RECAPITULATION AND CONCLUSION 431 



as showing how transient such impressions are, to remember that 

 the greatest discovery ever made by man, namely, the law of the 

 attraction of gravity, was also attacked by Leibnitz, "as sub- 

 versive of natural, and inferentially of revealed, religion." A 

 celebrated author and divine has written to me that "he has 

 gradually learned to see that it is just as noble a conception of 

 the Deity to believe that He created a few original forms capable 

 of self-development into other and needful forms, as to believe 

 that He required a fresh act of creation to supply the voids 

 caused by the action of His laws." 



Why, it may be asked, until recently did nearly all the most 

 eminent living naturalists and geologists disbelieve in the mu- 

 tability of species? It cannot be asserted that organic beings in a 

 state of nature are subject to no variation; it cannot be proved 

 that the amount of variation in the course of long ages is a 

 limited quantity; no clear distinction has been, or can be, drawn 

 between species and well-marked varieties. It cannot be main- 

 tained that species when intercrossed are invariably sterile and 

 varieties invariably fertile; or that sterility is a special endow- 

 ment and sign of creation. The belief that species were immu- 

 table productions was almost unavoidable as long as the history 

 of the world was thought to be of short duration; and now that 

 we have acquired some idea of the lapse of time, we are too apt 

 to assume, without proof, that the geological record is so perfect 

 that it would have afforded us plain evidence of the mutation of 

 species, if they had undergone mutation. 



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 

 m-any geologists, when Lyell first insisted that long lines of in- 

 land cliffs had been formed, and great valleys excavated, by the 

 agencies which we still see at work. The mind cannot possibly 

 grasp the full meaning of the term of even a million years; it 

 cannot add up and perceive the full effects of many slight varia- 

 tions, accumulated during an almost infinite number of genera- 

 tions. 



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 ex- 

 pect to convince experienced naturalists whose minds are stocked 

 with a multitude of facts all viewed, during 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 crea- 



