Page:EB1911 - Volume 22.djvu/339

Rh may be applied indifferently to all the members of the first sub-order. “Baboon” appears to be properly applicable to the dog-faced African species, and may therefore be conveniently restricted to the members of the genus Papio and their immediate relatives. “Ape,” on the other hand, may be specially used for the tailless man-like representatives of the order; while the term “monkey” may be employed for all the rest, other than lemurs; monkeys being, however, divisible into sub-groups, such as macaques, langurs, guerezas, mangabeys, &c. This usage cannot, however, be universally employed, and the term “monkeys” may be employed for the entire group.

Anthropoidea.—The Primates, as already mentioned, are divisible into two main groups, or sub-orders, of which the first includes man, apes, baboons and monkeys. For this group Professor Max Weber employs the name Simiae (in contradistinction to Prosimiae for the lemurs). Since, however, to take as the title for a group which includes man himself the designation of creatures so much lower in the scale is likely to be repugnant, it seems preferable to employ the designation Anthropoidea for the higher division of the order.

As the essential features distinguishing the Anthropoidea from the second sub-order may best be indicated under the heading of the latter, reference may at once be made to some of the more striking characters of the members of the former group. The proportions of the body as regards the relative lengths of the two pairs of limbs to one another and to that of the trunk vary considerably. Both pairs may be much elongated, as in Ateles and Hylobates, and either sub-equally, as in the first of these, or with the arms greatly in excess, as in the second. The legs may be excessively short, and the arms, at the same time, excessively long, as in the orang-utan. Both pairs may be short and sub-equal, as in many of the baboons (Papio). Only in Nyctipithecus and the Hapalidae does the excess in length of the lower limbs over the upper exceed or equal that which is found in man. The length of the tail presents some noteworthy points. It is found at its greatest absolute length, and also greatly developed relatively, being about twice the length of the trunk, in such monkeys as the Indian langurs; but its greatest relative length is attained in the spider-monkeys (Ateles), where it reaches three times the length of the trunk. The constancy of the degree of its development varies much in different groups. In the greater number of genera it is long in all the species, and in some (Simia, Anthropopithecus and Hylobates) it is absent in all. In others it may be long or short, or completely absent, as in macaques (Macacus).

The form of the head presents great differences—it may be rounded, as in Ateles; produced vertically, as in Simia; drawn out posteriorly to an extreme degree, as in Chrysothrix; or anteriorly, as in the baboons. A production of the muzzle, necessitated by the presence of large teeth, exists in the chimpanzee (Anthropopithecus), but in the baboons, not only is this prolongation carried farther, but the terminal position of the nostrils gives a dog-like aspect to the face.

The eyes may be small compared with the size of the head, as in the baboons; but they may, on the contrary, attain a relatively, enormous size, as in Nyctipithecus. They are always forwardly directed, and never much more separated one from another than in man; they may, however, be more closely approximated, as in the squirrel-monkeys (Chrysothrix) of South America.

The ears are always well developed, and very generally have their postero-superior angle pointed. They ma be large and small in the same genus, as in Anthropopithecus (chimpanzee and gorilla); but only in the gorilla do we find, even in a rudimentary condition, that soft depending portion of the human ear termed the “lobule.” The nose has scarcely ever more than a slight prominence, and yet an enormous development is to be met with in the proboscis-monkey (Nasalis); while in the snub-nosed monkeys (Rhinopithecus) we find a sharply prominent, though smaller and extremely upturned nose. The hoolock gibbon also possesses a prominent but slightly aquiline nose. The terminal position of the nostrils in the baboons has already been mentioned. These apertures may be closely approximated, as in all the man-like apes (Simiidae and Hylobatidae), or they may be separated one from the other by a broad septum, as in the Cebidae, its breadth, however, varying somewhat in different genera, as in Ateles and Eriodes, and Callithrix and Nyctipithecus. The lips are generally thin, but may be very extensile, as in the orang-utan.

