[Illustration:
_Frontispiece._
Canon Horsley in his study examining a rare variety of whelk
(var. _Babylonica_) from a stall in the Walworth Road. It is now
in the South Kensington Museum.]
OUR BRITISH SNAILS
BY THE
REV. CANON J. W. HORSLEY
AUTHOR OF "SOME FOLK-LORE AND LEGENDS OF BIRDS," ETC.
LONDON
SOCIETY FOR PROMOTING CHRISTIAN KNOWLEDGE
NORTHUMBERLAND AVENUE, W.C.
43, QUEEN VICTORIA STREET, E.C.
BRIGHTON: 129, NORTH STREET
1915
PRINTED BY
WILLIAM CLOWES AND SONS, LIMITED,
LONDON AND BECCLES.
LIST OF ILLUSTRATIONS
PAGE
Canon Horsley in his study examining a rare variety of whelk
(var. _Babylonica_) from a stall in the Walworth Road.
_Frontispiece._
_H. pomatia_, half natural size 11
Dextral _H. aspersa_ and _H. pomatia_ 13
Love-darts of _H. pomatia_, much magnified 15
_H. nemoralis_ at rest on hawthorn 17
Names of parts of shell and of body. _Unio_, _Limnæa_,
_Vivipara_, and _Arion_ 22
Body of snail and of slug 23
Three specimens of _Arion ater_, showing tentacles,
breathing orifice, and slime gland 31
_Testacella haliotidea_ 35
_Helicella virgata_ at rest on thistle, natural size 45
Some of our smaller shells 47
_Paludina contecta_ (two) and _Limnæa stagnalis_ on
water-weeds 57
_Neritina_ and _Ancylus_ 59
Freshwater mussel breathing and eating 61
OUR BRITISH SNAILS
It has been said that a child's education should begin thirty years
before its birth, since what he is, or becomes, or does, depends
largely upon what his parents were, and not solely on what he learns
at home or in school, or from his companions and surroundings.
But the principle of what is called "atavism" shows us that the
appearance, tastes, and character of a child's grandparents may
reappear, even more than those of his parents; and that, therefore,
his education begins sixty years before his birth.
My education, viewing me as a naturalist, began even earlier than
that, for nearly all my ancestors of whom I know anything more than
their names and abiding place were botanists or horticulturists, and I
cannot recollect the time when I was not an observer of nature and a
collector of the common objects of the field, the ditch, the seashore,
the wood, and the cliff. My father died before I was four, and I have
never had any remembrance of his words or looks, yet I remember his
cutting down a tree in the shrubbery of his Kentish vicarage garden
which forked curiously from the ground, and also of finding that
handsome fungus which is scarlet flecked with white. This shows that
the observation of the marvels and beauties of God's Green Bible, or
Book of Nature, began early in me. The habits of observation, of
comparison, and of method, are those which all naturalists and
collectors must have; habits which are of great value in other ways as
well. Firstly, one must have the seeing eye, and train it to notice
what many people do not. (Get and read the old book, much read when I
was young, called "Eyes and no Eyes.") Secondly, one must learn to
observe the difference (sometimes very small, although important)
between one object and others of the same family. Every one knows a
wild rose by sight; but nearly every one would be surprised to hear
that botanists make out twenty kinds of English wild roses, to say
nothing of varieties and hybrids. In all departments of natural
history a magnifying glass, for the dissection of inward parts, is
necessary in many cases to separate two kinds which look alike. And,
thirdly, if you want to make a collection, whether of dried plants, of
insects, of shells, or of anything else, you must cultivate ways of
order and method and neatness in the arrangement of your collection.
And then your increased powers of observation, of comparison, and of
method will stand you, and others, in good stead in higher matters of
thought and action, and the virtues of Prudence, Justice, Temperance,
and Fortitude will all increase in you as you learn more about what is
in man, what man should be, and how men should be treated. Let us take
Fortitude for example. I have known boys who collected one kind of
thing eagerly for a while, but soon got tired of it, and generally had
little power of "sticking" to anything. On the other hand, I was once
admiring the magnificent collection of shells owned by a middle-aged
doctor, and asked him, "When did you begin to collect?" "When I was
seven," was his answer. I should expect to find more Fortitude in that
doctor's character than in that of a boy who collected "all things in
turn and nothing long."
