jackals and wolves and near allies of the different species of fox, the
whole forming a family--_Canidæ_.
The otter has been already referred to, and it may be thought that
mention of the seals and sea-lions has been unintentionally omitted. But
the seals and sea-lions, in spite of a certain slight resemblance to
otters, due to similarity of habit, are not really near allies of the
latter. They (_i.e._, seals and sea-lions), together with the walrus,
form, indeed, a very distinct family, which is termed _Phocidæ_, because
its type, the common seal, belongs to a subordinate group, or "genus,"
named _Phoca_.
All these families, _Felidæ_, _Ursidæ_, _Canidæ_, and _Phocidæ_ form
together one greater group or "order," to which, of course, these four
families are subordinate. This order is called "_Carnivora_," because it
is made up of carnivorous or flesh-eating beasts.
The other familiar beasts first referred to--our domestic cattle of all
kinds--form, together with all swine, horses and all asses, deer,
antelopes and camels, another great order of beasts called _Ungulata_,
because the nails of their feet are so large and solid as to form
"hoofs." This order of hoofed-beasts, or ungulates, is a very large
order, and is divided into two sub-orders, and in each sub-order are
various families containing more or fewer genera.
The two sub-orders are characterized by the structure of the foot. The
toes of the hind foot, which are made use of in progression, are even in
number in one sub-order and are odd-numbered in the other sub-order.
The sub-order of odd-toed ungulates, or _Perissodactyla_, includes in
our day only the horses, asses, zebras, and quaggas (united together in
the family _Equidæ_); the tapirs, the rhinoceroses, and the little
hyrax--the coney of Scripture. In ancient times, however, this sub-order
was a very large one, but the great majority of the forms belonging to
it, which formerly lived, have now become extinct.
The sub-order of even-toed ungulates, or _Artiodactyla_, comprises all
oxen, sheep, goats, antelopes, giraffes, deer, chevrotains,[10] llamas,
and camels. All these, from their practice of "chewing the cud," are
called "ruminants," and they are multitudinous in kinds. The great
plains of Southern Africa are the special home of most kinds of
antelope, and the giraffe is exclusively African. Deer have their
head-quarters in Asia, though they exist in South America as well as
throughout the Northern Hemisphere.
Besides the ruminating artiodactyles there is also an extensive group of
non-ruminating artiodactyles, made up of all the various kinds of swine
(including the American peccaries), together with the hippopotamus, now
found nowhere but in Africa. Distinct as are the ruminating and
non-ruminating artiodactyles now, they were in ancient time connected by
a great number of intermediate forms which have utterly passed away.
The llamas of South America represent the camels of the Old World, where
the latter are to-day exclusively found. When South America was
discovered by the Spaniards, llamas were the only beasts of burthen
found there, and, indeed, the only cattle of any kind then and there
existing; although horses had formerly abounded and had become extinct
in South America at a long anterior period.
Somewhat allied to ungulates, but distinct from them, are the elephants,
which form an order (_Proboscidea_) by themselves--an order once rich in
many species widely distributed over the earth.
Hardly less familiar than our domestic animals, are our hares, rabbits,
mice, squirrels, and their allies, which together form an "order" called
_Rodentia_ from the gnawing habits of its members which nourish
themselves on vegetable substances. This order of rodents is very rich
in species, and consists of many genera grouped in several distinct
families--such, _e.g._, as the family of mice and rats (_Muridæ_), of
squirrels (_Sciuridæ_), of guinea-pigs and spine-bearing porcupines
(_Hystricidæ_), &c. The largest form of rodent is the capybara (or
river-hog of the Rio de la Plata),--which is preyed on by the jaguar.
Though a near ally of the little guinea-pig, it is as large as a hog.
Amongst the more interesting rodents may be mentioned beavers,[11] the
fur-bearing chinchilla, the jerboa (_Dipus_), the musk-rat (_Fiber_),
and the rat-mole (_Spalax_). The jerboa has very long hind legs, and a
habit of jumping, so that it resembles superficially (but not really) a
small kangaroo. The _Spalax_ is quite blind, and has the burrowing
habit, and somewhat the shape of the common mole. Some rodents are
fitted to flit through the air in long jumps, by means of the wide
extensibility of the skin of their flanks, which, when stretched out,
acts as a parachute. Such forms are the flying squirrels, and a curious
rodent called _Anomalurus_, from the exceptional clothing of the base of
its tail, which is furnished with large scales at its under part.
