EVIDENCE FROM MORPHOLOGY. 151 



natural selection are entirely inaccessible to the experiments of man, 

 and the relatively few forms which man has, in a greater or less 

 space of time, brought completely within his power, have been and 

 are being altered and modified by the so-called artificial selection. 

 The action of the natural selection, in Darwin's sense, is therefore 

 in general incapable of direct proof, and even for the origin of 

 varieties can only be illustrated and rendered probable by hypothe- 

 tical examples. Against this we must, however, set the fact that 

 there is a great probability in favour of the correctness of the 

 theories of descent and transmutation of species, which have never 

 received better support than from the natural selection theory of 

 Darwin ; and that this probability is supported, not only by the 

 whole weight of morphological evidence, but also by the testimony 

 of Palaeontology and of geographical distribution. 



EVIDENCE IN FAVOUR OF THE THEORY OF DESCENT. 



If the transmutation of species is to be regarded as an hypothesis, 

 because it is incapable of being demonstrated by direct observation, 

 then its value depends upon its correspondence with the facts and 

 phenomena of nature. 



Evidence from Morphology. The whole of Morphology tends to 

 show the correctness of the theory of transmutation of species. The 

 degrees of resemblance between species which was for a long time 

 expressed by the metaphorical term " relations/tip," and which rested 

 upon an agreement in more or less important characteristics, led 

 to the establishment of systematic groups, of which the highest, the 

 kingdom or type, was founded upon a similarity in the most general 

 features of organization and development. The agreement of numerous 

 animals in the general plan of their organization, e.g., the common 

 possession by fishes, reptiles, birds, and mammals of a rigid column 

 forming the axis of the body, and the dorsal position in regard to 

 this of the central nervous system and the ventral position of the 

 organs of nourishment and reproduction, are very well explained, 

 according to the theories of selection and descent, by the derivation of 

 all Vertebrates from a common ancestor possessing the characteristics 

 of the type, while the supposition of a plan of the Creator renounces 

 all explanation. In like manner is explained that similarity of 

 characteristics by which the remaining groups and sub-groups, from 

 class to genus, are distinguished, as well as the possibility of dividing 

 all organized beings into groups subordinated the one to the other. 



