CONCLUSION. 467 



But the chief cause of our natural unwillingness to admit 

 that one species has given birth to other and distinct species, 

 is that we are always slow in admitting great changes of 

 which we do not see the steps. The difficulty is the same 

 as that felt by so many geologists, when Lyell first insisted 

 that long lines of inland cliffs had been formed, and great 

 valleys excavated, by the agencies which we still see at work. 

 The mind cannot possibly grasp the full meaniDg of the term 

 of even a million years ; it cannot add up and perceive the 

 full effects of many slight variations, accumulated during an 

 almost infinite number of generations. 



Although I am fully convinced of the truth of the views 

 given in this volume under the form of an abstract, I by 

 no means expect to convince experienced naturalists whose 

 minds are stocked with a multitude of facts all viewed, dur- 

 ing a long course of years, from a point of view directly 

 opposite to mine. It is so easy to hide our ignorance under 

 such expressions as the " plan of creation," " unity of de- 

 sign," etc., and to think that we give an explanation when 

 we only restate a fact. Any one whose disposition leads him 

 to attach more weight to unexplained difficulties than to the 

 explanation of a certain number of facts will certainly reject 

 the theory. A few naturalists, endowed with much flexibil- 

 ity of mind, and who have already begun to doubt the immu- 

 tability of species, may be influenced by this volume ; but I 

 look with confidence to the future, to young and rising nat- 

 uralists, who will be able to view both sides of the question 

 with impartiality. Whoever is led to believe that species 

 are mutable will do good service by conscientiously express- 

 ing his conviction ; for thus only can the load of prejudice 

 by which this subject is overwhelmed be removed. 



Several eminent naturalists have of late published their 

 belief that a multitude of reputed species in each genus are 

 not real species ; but that other species are real, that is, have 

 been independently created. This seems to me a strange 

 conclusion to arrive at. They admit that a multitude of 

 forms, which till lately they themselves thought were spe- 

 cial creations, and which are still thus looked at by the 

 majority of naturalists, and which consequently have all the 

 external characteristic features of true species — they admit 

 that these have been produced by variation, but they refuse 

 to extend the same view to other and slightly different forms. 

 Nevertheless, they do not pretend that they can define, or 

 eyen conjecture, which are the created forms of life, and 



