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180 GEOGRAPHICAL ZOOLOGY. [part iv.
other. About this same time (but perhaps not contemporaneously)
Madagascar must have been connected with some
portion of Southern Africa, and the whole of the country would
possess no other Primates but Lemuroidea. After the Mada-
gascar territory (very much larger than the existing island)
had been separated, a connection appears to have been long
maintained (probably by a northerly route) between the more
equatorial portions of Asia and Africa ; till those higher forms
had become developed, which were afterwards differentiated into
Simia, Presbytes, and Cijnopithecus, on the one hand, and into
Troglodytes, Colobus, and Cynocephalus, on the other. In ac-
cordance with the principle of competition so well expounded
by Mr. Darwin, we can understand how, in the vast Asiatic and
African area north of the Equator, with a great variety of
physical conditions and the influence of a host of competing
forms of life, higher types were developed than in the less
extensive and long-isolated countries south of the Equator.
In Madagascar, where these less complex conditions prevailed
in a considerable land-area, the lowly organized Lemuroids have
diverged into many specialized forms of their own peculiar type
while on the continents they have, to a great extent, become
exterminated, or have maintained their existence in a few cases,
in islands or in mountain ranges. In Africa the nocturnal and
arboreal Galagos are adapted to a special mode of life, in which
they probably have few competitors.
How and when the ancestors of the Cebidse and Hapalidse
entered the South American continent, it is less easy to conceive.
The only rays of light we yet have on the subject are, the
supposed affinities of the fossil Cmnopithecns of the Swiss, and
the LemuravidsB of the North American Eocene, with both
Cebidae and Lemuroids, and the fact that in Miocene or Eocene
times a mild climate prevailed up to the Arctic circle. The dis-
covery of an undoubted Lemuroid in the Eocene of Europe,
indicates that the great Northern Continent was probably the
birthplace of this low type of mammal, and the source whence
Africa and Southern Asia were peopled with them, as it was,
at a later period, with the higher forms of monkeys and apes.
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