Another order of beasts may here be referred to, because it affords
interesting examples of the co-existence of external resemblance without
any real affinity. This order includes the insect-eating beasts, or
_Insectivora_, and comprises the moles, hedgehogs, shrew-mice (which are
not really "mice" at all), and their allies. The _Insectivora_ and
_Rodentia_ present us with a singular parallelism in the respective
modifications of structure, which are found in these two very distinct
orders. But the insectivorous forms (as might perhaps be expected from
their less abundant food) are always smaller in size than are the
parallel vegetable-eating groups of rodents. Indeed, one insectivore of
the genus _Sorex_ (the shrew-mouse genus) is the absolutely smallest
mammal which is known to exist.
As examples of the parallelism referred to may be mentioned the moles
(which resemble the rat-moles), the shrew-mice (which resemble true
mice), the hedgehogs, and the less known spiny tanrec of Madagascar
(which resemble porcupines in their clothing); certain graceful and
active tree-frequenting insectivores of the Indian Archipelago, _Tupaia_
(which resemble squirrels); an aquatic African form, _Potomogale_ (which
resembles the musk-rat); certain elephant shrews--long-legged, jumping,
African insectivores (which resemble the jerboa amongst rodents); and,
lastly, the so-called flying lemur of the Philippine Islands, or
_Galeopithecus_, which resembles the flying squirrel, and the curious
rodent _Anomalurus_ before referred to.
The only beasts, however, which _truly_ fly are the bats, which form an
order by themselves, well-named, from the structure of their wings,
_Cheiroptera_. The bats which fly about in the twilight in this country,
or sometimes in the afternoon of a warm day in winter, are all
insect-eating forms. But in the warm regions of the Old World, and of
Australia, there are large fruit-eating kinds, called "flying foxes;"
while in South America there are blood-sucking bats, or vampires, some
of which, as we shall hereafter see, present the most curious and
interesting modifications of structure in harmony with their peculiar
habits.
The creatures which are in some respects the most interesting to us,
because they are the most like ourselves in form, are the apes.
Moreover, not only are they so like us in form, but they are so widely
marked-off from all other creatures except ourselves, that it seems
impossible they can have any real affinity to one more than to another
group of mammals below man. Apes and man then together form one order,
which as ranking first was named by Linnæus, _Primates_. With the apes
are commonly associated certain animals called Lemurs, which inhabit the
vicinity of the Indian Ocean, especially Madagascar. They have not,
however, any real affinity to apes; and if they are to be placed in the
same order at all, they must be well distinguished from its other
members. It has therefore been proposed[12] to divide the order Primates
into two sub-orders (as the hoofed order is divided into the "odd-toed"
and "even-toed" sub-orders), one of these to include man and apes, and
to be called, from the resemblance to the human form pervading it,
"_Anthropoidea_;" the other sub-order to be termed "_Lemuroidea_."
The first "sub-order" is divisible into three "families." One of these
(_Hominidæ_) contains man (forming the genus _Homo_), the second
(_Simiadæ_) contains all the apes of the Old World only, while a third
(_Cebidæ_) contains all those of America.
Amongst the _Simiadæ_ are the orang, the chimpanzee, the gorilla, and
the long-armed apes (or Gibbons), which are the most man-like of all the
apes; and there can be no question but that there is very much less
difference in structure between these four kinds of apes and man, than
there is between them and the lowest of the apes--_i.e._, the marmosets.
Concerning this resemblance, Buffon has observed, when speaking of the
ape, the most man-like (and so man-like) as to brain:[13] "Il ne pense
pas: y a-t-il une preuve plus évidente que la matière seule, quoique
parfaitement organisée, ne peut produire ni la pensée, ni la parole qui
en est le signe, à moins qu'elle ne soit animée par un principe
supérieur?"
As to the second sub-order, it contains some very curious forms. The
typical lemurs (which inhabit Madagascar) have long fox-like snouts and
long tails. Certain African forms (the genus _Galago_) are very active
in their movements, and great leapers. A tailless group (the slender
loris) is interesting, as presenting a diminutive quasi-human form,
reflected, as it were, through a Lemurine prism, just as the rat-mole
shows us a mole-form reflected through a rodent prism.
