I myself follow the original division of the muscles into those which belong to the nostril and upper lip, in accordance with the principles of Duchenne, Darwin, Gamba,[66] and others, and I do so the more readily, since it is impossible not to perceive the manifold and lively mimetic action which takes place in this particular region of an ape’s head. The distinct action of the levator labii superioris alæque nasi, the dilation of the nostrils, the function of a strongly developed levator anguli oris, are especially characteristic of the gorilla; but they are also perceptible in the chimpanzee and gibbon. The orang’s face is the least mobile. I observed that in the gorilla the risorius was very long, branching slightly in the fore-part of the corner of the mouth, and behind into three distinct wide bundles. The lowest bundle covered the platysma myoides, but could not be regarded as part of the latter. In one chimpanzee I found that the risorius was slightly developed, and in other animals of that species I failed to trace it at all. Alix and Gratiolet represent the Aubry chimpanzee (Plate ix. Fig. 1, ~15~) with the risorius strongly developed. I have not observed this formation either in the orang or the gibbon, but it was apparent in one of the ateles (_Ateles leucophthalmos_). In this case the muscle covered the platysma myoides and Stenson’s duct, _i.e._ the duct leading out of the parotid gland (Fig. 50, *). For some time I was disposed to regard the risorius of this ape as only a radiation of the platysma myoides, but my opinion upon this point is again shaken.