The Cambridge Natural History Part 46

[Ill.u.s.tration]

FIG. 260.--Smith's Dwarf Lemur. _Microcebus smithii._ .

[Ill.u.s.tration]

FIG. 261.--Mouse Lemur. _Chirogale coquereli._ .

_Microcebus_ contains the most minute among the Lemurs. _M. smithii_ has a body only 5 inches long, the tail being another 6 inches. It occurs in Madagascar, and includes five species.

_Opolemur_, the Fat-tailed Lemur, was so called on account of a {545} deposit of fat formed chiefly at the root of the tail, and intended to tide over the time of the creature's hibernation. But, as a matter of fact, this peculiarity also exists in _Chirogale_. Of _Opolemur_ but two species are known, and of one of these, named after Mr. Thomas of the British Museum, only three examples are in existence in museums, that is to say in one museum--our own at South Kensington. Many of these dwarf Lemurs are exceedingly rare. In this genus and in the last two the palate has a pair of posterior fenestrae, of which there are also traces in other Lemurs, but which are particularly large in _Microcebus_. This is, of course, a well-known character of the Marsupials, and also, which is more important in the present connexion, of certain Insectivores.

SUB-FAM. 4. LORISINAE.--This sub-family is the only one with a wide distribution, and it contains, with the exception of _Tarsius_, the only Asiatic members of the group. Correlated with its wide distribution there is more divergence in anatomical characters than is the case with the other sub-families of the Lemuridae. In external features all the three genera of this sub-family agree in their small size, their short or entirely deficient tail, large staring eyes, and the rudimentary character, or absence, of the index finger, which is never provided with a nail; in all of them the thumb diverges widely from the other fingers, and the great toe is so divergent as to be directed backwards. In the brain there is one character common to all three genera, and that is the small length of the angular fissure. The caec.u.m, which is long, is supported by three folds, of which the median is anangious, and is sometimes attached to the longer of the two lateral folds, which are vascular. The members of this sub-family have more dorsal vertebrae than are found in other Lemurs; the range is from fourteen in _Loris_, to sixteen in _Nycticebus_.

The genus _Nycticebus_ contains only a single species, _N. tardigradus_, though four other names have been given to supposed varieties. Moreover, the genus itself has been named _Stenops_, as also the next genus _Loris_.

The body of this animal is stouter than that of the next to be described.

Professor Mivart has pointed out that, though Asiatic like the Loris, it presents more resemblances to the African Potto. The index finger is small; the inner of the two incisors is smaller than the outer, but both of one side are close together. They may be reduced to one on each side of the upper jaw. {546}

[Ill.u.s.tration]

FIG. 262.--Slow Loris. _Nycticebus tardigradus._ 1/3.

The animal has a wide distribution in the East, occurring in a.s.sam and Burmah, the Malay Peninsula, Siam, and Cochin-China, Sumatra, Java, Borneo, and the Philippines. Its vernacular names signify "Bashful Cat" and "Bashful Monkey" in allusion to its nocturnal and shy habits. It lives among trees, which it does not voluntarily leave. Its movements are deliberate, as its popular name, Slow Loris, implies; but it makes up for this by a vigorous tenacity of grasp. The animals "make a curious chattering when angry, and when pleased at night they utter a short though tuneful whistle of one unvaried note, which is thought by Chinese sailors to presage wind." Much superst.i.tion has collected round this harmless though rather weird-looking creature. Its influence over human beings is as active when it is dead as when it is alive. "Thus," writes Mr. Stanley Flower,[423] "a Malay may commit a crime he did not premeditate, and then find that an enemy had buried a particular part of a loris under his threshold, which had, unknown to him, compelled him to act to his own disadvantage." The life of the Loris, adds Mr. Flower, {547} "is not a happy one, for it is continually seeing ghosts; and that is why it hides its face in its hands!"

The genus _Perodicticus_ contains two quite recognisable species, known respectively as the Angwantibo and Bosman's Potto. The former has been regarded as referable to a distinct genus, _Arctocebus_. A curious internal character of the Potto which is visible, or at least can be felt, externally, is the long neural processes of the cervical vertebrae, which project beyond the level of the skin. The index finger is rudimentary and so is the tail, being only just visible (about an inch in length) in the Potto. The colour of both genera is a reddish grey, redder in the Potto.

