There are two distinct types of this ape. They are now regarded as two species. One of them is distributed throughout the entire habitat described, while the other is only known south of the equator and between the second and fifth parallels north of the Congo and west of Stanley Pool. Both kinds are found within this district, but the variety which is confined to that region is called, by the tribes that know the ape, the _kulu-kamba_, in contradistinction from the other kind known as _ntyigo_. This name is derived from _kulu_, the onomatope of the sound made by the animal and the native verb, _kamba_, to speak; hence the name literally means “the thing that speaks kulu.” In certain respects the common variety differs from the _kulu-kamba_ in a degree that would indicate that they belong to distinct species; but the skulls and the skeletons are so nearly alike that no one can identify them from the skeletons alone. In life, however, it is not difficult to distinguish them. The _ntyigo_ has a longer face and more prominent nose than the _kulu_. His complexion is of all shades of brown, from a light tan to a dark, dingy, mummy color. He has a thin coat of short, black hair, which is often erroneously described as brown; but that effect is due to the blending of the color of his skin with that of his suit. In early life his hair is quite black, but in advanced age the ends are tipped with a dull white, giving them a dingy gray color. The change is due to the same causes that produce gray hairs on the human body. But there is one point in which they greatly differ. The entire hair of the human becomes white with age, while only the outer end of it does so in the chimpanzee. In the human one hair becomes white, while others retain their natural color; but in this ape all the hairs appear to undergo the same change. In very aged specimens the outer part of the hair often assumes a dirty, brownish color. This is due to the want of vascular action to supply the color pigment. The same effect is often seen in preserved specimens, for the same reason that the hair of an Egyptian mummy is brown, though in life it had been, doubtless, a jet black. In this ape the hair is uniformly black, except the small tuft of white at the base of the spinal column and a few white hairs on the lower lip and the chin. I have examined about sixty living specimens, and I have never found any other color among them, except from the cause mentioned. The normal color of both sexes is the same. The _kulu_ has, as a rule, but little hair on the top of the head; but that on the back of it and on the neck is much longer than elsewhere on the body, and on these parts it is longer than that on other apes.