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with the neighbouring islands, each of these areas comprising nearly half of the
known species. The common chamseleon (C. vulyari*} is, however, found on the
African and Asiatic coasts of the Mediterranean, entering Europe in Andalusia;
while a second species inhabits the Isle of Socotra, a third Southern Arabia, and a
fourth India and Ceylon.

Evidently extremely specialised creatures, chameleons stand
altogether apart from the lizards, not only as regards their anatomical
structure, but likewise in their power of moving one eye independently of the other,
in the enormous extensibility and protrusive power of their tongues, and in their
slow and deliberate movements. According, however, to those who have had the
opportunity of observing them in their native haunts, chameleons do not move
(jnite so slowly as in confinement, where the}'- take half a minute in determining
which limb to move, or on which bough to replace it. Passing the whole of their




CHAMELEONS.



CHAM&LE ONS. 1 7 3

lives in trees, like most of their Malagasy compatriots, the lemurs, chameleons are
chiefly found only in regions where foliage is abundant, and where the fall of rain
or dew is sufficient to supply them with the amount of moisture they need. Conse-
quently, they are most numerously represented in coast districts and islands. A
few, however, frequent such parts of desert regions as come under the influence of
the sea moisture, and support a more or less scanty vegetation. Needless to say,
all the species live on insects, and more especially flies of various kinds, which are
caught by the viscid secretion of the tip of the protrusile tongue.

Being utterly defenceless creatures, and having a large number of enemies,
chameleons depend entirely upon their resemblance to their environment for
protection ; and for this end they have the power of changing colour, although not,
apparently, to such an extent as is the case with some li/ards of the genus Calotes.
At night they appear generally to be of a whitish yellow hue, but with the first
dawn of day assume the dark green colour characteristic of most of the species,
which exactly assimilates to the surrounding leaves, and continues to grow brighter
and brighter with advancing day. When resting on a bough, or when captured
in the hand, the colour changes, however, to brown ; this change in the latter case
iking place with exceeding rapidity, and the skin sometimes becoming nearly
lack, with the disappearance of all the bright marking. This change, according
Miss C. C. Hopley, is due to anger; the creature at the same time emitting a
nmd something between a hiss and the chirp or squeak of a very young bird, and
nng to bite its captor. " Meanwhile, it is all impatience to ascend, no matter
rhere, so that it climbs upwards. Up, up, always up ; it may be your dress, or
whatever is near. It seems to think it can be safe only at the top of something.
Lnd yet they are not found invariably on the upper branches of their bush, though
merally rather high. Released from the hand, its anger soon subsides, so does
dark hue, and the creature assumes the tint of the surface on which it is placed,
reyish, reddish, darker or lighter, green or yellow, as may be." Several individuals
not unfrequently met with on the same bush, where they cling tightly to the
mis among the crowded leaves, being alike difficult to detect and to detach, and
Iways exhibiting their displeasure at being disturbed by the aforesaid hissing
3und. Absolutely still they remain, continues the writer just quoted, hour after
lour, the only evidence of life about them being that revolving little globe of an
Bye, with its pupil turning as an axis, now up, now down, forwards or backwards,
while its owner clings motionless as death. In repose, the long tongue is folded
up within the dilatable skin of the chin, where it has a special sheath for its
reception ; but it can be darted out with such speed as to take a fly at a distance
of fully six inches. Although the majority of the species lay eggs, the pigmy
chameleon (C. pumilus) of the Cape, together with five nearly allied African
species, produce living young, which may be as many as eleven in number. In
confinement chameleons quickly become tame, and, if allowed to rest in peace, after
a few days cease to bite and hiss when handled, and soon venture to take a fly
from their owner's hand,



1 7 6



SNAKES.



