Part 5

The two halves of the lower jaw are not always co-ossified (as is the case in the Anthropoidea).

The opening in the base of the skull (the foramen rotundum) which transmits from the brain a branch of the fifth nerve {12}for the upper jaw, and the sphenoidal fissure, which gives exit to the third, fourth and sixth cranial nerves, have but one aperture, as in the Rabbit, which belongs to the Rodentia.

The sacral vertebræ are generally three in number, and the lumbar and dorsal together vary from nineteen to twenty-three.

The brain, as Sir William Flower has observed, departs considerably from the form of what may be called the primatial type, and approaches in form to that of the carnivorous animals. The hind-brain, or cerebellum, is not completely covered by the cerebrum. The latter has but few convolutions (indicating a low intelligence), but its posterior lobe is always present, though more or less rudimentary, and so also are many fissures, which are characteristic of its surface in the higher Primates. The olfactory lobes are usually large and not covered by the cerebrum.

The uterus and structures for the nutrition of the young prior to birth are low in type, and approximate to the conditions seen in the Pig, the Horse, the Chevrotains, and the Ruminants. The unborn Lemur is often encased (as among the Sloths) in a skin-like covering (epitrichium) which breaks into patches before birth.

The tongue has a horny supplementary under-tongue (sublingua) attached beneath it. The stomach is simple, not formed of several compartments. The transverse portion of the great intestine is convoluted in a remarkable manner upon itself, the cæcum also being very large. The main arteries of the arm and leg break up (as in the Sloths) into an immense number of small vessels (called retia mirabilia) parallel to one another instead of being simple branching trunks.

The long tendons of the muscles for flexing the digits (the {13}flexor longus digitorum) differ generally in arrangement from those of the higher Primates.

The Lemuroids are of no commercial value to Man.

As regards their distribution, the Lemuroidea are now absolutely confined to the Old World, and predominate in the island of Madagascar, where, as M. Grandidier remarks in his magnificent work on that country, there is scarcely a little wood in any district in which they are not found. Indeed, of the nearly seventy species of Mammals inhabiting that island, thirty-five, or one-half, are Lemurs. Members of the family also occur across the whole of the neighbouring continent of Africa, but their northern range does not reach quite to the tropic, whereas it extends some few degrees beyond it in the Southern Hemisphere. Elsewhere they are confined to the forests of the Oriental region. More or less isolated in Southern India, they re-appear in China, and spreading south to Java they reach as far east as Celebes and the Philippine Islands. The present isolation of the Lemurs in two such distant areas--in Africa and Madagascar and some of the Mascarene Islands on the one hand, and in Southern India, China, Ceylon, and the Malayan Islands on the other--has been considered by some naturalists as weighty evidence in favour of a former land connection between these distant regions.

Though so restricted in their distribution at the present day, this group was more widely represented in past ages of the world's history, as we shall have to point out later on. Abundant fossil remains prove that they lived in Europe and in North America, where to-day they are quite unknown.

The Lemuroidea are almost entirely arboreal, and seldom come to the ground, except the Sifakas, which then progress {14}on their hind legs by a series of bounds, holding their hands over their head in a ludicrous fashion. Most of them are nocturnal, or crepuscular, sleeping the greater part of the day in holes or on a branch of a tree coiled up in a ball. Their food consists chiefly of leaves, fruits, honey, birds' eggs, and birds, or any small animals they can pounce upon.

The Lemurs now living are divided into three families. The Aye-Aye and the Tarsiers, on account of their very special characters, constitute each a distinct family--named Chiromyidæ and Tarsiidæ respectively--while the True Lemurs form the third, the Lemuridæ, to which all the remaining forms belong.

THE AYE-AYES. FAMILY CHIROMYIDÆ.

This very aberrant family contains only one species; the characters of the family and of the genus Chiromys are, therefore, necessarily those of the single species known.

THE AYE-AYE. CHIROMYS MADAGASCARIENSIS.

Sciurus madagascariensis, Gmel., S. N., i., p. 152 (1788).

Daubentonia madagascariensis, Geoffr., Décad. Philos., iv., p. 193 (1795); Dahlbom, Studia, p. 326, t. 12.

Chiromys madagascariensis, Cuv., Leçons d'Anat. Comp., Tabl. de Class., 1 (1800); Owen, Tr. Z. S., vol. v., p. 33; Peters, Abhandl. K. Akad. Berlin, 1865, p. 79.

(Plate I.)

PLATE I.

