VI PREFACE. 



scientific friends as slips and cuttings from the Biological 

 Tree, in the belief that the great and absorbing question 

 with which they deal the problem of "Man's place in 

 Nature " will be found to invest even minute details 

 with a very real interest. 



And let me observe, in passing, that the doctrine of 

 the gradual development of organic types, if it does 

 not stand or fall with Embryology, yet must look for its 

 greatest support from, or be contradicted by, that 

 most important Science the true root-stock of Biology. 

 There is, however, no branch of human knowledge that 

 is so difficult to put into language which can be appre- 

 ciated by those who are not familiar with its special 

 methods, its facts, and its descriptive terms. 



One thing I cannot pass over without remark, and 

 that is, the strong and almost insuperable a priori 

 objection in many minds to the deductions of modern 

 Biology ; this must neither be lightly overlooked nor 

 treated flippantly. To these opponents the biologist 

 may say : " It is a very light thing that I should be 

 judged of you, or of man's judgment " ; and yet he is 

 pained at the thought of even seeming to be in oppo- 

 sition to much that the greatest and best minds hold 

 sacred. 



The biologist having given expression to this feeling 

 on his part, it is certainly the duty of the non-biological 

 opponent of his deductions to look these things fairly in 