single head with a facet on the side of each vertebra, in the same manner as in
lizards. Only certain groups of lizards have the vertebrae with the additional
articular facets on the front and back surfaces known as zygantra and zygo-
sphenes, but in snakes (as shown in the figure below) these are invariably
present ; and it is owing to this complicated system of articulation that a snake
is able to make the wonderful foldings and contortions characteristic of its kind
without fear of dislocating its spine. It may be added that no snake has any
trace of a breast-bone, nor any vestige of a pectoral arch, there being no rudiments
of either blade-bone, coracoid, or collar-bone. When progressing on a firm surface,
an ordinary snake, in common with the limbless lizards, walks entirely by the aid
of its ribs, which are but very loosely articulated to the vertebras, and thus readily
admit of a large amount of motion. In describing their mode of progression, Dr.
Giinther remarks that " although the motions of snakes are in general very quick,
and may be adapted to every variation of ground over which they move, yet all




SKELETON OF SNAKE.



the varieties of their locomotion are founded on the following simple process.
When a part of their body has found some projection of the ground which affords
it a point of support, the ribs, alternately of one and the other side, are drawn
more closely together, thereby producing alternate bends of the body on the
corresponding side. The hinder portion of the body being drawn after, some part
of it finds another support on the rough ground or a projection, and the anterior
bends being stretched in a straight line the front part of the body is propelled in
consequence. During this peculiar kind of locomotion, the numerous broad shields
of the belly are of great advantage, as, by means of the free edges of those shields,
they are enabled to catch the smallest projections on the ground, which may be
used as points of support. Snakes are not able to move over a perfectly smooth
surface." It may be added that a snake is only able to move by lateral undulations
of its body in a horizontal plane ; and that the pictures often seen in which these
reptiles are depicted as advancing with the folds of the body placed in a vertical
plane are altogether erroneous. In conformity with their elongated bodies, the



GENERAL CHARACTERS. i 77

internal organs of snakes are long and narrow ; and it is remarkable that, as a
rule, only one of the lungs is developed.

Resembling the other members of the order to which they
belong in that their teeth are never implanted in distinct sockets or
grooves, snakes exhibit some considerable degree of variation with regard to the
number and structure of their teeth. In the ordinary harmless forms there are
generally two rows of short, slender, and sharply-pointed teeth in the upper jaw,
the innermost of which are attached to the bones of the palate, while the lower
jaw carries only a single row of such weapons. One or two of the outer row of
upper teeth, either at the front or back of the series, may, however, be enlarged
beyond the rest, and grooved or tubular ; and it is probable that all snakes with
such a dental armature are more or less venomous. Some most deadly poisonous
serpents have, on the other hand, a type of dentition of their own ; and there is
no doubt that all snakes with teeth of this nature are extremely venomous. In
such snakes the forepart of the very short maxillary bone of each side of the
upper jaw is armed with an elongated tubular tooth, which ordinarily lies nearly

lat on the surface of the palate, but can be erected, by a peculiar mechanism of
the bones, when the jaws are opened. Although in this group the poison-fangs

re always tubular, in some of the other venomous serpents they are merely grooved

>r the conveyance of the venom from the secreting gland ; but there is a transition

3tween the two types, as the closed tube is formed merely by the edges of the groove

jing elevated until they unite in the middle line. In poisonous snakes, on each
side of the upper jaw, below and behind the eye, is situated the poison -gland

lerely an ultra-development of an ordinary salivary gland ; these glands in some
ses being so developed as to extend far back along the sides of the body. The
is overlain by a layer of muscles, for the purpose of forcing the secretion

ito the tooth (the base of which is always open) when required ; this action
ilways taking place when the snake opens its mouth to bite. The poison then
lows along the channel or tube of the tooth, and is discharged at its extremity into
the wound. Considerable force is used in the emission of the poison, as, when a
snake is irritated, the. fluid may be seen to spirt for some distance from its point of
lischarge. In some of the less specialised poisonous snakes, the venom-tooth,

fhich has an open channel, is not greatly longer than the others, and is placed
learly vertically when the mouth is closed. Although the poison-teeth are

