, 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 ("The geographical distribution of
Mammals", "Manchester Science Lectures", 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 (Anniversary address (Geological
Society, 1889), "Proc. Geol. Soc." 1889-90, page 67; "Quart. Journ."
XLVI 1890.), 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. page 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, experiment
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 universally, 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 wa