The hairy coat of the orang-utan consists of long, curved, waving bristles, and some scanty downy hairs. On the back of the head, on the shoulders, back, and hips I have measured hairs from 220 to 235 mm. in length. In other individuals they were, however, much shorter--20, 40, or 60 mm. long. There is often a natural parting of the hair of the head, which falls asunder on either side. In some cases there is no parting, and the hair streams wildly down; and in others, again, it stands upright, stiffening from the sides and top of the head in a demoniacal manner (Figs. 7 and 9). A beard frequently encircles the cheeks and chin. The hair grows upwards and outwards on the neck and fore-part of the throat, on the shoulders, back, breast, belly, upper arms, and thighs, while it takes the opposite direction on the forearm. On the wrist the hair grows in the manner described in the case of the gorilla. There is only a scanty growth of hair on the breast and belly, and it is also short and weak on the face, ears, and backs of the hands and feet. I have not observed eyebrows on the animals I have seen, but they may occur, and the eyelashes are fully developed. The hair is of a reddish brown colour, something like burnt sienna, and the hair-tips on the back parts of the body are generally brown. In some individuals the hair is darker, of a russet or blackish brown; in others it is lighter, and in the latter case the breast and belly are of a yellowish white. The beard is sometimes dark yellow. Some individuals almost devoid of hair have been observed. The gibbons, or long-armed apes (_Hylobates_), constitute the fourth group of anthropoids. Many kinds of this group are known, and I feel bound to describe, at any rate, a few of them, in order to be able to give an idea of their structure. With respect to these animals, I cannot only rely on the materials which are accessible to me, but must also make use of the descriptions given by others.[7] The gibbons have as a rule very long arms, reaching to their ankles when they stand upright. The face is not very prognathous, the crown of the head is rounded off, and the nails are flat. There are small callosities on their posteriors, which are absent in the gorilla, the chimpanzee, and the orang-utan.