given the striking case of the white and red-haired Uakarís. If these two forms, which are considered by the most eminent naturalists as distinct species, have originated, as the facts of their distribution plainly tell us they have, from one and the same stock, why may not the various species of Lemurs, of Baboons, of Gibbons, and so forth, given the necessary amount of time and climatal changes, have originated in the same way? And if we can thus account for the origin of the species of one genus, on what grounds can we deny that the genera of the same family, or the families of the same order, have also proceeded from a common stock? I throw out these suggestions simply for the consideration of thoughtful readers, but must add, that unless the common origin, at least, of the species of a family be admitted, the problem of the distribution of monkeys over the earth's surface must remain an inexplicable mystery, whilst, if admitted, a flood of light illuminates the subject, and promises an early solution to honest and patient investigation. These questions, also, show how interesting and difficult are the problems which Natural History, granted the right and ability of the human mind to deal with them, has to solve.
It is a suggestive fact that all the fossil monkeys which have been found in Europe and America, belong in each case to the types which are still peculiar to the continent which they inhabit. The European fossils are all of the Pithecidæ family, the South American all belong to the Cebidæ and Marmoset families. The separation of the two continental masses (at least of their warm zones) must therefore be of great geological
