The uterus and structures for the nutrition of the young prior to birth differ greatly in this Sub-order from the conditions existing in the _Lemuroidea_. The uterus is a simple and not a two-horned sac, and its inner layer, in which the foetal and maternal structures intermingle during the growth of the embryo, is shed after the birth of the young, which is not the case in the Lemurs. "The resemblance of Monkeys to Man," says Mr. Darwin, "is greatly caused by the relative position of the features of the face. The eyes are arched over; they are separated by a long nose, the end of which in some is very human. The mouth is not carried back, but occupies the same general position as in Man, and the forehead, so often wrinkled, is usually prominent and like that of a child. The likeness is increased by the fact that anger, sorrow, pleasure, and satisfaction, are displayed by the Monkey by nearly similar movements of the muscles and skin, chiefly above the eyebrows and round the mouth. Some few expressions are indeed almost the same, as in the weeping of certain kinds of Monkeys, and in the {126}laughing noise made by others, during which the corners of the mouth are drawn backward and the eyelids wrinkled. In Man the nose is much more prominent than in most Monkeys; but we may trace the commencement of an aquiline curvature in the nose of the Hoolock Gibbon, and this in the Great-nosed Monkey (_Nasalis larvatus_) is carried to a ridiculous extreme." In regard to the distribution of the _Anthropoidea_, excluding Man (_Hominidæ_), two families (the _Hapalidæ_ and _Cebidæ_) are known only from the New World; and two others (the _Cercopithecidæ_ and _Simiidæ_) are exclusively confined to the Old World. No fossil remains of Eastern Hemisphere forms have as yet been found in the Western, or _vice versâ_, a fact which indicates, doubtless, a separation of great antiquity between the two groups. The various species of these families are to be found chiefly in the warmer regions on both sides of the equator. In the New World some species range as far north as to 20° N. lat. in Mexico; and South, to 30° below the equator. In the Eastern Hemisphere, the Old World species predominate in the tropical and sub-tropical regions; but certain forms have spread as far north as Thibet and Japan, and others have made the high altitudes of the Himalaya Mountains their home; while to the southward they extend in Africa nearly to the Cape of Good Hope. No indigenous species have ever been found in New Guinea, Australia, New Zealand, or in the Pacific, or West Indian Islands.