8 Darwin, and after Darwin. 



facts, has been well-nigh universally superseded. But 

 this great gain has been attended by some measure of 

 loss. For while not a few naturalists have since erred 

 on the side of insufficiently distinguishing between fully 

 verified principles of evolution and merely specula- 

 tive deductions therefrom, a still larger number have 

 formed for themselves a Darwinian creed, and regard 

 any further theorizing on the subject of evolution as 

 ipso facto unorthodox. 



Having occupied the best years of my life in 

 closely studying the literature of Darwinism, I shall 

 endeavour throughout the following pages to avoid 

 both these extremes. No one in this generation is 

 able to imitate Darwin, either as an observer or a 

 generalizer. But this does not hinder that we should 

 all so far endeavour to follow his method, as always to 

 draw a clear distinction, not merely between observa- 

 tion and deduction, but also between degrees of 

 verification. At all events, my own aim will every- 

 where be to avoid dogmatism on the one hand, and 

 undue timidity as regards general reasoning on the 

 other. For everything that is said justification will 

 be given ; and, as far as prolonged deliberation has 

 enabled me to do so, the exact value of such justifica- 

 tion will be rendered by a statement of at least the 

 main grounds on which it rests. The somewhat 

 extensive range of the present treatise, however, will 

 not admit of my rendering more than a small percen- 

 tage of the facts which in each case go to corroborate 

 the conclusion. But although a great deal must thus 

 be necessarily lost on the one side, I am disposed to 

 think that more will be gained on the other, by 

 presenting, in a terser form than would otherwise be 



