[[p. 5]] Mr. President,--I beg to thank the Council of the Linnean Society for the very great honour they have done me, in coupling my name with that of Charles Darwin on the celebration of this anniversary, and for the still greater and more exceptional honour, of perpetuating my features with those of my illustrious forerunner, upon the Medal you have now awarded me.

    With your permission I propose to make a few remarks both as to the actual relations between Darwin and myself prior to July 1858, and also to some peculiarities of our respective life-histories which brought about those relations, and which will, I hope, be both novel and of some general interest.

    Since the death of Darwin in 1882, I have found myself in the somewhat unusual position of receiving credit and praise from popular writers under a complete misapprehension of what my share in Darwin's work really amounted to. It has been stated (not unfrequently) in the daily and weekly press, that Darwin and myself discovered "natural selection" simultaneously, while a more daring few have declared that I was the first to discover it, and that I gave way to Darwin!

    In order to avoid further errors of this kind (which this Celebration may possibly encourage), I think it will be well to give the actual facts as simply and clearly as possible.

    The one fact that connects me with Darwin, and which, I [[p. 6]] am happy to say, has never been doubted, is that the idea of what is now termed "natural selection" or "survival of the fittest," together with its far-reaching consequences, occurred to us independently, and was first jointly announced before this Society fifty years ago.

    But, what is often forgotten by the press and the public, is, that the idea occurred to Darwin in October 1838, nearly twenty years earlier than to myself (in February 1858); and that during the whole of that twenty years he had been laboriously collecting evidence from the vast mass of literature of Biology, of Horticulture, and of Agriculture; as well as himself carrying out ingenious experiments and original observations, the extent of which is indicated by the range of subjects discussed in his 'Origin of Species,' and especially in that wonderful store-house of knowledge--his 'Animals and Plants under Domestication,' almost the whole materials for which works had been collected, and to a large extent systematised, during that twenty years.

    So far back as 1844, at a time when I had hardly thought of any serious study of nature, Darwin had written an outline of his views, which he communicated to his friends Sir Charles Lyell and Dr. (now Sir Joseph) Hooker. The former strongly urged him to publish an abstract of his theory as soon as possible, lest some other person might precede him--but he always refused till he had got together the whole of the materials for his intended great work. Then, at last, Lyell's prediction was fulfilled, and, without any apparent warning, my letter, with the enclosed Essay, came upon him, like a thunderbolt from a cloudless sky! This forced him to what he considered a premature publicity, and his two friends undertook to have our two papers read before this Society.

    How different from this long study and preparation--this philosophic caution--this determination not to make known his fruitful conception till he could back it up by overwhelming proofs--was my own conduct. The idea came to me, as it had come to Darwin, in a sudden flash of insight: it was thought out in a few hours--was written down with such a sketch of its various applications and developments as [[p. 7]] occurred to me at the moment,--then copied on thin letter-paper and sent off to Darwin--all within one week. I was then (as often since) the "young man in a hurry": he, the painstaking and patient student, seeking ever the full demonstration of the truth that he had discovered, rather than to achieve immediate personal fame.

    Such being the actual facts of the case, I should have had no cause for complaint if the respective shares of Darwin and myself in regard to the elucidation of nature's method of organic development had been thenceforth estimated as being, roughly, proportional to the time we had each bestowed upon it when it was thus first given to the world--that is to say, as 20 years is to one week. For, he had already made it his own. If the persuasion of his friends had prevailed with him, and he had published his theory, after 10 years'--15 years'--or even 18 years' elaboration of it--I should have had no part in it whatever, and he would have been at once recognised, and should be ever recognised, as the sole and undisputed discoverer and patient investigator of the great law of "Natural Selection" in all its far-reaching consequences.

    It was really a singular piece of good luck that gave to me any share whatever in the discovery. During the first half of the 19th Century (and even earlier) many great biological thinkers and workers had been pondering over the problem and had even suggested ingenious but inadequate solutions. Some of these men were among the greatest intellects of our time, yet, till Darwin, all had failed; and it was only Darwin's extreme desire to perfect his work that allowed me to come in, as a very bad second, in the truly Olympian race in which all philosophical biologists, from Buffon and Erasmus Darwin to Richard Owen and Robert Chambers, were more or less actively engaged.

    And this brings me to the very interesting question: Why did so many of the greatest intellects fail, while Darwin and myself hit upon the solution of this problem--a solution which this Celebration proves to have been (and still to be) a satisfying one to a large number of those best able to form a judgment on its merits? As I have found what seems to me [[p. 8]] a good and precise answer to this question, and one which is of some psychological interest, I will, with your permission, briefly state what it is.

    On a careful consideration, we find a curious series of correspondences, both in mind and in environment, which led Darwin and myself, alone among our contemporaries, to reach identically the same theory.