Yet I myself was middle-aged before I felt disgusted with myself, when
gazing on a lad's collection of British land shells, that I should so
long have been groping in hedges and ditches, and yet never have
noticed the variety and the beauty of members of the snail family.
(That lad, by the bye, is now a Professor in an American University,
and a great authority on shells and other matters.) Since then I have
gathered a complete collection of the British land and fresh-water
shells, and a very large and valuable one of the _Helicidæ_--_i.e._
the family to which the common or garden snail belongs--of every
country in the world; and have been President of the Conchological
Society of Great Britain and Ireland.
I am now, therefore, writing about our British land shells, "slugs and
snails" in common speech, with the hope that it may add a new interest
to the country walks of lads and lasses.
I could show you a wall-case I made for a school. It contains
specimens of all the British land shells with the exception of the
slugs, which (with the exception of one of which I shall speak in its
place) have no external or covering shell, although a small sort of
shell, or at any rate some chalky grains, is found inside most of
them. You would see that some are as small as a pin's head although
full grown, and they would require a magnifying glass to distinguish
one from the other. The largest is _Helix pomatia_ (figured on pp. 11
and 12), which often goes by the name of "the edible snail." All
snails are edible and nutritious; but this is the one cultivated in
snail farms and sold as food abroad. Sometimes it is called "the Roman
snail," from an idea, probably wrong, that it was introduced by
Cæsar's soldiers, although as a matter of fact it is unknown in South
Italy. Sometimes also it is called "the apple snail," partly because
it is as large as a middle-sized apple, and partly because people
thought the name _pomatia_ came from the Latin _pomum_, "an apple,"
whereas it really comes from the Greek [Greek: pôma]. This word means
a lid, or closing arrangement, and this mollusc makes a hard front
door for itself when it hibernates, _i.e._ suspends active life and
buries itself in the winter.
[Illustration: _H. pomatia_, half natural size.]
It is much to be regretted that in most cases scientific names fail to
give much information to the young student, and in some cases they
give none at all. The first or generic name is supposed to be formed
from Greek, the second, or specific, from the Latin, but there are
some hybrids and many mere "nonsense names" to puzzle beginners. Thus
the slug Limax gets its name from _limus_, "mud"; but a scientist, who
ought to have known better, when wanting a name for another kind of
slug, transposed the initial letters and made Milax! Vitrina is a
sensible and descriptive name, the Latin for glassy, given to a shell
like thin glass; but the Greek Arion recalls either a certain musician
or a certain swift steed, neither of whom naturally suggests a slug.
For Balea at least four derivations have been suggested--none of them
probable. Two facts concerning the life or appearance of a mollusc we
should learn from its two names, but this is not the case with
_Agriolimax agrestis_, which is by interpretation "the field slug
inhabiting fields." Nor are we helped by the specific name _virgata_
or striped when so many land shells are striped or banded, and still
less by _terrestris_ for one land shell when all land shells are
terrestrial.
You would note, however, in this wall-case that the species are not
many (a good many of the specimens are varieties, not separate
species), and that, therefore, one can collect with the hope of
speedily forming a complete collection without that inevitable absence
of finality found when one collects postage stamps, or, still more,
picture postcards, of which one might secure thousands, only to find
that fresh thousands were brought out next year. Here, however, is no
impossible ideal of perfection. There are but eighty-two land and
forty-five freshwater shells in Britain.
[Illustration: Dextral _H. aspersa_ and _H. pomatia_. The right-hand
shell at the bottom shows the winter epiphragm of _H. pomatia_.]
Let us imagine we are starting for an afternoon snailing near London.
Which way? To Oxshott? To Caterham? To the latter for choice, since it
is on the chalk, whereas the former is on the sand. Snails require
lime to make shells, and only on chalk or limestone will you find an
abundance. Here, too, as at Box Hill, we shall find the big _Helix
pomatia_, only found in a few English counties, and very local there.
If we were very fortunate, we might find a sinistral, or "left-handed"
specimen. In the case of the _pomatia_ on the right hand there is
shown the thick epiphragm which the mantle secretes before the mollusc
hibernates. It hardens on exposure to the air like plaster-of-paris;
but is not a true operculum, for that is a constant possession of the
shells which have it. Opercula are mainly found in marine or
fluviatile shells, and may be either horny (like the winkle) or stony.
