Bailey.] ^ ^^ [Mayl. 1S9G. 



conviction. I have no proof. I have no proof that the sun will rise to- 

 morrow. But the greater the collection of facts and of data which we 

 make respecting the evolution of the world in the past, the more are tlie 

 clianges seen to be continuous and gradual ; and it seems to me that if 

 evolution has taught us anything it has been to show that there is a law 

 of evolution, continuous throughout time. I believe, myself, that evolu- 

 tion is true from beginning to finish of creation ; and if we could not 

 prophesy that our race has nobler possibilities for the future I should lose 

 my zest to live. 



Spontaneous variations are not necessarily sports in the sense in which 

 I refer to them. Sports are those forms of variation which appear to lie 

 outside the general or customary type of variation of the species — or phy- 

 lum — with which we are dealing. They are those forms which are so 

 unusual as to be ordinarily considered to be a taxonomic variety or divi- 

 sion or subspecies. Tiie causes of sports are unknown to us, as are also 

 the causes of all spontaneous differences whicli may be of much less 

 moment. The fact that Darwin dwelt upon the origin of sports in domes- 

 tic animals is a matter which I discussed in my paper and, I believe, it is 

 the chief line of effort in which man's work differs from nature's — the fact 

 that he does save the sports and breed them up. I have no evidence 

 that nature does the same ; and so far as the plant creation is concerned, 

 I am more and more convinced that sports have had but comparatively 

 small influence upon the phylogenies of our present types. 



I wish to add just one word in reference to a matter which Prof. Conk- 

 lin introduced. He took issue with Prof. Cope with respect to the doc- 

 trine of natural selection and the notion that Darwin did not attempt to 

 account for variation. The doctrine of natural selection itself does not ac- 

 count for variation. It has been the misfortune of Darwin's writings that 

 his doctrine of natural selection has been so emphasized as to overshadow 

 everything else which he did. Amongst the causes of variability which 

 Darwin enumerates are external stimuli, soil, weather, food, climate and 

 other impinging factors ; so that Darwin conceived the idea that imping- 

 ing stimuli were the causes of variations which, when they have arisen, 

 have been bred up by natural selection. 