    First (and most important, as I believe), in early life both Darwin and myself became ardent beetle-hunters. Now there is certainly no group of organisms that so impresses the collector by the almost infinite number of its specific forms, the endless modifications of structure, shape, colour, and surface-markings that distinguish them from each other, and their innumerable adaptations to diverse environments. These interesting features are exhibited almost as strikingly in temperate as in tropical regions, our own comparatively limited island-fauna possessing more than 3000 species of this one order of insects.

    Again, both Darwin and myself had, what he terms "the mere passion of collecting,"--not that of studying the minutiæ of structure, either internal or external. I should describe it rather as an intense interest in the mere variety of living things--the variety that catches the eye of the observer even among those which are very much alike, but which are soon found to differ in several distinct characters.

    Now it is this superficial and almost child-like interest in the outward forms of living things, which, though often despised as unscientific, happened to be the only one which would lead us towards a solution of the problem of species. For nature herself distinguishes her species by just such characters--often exclusively so, always in some degree--very small changes in outline, or in the proportions of appendages, as give a quite distinct and recognisable facies to each, often aided by slight peculiarities in motions or habits; while in a large number of cases differences of surface-texture, of colour, or in the details of the same general scheme of colour-pattern or of shading, give an unmistakable individuality to closely allied species.

    [[p. 9]] It is the constant search for and detection of these often unexpected differences between very similar creatures, that gives such an intellectual charm and fascination to the mere collection of these insects; and when, as in the case of Darwin and myself, the collectors were of a speculative turn of mind, they were constantly led to think upon the "why" and the "how" of all this wonderful variety in nature--this overwhelming, and, at first sight, purposeless wealth of specific forms among the very humblest forms of life.

    Then, a little later (and with both of us almost accidentally) we became travellers, collectors, and observers, in some of the richest and most interesting portions of the earth; and we thus had forced upon our attention all the strange phenomena of local and geographical distribution, with the numerous problems to which they give rise. Thenceforward our interest in the great mystery of how species came into existence was intensified, and--again to use Darwin's expression--"haunted" us.

    Finally, both Darwin and myself, at the critical period when our minds were freshly stored with a considerable body of personal observation and reflection bearing upon the problem to be solved, had our attention directed to the system of positive checks as expounded by Malthus in his 'Principles of Population.' The effect of this was analogous to that of friction upon the specially-prepared match, producing that flash of insight which led us immediately to the simple but universal law of the "survival of the fittest," as the long-sought effective cause of the continuous modification and adaptation of living things.

    It is an unimportant detail that Darwin read this book two years after his return from his voyage, while I had read it before I went abroad, and it was a sudden recollection of its teachings that caused the solution to flash upon me. I attach much importance, however, to the large amount of solitude we both enjoyed during our travels, which, at the most impressionable period of our lives, gave us ample time for reflection on the phenomena we were daily observing.

    This view, of the combination of certain mental faculties [[p. 10]] and external conditions that led Darwin and myself to an identical conception, also serves to explain why none of our precursors or contemporaries hit upon what is really so very simple a solution of the great problem. Such evolutionists as Robert Chambers, Herbert Spencer, and Huxley, though of great intellect, wide knowledge, and immense power of work, had none of them the special turn of mind that makes the collector and the species-man, while they all--as well as the equally great thinker on similar lines, Sir Charles Lyell--became in early life immersed in different lines of research which engaged their chief attention.

    Neither did the actual precursors of Darwin in the statement of the principle--Wells, Matthews or Prichard--possess any adequate knowledge of the class of facts above referred to, or sufficient antecedent interest in the problem itself, which were both needed in order to perceive the application of the principle to the mode of development of the varied forms of life.

    And now, to recur to my own position, I may be allowed to make a final remark. I have long since come to see that no one deserves either praise or blame for the ideas that come to him, but only for the actions resulting therefrom. Ideas and beliefs are certainly not voluntary acts. They come to us--we hardly know how or whence, and once they have got possession of us we cannot reject or change them at will. It is for the common good that the promulgation of ideas should be free--uninfluenced by either praise or blame, reward or punishment.

    But the actions which result from our ideas may properly be so treated, because it is only by patient thought and work, that new ideas, if good and true, become adopted and utilised; while, if untrue or if not adequately presented to the world, they are rejected or forgotten.

    I therefore accept the crowning honour you have conferred on me to-day, not for the happy chance through which I became an independent originator of the doctrine of "survival of the fittest," but, as a too liberal recognition by you of the moderate amount of time and work I have given to [[p. 11]] explain and elucidate the theory, to point out some novel applications of it, and (I hope I may add) for my attempts to extend those applications, even in directions which somewhat diverged from those accepted by my honoured friend and teacher--Charles Darwin.