Amongst our British land shells _Cyclostoma elegans_ and _Acicula
lineata_ alone have true opercula, though others form some thin
epiphragm for the exclusion of cold air and enemies when they
hibernate.
Most shells grow to the right, and a freak which does the contrary is
so rare that of the millions of the common _H. virgata_ that I have
seen and handled, only one delighted me with its left-handedness. If
it is early summer (nearly all snails hide, burrow, and sleep during
the winter), look about on the grass for some half-chalky, half-stony
shields, which are the winter front doors of _H. pomatia_, now
discarded; while sharper eyes might even descry the flinty little
darts with which they have been love-making. The illustration on p. 15
shows three of these darts, much magnified. Only the most highly
developed Helices possess these courting weapons, not unlike bayonets
in form, sometimes rounded and smooth, and sometimes with two or even
four lateral blades, so that the section of the dart of _H. pomatia_
is in the form of a Greek cross. Not many British shells have these
darts, but in one case their study is useful, since _H. nemoralis_ and
_H. hortensis_, though so closely allied that early conchologists
considered them to be of the same species, have darts remarkably
distinct one from the other, so that they become a court of final
appeal if from outward appearance it is difficult to distinguish, say,
a white-mouthed _nemoralis_ from a dark-mouthed _hortensis_.
[Illustration: Love-darts of _H. pomatia_, much magnified.]
Whenever you see a stone, a brick, a branch of dead wood, or even an
old boot or a piece of newspaper in the hedge or on the grass, turn it
over, for many of the smaller shells are thus found, and "leave no
stone unturned" is eminently a motto for the conchologist. Some of the
shells will be tiny, and must be studied under a magnifying
glass--which all naturalists should always have in their pockets--or
even under a microscope at home, in order to discover, not only their
beauty of marking or sculpture, but even to what species they belong.
When you see a man sweeping herbage with a net, or beating hedges and
shrubs over an inverted umbrella, he is probably an entomologist in
search of caterpillars or beetles; but the same methods will often
reward the snail-hunter.
Especially in the hedges will you find the two allied species _Helix_
(_Cepea_) _nemoralis_ and _hortensis_, to which the attention of
beginners should first be directed, inasmuch as they are so common, so
beautiful, and so varying both in colour and the number of the
chocolate bands they usually bear. See the illustration of some of
these at rest on hawthorn, p. 17. Canary-yellow, flesh-colour,
chocolate, and almost white, are the prevailing ground-colours. Five
is the normal number of bands on the largest or body-whorl, although
sometimes all run into one, and often one, some, or all are wanting.
Where only one band is found--throughout the Helicidæ--it is usually
that on the periphery or middle of the whorl, and a shell in which
this band is wanting, while others are found, is a rarity. People are
usually astonished, on seeing a good series of the colour and
variations of these two shells, how they vie with those of warmer
regions.
[Illustration: _H. nemoralis_ at rest on hawthorn.]
Next search trunks of trees, and especially the smooth boles of the
beeches. The rough bark of the elm or oak is not congenial to slugs or
snails. Where trees are moss-covered at their foot, or walls at their
top, many of the smaller shells may be expected; while handfuls of
dead leaves may be shaken over something white, or taken home in a
large bag to be treated there. Hurdles leaning against a hedge are
often found to bear a good crop of snails. Damp places must be sought
in dry weather; but a rainy day, that troubles some kinds of
naturalists, sends the conchologist forth rejoicing, especially if a
warm evening follows a wet day. A night search with a lantern will
often be profitable. Where they will be undisturbed, traps may be set,
such as flat pieces of wood (the older the better), or cardboard,
lying on the grass; while most of those species that belong to the
group which seems to prefer the sun, _e.g._ _H. itala_, _virgata_,
etc., are fond of a newspaper for food rather than for shelter.