A little animal, the Tarsier, which is found on the islands of Celebes
and Borneo, is very exceptional in its structure. Still more so is the
aye-aye (_Cheiromys_). This very remarkable species was discovered by
Sonnerat in Madagascar in 1770, and was never again seen till 1844, when
a specimen was forwarded to Paris. It has now, however, become well
known.
Inhabiting the sea are many beasts, which are, by mistake, popularly
spoken of as "fishes." Such are the whales and the porpoises--animals
which, in spite of their form and habit, suckle their young, and have
hot blood, as all other mammals have. These creatures form an order by
themselves, called _Cetacea_.
Another order of aquatic beasts is termed _Sirenia_, and the animals
which compose it were long confounded with the _Cetacea_, from which,
however, they are widely divergent in structure, in spite of the
general similarity which exists between them in external appearance. The
order _Sirenia_ contains but two existing genera. One of these is the
now well-known manatee (_Manatus_), the other is the dugong
(_Halicore_)--an animal very similar to the manatee, and found in the
rivers of regions about the Indian Ocean. A third form, the _Rhytina_,
existed in the Aleutian Isles till recent times, but was extirpated
almost as soon as discovered, from its incapacity for flight or defence,
and from its flesh affording a welcome change of diet to hungry sailors.
The _Cetacea_ and _Sirenia_ are examples of creatures organized for a
completely aquatic life--for never coming to land.
The forest-regions of South America offer to animal life so enormous a
mass of foliage that it may not unjustly be termed a sea of verdure, and
creatures there exist which are specially organized for a completely
arboreal life--for never coming to the ground. Such creatures are the
sloths, which pass their lives hanging back-downwards, suspended to the
branches by their huge claws. Thus, they sleep without effort (from the
peculiar mechanism of their limbs), and they move slowly from tree to
tree, having no need to hurry after food, since they live suspended in
the midst of a perennial banquet.
Nearly allied to the sloths were certain huge beasts, now extinct, which
formerly inhabited the same Continent--such as the _Megatherium_ and
_Mylodon_, which rivalled or exceeded our largest rhinoceroses in bulk.
They fed on the same food which nourishes the sloth, but obviously the
branches of no tree could sustain such monsters. They obtained their
leafy pasture, therefore, by a different method. Rearing themselves on
their massive hind legs and powerful tail, as on a tripod, they embraced
the trees with their vigorous arms, and swayed them to and fro, till the
tree embraced was prostrated, and literally fell a prey to their
efforts. These bulky creatures were protected against that danger which
such a mode of life rendered imminent by a specially strong skull
structure, which enabled them to bear a broken head with but little
inconvenience.
In the same region of the earth are found the ant-eaters and armadillos,
and more or less allied to them are the pangolins (_Manis_) of Africa
and Asia. The horny scales which cover the bodies of the last-named
animals caused them for some time to be associated with reptiles rather
than with beasts, though they are true and perfect mammals. Lastly must
be mentioned the aard-vark (_Orycteropus_) of South Africa.
All these creatures, from the sloths to the aard-vark, are commonly
associated together in an order which is termed _Edentata_.
The whole of the orders of mammals yet mentioned agree in certain
important details with respect to their reproductive processes, as well
as in certain smaller anatomical peculiarities, and the whole of the
creatures included within these orders are (and will be) often spoken of
as _Placental Mammals_.
The only beasts which it yet remains to speak of are grouped in two
other orders.
The first of these is called the order _Marsupialia_, and comprises all
opossums (_Didelphys_), kangaroos (_Macropus_), phalangers
(_Phalangista_), the Tasmanian wolf (_Thylacinus_), the dasyures
(_Dasyurus_), the bandicoots (_Perameles_), and their allies. With the
exception of the true opossums (_Didelphys_), all the members of the
order are found in Australia or its vicinity, and nowhere else in the
present day; although, as we shall better see hereafter, Europe once
possessed animals closely allied to Australian forms of to-day--notably
to a pretty little quadruped which bears the generic name _Myrmecobius_.
