PREFACE. 



PERHAPS it may be thought that, on the whole, I might 

 very well have spared myself this small venture ; but 

 the truth is that, days, weeks, months, years, I have 

 remained so assiduously by these matters, that I cannot 

 but seem to myself to be still burthened with a certain 

 responsibility in their regard. 



Mr. Darwin (Life and Letters, ii. 222) tells W. B. 

 Carpenter : " I have found the most extraordinary diffi- 

 culty in making even able men understand at what I 

 was driving." Nor can he always withhold similar 

 expressions of inquietude from others of his corre- 

 spondents. " This review and Harvey's letter have 

 convinced me that I must be a very bad explainer; 

 neither really understand what I mean by natural 

 selection; I am inclined to give up the attempt as 

 hopeless : those who do not understand, it seems, cannot 

 be made to understand." So he complains (p. 316) to Sir 

 Joseph Hooker; while to Sir Charles Ly ell (p. 317) he 

 writes thus : " I am beginning to despair of ever making 

 the majority understand my notions ; several reviews and 

 several letters have shown me too clearly how little I am 



ix 



