RECAPITULATION AND CONCLUSION 433 



tuis' philosophical axiom of "least action" leads the mind more 

 willingly to admit the smaller number; and certainly we ought 

 not to believe that innumerable beings within each great class 

 have been created with plain, but deceptive, marks of descent 

 from a single parent. 



As a record of a former state of things, I have retained in the 

 foregoing paragraphs, and elsewhere, several sentences which 

 imply that naturalists believe in the separate creation of each 

 species ; and I have been much censured for having thus expressed 

 myself. But undoubtedly this was the general belief when the first 

 edition of the present work appeared. I formerly spoke to very 

 many naturalists on the subject of evolution, and never once met 

 with any sjnupathetic agreement. It is probable that some did 

 then believe in evolution, but they were either silent or expressed 

 themselves so ambiguously that it was not easy to understand 

 their meaning. Now, things are wholly changed, and almost every 

 naturalist admits the great principle of evolution. There are, 

 however, some who still think that species have suddenly given 

 birth, through quite unexplained means, to new and totally differ- 

 ent forms. But, as I have attempted to show, weighty evidence 

 can be opposed to the admission of great and abrupt modifications. 

 Under a scientific point of view, and as leading to further in- 

 vestigation, but little advantage is gained by believing that new 

 forms are suddenly developed in an inexplicable manner from old 

 and widely different forms, over the old belief in the creation of 

 species from the dust of the earth. 



It may be asked how far I extend the doctrine of the modifica- 

 tion of species. The question is difficult to answer, because the 

 more distinct the forms are which we consider, by so much the 

 arguments in favor of community of descent become fewer in 

 number and less in force. But some arguments of the greatest 

 weight extend very far. All the members of whole classes are 

 connected together by a chain of affinities, and all can be classed 

 on the same principle, in groups subordinate to groups. Fossil 

 remains sometimes tend to fill up very wide intervals between 

 existing orders. 



Organs in a rudimentary condition plainly show that an early 

 progenitor had the organ in a fully developed condition, and this 

 in some cases implies an enormous amount of modification in the 

 descendants. Throughout whole classes various structures are 

 formed on the same pattern, and at a very early age the embryos 

 closely resemble each other. Therefore I cannot doubt that the 

 theory of descent with modification embraces all the members of 