The incisors are equal and minute. Both species are confined in their range to West Africa, and are arboreal like the other members of the sub-family.

The Potto seems to share the leisurely mode of progression of its Asiatic relatives, if Bosman, its original describer, is to be trusted. He says: "By the negroes called Potto, but known to us by the name of Sluggard, doubtless from its lazy, sluggish nature; a whole day being little enough for it to advance ten steps forward." The same writer did not at all appreciate his addition to zoological knowledge, for he remarked that the Potto "hath nothing very particular but his odious ugliness." The Angwantibo is rare and but little known. Our knowledge of its anatomy is derived from a paper by Huxley.[424] It is an animal measuring about 10 inches in total length to the end of the tail, which is only a quarter of an inch long. The hands and feet are smaller than those of _Perodicticus_.

The index finger is rudimentary and has but two phalanges, and it has no trace of a nail. In this it agrees with the Potto, but "the spinous processes of the cervical vertebrae do not project in the manner described by van der Hoeven in the Potto, though they can be readily felt through the skin." The dental formula of this genus as of the last is I 2/2 C 1/1 Pm 3/3 M 3/3. The last lower molar has a fifth cusp, which is wanting in the Potto. The last upper molar is tricuspid. It is bicuspid in the Potto.

It seems impossible to avoid agreeing with Professor Huxley that the Angwantibo is ent.i.tled to generic separation.

The genus _Loris_ also contains but a single species, _L. gracilis_, and is, as its name denotes, an animal of more slender build than the Slow Loris. Its eyes are very large, and the limbs excessively {548} slender.

The index finger is much as in _Nycticebus_. The colour, too, is not widely different, being of a yellowish grey, but it lacks the dorsal stripe which distinguishes its relative. The incisor teeth are equal and very small. The last upper molar has four cusps instead of the three of _Nycticebus_. This Lemur is confined to Southern India and Ceylon, and has much the same habits as the last. But it is rather more active, and can capture small birds when sleeping upon the trees; its diet, however, is mixed, and is vegetarian as well as animal.

A mysterious Lemur, which we conveniently place as a kind of appendix to the present family on account of its locality, has been shortly described by Nachtrieb from the Philippines. The tail is rudimentary; there are two upper incisors, but as many as six lower. It is doubtful what the beast really is.

[Ill.u.s.tration]

FIG. 263.--Aye-aye. _Chiromys madagascariensis._ 1/10.

FAM. 2. CHIROMYIDAE.--This family contains but a single genus and species, the Aye-aye, _Chiromys madagascariensis_, whose characters therefore are for the present those of the family as well as of the genus and species.

The external features of this extraordinary animal will be gathered from an inspection of Fig. 263, from which it will be seen that the earlier name of _Sciurus_ given to the creature was not by any means a misnomer. The Squirrel-like appearance is due, of course, chiefly to the strong and long incisor teeth. As to the external characters, which are of systematic importance, {549} attention may be called to the long and bushy tail, to the greater length of the hind-limbs, to the abdominal teats (one pair) in the female, and above all to the singular third digit of the hand, which is thin and elongated. The thumb is, as in other Lemurs, opposable, and has a flat nail; the remaining digits have claws, as have also the toes with the exception of the great toe, which has a flat nail like the thumb.

The anatomy of this animal has occupied the attention of a considerable number of observers, dating from Sir R. Owen, who was the first to give a connected account of its entire organisation. The most recent paper of importance is by Dr. Oudemans.[425] The teeth are very unlike those of other Lemurs. The most remarkable divergence is in the incisors, which are present to the number of but a single pair in each jaw, and are shaped like those of the Rodentia, and in the same way as in that group grow from persistent pulps. There are likewise, as in the Rodents, no canines. There are two premolars in the upper jaw (none in the lower) and altogether twelve molars, so that there is a total of eighteen teeth. The intestine has a moderately long caec.u.m. The brain has been most fully described by Oudemans, who had fresh material to work with, the brain described by Owen having been extracted from a spirit-preserved carcase. The angular fissure is well developed, as in Lemur and the Indri; but it does not join the infero-frontal. The antero-temporal fissure is also well developed.

