The forest is the home of the snail, where these interesting little
animals may be found by any one desiring a closer acquaintance. They are
not generally easy to find, being mostly nocturnal in habits and
remaining hidden away under leaves, stones and old logs during the
daytime. On rainy days, however, they may be seen crawling about,
enjoying the delicious moisture.
In our last article we reviewed a few of the most interesting families
of bivalve shells, and in the present paper we desire to draw the
attention of the reader to the order Pulmonata, which includes those
snails breathing air by means of a modified lung. The snails differ from
the clams in having the body generally protected by a spiral shell which
is capable of containing the entire animal. The former have a more or
less expanded creeping disk which we call a foot, a head generally
separated from the body by a neck (the reader will remember that the
clams are headless), and also a pair of rather long eye peduncles
protruding from the top of the head, which bear at their tips the round,
black eyes, and a pair of short tactile organs, or tentacles, extending
from the lower part of the head. The eye-peduncles are peculiar in being
invertible in the same manner that a kid glove finger is pulled inside
out.
The mouth is placed in the lower plane of the head and is recognized
externally as a simple slit. Inside of the mouth is placed one of the
most wonderful dental apparatuses known to science. This is called the
radula, odontophore or tooth-bearer, and is a belt of chitinous,
transparent, yellowish or colorless material, its upper surface being
armed with numerous siliceous teeth arranged in longitudinal and
parallel rows. The radula is placed in an organ called the buccal sac
and occupies a position in the sac analogous to that of the tongue in a
cat or dog, viz., on the floor of the mouth. It is formed from a layer
of cells in the posterior part of the buccal sac, called the radula sac,
and new teeth are constantly forming here to take the place of those
which have become worn by use. The whole radula rests upon a cartilage,
is strongly fastened at the anterior end, and is brought down between
the two fleshy lips of the mouth where it performs a backward and
forward movement, thus rasping off with the sharp teeth particles of
food which have been cut into small pieces by the horny jaw. During this
process the morsel of food is pressed against the top or roof of the
mouth. The jaw is placed in the upper part of the mouth in front of the
radula, and is frequently armed with ribs to aid in cutting or biting
off pieces of food, as leaves or vegetables.
As before remarked, the radula is made up of parallel rows of teeth, the
whole area being usually divided into five longitudinal rows, each row
differing from the one next to it. We have first a central row, on each
side of this a lateral row and finally a marginal row. Each tooth in
each row is made up of different parts, a basal part attached to the
radula belt and an upper part which is turned over or reflexed and bent
backward so as to tear off food particles by a backward movement of the
whole apparatus. This diversity of form in the teeth has led
conchologists to adopt a tooth formula similar to that adopted for
vertebrate animals, so that the teeth of different species can be
compared and the animals classified thereby. Thus each tooth has certain
prominences called cusps, which vary in size, number and position, and
serve admirably to describe the different groups of snails. All the
mollusca, except the bivalves, are provided with this radula.
[Illustration: ]
First row:
Helix fidelis (California)
Helix pomatia (Europe)
Liguus fasciatus (Florida)
Second row:
Cyclophorus appendiculatus (Philippines)
Bulimus chiliensis (South America)
Third row:
Helix albolabris (U. S.)
Helix haemastoma (India)
Fourth row:
Helix profunda (U. S.)
Nanina lamarkiana (Philippines)
Glandina truncata (Florida)
Fifth row:
Zonites fuliginosus (U. S.)
Achatinella (Sandwich Islands)
Helix intorta (Philippines)
Bottom row:
Cerion microstoma (Cuba)
Clausilia macarana (Dalmatia)
Bulimulus multilineatus (Florida)
Helix nemoralis (Europe)
One of the most wonderful and interesting facts connected with the
radula is the large number of teeth on each membrane. Thus in some
species of our common snails there are seventy-one teeth in a single
row, and the whole radula is made up of a hundred rows of teeth, making
a grand total of seventy-one hundred teeth in the mouth of a single
snail!
Land snails are found almost everywhere, in valleys, high up on
mountains, and even in deserts. They may be found in the cold climate of
Alaska or in the tropical zone under the equator. As a rule, they prefer
moist localities, where there is an abundance of vegetation and where
the ground is strewn with rotting logs, beds of decaying leaves or
moss-covered rocks. Open woodlands may be said to be their best habitat
in the northern part of the United States.
