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 find 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 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, color 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 temperature as in tropical regions, our own comparatively limited island fauna possessing more than 3,000 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 minutiae 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 recognizable facies to each, often aided by slight peculiarities in motions or habits; while in a large number of cases differences of surface-texture, of color, or in the details of the same general scheme of color-pattern or of shading, give an unmistakable individuality to closely allied species.
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