208 EVOLUTION [CHAP. Ill 



Letter 143 causes a failing group in many parts of the world, I should 

 not have anticipated the formation of new races. 



You make important remarks versus Natural Selection, 

 and you will perhaps be surprised that I do to a large 

 extent agree with you. I could show you many passages, 

 written as strongly as I could in the Origin, declaring that 

 Natural Selection can do nothing without previous variability; 

 and I have tried to put equally strongly that variability is 

 governed by many laws, mostly quite unknown. My title 

 deceives people, and I wish I had made it rather different. 

 Your phyllotaxis 1 will serve as example, for I quite agree 

 that the spiral arrangement of a certain number of whorls of 

 leaves (however that may have primordially arisen, and 

 whether quite as invariable as you state), governs the limits 

 of variability, and therefore governs what Natural Selection 

 can do. Let me explain how it arose that I laid so much 

 stress on Natural Selection, and I still think justly. I came 

 to think from geographical distribution, etc., etc., that species 

 probably change ; but for years I was stopped dead by my 

 utter incapability of seeing how every part of each creature 

 (a woodpecker or swallow, for instance) had become adapted 

 to its conditions of life. This seemed to me, and does still 

 seem, the problem to solve ; and I think Natural Selection 

 solves it, as artificial selection solves the adaptation of 

 domestic races for man's use. But I suspect that you mean 

 something further, that there is some unknown law of 

 evolution by which species necessarily change ; and if this 

 be so, I cannot agree. This, however, is too large a question 

 even for so unreasonably long a letter as this. Nevertheless, 

 just to explain by mere valueless conjectures how I 

 imagine the teeth of your elephants change, I should look 

 at the change as indirectly resulting from changes in the 

 form of the jaws, or from the development of tusks, or in the 

 case of the primigenius even from correlation with the woolly 

 covering ; in all cases Natural Selection checking the variation. 

 If, indeed, an elephant could succeed better by feeding on 

 some new kinds of food, then any variation of any kind in 

 the teeth which favoured their grinding power would be 



1 Falconer, p. 80 : " The law of Phyllotaxis ... is nearly as constant 

 in its manifestation as any of the physical laws connected with the 

 material world." 



