298 THE STRUCTURAL EVIDENCE OF EVOLUTION. 



side of the man who asserts that transitions have not taken place 

 between forms which are now distinct. 



We are told that we find no sort of evidence of that transition 

 in past geological periods ; we are assured that such changes have 

 not taken place ; we are even assured that no such sign of such 

 transition from one species to another has ever been observed — a 

 most astonishing assertion to make to a biologist, or by a biolo- 

 gist ; and such persons have even the temerity to cite such a 

 special case as that between the wolf and the dog. Many of our 

 domestic dogs are nothing but wolves, which have been modified 

 by the hand of man to a very slight extent indeed. Many dogs, 

 in fact nearly all dogs, are descendants of wild species of various 

 countries, and are variously modified. 



To take the question of the definition of species. Supposing 

 we have several species well defined, say four or five. In the 

 process of investigation we obtain a larger number of individuals, 

 many of which betray characters which invalidate the definitions. 

 It becomes necessary to unite the four or five species into one. 

 And so, then, because our system requires that we shall have ac- 

 curate definitions (the whole basis of the system is definitions ; 

 you know the very comprehension of the subject requires defini- 

 tions), we throw them all together, because we can not define all 

 the various special forms as we did before, until we have but one 

 species. And the critic of the view of evolution tells us, "1 told 

 you so ! There is but one species, after all. There is no such 

 thing as a connection between species : you never will find it." 

 Now, how many discoveries of this kind will be necessary to con- 

 vince the world that there are connections between species ? How 

 long are we to go on finding connecting links, and putting them 

 together, as we have to do for the sake of the definition, and then 

 be told that we have, nevertheless, no intermediate forms between 

 species ? The matter is too plain for further comment. We 

 throw them together, simply because our definitions require it. 

 If we knew all the known individuals which have lived, we should 

 have no species, we should have no genera. That is all there is 

 of it. It is simply a question of a universal accretion of material, 

 and the collection of information. I do not believe that the well- 

 defined groups will be found to run together, as we call it, in any 

 one geological period, certainly in no one recent period. We 

 recognize, however, in looking backward, that they converge to 

 a wonderful extent : one group has diverged at one period, and 