The shells of the Pulmonata vary to a wonderful degree in size, shape
and coloration. Some are so small that they can scarcely be seen with
the unaided eye, while others attain a length of six inches; some have
the aperture of the shell armed with numerous folds or teeth, while
others are smooth and the colors vary from whitish or horn-colored to
the gorgeously colored helices of the tropics with their bands and
blotches of red, brown, white or green. With all this diversity the land
shells or helices may always be distinguished from their salt or
fresh-water relatives. The land snails breathe by means of a so-called
lung which is a sac lined with a network of blood vessels and occupying
the last turn or whorl of the shell. The air taken into this lung
purifies the blood.
Much is written at the present time upon our new possessions, the
Philippine Islands, but few people are aware that these islands are
tenanted by the most interesting and beautiful group of all the land
shells, the Cochlostylas, or tree snails. The animals live for the most
part in the trees and bushes of the islands, the island of Luzon having,
probably, the best known fauna. The animals are large and quite bold and
the shells are of surpassing beauty, with their colors of white, green,
brown, etc. Now that these islands have come into the possession of the
United States it is to be hoped that these handsome creatures will
receive the study they deserve.
The land shells of the United States, while numerous in species, are not
as conspicuous in color-pattern as those of Europe, South America or the
islands of the Indian and Pacific Oceans, although California produces
some highly-colored species, as will be seen by consulting the figure of
Helix fidelis, on our plate. The majority of our species are uncolored,
like the figure of Polygyra albolabris.
One of the largest and most interesting of American shells is the
Bulimus, found in South America. The shell of Bulimus ovatus attains a
length of six inches and the animal is correspondingly large. In the
markets of Rio Janeiro this mollusk is sold as food and is eagerly
sought by the poorer people, among whom it is considered a great
delicacy. Another interesting fact in connection with this species (as
well as others of the genus) is the size of the eggs which it deposits,
they being as large as pigeons’ eggs. These are also eaten with avidity
by the negroes of Brazil.
One of the most beautiful of the land shells found in the United States
is the Liguus fasciatus, found in Florida and Cuba. The shell is about
two inches long and is encircled by bands of white, brown and green.
This species lives in great numbers at Key West, associated with many
small shells of the Bulimus group. Closely related to the last-mentioned
shell (Liguus) is the agate shell (Achatina), which attains a length of
seven inches and is the largest of the land shells. Like the Bulimus
mentioned above it lays eggs of large size with a calcareous shell, some
being over an inch in length. Both the animal and the egg are eaten by
the natives of Africa. The shells are very attractive, being variegated
with different colors, like agate, from which they receive their common
name.
Another of our new political possessions, the Hawaiian Islands, has a
molluscan fauna peculiar to itself. This is the family Achatinellidae
which is confined solely to the Sandwich Islands. There are no shells
which can compare in beauty with the Achatinella with their encircled
bands of black, yellow, white, red, etc. They live on the bushes,
generally rather low and near the ground, and recently they have been
threatened with extinction because of the cattle which have been
introduced into the islands. In feeding on the bushes, they also consume
large quantities of these snails. A bush inhabited by these little
creatures must be a beautiful sight, with the green foliage set off by
the handsomely colored shells, like jewels on a costly dress.
Among the edible snails none excel in public favor the common edible
snail of Europe (Helix pomatia). The cultivation of this animal has
become an established business, like our oyster fisheries, and thousands
are consumed annually. The early Romans considered this animal a dainty
dish, and the inhabitants of France, Spain and Italy have inherited or
cultivated a liking for the succulent “Shell-fish.” This species has
been introduced into New Orleans where it is eaten by the French
inhabitants. Helix nemoralis, an edible snail of England, with a
beautifully banded shell, is sold in the streets of London and eaten
much as we eat walnuts, by picking out the animal with a pin! The edible
snails, as well as many others, make good and interesting pets in
captivity, the Helix pomatia being of such a size that it may be easily
studied. It is interesting to watch one of these snails feeding upon a
piece of lettuce. First the jaw is seen to protrude and to cut off a
small piece of the leaf, which is drawn into the mouth and reduced to
still smaller pieces by the rasp-like radula. A large piece of lettuce,
after this snail has made a meal upon it, looks as if an army of worms
had been at work. The pomatia is also of an inquisitive disposition and
will wander about the snailery (or even the whole house if he can get
out), examining everything in a very curious manner. No more interesting
object can be placed in a library or study than a snailery with several
species of snails. They are far superior in interest to goldfish or
canaries.
