CHAP, 1] 3 INTRODUCTORY. 5 
Having thus defined our subject, let us glance at the opinions 
that have generally prevailed as to the nature and causes of 
the phenomena presented by the geographical distribution of 
animals. 
It was long thought, and is still a popular notion, that the 
manner in which the various kinds of animals are dispersed 
over the globe is almost wholly due to diversities of climate and 
of vegetation. There is indeed much to favour this belief. The 
arctic regions are strongly characterised by their white bears 
and foxes, their reindeer, ermine, and walruses, their white 
ptarmigan, owls, and falcons; the temperate zone has its foxes 
and wolves, its rabbits, sheep, beavers, and marmots, its sparrows 
and its song birds ; while tropical regions alone produce apes and 
elephants, parrots and peacocks, and a thousand strange quadru- 
peds and brilliant birds which are found nowhere in the cooler 
regions. So the camel, the gazelle and the ostrich live in the 
desert; the bison on the prairie; the tapir, the deer, and the 
jaguar in forests. Mountains and marshes, plains and rocky 
precipices, have each their animal inhabitants ; and it might well 
be thought, in the absence of accurate inquiry, that these and 
other differences would sufficiently explain why most of the 
‘ regions and countries into which the earth is popularly divided 
should have certain animals peculiar to them and should want 
others which are elsewhere abundant. 
A more detailed and accurate knowledge of the productions of 
different portions of the earth soon showed that this explanation 
was quite insufficient; for it was found that countries exceed- 
ingly similar in climate and all.physical features may yet have 
very distinct animal populations. The equatorial parts of Africa 
and South America, for example, are very similar in climate 
and are both covered with luxuriant forests, yet their animal life 
is widely different; elephants, apes, leopards, guinea-fowls 
and touracos in the one, are replaced by tapirs, prehensile- 
tailed monkeys, jaguars, curassows and toucans in the other. 
Again, parts of South Africa and Australia are wonderfully 
similar in their soil and climate; yet one has lions, antelopes, 
zebras and giraffes ; the other only kangaroos, wombats, phalan- 
