FUNDAMENTAL RELATIONS OF ANIMALS 43 



said that the majority of them have an extensive geographical range. 

 This amounts to the most complete evidence that, as far as any of 

 these genera extends in its geographical distribution, animals the 

 structure of which is identical within this range of distribution are 

 entirely beyond the influence of physical agents, unless these agents 

 have the power, notwithstanding their extreme diversity, within 

 these very same geographical limits, to produce absolutely identical 

 structures of the most diversified types.^'^ 



It must be remembered here that there are genera of Vertebrata, 

 of Articulata, of Mollusks, and of Radiata which occupy the same 

 identical and wide geographical distribution, and that while the 

 structure of their respective representatives is identical over the 

 whole area, as Vertebrata, as Articulata, as Mollusks, as Radiata, they 

 are at the same time built upon the most different plans. I hold this 

 fact to be in itself a complete demonstration of the entire inde- 

 pendence of the structure of animals of physical agents, and I may 

 add that the vegetable kingdom presents a series of facts identical 

 with these. This proves that all the higher relations among animals 

 and plants are determined by other causes than mere physical in- 

 fluences. 



While all the representatives of the same genus are identical in 

 structure,^^ the different species of one genus differ only in their 

 size, in the proportions of their parts, in their ornamentation, in 

 their relations to the surrounding elements, etc. The geographical 

 range of these species varies so greatly that it cannot afford in itself 

 a criterion for the distinction of species. It appears further that while 



•" An example may serve to bring this argument nearer to those not familiar with 

 Natural History. From the Arctic Ocean to Cape Horn, America embraces such a 

 variety of physical features that we may well suppose all the natural causes to which 

 the origin of organized beings could be ascribed to be or to have been active within 

 this range. Now there is a peculiar kind of fox in Arctic America; others occur in 

 the temperate zone of that continent, and others again in more southern latitudes. 

 With them the most diversified animals of every class are associated, among which 

 there are many types, the geographical range of which is circumscribed with the nar- 

 rowest limits; although a large number of them have representatives in other parts of 

 the world. It is plain, therefore, that physical agents cannot be the cause of the exist- 

 ence of any of them, unless these agents act with discrimination, producing mam- 

 malia of the same genus over the whole continent, and by the side of them other 

 animals belonging to the most diversified types and agreeing with the extra-American 

 representatives of these types in every essential feature. This is tantamount to assuming 

 that such an action is the work of a rational being. 



^ See Chap. II, Sect. v. 