The most interesting snails are by no means the largest. Frequently the
small snail shells with their animals have habits or shell structures of
absorbing interest. Among these are the Pupas, whose tiny shells
frequently reach the astounding size of one-sixteenth of an inch in
length! It is not until we place these mites under the microscope that
their interesting characters are seen and appreciated. By such an
examination we find that the little apertures are armed with many teeth
and folds, and sometimes we wonder how it is that the animal ever gets
in and out through such a labyrinth of apparent obstructions. These
teeth serve in a manner to protect the little animal from its enemies.
These tiny shells are always to be found plentifully under starting bark
and under chips, stones and debris, in more or less moist localities.
In another genus of Pupidae, Clausilia, nature has provided the aperture
of the shell with a little valve called a “clausilium,” which acts as a
spring door to close the shell against all its enemies. This door is an
additional safeguard as the aperture is already provided with numerous
teeth and folds. In this manner does Mother Nature look after her
children.
It is a curious fact that in all the larger groups of animals there are
one or more genera which have the cruel and bloodthirsty propensities of
the shark. The Mollusca are no exception to this rule, and we find in
the genus Testacella an animal having all the ferocious propensities of
the terrible man-eating tiger. This mollusk has a long, worm-like body,
the shell being very small and rudimentary, ear shaped, and placed on
the extreme posterior end of the animal. Its principal food consists of
earth-worms, although it will attack other mollusks and even its own
species. It has been likened to the tiger and the shark in its cunning
while pursuing its prey and in its ferocity when attacking it. The poor
earth-worm stands but a slight chance of escape when Testacella scents
it and starts in pursuit. The worm tries to escape by retreating into
its underground galleries, but this is of no avail because the mollusk
has a long, narrow body and can go wherever the worm does. If the worm,
perchance, has the opportunity of retreating far into its galleries, the
mollusk will dig tunnels to intercept it. Frequently the mollusk will
make a sudden spring upon its victim, taking it by surprise. This
slug-like snail will frequently devour a snail much larger than itself,
but if the victim is too large for one meal it will be broken in the
middle and one half eaten and digested and then the meal completed with
the other half.
The Testacella also resembles the tiger and the shark in the possession
of long, fang-like teeth upon its radula. These teeth are recurved and
aid the mollusk in getting a firm hold upon its victim, and also assist
in the operation of swallowing. It is a curious fact that this animal
will not feed upon other dead animals nor upon fresh meat, nor
freshly-killed worms. Like the snake, which it greatly resembles in
habits, it must hunt and kill its own food. Its wanderings are nocturnal
and during the day it remains concealed, buried in the earth. Testacella
is quite long lived, as snails go, its duration of life being about six
years.
A genus allied to Testacella, and having the same predaceous habits, but
being protected by a large shell into which the whole animal can
withdraw, is the Oleacina or Glandina. The shell is long, with a narrow
aperture and a dome-shaped spire; the animal is long and narrow and the
head near the mouth is furnished with a pair of elongated lips which may
be used as tentacles. The South American species feed on the larger
mollusks, as the Bulimus before spoken of, and the aperture of each
intended victim’s shell is carefully examined before any attempt is made
to enter. When our “tiger” is satisfied that its victim is really
within, it will enter the aperture and devour the animal. Sometimes it
will make a hole for itself in the shell of its victim and will eat the
contents through this aperture instead of the natural one. In Florida
these animals prey upon the large pulmonates like Lignus and Orthalicus.
Before closing this brief sketch of the Land Mollusks we must not
neglect to mention their wonderful protection against the cold of winter
and the heat of summer. This is a tough, leathery secretion, which
completely covers the aperture, and its formation is thus described by
Mr. W. G. Binney in his “Manual of American Land Shells.”