"The name of Aye-aye," wrote Sonnerat, the discoverer of the animal, "which I have retained for it, is a cry of surprise of the inhabitants of Madagascar." It is, however, usually said that the animal itself makes a sound which may be written in the same way (or with an initial H). It is an arboreal and nocturnal animal, which accounts for its excessive rarity at one time. In one of his many eloquent essays upon natural history the late Mr. P. H. Gosse adduced the Aye-aye as an example of a creature on the verge of extinction. It is, however, now more frequently met with, though the superst.i.tion of the natives renders its capture a matter of some difficulty. There is a specimen at the moment of writing in the Zoological Society's Gardens. There has been some discussion as to the use of the slender middle finger: it is stated that it can thrust it into the {550} borings of the larva of a certain beetle of which the Lemur is particularly fond, and can extract the insect, or at any rate discover its position, when it may be extracted by the powerful chisel-shaped teeth. The partiality of the Aye-aye for animal food of any kind including insects has been both reaffirmed and denied; and Mr. Bartlett has seen the creature use its slender finger for combing out its hair, and for other purposes of the "toilet." Dr. Oudemans has figured in his paper an apple which has been largely eaten by the _Chiromys_; the fleshy pulp has been entirely excavated, leaving only the core and the skin, which are untouched. The Rev. Mr. Baron is one of the latest writers upon the ways of life of _Chiromys_.[426] He states that it inhabits the most dense parts of the forests. It has the habit of prowling about in pairs, and the female produces but a single young one at a birth. A nest, which is about 2 feet across, is made of twigs in lofty branches. This is occupied during the day, and entered by a hole in the side. With regard to the superst.i.tious veneration in which the animal is held, it is said that if a person sleeps in the forest the Aye-aye will bring him a pillow. "If a pillow for the head, the person will become rich; if for the feet, he will shortly succ.u.mb to the creature's fatal power, or at least will become bewitched." But a counter-charm may be obtained. It is said that the reverence for this beast leads the natives to bury carefully a specimen found dead.

FAM. 3. TARSIIDAE.--This family also consists of but a single genus, _Tarsius_, to which it is the general opinion that but a single species belongs; there are, however, at least four different specific names on record. The general aspect of the animal is not unlike that of a Galago, with which it also agrees in the elongation of the ankle; but the elongation is more p.r.o.nounced in the present genus. The ears are large, and the eyes are extraordinarily developed. The fingers and toes terminate in large expanded discs, and are furnished with flattened nails except on the second and third toes, which have claws. The tail is longer than the body and is tufted at the end. The skull is more like that of the Anthropoidea than is the skull of any other Lemur. The resemblance is by reason of the almost complete separation of the orbit and the temporal fossa by bone; {551} there is, however, a gap left to mark the Lemurine characters of the animal. The placenta, too, has been compared to that of the Apes. The dental formula is that of the genus _Lemur_, save for the absence of an incisor on each side of the lower jaw; the number of teeth is therefore thirty-four. The incisors of the lower jaw are upright, and not proc.u.mbent as in other Lemurs. The caec.u.m is of moderate length. The brain is almost smooth, but there is a Sylvian fissure and an antero-temporal, which latter does not reach the lower margin of the brain, but divides the middle part of the temporal lobe. The name Tarsier, as may be inferred, was originally given to this creature by Buffon on account of the abnormal ankle, and it was compared by him with the Jerboa, like which animal the Tarsier leaps when it descends to the ground. The genus is Malayan, but its range extends to the Philippines and to Celebes and Borneo. The Tarsiers are nocturnal and particularly arboreal; they live in pairs, in holes in tree stems, and are mainly insectivorous in their food. One, rarely two young are produced at a birth. Contrary to what is found in many Lemurs, the Tarsier is a silent creature, and at most emits a "sharp, shrill call." Dr. Charles Hose, who has studied this creature, has noticed that the mother often carries her young one about in her mouth like a Cat. Like so many Lemurs this animal is held in superst.i.tious dread, which no doubt is the result of its most weird appearance.[427]

[Ill.u.s.tration]

FIG. 264.--Right pes of _Tarsius spectrum_. (Nat. size.) _a_, Astragalus; _c_, calcaneum; _c_^1, internal cuneiform; _c_^2, middle cuneiform; _c_^3, external cuneiform; _cb_, cuboid; _n_, navicular; _I-V_, the digits. (From Flower's _Osteology_.)