During the hibernating season, which extends from November to April,
we turn rather to ditches than to hedges, and, armed with a perforated
scoop at the end of a long stick, we dredge among the water-weeds, or
sift, like gold-washers, the sand or mud in ditches, ponds, and
backwaters of rivers. Here we are introduced to the great bivalve
family which is unknown on land, and our trophies range from the
freshwater mussels, as large as our hand, to others hardly larger than
a pin's head. These must be sought at the bottom; but on the weeds, or
on the bottom, will be found not a few species of gasteropods or
univalves, some of which we may have noticed in a freshwater aquarium.
These, of course, are closely connected with the land shells, which
the bivalves are not. They can be brought home alive in a tin box with
a little moss, whereas for the land shells a calico bag with a little
foliage therein is best. In both cases some small glass tubes with
corks should be brought in a tin box in order to keep safely and
separately the tinier kinds. You can often discover what small shells
inhabit a particular ditch or pond by noticing the cases of
caddis-worms, some of which are formed almost entirely of shells
instead of vegetable fragments.
Using the precious gift of observation, we have found our shells; at
home we exercise the other gifts of comparison and order, in the
preparation and arrangement of our collection. A dash of quite boiling
water kills instantaneously any molluscs whose shells we want to
preserve, and then the body is extracted after the fashion observed
with regard to winkles at tea. Be careful to get out all the body of
the animal, and then it is well to wash out any slime or particles by
directing a fine but strong jet of cold water into the shell. This can
be done by holding your thumb nearly over the mouth of a watertap,
while the shell is held in the left hand. Only adult shells should
usually be taken, and those which are weather-worn or bleached should
be neglected. In most the lip, or opening, of the shell will be hard
if adult, and membranous if young; but experience alone will enable
you to discriminate, especially where the young of one species is like
the adult of another.
Get into the way of carrying a note-book with you to record not only
what shells, or varieties of a species, are found in any particular
spot, but also anything you observe as to the habits or peculiarities
of the objects of your search. Notes as to protective colouring or
mimicry; the influences of a wet or a dry season on the relative
thickness of shells; the difference in size caused by abundance or
scarcity of diet; what plants are preferred and what avoided as food
by particular helices,--are some of the points of interest, apart from
the earliest and latest dates at which certain species are abroad and
active.
If you possess, or borrow, a microscope, many new wonders and fresh
lines of inquiry will open out. I know one professor who devotes
himself to the study of the teeth of molluscs. A snail may possess
over twenty thousand tiny flinty teeth set on a ribbon so as to make a
mowing-machine for the vegetable matter on which it feeds. With its
aid also you might study the life-history of a mollusc from the egg
onwards, and be able to determine by minute anatomical points whether
two molluscs were of the same species or not--a matter in which the
shape or appearance of the shell is not always a safe guide.
Here, then, is a new hobby for some of my readers, or, at any rate, a
fresh source of interest when they are in the country. If any
collector lives near you, I am sure he or she would be delighted to
have your company during an expedition, and you would learn more by
sight and hearing than by reading. If, however, you must fall back
upon a book, get _The Collector's Manual_ by L. E. Adams, published by
Taylor Bros., Leeds. This is invaluable both to the beginner and to
the owner of a good collection.
From this I borrow by leave the plate on p. 22, which will enable the
beginner to understand from the first certain names of parts of the
shell or the body of the bivalve, univalve, or slug which otherwise
might not be clear. The "muscular scars" are indents in the shell
which mark where the muscles were fixed whose function was to bring
close together the two valves of the shell when it has need to exclude
air or enemies.
[Illustration: Names of parts of shell and of body. _Unio_, _Limnæa_,
_Vivipara_, and _Arion_.]
The figures of the snail and the slug below are introduced to give
further knowledge of the soft parts. B is the body, soft and with a
surface generally wrinkled or covered with small tubercles. F is the
foot or muscular pad which forms the foot by the wavelike contractions
of which it moves. H is the head, bearing the tentacles T_{1} and
T_{2}, of which the upper pair have the eyes, E. The mantle, M, makes
the shell by secreting lime, etc. In it is the breathing orifice, BO,
obvious in the slug, but in the snail nearly hidden by the shell. L in
the snail is the spiral part, the liver, and it occupies a large part
of the shell.
[Illustration: Body of snail and of slug.]