“Withdrawing into the shell, it forms over the aperture a membraneous
covering, consisting of a thin, semi-transparent mixture of lime, mucus
or gelatine, secreted from the collar of the animal. This membrane is
called the epiphragm. It is formed in this manner: The animal being
withdrawn into the shell, the collar is brought to a level with the
aperture, and a quantity of mucus is poured out from it and covers it. A
small quantity of air is then emitted from the respiratory foramen,
which detaches the mucus from the surface of the collar, and projects it
in a convex form, like a bubble. At the same moment the animal retreats
farther into the shell, leaving a vacuum between itself and the
membrane, which is consequently pressed back by the external air to a
level with the aperture, or even farther, so as to form a concave
surface, where, having become desiccated and hard, it remains fixed.
These operations are nearly simultaneous and occupy but an instant. As
the weather becomes colder the animal retires farther into the shell,
and makes another septum, and so on, until there are sometimes as many
as six of these partitions.”
The air-breathing snails which we have so briefly discussed in this
article, are but a very limited number of the many thousand species of
this very interesting group of animals. Their shells are easily gathered
and require but little trouble to prepare for the cabinet and for study.
The writer, therefore, trusts that what has been written may act as a
stimulus and induce many to take up the collection and study of these
beautiful objects.
Frank Collins Baker.
THE GILA MONSTER.
(_Heloderma suspectum_.)
The reptile fauna of the North American continent includes a curious
lizard known as Gila Monster, in science called Heloderma. It represents
a family all to itself, with only two species: Heloderma horridum and
Heloderma suspectum.
Francisco Hernandez, a Spanish physician and naturalist, was the first
to know of its existence when he found it in Mexico in the year 1651. In
an account of his explorations he mentions a lizard three feet long,
with a thick-set body, covered with wart-like skin, gaudily colored in
orange and black, and generally of such horrid appearance that Wiegmann,
another scientist, two hundred years later, called it Heloderma
horridum.
For a long time this name was given indiscriminately to all lizards of
this kind, living either south or north of the boundary line of Mexico
and the United States, till Professor Cope discovered a difference
between them and called the variety found in our southwestern
territories and states Heloderma suspectum.
Many other naturalists have since taken up the study of this interesting
reptile. The result of their observations and experiments was that they
all agree in acknowledging the Heloderma as the only poisonous lizard in
existence, although their opinions are at variance as to the effect of
its venom on the human system. Dr. van Denburgh in his latest researches
has found two glands, one on each side of the lower jaw, located between
the skin and the bone. Such a venom-producing gland being taken out of
its enveloping membrane proves to be not a single body, but an
agglomeration of several small ones, differing in size, and each
emptying through a separate duct. These glands are not directly
communicated to the teeth. When the animal is highly irritated, caused
by constant teasing or rough handling or by being trodden upon, the
poison is emitted by the glands, gathers on the floor of the mouth,
where it mixes with the saliva, and is transmitted through the bite.
A Heloderma has no fangs, but a goodly number of sharp, pointed teeth,
both on the upper and lower jaws. They are curved backward and about an
eighth of an inch long, or even less than that. The principal
characteristic of these teeth is that they are grooved, facilitating
thus the flow of the venom into the wound. It bites with an extremely
swift dash, directed sideways, and holds on tenaciously to whatever is
seized with its powerful jaws. Sumichrast says when the reptile bites it
throws itself on its back, but none of the later naturalists makes
mention of this peculiarity.
The venom of the Gila Monster injected into the veins and arteries of
smaller animals as rats, cavies and rabbits and into the breast of
pigeons and chickens, causes death within twenty seconds to seven
minutes. Brehm relates that a young Heloderma, and in poor physical
condition besides, was induced to bite the leg of a large, well-fed cat,
which did not die, but gave signs of prolonged terrible sufferings. It
became dull and emaciated and never regained its former good spirits.
Among several cases of Gila Monster bites inflicted on human beings can
be quoted that of Dr. Shufeldt, who, in “The American Naturalist,” gave
an interesting account of the sensations he experienced. It is
sufficient to say that the pain, starting from a wound on the right
thumb, went like an electric shock through the whole body and was so
severe as to cause the victim to faint. Immediate treatment prevented
more serious consequences. The Doctor, nevertheless, was a very sick man
for several days and began to recover only after a week had elapsed.
[Illustration: ]
The constituents of the venom are as yet not thoroughly known, but it is
said to be of an alkaline nature, the opposite of snake poison, which is
acid. It acts upon the heart, the spine and the nerve centers and causes
paralysis.