FOSSIL LEMURS.--The Lemuroids are a very ancient race; they extend back to the very earliest strata of the Eocene, the Torrejon and Puerco beds, which, as already said, are thought to be more referable to the Cretaceous than to the Tertiary epoch. {552} One of these early forms is referred to the genus _Mixodectes_, a genus which has been placed, though with a query, in the order Rodentia. It appears, however, to be a Lemuroid, and is of American range. The incisor teeth have been held to argue that it lies on the direct track of _Chiromys_; but other features, more especially the form of the astragalus, have been used to argue the justice of the inclusion of this type within the order Rodentia. Allied, as it is supposed, to this form is _Indrodon_, also of the lowest Eocene deposits of the United States. _Indrodon malaris_ is known from fragments of nearly all parts of the skeleton. They indicate the existence of a creature of about one-half the size of _Lemur varius_. It had slender limbs and a long and powerful tail. The humerus, as in so many archaic beasts, has an entepicondylar foramen. The femur has three trochanters, and the fibula articulates with the astragalus. It is not always easy to distinguish these primitive mammals from each other, so that the minutest of characters have to be called in to our a.s.sistance. One of the contemporaneous groups with which these early Lemurs might be confused is that of the Condylarthra; it is important, therefore, to note that in _Indrodon_ the calcaneo-cuboidal articulation is nearly flat, and not bent as it is in the former group. The teeth are of the tritubercular pattern. The incisors are not known, but the molars and premolars are each three. To the same family, which has been termed ANAPTOMORPHIDAE, is referred the genus _Anaptomorphus_, which has been specially compared to _Tarsius_. This small animal has a Lemurine face with huge orbits. It has a premolar less than _Indrodon_. It has been ascertained that _A. homunculus_ had an external lachrymal foramen.[428]

Another family, that of the CHRIACIDAE, appear to hover on the border line of Lemurs and Creodonts, having been referred to both by various palaeontologists. Professor Scott suggests their Lemurine or at least Primate relations.h.i.+ps, while Cope urged their Creodont affinities. A difficulty raised by Scott was, that in _Chriacus_ the premolars of the lower jaw were s.p.a.ced. But it appears that this is not fatal to their inclusion in the Primates, since _Tomitherium_, an "undoubted Primate,"

shows the same feature. If _Chriacus_ is a Lemur it is an earlier type than those {553} which have been considered; for it has the typical Eutherian dent.i.tion of four premolars and three molars. These teeth, especially the superior molars, are particularly compared to the corresponding teeth of _Lemur_ and _Galago_. Of this and the allied genus, _Protochriacus_, several species are known.

_Adapis_, a representative of another family, is one of the best known of ancient Lemuroids. It has the typical mammalian dent.i.tion of forty-four teeth in a close series without diastemata. The orbits are completely separated from the temporal cavity, the eyes looking forwards. The canines are large and caniniform. The skull is deeply ridged behind with the usual sagittal crest. This genus is European, and corresponds to the already mentioned American Eocene _Tomitherium_, perhaps belonging to the same family.

_Nesopithecus_ is an extinct genus from Madagascar, lately described by Dr.

Forsyth Major.[429] There are two species, _N. roberti_ and _N. australis_.

The dental formula is I 2, C 1, Pm 3, M 3, for the upper jaw, the lower jaw having but a single pair of incisors. The lachrymal foramen is just inside, or on the edge, of the orbit, so that one distinctive Lemurine character is lost. The genus is also Ape-like in the form of the canines and incisors, these having been especially compared by Dr. Forsyth Major with those of the Cercopithecidae. The molars, too, agree with those of the same family.