As last of the class of beasts, we have two extremely exceptional
mammals (both found only in the Australian region), the duck-billed
platypus (_Ornithorhynchus_), and the _Echidna_. The first of these, as
its name implies, has a muzzle quite like the bill of a duck, with a
squat, hairy body, and short limbs. The echidna is covered with strong,
dense spines, and has a long and slender snout. These creatures together
form the order _Monotremata_--an order which differs very much more from
any other Mammalian order than any of the other orders of mammals differ
one from another.
Thus, that great group which embraces man and beasts, and which group
ranks as a "class"--the _class_ Mammalia--comprises (as we have now
seen) a number of subordinate groups termed "orders," the orders being
made up of families, and these again of genera.
It would be impossible as yet (when hardly any anatomical facts have
been even referred to) to give the characters of the class _Mammalia_.
It must at present suffice to point out that, in addition to mammary
glands, the creatures have hot blood, and the body bears more or less
hair--at least at some time of life.
We may now pass to the next class, that of birds--the class _Aves_. In
spite of the great multitude of kinds which ornithologists
enumerate--upwards of ten thousand species--there is very much less
diversity of form amongst birds than there is amongst beasts.
Starting in the present class as in the preceding one from the most
familiar kinds, we may begin with the domestic fowl. This is one of an
"order" to which belong the peacock, all pheasants and tragopans (three
forms which have their home in Central and Southern Asia), also the
Guinea fowls (African forms), and the turkeys and curassows, which are
American representatives of the order. Besides these may be mentioned
partridges, grouse, black-cock, the capercalzie and quails, and, lastly,
the megapodius or bush-turkey of Australia. This last is the only bird
which hatches its eggs by artificial heat, depositing them in a mound of
earth and decaying vegetable matter, wherein they are hatched
fully-fledged, so that they can fly away immediately on leaving the egg.
All the birds yet mentioned are called gallinaceous birds, or _Gallinæ_,
and sometimes _Rasores_ or "Scratchers."
More or less allied to them are the doves and pigeons, which form the
order _Columbæ_, in which the curious ground-pigeon _Didunculus_ is
included--a form which presents an interesting resemblance to the
celebrated and extinct dodo of Mauritius, long known only by certain
pictures, and a foot and head preserved, one in the British Museum, and
the other in the Ashmolean Museum of Oxford.
Our sparrows, robins, and all our song birds are members of an
exceedingly numerous "order" "_Paseres_." In it are included the crows
(with those gaily-decorated crows, the Birds of Paradise, found only in
New Guinea and the Moluccas), the bower birds and the lyre bird of
Australia; the flycatchers, the pittas (or ground thrushes), the
water-ouzel, the weaver birds, the wrens, the tits, the creepers, the
honey-eaters, those African gems, the sun birds, and also the swallows.
To another order--the order _Macrochires_--belong those most beautiful
of all birds, the humming birds, found only in America, and long thought
to be allied with the really very different sun birds just mentioned.
With these may be associated the swifts (which have such marvellous
powers of flight) and the wide-gaped goat-suckers or nightjars.
Woodpeckers are considered to form an order (_Pici_) by themselves,
while the cuckoos are thought to be near relations of the beautiful and
eccentric toncans, the plaintain-eaters, the touracous, the kingfishers,
the hoopoes, the bee-eaters, the hornbills, and the trogons, all, from
the cuckoos to the trogons, being included in the order _Coccyges_.
The parrots form an isolated group of birds--the order _Psittaci_. Their
most peculiar forms are the macaws on the one hand, and the brush-tailed
loris on the other. The order _Accipitres_ includes all the birds of
prey--that is to say, the eagles, falcons, hawks, buzzards, vultures,
and owls. In this order is included the long-legged secretary bird,
which looks like a cross between a hawk and heron.
Pelicans, gannets, cormorants (or shags), and darters go together to
constitute the order called _Steganopodes_. The flamingoes are isolated,
and by themselves form the order _Odontoglossæ_. The same is the case
with the penguins, which have the order _Impennes_ assigned exclusively
to them.
The ducks and geese form alone the order _Lamellirostres_, in which is
included the curious bird _Palamedea_, which is a goose adapted to live
in trees in harmony with its South American forest habitat.