Other scientists claim the saliva of the Heloderma is poisonous only in
certain cases and under certain circumstances. It may also depend upon
the physical condition of the victim at the time the venom enters into
the system. Yet there is little doubt that, if help is not at hand
immediately, the bite may prove fatal.
The Apaches stand in dire fear of this animal, so that, at least, with
their older people no amount of money seems tempting enough to make them
go near it, much less to capture one. A former resident of the
territories says both Indians and Mexicans believe firmly that if a Gila
Monster only breathes in your face it is quite sufficient to cause
immediate death. On an old Indian trail, a good day’s journey west from
the present site of Phoenix, can be found, crudely outlined on the face
of a rock, the picture of two Helodermas pursuing a man who runs to save
his life. Numerous hieroglyphic inscriptions tell probably the story of
the event and prove not only the prehistoric origin of this primitive
piece of art, but also the erroneous ideas which were prevalent in these
remote times, for the reptile never attacks and never pursues. It is
safe to say that the animal has been vastly misrepresented at all ages.
Nature has kindly provided the Heloderma with a compensation for its
partially undeserved bad reputation in giving it beauty. For whosoever
looks upon a fine specimen with unprejudiced eyes cannot fail to admire
at least the combination of its colors and especially the odd,
capriciously disposed markings; the delicately tinted skin, studded in
transverse rows with shiny tubercles, like so many beads on strings.
The illustration to this paper is so excellently made that scarcely any
description is necessary as to the animal’s exterior in color and
markings. This Heloderma is a little over nineteen inches in length by
ten inches in circumference of the body and five inches at the thickest
part of the tail, which makes one-third of the total length of the body.
When such a reptile grows to the size of eighteen inches it is called
adult. Those growing beyond these figures are unusually large specimens
and in very rare instances the species of our illustration reaches the
extraordinary length of two feet. An adult Gila Monster weighs about two
or three pounds, and in winter less than in summer.
The four short and stubby legs seem quite out of proportion to the
massive body, much more so as the two pairs are widely separated
lengthwise of the body. When walking the body is elevated, while in rest
it lies flat on the ground. Each foot is provided with five digits armed
with curved white claws.
The skin has generally the appearance as if covered with rows of uniform
beads; but, on closer examination, these beads, or more correctly,
tubercles, prove to have different shapes and are differently set,
according to the part of the body which they cover. On the head from the
nose up to between the eyes they are flat, irregularly cut, closely
joined and adhere completely to the skull. Those following form
polygonal eminences, each one separated from the other by a circle of
tiny dermal granulations, while behind the eyes on both sides of the
head they are larger, semi-spherical and stand far apart. The throat and
the nape of the neck are studded with very closely set small tubercles,
increasing in size only above the forelegs, whence they extend in
well-defined, transverse rows along the whole upper side of the body and
the tail. The under side of the latter and the abdomen are covered with
tessellated scales of a light-brown and dull yellow color arranged in
another handsome pattern.
A Heloderma’s head, with its triangular shape, is very like that of a
venomous snake; it gives the animal—especially when it is raised in
anger—a truly awe-inspiring appearance.
The wide-cleft mouth reaches far behind the eyes. These are very small
and, like all lizards, provided with eye-lids that close when the animal
sleeps. The eye itself has a dark-brown iris, with the round pupil that
indicates diurnal or at least semi-nocturnal habits. Between the
nostrils, well in front of the blunt nose, is a wide space. The nostrils
are so far down as to nearly touch the margin of the supra-labial
scales. This position denotes terrestrial habits in reptiles rather than
an all aquatic life. For to most of them water is indispensable to their
welfare. Thus the Gila Monster shows this structure as it likes to bathe
in shallow water, often for many hours at a time.
The crescent-shaped openings of the ears are situated not far from the
edge of the mouth, between the head and the neck, and are partly
concealed and also protected by the overlapping gular fold; the tympanum
is exposed. The animal sees and hears well. The remaining three senses
are more or less concentrated in the tongue which is one of the most
remarkable features of the Heloderma. It is slightly forked at the tips,
half an inch wide and two to three inches long; it is dark reddish-brown
with a shade of purple. When in rest it is drawn together into a small,
conical shaped mass, scarcely an inch in length. But as soon as
something disturbs the usual quietude of the animal the tongue is thrown
out immediately. In fact, it is used for smelling, tasting, feeling. It
is used for measuring depth and distance, for expressing desire and
satisfaction; and with what rapidity is this instrument of communication
projected and retracted!
