The Discovery of Natural Selection 



diverse environments. These interesting features are ex- 

 hibited almost as strikingly in temperate as in tropical 

 regions, our own comparatively limited island-fauna pos- 

 sessing more than 3,000 species of this one order of insects. 



Again, both Darwin and myself had what he terms 

 " the mere passion for collecting,*' not that of studying 

 the minutiae of structure, either internal or external. I 

 should describe it rather as an intense interest in the 

 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 w^hich, 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 motion or 

 habit ; while in a larger number of cases differences of sur- 

 face-texture, of colour, or in the details of the same general 

 scheme of colour-pattern or of shading, give an unmistak- 

 able indi^4duality 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 when, as in the case of Dar- 

 win and myself, the collectors were of a speculative turn of 

 mind, they w^ere constantly led to think upon the ^' why '* 

 and the ** how '' of all this w^onderful 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 acci- 

 dentally) 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, 



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