)mmonly regarded as purely defensive weapons, their chief use is for the de-
struction of the prey of their owners, which is always killed before being swallowed.
The venom-tooth of the more specialised poisonous snakes is exceedingly likely to
be broken off during use ; but to take its place there are always several others
lying on the gum behind it in different stages of development.
Harmless and Poi- Before the doctrine of parallelism in development received from

sonous Snakes, naturalists the attention it undoubtedly merits, snakes were generally
divided into harmless and poisonous groups ; but since we have become better
acquainted with that important factor in evolution, it has been recognised that
such a distinction is a purely artificial one, and has nothing to do with real affinity.
Certain groups of snakes, such as the members of the viper family, may, however }
be wholly poisonous; while in other groups, such as the typical snakes, some
VOL. v. 12



178 SNAKES.

species may be venomous and others innocuous. Many attempts have been made
to draw up a list of characters by means of which the harmless members of the
suborder can be distinguished at a glance from those which are hurtful. On this
point Mr. Boulenger writes " that there is no sure method of distinguishing the
two kinds of external characters ; except, of course, by a knowledge of the various
forms. And even then, a cursory examination is not always sufficient, since there
is, in some cases, a striking resemblance between snakes of totally different affinities,
by which even specialists may at first be deceived. In short, nothing but an
examination of the dentition can afford positive information as to the poisonous
or non-poisonous nature of an unknown snake."

Geologically speaking, snakes are a comparatively modern group,
Distribution. J

being scarcely known below the lowest portion of the Eocene division

of the Tertiary period, although one or two forms have been described from the
underlying Cretaceous rocks, and one has recently been recorded from the Gault of
Portugal a formation underlying the Chalk. It is noteworthy that one of the
North American lower Eocene snakes has the additional articular facets of the
vertebrae but very imperfectly developed ; and there can be little or no doubt but
that the whole group is an offshoot from the lizards. From the commencement of
the Tertiary period, the group seems to have gone on steadily increasing in
numbers ; and it is now represented by some fifteen hundred species, ranging all
over the world except New Zealand. Snakes are, however, much more abundant
in the moist tropical regions of the globe than in colder regions, and it is there only
that they attain their maximum development in point of size. India and the
Malayan countries, where there are representatives of the whole of the nine families
into which the suborder is divided, are the home of a greater number of both
genera and species of snakes than any other part of the world, Tree-snakes are
very common in this region; while the gigantic pythons are shared by it in
common with Africa. The proportion of poisonous to innocuous species is likewise
very high in the Oriental region, and has been estimated at about one in ten.
Africa has scarcely half the number of snakes found in the Oriental region : and
it is noteworthy that the forms inhabiting Madagascar have but little in common
with those of the mainland; the so-called lycodonts, which are so common in
Africa, being unknown in Madagascar, while some of the forms from that island
are closely allied to South American types. Whereas pit-vipers are absent, an
especial feature of Africa is the number of typical vipers which inhabit that
country: and Australia, which differs so remarkably from India in its tortoises,
possesses snakes (and likewise lizards) closely allied to African forms. Next
to the Oriental region, tropical America is richest in ophidians, although
the number of generic types is not so great. The proportion of poisonous species
is, however, high, and has been estimated at as much as one in eight. In Southern
Argentina and Patagonia snakes become scarce. Unlike its chelonians, the snakes
of North America present a resemblance to those of Central America. Indeed,
a feature of the whole of America is the absence of typical vipers, and the
abundance of pit-vipers, although several genera of the latter are common to Asia.
Europe and Northern Asia are comparatively poor in snakes, but (next to Africa)
are characterised by the number of typical vipers and colubrine water-snakes.



HABITS. 179

Although a few members of the suborder subsist on eggs, snakes

Habits

as a rule capture and devour living animals, which are in all cases
swallowed whole, as these reptiles have no apparatus for rending or masticating
their food. And it is in order that they may be able to swallow larger animals
than would otherwise be possible, that they have the power of dilating their jaws
in the manner already indicated. Not only can the jaws be thus enlarged, but the
throat and stomach are capable of dilatation, owing to the circumstance that
the lower ends of the ribs, from the absence of a breast-bone, are quite free; and
in swallowing, a snake seems gradually to draw itself over the object to be devoured.
The majority of snakes devour their prey alive, and a frog may be seen struggling
in the stomach of a common English water-snake long after it has been swallowed.
Other snakes, however, kill their prey either by striking it with their poison-teeth,
after the manner of the vipers, or by encircling and smothering it in the folds of the
body, like the boas. Although the process of digestion is very rapid, snakes feed
but seldom ; and it has been asserted that two or three frogs are sufficient to supply
the needs of the English water-snake for a whole year. All snakes drink much,
water being absolutely essential to their existence.