There is, however, one important feature in which _Nesopithecus_ resembles not only the Lemurs as opposed to the Apes, but the Malagasy Lemurs. As already mentioned (p. 544), Dr. Major has shown that in the Malagasy Lemurs, even including the aberrant _Chiromys_, and in the Tertiary and European _Adapis_, the bulla tympani is not produced by an ossified extension of the annulus tympanicus, but from the adjacent periotic bone, the annulus remaining separate and lying within the fully-formed bulla.

This feature shows conclusively that _Adapis_ is a Lemur, and that _Nesopithecus_, originally supposed to be a Monkey, cannot be removed from the Lemuroidea, many though its likenesses to the higher Primates undoubtedly are. However, this feature, combined with the fact that the orbital and temporal cavities are in communication, shows the Lemuroid position of _Nesopithecus_, though it is quite conceivable that it is on the way to become an Ape. {554}

A family, MEGALADAPIDIDAE, has been quite lately founded by Dr. Forsyth Major[430] to include the remains of a gigantic extinct Lemur from Madagascar, which when alive, so far as we can judge from the skull, must have been three or four times the size of the Common Cat. The name _Megaladapis madagascariensis_ was given to the fossil on account of certain resemblances to the also extinct _Adapis_. It differs from other Lemurs in a number of characters which jointly warrant its inclusion in a distinct family. The small size of the orbits suggest a diurnal life; the deep mandibles, which, unlike what is found in other Lemurs, are completely blended at the suture, point to the existence of a howling apparatus, as in _Mycetes_. The low brain-case is a character which is found in so many extinct Mammalia belonging to many different orders that it weighs neither one way nor the other in considering the systematic position of the animal.

The shape of the molars, which are three in each half of each jaw as in other Lemurs, is, according to the discoverer, like that of the genus _Lepilemur_. The incisors and the canines are not known. Of a still larger form, _M. insignis_, the molar teeth are known.[431]

SUB-ORDER 2. ANTHROPOIDEA.

The Apes differ from the Lemurs in that the teats are always restricted to the thoracic region; the orbit, though surrounded by bone as in the Lemurs (and in _Tupaia_, a very Lemur-like Insectivore), does not open freely behind into the temporal fossa as in Lemurs (except _Tarsius_). The lachrymal opening is inside the orbit instead of outside; the cerebral hemispheres are more highly developed, and conceal, or nearly conceal, the cerebellum; the upper incisors are in close contact; a few other points are mentioned under the description of the characters of the Lemurs. There are altogether about 212 species of Monkeys and Apes. They are tropical and subtropical in range, and, with but few exceptions, are impatient of cold.

The Monkeys are primarily divisible into two great divisions, which have been termed, on account of the characters of the nose, {555} the Catarrhines and Platyrrhines. In the former the nostrils look downward and are close together; in the latter they are separated by a broad cartilaginous septum, and the apertures are directed outwards. But numerous other points of difference separate these two groups of the Monkey tribe.

The Catarrhines often have those remarkable ischial callosities, patches of hard skin brightly coloured; the tail may be totally wanting as a distinct organ, as is the case, for instance, with the Anthropoid Apes; there are often cheek pouches, so that, as Mr. Lydekker has remarked, if a Monkey be observed to stow nuts away in its cheeks for future reference, we may be certain that its home is in the Old World, for the Catarrhines are exclusively denizens of the Old World, while the Platyrrhines are as exclusively New World in range. Again, those of the Catarrhines which do possess a long tail, such as the members of the genus _Cercocebus_, never show the least sign of prehensility in that tail. The teeth of the Catarrhines are invariably thirty-two in number, the formula being I 2/2 C 1/1 Pm 2/2 M 3/3 = 32.

In the Old-World Apes there is a bony external auditory meatus, which is wanting (as a bony structure) in the Platyrrhines. The late Mr. W. A.

Forbes pointed out that in most of the New-World forms the parietals and the malars come into contact; in the Monkeys of the Old World they are hindered from coming into contact by the frontals and the alisphenoids. The Platyrrhines may have the same number of teeth; this is the case with the Marmosets, but in them there are three premolars and two molars; in the remaining New-World Monkeys there are thirty-six teeth, but of these three are premolars and three molars.

