The colour of the hair not only differs on different parts of the body, but also in different individuals. On the crown of the head it is of a reddish brown, or rarely of a decided brown or black. The hairs in this region are sometimes dun-coloured at the root, greyish white in the centre, and brownish red, shading into the dark brown tip. The hair on the lips is sometimes of a blackish brown, sometimes whitish, or both colours are found together. The hair growing at the sides of the face is grey below, dark brown or almost black above. On the neck and shoulders the hair is of a grey colour at the root, and gradually becomes lighter towards the tip. In the centre it is brown, shading into a lighter colour at either end, but this ringed form of colour is not universal. The tips of the hair are dark, sometimes brown or reddish. The hair on the back, on the upper arms and thighs, is whitish or light grey for half its length, with a blackish brown ring towards the tip, which is of a dark grey colour. Many of these hairs on the back have two brown rings on them. The forearms, hands, shanks, and feet are covered with hairs which are grey at the root, brownish grey, dark brown, or black at the tip. Round the posteriors there is a circle of white, grey, or brownish yellow hairs from 10 to 20 mm. in length. In both sexes variations from the colour of the coat here described are not rare. It has been already observed that the brownish red colour of the hair on the head is sometimes exchanged for another shade. In many individuals the neck, shoulders, and back are of a dark grey, brown, or even black colour. In others the forearms, hands, shanks, and feet are covered, like the rest of the body, with grey and brown hair intermingled. The second species of anthropoid apes is the chimpanzee. In this case also we must consider successively the aged and young male, and the aged and young female animals. The full-grown chimpanzee is smaller than the adult gorilla. In this species also the male is larger than the female. The chimpanzee is, speaking generally, of a slighter build than the gorilla.