As might have been expected from their numbers, snakes exhibit great
diversity in their modes of life ; and while those of the tropical regions remain
active throughout the year (unless they lie by during periods of drought) the
species inhabiting colder regions hibernate during the winter. The most remark-
able diversity from the ordinary mode of ophidian life is displayed by the blind-
snakes, which lead a completely subterranean existence, very seldom making their
appearance above the surface. The great majority of serpents are terrestrial in
their habits, seldom entering the water or climbing trees ; and these ground-
snakes, as they may be called, are characterised by their cylindrical form and the
width of the shields on the inferior surface of the body. Tree-snakes, on
the other hand, which are mostly remarkable for their brilliant coloration, lead
in almost completely arboreal life. Frequently they have the body very slender,
or the shields on its under surface may be keeled in order to afford a firmer hold
in climbing ; while in other instances the tail is prehensile. It is among this
roup that the egg-eating species are found. Then, again, we have freshwater-
snakes, which swim and dive with facility in the waters of rivers and lakes, where
they spend a large portion of their time, feeding on such aquatic creatures as they
can capture therein. As a rule, these snakes are distinguished by having the
nostrils placed at the top of the muzzle, and likewise by the tapering form of the
tail. Lastly we have the sea-snakes, which, while having the nostrils situated as
in the last group, are distinguished by the lateral compression of their tails. In
all cases extremely poisonous, these snakes are almost entirely pelagic in their
mode of life, and seldom approach the land, although in one genus the shields
on the under surface of the body are sufficiently developed to admit of terrestrial
progression.

By far the greater majority of the members of the suborder lay eggs, of an
oblong form and enclosed in soft leathery shells, which are hatched by the natural
heat of the places where they are deposited. The pythons, however, incubate
their eggs, and at such periods develop a temperature a few degrees above that



i8o SNAKES.

of the surrounding air. On the other hand, both in the freshwater- and sea-snakes
the eggs are retained within the body of the mother until they are hatched.

THE BLIND-SNAKES.
Families TYPHLOPID^E and



The blind -snakes, which are now arranged under two families, are small,
worm-like creatures, with cylindrical bodies and short heads and tails, entirely
adapted for a subterranean burrowing life. Lacking the large inferior transverse
shields, characterising ordinary snakes, the blind-snakes have the body and tail
covered on all sides with round overlapping scales of equal size on both the upper
and lower surfaces ; while there are large shields on the forepart of the head, one
of which on each side covers the rudimentary eye. The cleft of the mouth, which
is very small, is placed on the lower surface of the head, and the jaws admit of
scarcely any dilatation. An important point of difference from all the other
members of the suborder is that teeth are absent in either the upper or lower jaws,
while in all cases larger or smaller vestiges of the pelvis remain. The most
important distinction is, however, to be found in the palate of the dried skull,
which differs from that of all other snakes in lacking the so-called transverse or
transpalatine bone, which connects the pterygoid or hindmost bone of the palate
with the posterior extremity of the jawbone or maxilla. In the first, or typical
family of the blind- snakes, the upper jaw, which is but loosely attached to the
rest of the skull, is furnished with teeth, while the lower jaw is toothless ;
the pelvis being represented merely by a single bone on each side. On the other
hand, in the second family (Glauconiidce) while the lower jaw is devoid of teeth,
there are a few teeth in the upper one, the pelvis being represented by a pair of
bones on each side, of which the two anterior ones meet in the middle line. As
regards their origin, it seems probable that the blind-snakes have little or no near
relationship with the other members of the suborder to which they belong.

