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Darwin Correspondence Project

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

CD annotations

1.1 Remarks … balancing; 1.10] crossed blue crayon
1.14 A remarkable … phalanges. 1.17] double scored red crayon
1.21 whereas … soles. 1.24] crossed pencil
1.25 In H. hoolock, … fuscous. 1.27] double scored blue crayon
1.29 the Bos … female. 1.30] scored blue crayon; ‘Bosblue crayon
1.30 Again … berus?) 1.32] heavily crossed blue crayon
1.32 In Hylobates … colouring. 1.37] crossed blue crayon
1.36 Thus … colouring. 1.37] double scored blue crayon
1.37 When … parents—] 1.44 crossed blue crayon
In margin: ‘Blyth March [del] April 3— 68’ blue crayon

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


The date is established by CD’s annotations.
Hylobates is the genus of gibbons.
Blyth refers to Thomas Henry Huxley’s Man’s place in nature (T. H. Huxley 1863a), p. 72. There is an annotated copy of T. H. Huxley 1863a in the Darwin Library–CUL (see Marginalia 1: 424).
Carl von Linné named the white-handed gibbon Homo lar (now Hylobates lar; see Koerner 1999, pp. 87–8).
The pollex and hallux are the innermost digits of the upper and lower limbs in vertebrates (thumb and big toe in humans and other primates).
Hylobates syndactylus is the siamang, H. agilis is the agile gibbon, H. leuciscus, now H. moloch, is the silvery gibbon, and H. lar is the white-handed gibbon. CD added Blyth’s information in Descent 1: 140 n. 63.
The reference is to Abraham Dee Bartlett. The keeper at the Zoological Gardens, Regent’s Park, London, who had syndactylous toes has not been identified.
Hylobates hoolock is the hoolock gibbon.
CD added the information about colour to Descent 2: 291.
Bubalus brachyceros is the West African buffalo (now Syncerus caffer brachyceros, a subspecies of the African buffalo).
Crotalus durissus, the neotropical rattlesnake, has several subspecies with a wide range of colour variation. All the subspecies are restricted to South America. The Zoological Gardens had received two North American Crotalus horridus (timber rattlesnakes) in 1862 (Proceedings of the Zoological Society of London (1862): 322); this may be the species Blyth was referring to. Vipera berus, the common viper or adder, has a melanic form, but it is not restricted to males. Albert Günther had accurately described colour differences in snakes in a letter of 19 December 1867 (Correspondence vol. 15). In Descent 2: 29, CD discussed colour differences in rattlesnakes and vipers.
Isidore Geoffroy Saint-Hilaire was the author of the name Hylobates entelloides (now Hylobates lar entelloides, the central white-handed gibbon). For an overview of the taxonomy of the genus Hylobates, see Groves 1969.
Phasianus colchicus is the ring-necked pheasant; P. versicolor is the green pheasant.
The linnet is now Carduelis cannabina; the canary is Serinus canarius.
CD refers to I. Geoffroy Sainte-Hilaire 1832–7 (see 1: 671–702 for his discussion of abnormalities of the digits, especially polydactyly).
Possibly a reference to Leonard Darwin.


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.

Letter details

Letter no.
Edward Blyth
Charles Robert Darwin
Sent from
Source of text
DAR 45: 29, DAR 83: 156
Physical description
Amem 2pp ††

Please cite as

Darwin Correspondence Project, “Letter no. 6089,” accessed on 26 April 2017,

Also published in The Correspondence of Charles Darwin, vol. 16