The hands are generally provided with thumbs, though these organs (as in the African guerezas, Colobus, and the American spider-monkeys, Ateles) may be represented only by small nailless tubercles. The thumb is more human in its proportions in the chimpanzee than in any other of the higher apes. As compared with the length of the hand, it is most man-like in the lowest American monkeys, such as Chrysothrix and Hapale. In spite of greater relative length it may, however, little merit the name of thumb, as it is but slightly opposable to the other digits in any of the American monkeys, and is not at all so in the Hapalidae. The “great toe” is never rudimentary and, except in man, in place of being the

longest digit of the foot, is constantly the shortest. As compared with the entire length of the foot, it is most man-like in the chimpanzee and some gibbons, and smallest of all in the orang-utan, and next smallest in Hapale. Every digit is provided with a nail, except the great toe of the orang-utan and the rudimentary tubercle representing the thumb in Ateles and Colobus. The nail of the great toe is flat in every species, but the other nails are never so flat as are the nails of man. The lateral compression of the nails becomes more strongly marked in some Cebidae, e.g. Eriodes, but attains its extreme in the Hapalidae, where every nail, except that of the great toe, assumes the form of a long, curved and sharply pointed claw.

With the single exception of man, the body is almost entirely clothed with copious hair, and never has the back naked. In the gibbons, the langurs, the macaques and the baboons, naked spaces (ischiatic callosities) are present on that part of the body which is the main support in the sitting posture. These naked spaces are subject to swelling at the season of sexual excitement. Such naked spaces are never found in any of the American monkeys. No ape or monkey has so exclusive and preponderating a development of hair on the head and face as exists in man. As to the head, long hair is found thereon in Hapale oedipus and in some of the langurs and guerezas, whilst certain macaques, like the Chinese bonnet-monkey (Macacus sinicus), have the hair of the head long and radiating in all directions from a central point on the crown. A beard is developed in the male orang-utan; and the Diana monkey (Cercopithecus diana) has long hair on the cheeks and chin. The wanderoo (Macacus silenus) has the face encircled by a kind of mane of long hairs; and many of the marmosets have a long tuft of hairs on each side of the head. American monkeys exhibit some extremes respecting hair-development. Thus in some of the howlers (as in some of the guerezas of the Old World) the hair of the flanks is greatly elongated. Some also have an elongated beard, but the latter structure attains its maximum of development in the couxio (Pithecia satanas). Some of the species of the American genus Pithecia have the hair of the body and tail very long, others have the head of the female furnished with elongated hair; while the allied Uacaria calva has the head bald. Long hair may be developed from the shoulders as in Papio hamadryas and Theropithecus gelada. Very long hair is also developed on the back of the snub-nosed monkeys (Rhinopithecus) in winter. The direction of the hair may sometimes vary in nearly allied forms, the hairs on the arm and fore-arm respectively being often so directed that the tips converge towards the elbow. Such is the case in most of the higher apes, yet in Hylobates agilis all the hair of both these segments is directed towards the wrist. The hair presents generally no remarkable character as to its structure. It may, however, be silky, as in Hapale rosalia, or assume the character of wool, as in the woolly spider-monkeys (Eriodes) and Macacus tibetanus, which inhabits Tibet.

2.—Skeleton of Chacma Baboon (Papio porcarius), showing the great relative length of the facial part of the Skull.

Great brilliance of colour is sometimes found in the naked parts of the body, particularly in the baboons and some of the other Cercopithecidae, and especially in the regions of the face and sexual organs. Among these latter rose, turquoise-blue, green, golden-yellow and vermilion appear, in various combinations, in one or other or both of these regions, and become especially brilliant at the period of sexual excitement.

The skeleton, more especially in the higher forms, is in the main similar to that of man, so that only a brief notice is necessary. In the skull considerable variation in regard to the proportionate length of the face to that of the brain-case (cranial portion) exists in the two sexes, owing to the general development of large tusks in the males (other than in man, who is not now under consideration). Generally speaking, the elongation of the facial portion, as compared to the cranial, increases as we pass from the higher to the lower forms. The increase does not, however, occur regularly, being