darwin, in a letter to Wallace, telling of his doubts and fears concerning the reception of his book, had added the postscript:  “I think I told you before that Hooker is a complete convert.  If I can convert Huxley, I shall be content.”  When he received Huxley’s letter he replied at once: