94 PROF. ERNEST W. MACE-RIDE^ M.A., F.R.S., ON 



Darwin's work stands or falls with the validity of the proof 

 which he offers that there are processes now in operation which 

 must inevitably lead to just such an evolution as many theorists 

 had postulated. To all such theorists the naturalists then in 

 authority had replied that the evidence available compelled them 

 to assume that specific form was invariable — that like begets 

 like after its kind, and that there was no natural process known 

 w T hich could alter it. 



Now Darwin begins by pointing out that these same authori- 

 tative naturalists recognized the existence of varieties within 

 the same species, and that all of them agreed that these varieties 

 did not owe their origin to separate acts of creation, but had 

 somehow been produced by the transformation of the parent 

 species of which they were varieties. But if this be admitted, 

 we then discover that it is impossible to draw the line between 

 a species and a variety ; that in the case of many species of 

 animals, and more especially of plants, leading authorities are 

 hopelessly at variance as to what are species and what are 

 varieties, and it is rather absurd to imagine that a certain amount 

 of difference between two forms is explicable by natural causes, 

 but that to explain a slightly greater amount of difference direct 

 Divine interference must be postulated. 



Darwin then points out that the breeds of animals domesti- 

 cated by man differ in most remarkable ways from the parent 

 species from which they have been derived : that, to take the 

 case of the pigeon for instance, of which he had made a special 

 study, differences in the number of feathers in the tail, in the 

 length and proportion of the bones of the wings and legs, in the 

 shape of the skull, are all exhibited by these breeds. So 

 different indeed are many of them from the wild rock pigeon, 

 Columba livia, that many fanciers would give no credence to the 

 suggestion that they had been derived from that species, but 

 supposed that they must have originated from unknown species 

 or had been produced by the crossing of several distinct species. 

 Darwin points out, however, that among all the known wild 

 species of the genus Columba, there is none that shows anything 

 like the enormous tail of the fan-tail, with a number of feathers 

 greater than that found in any bird of even the order to which 

 Columba belongs. 



We may perhaps make the matter clearer by taking another 

 case which Darwin discusses in that w T onderful book read by so 

 few, viz., The Variation of Animals and Plants under Domestica- 

 tion, and that is the case of the dog. After examining with the 

 greatest care all the evidence which he could collect as to the 