A Gila Monster may be trusted to some extent as long as the tongue is
freely used, but if that is not the case it is wise to be careful in
handling it. Fear and hostility are expressed by deep, long-drawn
hisses; by opening the mouth to its fullest extent and by quick jerks of
the head from one side to the other.
At the present time these reptiles are not so very common.
Ever-prevailing superstition among the ignorant and exaggerated bad
reputation have brought on a relentless war of extermination against
them, so that now in the neighborhood of settlements they are seen
seldom if ever. Their center of distribution is more and more confined
to the region along the banks of the Gila river in Arizona, although
less frequently they may still be found as far west as the Mojave desert
in California. But those are wrong who believe that the Heloderma is
living only in the most arid portions of the southwest. There are
several reasons why the reptile seeks eagerly irrigated places, which
are productive of some vegetation, for it needs water, food and shady
hiding-places.
In the middle of summer, when even the larger streams are dried up, the
Gila Monster retires to some burrow, abandoned by another animal, or to
deep crevices in the rocks, and spends there in a torpid state several
weeks, until the great rainfalls relieve the country, give fresh plant
life and fill again the barren riverbeds. This is the animal’s summer
retreat. During the course of a year it takes a second and longer one,
the regular hibernation, that lasts about from November to the middle of
February, when it resumes its outside life again. It loves to bask in
the still mild rays of the sun, but as soon as the heat increases the
Gila Monster seeks shelter for the day behind stones and bowlders, under
clumps of cacti and in small mesquite groves along the river banks. It
roams about only after sunset or early in the morning. The idea that
this lizard enjoys the quivering heat on an open Arizona plain, while
other sun and heat-loving reptiles keep in hiding, is as erroneous as
many others. Nothing is so absolutely fatal to the Heloderma as to be
exposed only for half an hour to the direct rays of the sun in
midsummer. Another reason why it prefers to live in the neighborhood of
streams where plant life is more abundant explains itself by the
necessity to provide for food.
Whoever has an opportunity to observe reptiles in confinement for an
extended period of time can easily draw conclusions as to their mode of
living in freedom. A captive Gila Monster is fed on hens’ eggs; in
summer one each week, in winter one every two or three weeks. It refuses
every other kind of food, however temptingly it may be offered, such as
mice, frogs, angleworms, mealworms and the like. It is more than
probable that in their wild state they live on a similar diet,
consisting then of eggs of other lizards, of turtles and of birds. The
animal has the reputation of being destructive to the Arizona quail.
Several writers of Natural History add to this a diet of insects, but
the embarrassed locomotion of the Heloderma seems to exclude flying and
fast-running prey. Nearly all reptiles which feed on eggs climb, as do
some snakes, and as does the slow and clumsy Gila Monster. They are not
able to ascend high and straight trees, which, however, are not found in
these regions, but they are able to climb bushes and low trees, having
somewhat leaning trunks and rough bark. And it is wonderful to see how
cleverly it disposes of the sharp claws and the muscular,
half-prehensile tail, both in dragging itself up and in retarding an
often too rapid descent.
The inquiry may be made: How is it possible that a Heloderma lives on
eggs alone when it can find them only during the relatively short time
of five or six months? First, it may be remembered that this period
corresponds nearly to the active life of the animal before and after
estivation. The second and more important reason is its remarkable
frugality. The digestive organs are so constructed that they adapt
themselves to a fast of many months without injury to the animal.
In captivity the Gila Monster begins to slough about January and
continues this process during several months. The epidermis comes off
not like a snake’s, in a whole piece, but in several, or more frequently
in many, fragments.
There is still a wide field open for accurate observation and definite
knowledge that we relinquish to the professional naturalist and to those
fortunate ones who can study the animal in freedom.
Amelia Walson.
[Editor’s Note: The Gila Monster of the illustration is still living and
has for some years been the interesting pet of one whose love of nature
in all forms has found beauty in the reptile usually shunned alike by
the savage and by civilized man.]