vision of the land into regions does not occur in the
_Origin_, Ed. i.

{342} _Origin_, Ed. i. p. 346, vi. p. 493.

{343} Opposite this passage is written "_not botanically_," in Sir
J. D. Hooker's hand. The word _palms_ is underlined three times and
followed by three exclamation marks. An explanatory note is added
in the margin "singular paucity of palms and epiphytes in Trop.
Africa compared with Trop. America and Ind. Or." <=East Indies>.

Furthermore it may be observed that _all_ the organisms inhabiting any
country are not perfectly adapted to it{344}; I mean by not being
perfectly adapted, only that some few other organisms can generally be
found better adapted to the country than some of the aborigines. We must
admit this when we consider the enormous number of horses and cattle
which have run wild during the three last centuries in the uninhabited
parts of St Domingo, Cuba, and S. America; for these animals must have
supplanted some aboriginal ones. I might also adduce the same fact in
Australia, but perhaps it will be objected that 30 or 40 years has not
been a sufficient period to test this power of struggling <with> and
overcoming the aborigines. We know the European mouse is driving before
it that of New Zealand, like the Norway rat has driven before it the old
English species in England. Scarcely an island can be named, where
casually introduced plants have not supplanted some of the native
species: in La Plata the Cardoon covers square leagues of country on
which some S. American plants must once have grown: the commonest weed
over the whole of India is an introduced Mexican poppy. The geologist
who knows that slow changes are in progress, replacing land and water,
will easily perceive that even if all the organisms of any country had
originally been the best adapted to it, this could hardly continue so
during succeeding ages without either extermination, or changes, first
in the relative proportional numbers of the inhabitants of the country,
and finally in their constitutions and structure.

{344} This partly corresponds to _Origin_, Ed. i. p. 337, vi. p.
483.

Inspection of a map of the world at once shows that the five divisions,
separated according to the greatest amount of difference in the
mammifers inhabiting them, are likewise those most widely separated from
each other by barriers{345} which mammifers cannot pass: thus Australia
is separated from