Without going into details of classification and anatomy, which would
only deter or puzzle a beginner, let me take two typical molluscs of
those which we shall find in England, the common garden snail _Helix
aspersa_, and a freshwater mussel, _Unio margaritifer_, and see where
they come in the scale of creation and what are their powers and
peculiarities.
Molluscs (_mollis esca_, soft food--boneless creatures) are below the
aristocracy of the vertebrates or backboned creatures, and so they
come just below the Fishes, but above the Insects. They are divided
into those possessing a head and those possessing no head (although
with some sort of a brain or organ of sense), the snail being of the
former class and the mussel of the latter. The former are univalves
and the latter bivalves having two shells for protection. The latter
also are restricted to life in water, whereas the former are found
both on land and in water, _e.g._ the snail and the whelk, although
for ages probably no molluscs were air-breathing land dwellers. In the
class of Cephala, to which our snail belongs, there is the sub-class
of Gasteropoda, or stomach-footed, because on the ventral side of the
body a sole-like disc or foot exists, by the wave-like expansions and
contractions of which the animal progresses.
In this sub-class there is a division according to their having or not
having an operculum, or means of closing and protecting the orifice of
the shell. Most gasteropods which live in water have this; most which
live on land (only two exceptions in British molluscs) have not. Here
again we must trace our snail down to the sub-order of Pulmonata, or
lung or air-sac breathers as distinct from its sisters which inhabit
water and breathe by gills. This sub-order is again divided into
various families, Arion, Limax, Testacella, Vitrina, Zonites, Helix,
etc., and Helix again is divided into various genera, of which Helix
is one, and even this is subdivided into sub-genera, Patula, Punctum,
Acanthinula, Vallonia, Chilotrema, Gonostoma, Pomatia, Tachea, etc.,
and to the sub-genus Pomatia our garden snail as well as the "Roman
snail" belongs. Looking backwards we, therefore, place our friend as
the species _aspersa_, of the sub-genus _Pomatia_, of the genus
_Helix_, of the family _Helicidæ_, of the sub-order _Pulmonata_, of
the order _Inoperculata_, of the sub-class _Gasteropoda_, of the class
_Cephala_, of the sub-kingdom of _Mollusca_, of the kingdom
_Invertebrata_ or backboneless animals.
It belongs by origin not to the earliest form of snail, but to the
most highly organized group in the world, especially characteristic of
the European region, and possessing in their superiority the power to
colonize and dispossess the original native snails of other lands. The
shell is globular in form with five whorls (the Greek word "helix"
means a coil), each usually marked with five bands of pigment. It is
mainly a vegetarian, and by habit a lover of the twilight and of
moisture. With the exception of _H. pomatia_ it is the largest of our
native shells, and is too common to satisfy gardeners. A powerful
animal of its kind, it can travel a yard in twelve minutes, or at the
rate of a mile in a fortnight, can bear or draw on level ground a
weight fifty times its own. It breathes about four times a minute, and
its heart-beat varies from sixty to eighty per minute according to
temperature, or its activity. It takes its winter rest in clusters,
closing its mouth with a membranous film, while if the cold increases
it shrinks farther into its shell and makes more epiphragms or film
curtains to keep out the cold. Not only on the Continent, but in
several parts of England, notably about Bath and Bristol, it is
sought, sold, and used for food, and in Belgium it is said to be
preferred to the larger and more firm-fleshed _H. pomatia_. The eggs,
from forty to a hundred, are laid in the earth and hatched in from a
fortnight to a month, according to the weather. I had observed them as
a boy, and used to call tapioca pudding "snail's egg pudding." In the
year of their hatching they attain but half their proper size, but
after hibernation they eat voraciously and grow rapidly, so as to
attain full size in a little more than a year. Most die in their
second hibernation (if not destroyed by their many enemies, gardeners,
collectors, rats, rabbits, ducks, thrushes, and beetles); but when
kept and protected for observation they have achieved the great age of
even ten years.
