418 MY LIFE 



rate of change of insects, he asked me for a short statement 

 of my conclusions on these subjects. On the latter point I 

 wrote : — 



" As regards insects changing rapidly, I see nothing 

 improbable in it, because, though in a totally different way, 

 they are as highly specialized as are birds or mammals, and, 

 through the transformations they undergo, have still more 

 complicated relations with the organic and inorganic worlds. 

 For instance, they are subject to different kinds of danger 

 in their larva, pupa, and imago state ; they have different 

 enemies and special means of protection in each of these 

 states, and changes of climate may probably affect them 

 differently in each state. We may therefore expect very 

 slight changes in the proportions of other animals, in physical 

 geography, or in climate, to produce an immediate change in 

 their numbers, and often in their organization. The fact that 

 they do change rapidly is, I think, shown by the large number 

 of peculiar species of insects in Madeira as compared with 

 the birds and plants ; the same thing occurs in Corsica, where 

 there are many peculiar species of insects ; also, we see the 

 very limited range of many insects as found by Bates and 

 myself. Again, your rule of the slow change of mollusca 

 applies to aquatic species only. The land-shells, I presume, 

 change much more rapidly ; or why are almost every species 

 in Madeira and in each of the West Indian islands peculiar? 

 Being terrestrial, they are affected as insects are by physical 

 changes, and more still by organic changes. Such changes 

 are certainly much slower in the sea." 



Later on, in May, after reading my article on " The Races 

 of Man and Natural Selection," which Darwin thought so 

 highly of, though at the same time he was quite distressed 

 at my conclusion that natural selection could not have done 

 it all, Sir Charles objected (May 22, 1864) — very naturally 

 for a geologist, and for one who had so recently become a 

 convert to Darwin's views — that my suggestion of man's pos- 

 sible origination, so early as the Miocene, was due to my 

 " want of appreciation of the immensity of time at our disposal, 

 without going back beyond the Newer Pliocene." 



