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, i. 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 great 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. 
1 «¢ The geographical distribution of Mammals,”’ Manchester Science Lectures, 1874. 
2 Anniversary address (Geological Society, 1889), Proc. Geol. Soc. 1889—90, p. 67; 
Quart. Journ. xLv1. 1890. 
