DARWIN'S FINAL VIEWS 17 



independently of their habits of Hfe, the same fundamental type of struc- 

 ture, and because they graduate into each other. Moreover, members of 

 the same class can in most cases be shown to be closely alike at an early 

 embryonic age. These facts can be explained on the belief of their descent 

 from a common form; therefore it may be safely admitted that all the 

 members of the same class are descended from one progenitor. But as the 

 members of quite distinct classes have something in common in structure 

 and much in common in constitution, analogy would lead us one step 

 further, and to infer as probable that all Hving creatures are descended 

 from a single prototype. 



I hope that the reader will pause before coming to any final and hostile 

 conclusion on the theory of natural selection. The reader may consult my 

 " Origin of Species " for a general sketch of the whole subject; but in that 

 work he has to take many statements on trust. In considering the theory 

 of natural selection, he will assuredly meet with weighty difficulties, but 

 these difficulties relate chiefly to subjects — such as the degree of perfec- 

 tion of the geological record, the means of distribution, the possibility of 

 transitions in organs, etc., on which we are confessedly ignorant; nor do 

 we know how ignorant we are. If we are much more ignorant than is 

 generally supposed, most of these difficulties wholly disappear. Let the 

 reader reflect on the difficulty of looking at whole classes of facts from a 

 new point of view. Let him observe how slowly, but surely, the noble 

 views of Lyell on the gradual changes now in progress on the earth's sur- 

 face have been accepted as sufficient to account for all that we see in its 

 past history. The present action of natural selection may seem more or 

 less probable; but I believe in the truth of the theory, because it collects, 

 under one point of view, and gives a rational explanation of, many ap- 

 parently independent classes of facts. 



In his earlier statements of his theory, Darwin does not 

 seem to have paid much attention to the source of variations 

 or to the manner of their inheritance, but these subjects re- 

 ceive much attention in his great work on the Variation of 

 animals and plants under domestication, from which we 

 have just quoted. He seems to have come more and more to 

 hold views similar to those of Lamarck, his great French pre- 

 decessor, regarding the direct effect of environment as a cause 

 of variation, and the inheritance of effects so produced. Con- 

 cerning the general nature of Lamarck's views we should 

 therefore inform ourselves. 