The rails and coots go with the bustards and cranes to constitute the
order _Alectorides_. Similarly the auks, divers, puffins, terns, and
grebes, noddies, and guillemots may be associated together in one
order--the order _Pygopodes_. The gulls and petrels form another
association--the order _Gaviæ_; while the plovers, snipes, curlews,
peewits, turnstones, &c., constitute the order _Limicolæ_. The order
_Heridiones_ includes the herons, the bitterns, the storks, spoonbill,
ibis, &c.
All the foregoing birds have a multitude of points in common; indeed, so
close is the similarity of their structure that their subdivision into
orders is a matter of much difficulty and dispute. They are collectively
spoken of as the _Carinatæ_, from the keeled form of their breast-bone.
Widely apart from them stands another group made up almost entirely of
large birds, which agree not only in having no power of flight, but also
in certain significant structural characters, amongst which may be
mentioned the absence of a keel on the breast-bone.
This latter group is sometimes spoken of as the order _Struthiones_ from
the ostrich (_Struthio_), which is its typical form. Sometimes these
keelless birds are called _Ratitæ_. Besides the ostrich, the rhea,
cassowary, and emeu are included within the group; also the small and
nocturnal _Apteryx_ of New Zealand and those giants of featherdom, the
huge species of dinornis, all also of New Zealand and all now extinct.
With this our list of birds might close, but for a bird which anciently
existed in Europe so strangely different from all modern kinds, that it
must certainly be here adverted to. This bird is the _Archeopteryx_,
found in fossil in the Solenhofen States.
The class Aves, like the class Mammalia, consists of animals with hot
blood, but all birds have feathers and a number of other peculiarities
of structure, as will appear later.
The next class to be adverted to is the class which includes all
reptiles properly so-called--the class _Reptilia_.
The reptiles which exist in the world to-day may be classed in four
well-marked sets, each of which has the value of an "order"--(1)
crocodiles, (2) lizards, (3) serpents, and (4) tortoises. The names of
these creatures alone suffice to indicate the fact that the class of
reptiles presents us with an extraordinary amount of diversity of form
as compared with the class of birds with which, nevertheless, reptiles
have, as we shall hereafter see, very close relations. Indeed, in the
diversity of kinds which it contains, the class _Reptilia_ at the least
fully equals the class Mammalia, especially if the extinct kinds are
taken into consideration. The number of species of reptiles, both living
and extinct, much exceeds also the number of living and extinct mammals.
To begin once more with forms which are the least strange and unknown,
we may start with the little elegant and harmless lizards of our heaths
and commons, which will serve as types of the order to which they
belong--the order _Lacertilia_. That order is an extremely numerous one,
containing many families, differing much in form. Our English lizards
are true lizards, belonging to the typical genus _Lacerta_ and to the
typical family _Lacertidæ_. The rather well-known large American lizard,
_Iguana_, is the type of another and very extensive family (almost
entirely confined to America), while a nearly-allied family (_Agamidæ_)
is an Old World group. Amongst the curious forms found in the latter
family may be mentioned the frilled and moloch lizards of Australia, and
those little harmless lizards of India which go by the formidable name
of "flying dragons" (_Draco_). They are the only existing aërial
reptiles--not that they can truly "fly" at all, but they are enabled to
take prolonged jumps, and to sustain themselves to a considerable extent
in the air by means of the extremely distensible skin of their flanks
which, when extended, is supported by a peculiar solid framework
hereafter to be described. Some of the largest lizards are called
"monitors," and are common in Egypt; they belong to the family
_Monitoridæ_.
In the warmest period of the year, certain lizards are found in the
South of Europe, called geckos. They have a power of running, not only
up walls, but across ceilings by means of a peculiar structure of their
toes. They are types of a large family (_Geckotidæ_) widely spread over
the world.
Another large family (_Scincidæ_) has also its type in the South of
Europe in the skink (_Scincus_), which was formerly supposed to possess
much medicinal value. This large family contains a number of species
which exhibit a series of gradations in structure leading to forms which
have the external aspect of serpents. One such form is the perfectly
harmless slow-worm, or blind-worm, of our own country, which in spite of
its scientific name, _Anguis fragilis_[14], is a legless lizard, and no
snake.