322 Geographical Distribution of Animals 



(1) Austro-Columbia (an unfortunate substitute for the neotropical 

 region), (2) Australasia, and (3) New Zealand, the number of big 

 regions thus being reduced to three but for the separation of New 

 Zealand upon rather negative characters. Sclater was the first 

 to accept these four great regions and showed, in 1874\ that they 

 were well borne out by the present distribution of the Mammals. 



Although applicable to various other groups of animals, for 

 instance to the tailless Amphibia and to Birds (Huxley himself had 

 been led to found his two fundamental divisions on the distribution 

 of the Gallinaceous birds), the combination of South America with 

 Australia was gradually found to be too sweeping a measure. The 

 obvious and satisfactory solution was provided by W. T. Blanford^, 

 who in 1890 recognised three main divisions, namely Australian, South 

 American, and the rest, for which the already existing terms (although 

 used partly in a new sense, as proposed by an anonymous writer in 

 Natural Science, iii. p. 289) Notogaea, Neogaea and Arctogaea have 

 been gladly accepted by a number of English writers. 



After this historical survey of the search for larger and largest or 

 fundamental centres of animal creation, which resulted in the mapping 

 of the world into zoological regions and realms of after all doubtful 

 value, we have to return to the year 1858. The eleventh and twelfth 

 chapters of The Origin of Species (1859), dealing with "Geographical 

 Distribution," are based upon a gi-eat amount of observation, experi- 

 ment and reading. As Darwin's main problem was the origin of 

 species, nature's way of making species by gradual changes from 

 others previously existing, he had to dispose of the view, held uni- 

 versally, of the independent creation of each species and at the 

 same time to insist upon a single centre of creation for each species ; 

 and in order to emphasise his main point, the theory of descent, he 

 had to disallow convergent, or as they were then called, analogous 

 forms. To appreciate the difficulty of his position we have to take 

 the standpoint of fifty years ago, when the immutability of the species 

 was an axiom and each was supposed to have been created within 

 or over the geographical area which it now occupies. If he once 

 admitted that a species could arise from many individuals instead of 

 from one pair, there was no way of shutting the door against the 

 possibility that these individuals may have been so numerous that 

 they occupied a very large district, even so large that it had become 

 as discontinuous as the distribution of many a species actually is. 

 Such a concession would at once be taken as an admission of multiple, 

 independent, origin instead of descent in Darwin's sense. 



^ " The geographical distribution of Mammals," Manchester Science Lectures, 1874. 

 2 Auniversary address (Geological Society, 1889), Proc. Geol. Soc. 1889—90, p. 67; 

 Quart. Journ. xlvi. 1890. 



