Asia by a shallow sea, whilst they are separated from New Guinea by a channel of very deep water; the shallow sea pointing to a former, but recent, union of the lands which it connects, the deep channel a complete and enduring severance of the lands which it separates. Now, with regard to monkeys, these four land masses seem to have had these animals allotted to them in the most capricious way possible, if we are to take for granted that the species were arbitrarily created on the lands where they are now found. Australia, with soil and climate as well adapted for Baboons as Africa, where they abound, and New Guinea, with rich humid forests as suitable for Orangs and Gibbons as the very similar island of Borneo, have, neither of them, a single species of native monkey. Madagascar possesses only Lemurs, the most lowly-organised group of apes, although the neighbouring continent of Africa contains numerous species of all families of Old World apes. America, as we have seen, has no Lemurs, and not a single representative of the Old World groups of the order, but is well peopled by genera and species belonging to two distinct groups peculiar to the continent. Lastly, the Old World continental mass, with a few anomalous forms of Lemurs scattered here and there, is the exclusive home of the whole of the Pithecidæ family, which presents a series of forms graduating from the debased Baboon to the Gorilla, which some zoologists consider to approach near to man in his organisation.
What does all this mean? Why are the different forms apportioned in this way to the various lands of the earth? Why is Australia with New Guinea desti-
