From Edward Blyth [3 April 1868]1
Remarks on Hylobates, chiefly.2 It is a mistake to suppose that the gibbons are more nearly allied to the orang-utan than to the chimpanzee, as the habitat might be thought to indicate. Though quite distinct as a group, they are much more nearly allied to the chimpanzee, as strongly indicated in the living animal by the expression of visage, as well as by the voice. As remarked by Huxley, in consequence of the inordinate length of their arms, it has been generally overlooked that the lower limbs are really more developed than in the other apes, and when upon level ground they walk with the lower limbs only3 (a fact which Linnæus might have known when he designated one of them Homo lar),4 holding the arms up more to be out of the way than for the purpose of balancing; but they are always ready to seize hold of a bough or any other object to help them forward when on the ground, though they never touch the ground with the hands to assist in progression. I have repeatedly seen a pair of H. lar ascend a considerable flight of steps without once touching them with the hands. A remarkable fact which it is surprising that no one but myself seems to have noticed, though observable in every stuffed specimen, is that both pollux and hallux 5 are separate for a joint further than in any other of the Primates, exhibiting thus three free phalanges. In H. syndactylus, the second and third toes are usually (if not always) joined. In H. agilis, leuciscus, & lar, this character occurs irregularly, as not rarely in man.6 So Bartlett assures me, and one of the Keepers now at the Z. G. is an example at hand.7 Of many specimens of H. hoolock examined,8 I never found this character to occur. The gibbons have the hallux particularly well developed, whereas the reverse is exemplified by the orang-utan. In the gorilla both hands and feet have the four fingers and toes syndactylous for a joint further than in man, &c, extending thus the palms & soles. About colour, in the Siamang (H. Syndactylus) both sexes (so far as known) are always black. In H. hoolock, the male is always black (according to my considerable experience), the female never so, unless very partially, being of all shades of brown from fulvous-white to fuscous. All have the white frontal band, but more or less broad.9 (This is another instance of black males & brown females, & I may remark that the Bos or Bubalus brachyceros has a slaty-blue male and a bright chestnut female.10 Again, the N. American rattle-snake (Crotalus durissus) has the males much darker than in the other sex—vide specimens in Z. G. This is an interesting case, and how about the black examples of Vipera berus?)11 In Hylobates leuciscus, agilis, and lar, both sexes vary alike in colour, from black to that of a whitish blanket, and I have been told that there are communities of these pale examples of H. lar in the Malayan peninsula, upon which variety is based the H. entilloidis of Is. Geoffroy.12 Thus we have the Siamang always black, the hoolock black in the male sex only, and other gibbons in which both sexes are alike variable in colouring. When upon a tree the gibbons use the arms only in progressing, swinging with amazing force and speed from tree to tree, and however great that speed, they can stop themselves most abruptly, then resting crouched on the feet and callosities only.— Have you remarked the tendency of hybrids to be larger than the parent species? This is notably the case with hybrid pheasants of the P. colchicus type, which are fertile inter se, as the hybrid between P. colchicus & P. versicolor. 13 The linnet and canary mule is always much larger than its parents—14
Verso, first sheet: ‘Man |
pointy hand (See Isidore Geoffroy15 if holds excellent case of analagous variation)’ pencil; ‘2d & 3d toes— is great toe counted?? does it throw light on muscles in common to ones 2d & third finger. ie not counting Thumb?? | Leonard.16 How in.’ ink; ‘Isidore Geoffroy does not say any particular finger oftener wanted’ pencil; ‘Add when I mention the varying Hallux of the Orang’ pencil, circled pencil, asterisk red crayon, del pencil; ‘Ch. 3’ red crayon, circled red crayon; ‘When I speak of [illeg] [marking]’ red crayon
Discusses apes and their relationships to each other. Writes particularly of the gibbon, its structure and well-developed legs giving it the ability to walk without using its hands.
Please cite as
Darwin Correspondence Project, “Letter no. 6089,” accessed on 24 October 2016, http://www.darwinproject.ac.uk/DCP-LETT-6089