Not only are these two groups of the Primates absolutely distinct at the present day, but they have been, so far as we know, for a very long time, since no fossil remains of Monkeys at all intermediate have been so far discovered. This has led to the suggestion that the Monkeys are what is termed diphyletic, _i.e._ that they have originated from two separate stocks of ancestors. It is hard, however, to understand on this view the very great similarities which underlie the divergences that have just been mentioned. But, on the other hand, it is equally hard to understand how it is that, having been separated from each other for so long a period, they have not diverged further in {556} structure than they have. The Platyrrhines seem to stand at the base of the series. This is another example of the existence of archaic creatures in South America.

GROUP I. _PLATYRRHINA._

FAM. 1. HAPALIDAE.--We may begin the account of the Platyrrhine Monkeys with the Hapalidae or Marmosets; for this family is structurally lower than the rest. They have thirty-two teeth, arranged as in the following formula: I 2/2 C 1/1 Pm 3/3 M 2/2 = 32. The molars have three main tubercles, and not four as in the higher forms. The digits are for the most part clawed, not nailed, as in the higher types; the great toe alone bears a flat nail.

The tail, too, is ringed, a condition which is characteristic of many of the lower groups of mammals, but not of the higher Apes. The cerebral hemispheres are smooth, but this is a matter rather connected with their small size than with low zoological position. The tails of the Marmosets, unlike those of so many other American Monkeys, are not prehensile though they are long.

The genus _Hapale_ is broadly distinguished from the other genus, _Midas_, by the fact that the lower incisors slant forwards as in the Lemurs. They are small, soft-furred, long-tailed Monkeys, familiar to every one. There are some seven species, which are entirely restricted in range to Brazil, Bolivia, and Colombia, one species only, _H. pygmaea_, extending northward into Mexico.

Of Tamarins, genus _Midas_, there are rather more species--about fourteen.

They are South and Central American in distribution. Since both these genera are arboreal in habit, it is extraordinary that they have not the prehensile tails of their American allies. As, however, the late Mr. Bates observed an individual of the species _M. nigricollis_ fall head-foremost from a height of at least 50 feet, alight on its feet, and run off as if nothing in particular had occurred, it is evident that no extra prehensile powers are absolutely necessary. Some of the Tamarins have a long mane; this is well seen in _M. rosalia_, or rather in _M. leoninus_, which, if not identical with it, is at least very closely allied to it. The name is obviously derived from the character {557} referred to, and the Monkey, originally described by the traveller von Humboldt, is said to have "the appearance of a diminutive lion." _M. bicolor_ is an example of the species with no mane, but with a patch of white round the mouth, looking like "a ball of snow-white cotton" held in the teeth.

FAM. 2. CEBIDAE.--The remaining American Monkeys are comprised in the family Cebidae. This is to be distinguished from the last by the fact that there is an additional molar, thus making thirty-six teeth in all. The tail, sometimes very short, is more generally long and highly prehensile, being nude at the extremity, which part is therefore especially prehensile; this state of affairs is often to be seen in animals with prehensile tails.

The Cebidae, though for the most part larger than the Marmosets, never approach in size the Old-World Apes.

Typical of the family is the genus _Cebus_, including the "Capuchin"

Monkeys, and consisting of nearly twenty species; the tail, though prehensile, is covered with hair to the tip, a fact which is indicative of a less perfect prehensility than is exhibited in some Monkeys with a naked under surface to the tip of the tail. The thumb is well developed. The genus ranges from Costa Rica to Paraguay. The commonest Monkey which accompanies the street organs of this country is a _Cebus_. It is a popular delusion that these and other monkeys are purely vegetable-feeding animals.

_Cebus_ is in fact particularly fond of caterpillars, as are also the Marmosets.

Allied to _Cebus_ is _Lagothrix_, the Woolly Monkey, of which _L.

humboldti_ is the best-known species, there being indeed but one other. It is a larger and heavier animal than any species of _Cebus_; and the Hare-like woolliness of the fur suggested its scientific name to its original describer, von Humboldt. It has a perfectly prehensile tail, naked at the tip. The thumb and great toe are well developed. These are purely fruit-eating Monkeys, and are known as "Barrigudos" by the Portuguese of the Amazon country on account of their prominent belly, due apparently to the immense amount of fruit consumed. They are, or were, much eaten by natives.