424 CONCLUSION. [Chai>. XV 



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 sympathetic 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, how- 

 ever, some who still think that species have suddenly given birth, 

 through quite unexplained means, to new and totally different 

 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 investigation, 

 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 modification 

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

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

 in favour 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 

 the same great class or kingdom. I believe that animals are 

 descended from at most only four or five progenitors, and plants 

 from an equal or lesser number. 



Analogy would lead me one step farther, namely, to the belief 

 that ail animals and plants are descended from some one prototype. 

 But analogy may be a deceitful guide. Nevertheless all living 



