Chap. V. 
DISTRIBUTION OF MONKEYS. 
329 
tute of monkeys, and why should Madagascar have 
stopped short at Lemurs, whilst America has gone on 
to prehensile-tailed Cebidae, and the Old-World con- 
tinent continued to Gibbons, Orangs, Chimpanzee, and 
Gorilla ? Is it that the greater land masses have seen 
a larger amount of geological and climatal changes with 
corresponding changes in the geographical relations of 
species ? Moreover, why should the smaller groups of 
the order be confined to smaller areas within .the greater 
areas peopled by the families to which they belong? 
For, it must be added, the true Lemurs are confined to 
Madagascar, the Gibbons and others to South Eastern 
Asia, the dog-faced baboons to Africa, and, as we have 
seen, the scarlet-faced monkeys to a limited area on the 
Upper Amazons. May we be allowed to explain the 
absence of these animals from New Guinea with Aus- 
tralia, by the supposition that those lands were separated 
from South Eastern Asia before the first forms of the 
order came into existence ? If so, it may be concluded 
that Madagascar became separated from Africa, and 
America from the continental mass of the old world 
before the Pithecidse originated. But, if these explana- 
tions, founded on natural causes, be entertained, we 
commit ourselves, by the fact of entertaining them, to the 
admission that natural causes are competent to explain 
the existence or non-existence of forms in a given area, 
and why may not the exercise of our reason, founded on 
carefully observed and collated facts, be carried a step 
farther, namely to the origin of the species of monkeys 
themselves? I have already shown how singularly 
species of monkeys vary in different localities, and have 