The typical blind-snakes, or those belonging to the first of the two families,
are inhabitants of all the warmer regions of the globe, and are represented by
nearly a hundred species arranged under three genera. By far the greater number
of these species belong to the genus Typhlops, which has a distribution coextensive
with that of the family; the other two, genera, namely, Helmintli <>/)/// with five
species, and Typklophis with one, being confined to Central and South America.
The second family contains only the single genus, Glauconia, of which there are
nearly thirty species, found in America, Africa, and South- Western Asia. Very little
has been recorded in regard to the habits of these curious snakes, although it is
ascertained that they lay eggs, which are few in number, large in size, and elongate
in form. Although they generally remain in their subterranean burrows, in
showery weather these snakes not unfrequently come to the surface for a short
time. The remains taken from their stomachs show that they feed largely upon
millipedes and ants, and they probably also consume the larva' of many insects.
Captive specimens have been observed to drink freely. The European blind-snake
(Typklops vemnicidaria) is an inhabitant of Greece and several of the adjacent
islands, Asia Minor, Syria, Arabia Petraea, and the Caucasus as far as Transcaspia.



PYTHONS AND BOAS.



181



THE PYTHONS AND BOAS.

Family HofiLF.

Including the largest of living snakes, this family is now regarded as being
the most generalised of the entire suborder (exclusive of the blind - snakes), all
the others presenting such characters as would admit of their having taken
origin from ancestral types belonging to the one under consideration. In
common with the remaining families, the boas and pythons differ essential^




INDIAN PYTHON CRUSHING ITS PREY ( T 1 llilt. .size).

from the blind-snakes in that both jaws are fully toothed, and likewise in the
presence of a transverse bone to the palate. The characters specially dis-
tinguishing the present from the other families of the suborder are, un-
fortunately, largely derived from the structure of the skull, and therefore
require some degree of anatomical knowledge for their proper appreciation, while
they cannot be described without the use of a considerable number of technical
terms. It may be mentioned, however, that the lower jaw has on the inner side
of each branch a thin bone known as the coronoid ; while on the top of the skull
the prefrontal bones, which lie on the outer side of the forepart of the frontals,
articulate with the nasal bones, or those roofing the front of the cavity of the nose.
In the hinder part of each side of the skull lies a large bone, termed the supra-



1 82 SNAKES.

temporal, from which is suspended the quadrate-bone for the articulation of the
lower ja\**; while a further important characteristic is to be found in the presence
of vestiges of the pelvis and hind-limbs, the latter usually taking the form of a
claw-like spur situated on either side of the vent. The family, which contains
a very large number of genera and species, has an extensive geographical dis-
tribution, being represented in South-Eastern Europe, Central and Southern Asia,
Africa, Australia, the West Indies, Western North America, and Central and South
America; it is thus essentially characteristic of the warmer regions of the globe.
Pythons belonging to extinct genera lived on the Continent and in England
during the earlier part of the Tertiary period.

The large snakes to which the term python properly belongs are
True Pythons.

the typical representatives of the first of the two subfamilies into

which the Boid<v are divided; the essential feature of this subfamily (Pythoni/nce)
being the presence on the upper aspect of the skull of a supraorbital bone lying on
each side of the frontal bones, and forming the upper border of the socket of the
eye. Agreeing with three other less important .genera in the presence of teeth in
the premaxillse or anterior upper jawbones, and also in generally having two rows
of shields on the under surface of the tail, the pythons are specially characterised by
the distinctly prehensile tail, and likewise by the presence of deep pits in the rostral
and anterior upper labial shields of the head. As minor characteristics, it may be
mentioned that the teeth, none of which are grooved, gradually decrease in si/e
from the front to the back of the jaws ; while the eye is of moderate si/e, with a
vertical pupil. The head is distinct from the neck, and has the extremity of the
snout covered with large shields, while its hinder portion may be overlain either
with symmetrical shields, or with small scales; and each nostril is placed in a
half-divided nasal shield, separated from its fellow on the opposite side by a pair
of internasal shields. The body in these snakes is more or less compressed, while



Online LibraryRichard LydekkerThe new natural history (Volume 5) → online text (page 20 of 62)