{15}CHARACTERS.--Head short and round; face short-snouted, with a patch of bristles below the eye, between the ear and the angle of the mouth; eyes round, prominent; eyebrows long and bristly; pupils wide, furnished with a false eyelid (a nictitating membrane); ears large, rounded, directed backwards, naked, and studded with small protuberances; tail longer than the body, bushy, with hair 3-4 inches long; hind-limbs longer than the fore-limbs, the thigh-bone being one third longer than the humerus, the hand the longest segment of the fore-limb; fingers long--the fourth the longest--with compressed and pointed claws, which are proportionately much longer than the toes; the middle or third digit slender and very remarkable, being extremely attenuated and wire-like; thumb opposable, and placed at an acute angle to the short index; great toe opposable, set at an open angle to the other digits, its nail flat; the remaining toes with pointed compressed claws (like the second toe of Lemuridæ and second and third of Tarsiidæ). Teats, two, placed low down on the abdomen. Length of body and tail together 36 inches. Skull highly arched, convex transversely; muzzle short and deep; bony palate not extending behind the middle of the posterior molar tooth; lower jaw with condyle elongated from before backwards and on a level with the cheek-teeth, its two halves united at an acute angle by elastic tissue, allowing each half to play independently of the other. Its dental formula, I1/1, C0/0, P1/0, M3/3 = 18. Incisors very large, curved, with persistent pulp, and enamel only in front, growing up as fast as worn away; canines absent (the last two characters as in the Rodents); long vacuity between incisors and pre-molar; pre-molar much smaller than molars; molars with flat crowns and very indistinct tubercules; milk-teeth agreeing more in number and form with those seen among Lemurs than with the permanent set; the upper jaw having its full set of two incisors, one canine, and a pre-molar tooth present; the lower jaw having one incisor, no canine, and one pre-molar tooth on each side. Dorsal and lumbar vertebræ together 18, sacral 3, and caudal 22-27.

{16}Olfactory lobes of brain covered by the cerebrum; convolutions and grooves of cerebrum similar to those in normal Lemurs. Intestine 26 inches long; no striped tissue in the muscular sheath of the gullet at the anterior end of the stomach. Digastric muscle (for moving the jaws) very much developed in accordance with the great gnawing powers of the species.

Fur on back, flanks, tail, and limbs dark brown, nearly black, but with the white of the basal half of the hairs shining through; hair woolly at base; long hairs on top of head and back of neck tipped with white; short hairs of face dirty white. Nose and lips naked, flesh-coloured; ears black; sides of head and throat greyish-yellow; chest often bright yellow, the chin paler. Inner sides of limbs yellowish-white, and on the under surface of the body the basal part of hairs showing through, producing a pale yellowish-white, or sub-rufous, colour. Feet and digits black. Tail black, at its base greyish-white or greyish-brown, and often with long white hairs throughout. The species is more nearly related to the members of the genus Galago to be described later on, than to any other of the Lemuroidea.

DISTRIBUTION.--The Aye-Aye is confined to the island of Madagascar. It makes its home in the dense parts of the great forest that runs along the eastern border of its central plateau, but only in that part of it which separates the Sihànaka Province from that of the Betsimisàraka, which is about 25 miles from the east coast, in latitude 17° 22[prime] S. It is more common than has been supposed, its noctural habits and the superstitious awe with which it is regarded accounting for its apparent rarity, and for the contradictory reports given of its habits.

HABITS.--The Aye-Aye, whose name is derived from its call of "hai-hay," is one of the most singular of living animals. It was first discovered by Sonnerat during his travels in {17}Madagascar in 1780, and by him sent to Paris. The skin remained unique in Europe for the best part of a century. Greatly owing to the superstitious dread in which the creature is held by the natives, it was for a long period, and is still, very difficult to procure, or to induce the natives to capture, specimens. Mr. Baron says that it is sometimes accidentally caught in traps by the natives, "but the owner of the trap, unless one of those versed in the Aye-Aye mysteries who know the charm by which to counteract its evil power, smears fat over it, thus securing its forgiveness and goodwill, and sets it free." In 1863 Dr. Sandwith sent a second example to Europe, the anatomy of whose body was made the subject of an exhaustive monograph by the late Sir Richard Owen. Since that date more than one specimen has been received alive, and its habits and constitution are now fairly well known. The Aye-Aye is entirely arboreal and nocturnal, sleeping during the day, with its body coiled round, lying on its side with its bushy tail spread over it as a covering. It suspends itself by its hind-limbs, and in this position it has been observed in captivity by Mr. Bartlett, using its hook-like finger to comb out its tail, to cleanse its face, the corners of its eyes, its nose, mouth, and ears, keeping meanwhile its other fingers closed. It lives in the depths of the forests, going about in pairs. Exquisitely keen of hearing, it can detect by sound the boring of insects within the dead branches of trees. Its attenuated wire-like finger acts as a probe to discover their position, and its powerful incisor teeth are used to cut down upon the tunnel of its prey, which consists principally of the Andraitra, the larva of a Beetle, which it then extracts with the same digit. The juices of plants are also supposed to form part of its food. It drinks after the manner of many Monkeys, by dipping its fingers into the water, and {18}drawing them through its mouth. The Aye-Aye is fearless of Man, but in its wakeful hours, during the night, when irritated it can be very savage and strike out with its hands. The female produces but one young at a birth, and builds, in the fork of a tree, a ball-like nest, two feet in diameter, with an entrance hole in the side, forming it of the rolled up leaves of the Travellers'-tree, and lining it with small twigs and dry leaves. (Baron.)

THE TARSIERS. FAMILY TARSIIDÆ.

This family, like the preceding, has been constituted for the reception of two animals which are so remarkably distinct from all the other species of Lemurs, as to necessitate their being thus segregated. Between these two forms however, so close a relationship exists, that they have often been considered as only varieties of the same species. The family, therefore, consists, as in the Chiromyidæ, of a single genus, the characters of which constitute also those of the family.

THE TARSIERS. GENUS TARSIUS.