They have a great power of "homing" like pigeons, however far (for
them) is their journey after favourite food. The slime-marked journeys
or feeding tracks of this species (and still more of slugs) afford
matter of great interest. As to sight the two eyes are the dark specks
on the tip of the upper pair of "horns," but the range of vision is
very short indeed, and the difference between light and approaching
darkness is all that some seem able to perceive. The organs of hearing
are two small sacs filled with fluid in which are some calcareous
grains. They hear little which is audible to human ears, and if not
altogether deaf they are dumb as far as we can hear. The power of
taste they possess, as is shown by the preference of some foods to
others. The sense of touch is acute and resides in all parts of the
soft and moist external skin, and especially in the upper tentacles or
horns in the _Helicidæ_. Jaws they have with which to seize and to
bite off food, and in _H. aspersa_ and others these bear teeth, but
the chief work is done by a sort of toothed tongue, the radula, which
rasps off particles of food with a side to side motion of the head as
the animal advances. Our _aspersa_ has 12,615 teeth on this ribbon,
contained in 145 transverse rows. The organs of digestion are complex
and practically much the same as our own. Little vegetation would be
left in nature had not, on the one hand, snails been kept down by many
enemies as well as by their need of hibernation and their short life;
while on the other by numerous devices in the course of ages many
plants have protected themselves against the moving machine of a
snail's mouth. Cultivated plants, which generally lose their natural
protections, have to be guarded by human guards or gardeners. Some
plants defend themselves by prickles or hairs, some by hardening
themselves with lime or flint, some by bitter or acrid juices. A heart
of two chambers, veins, arteries, and blood our snail possesses, and,
like man, the old snail has a slower pulse than the young one, and in
both exercise increases the pulse rate and also warmth. Breathing is
accomplished by a single chamber or air-cell, but also through the
skin. As in the case of plants, some kinds are male and female
separately, and as some have both powers and products in the same
plant, so also is it with mollusca. _H. aspersa_ and most Gasteropoda
are of the latter kind.
Having now taken _H. aspersa_ as the representative of our univalves,
let us take the "Pearl Mussel"--_Unio margaritifer_--as that of our
bivalves, all of which live in the water, whereas of univalves some
are "land snails" and some "water snails." It would say of itself, "I
am a species of the genus Unio (_unio_, a pearl), which belongs to the
family Unionidæ, which belongs to the sub-order Isomya (_i.e._ having
muscles of equal power to close the two valves of the shell), which
belongs to the order Lamellibranchiata (_i.e._ having gills arranged
in leaf-like fashion), which belongs to the sub-class Pelecypoda
(_i.e._ having a foot somewhat of an axe-shape), which belongs to the
class Acephala (headless), which is the second of the two chief
classes into which Mollusca are divided.
"I differ from the Gasteropoda (whether they be terrestrial or
aquatic) in that I and my near relations are exclusively aquatic and
of a sedentary life, which makes the protection of two encompassing
shells necessary. These shells are secreted by my mantle lobes, and
are united by a ligament which tends to make the valves 'gape' for
water and food and by two contracting muscles which close them in
danger. I have a degenerate brain and no eyes. My mouth has neither
jaw nor teeth, but possesses nervous lips covered with cilia, the
vibration of which carries food-laden water to my mouth. My foot, when
protruded, is seen as a large muscular appendage, and, by alternately
expanding and contracting, it enables me to burrow or plough through
mud or even sand, and so disturb the minute organisms on which I
feed. I can thus travel fifteen feet a day, or about a mile in a year.
"I have no eyes, but distinguish well between light and shade by means
of the surface of my body when exposed. I breathe, that is, get oxygen
from the water, by means of gill-plates. As regards other internal
organs, I differ not much from _H. aspersa_, but I am either male or
female. Outside I am black and uncomely; but within I am pearly-white,
and but for my power of forming pearls round an irritating grain of
sand the civilization of England would have come to pass later than it
did, for it was the report of my pearls which brought Cæsar to
Britain."
* * * * *
Now let us enumerate the species of land and freshwater shells to be
found, (all but two) in England, and most of them in Ireland or
Scotland.
_Arion ater_ is a large (3 to 5 inches) and common slug, usually black
(whence its name _ater_), but also red, brown, or white. In some
varieties the foot-fringe is orange. When irritated it contracts into
a hemispherical lump. A few chalky granules under the mantle are the
representatives of a shell. See the illustration of three specimens on
p. 31. That hole in the mantle is the breathing orifice, and its
forward position is a characteristic of the group _Arion_. The body of
slugs is kept moist by a constant exuding of slime from a gland in the
tail.
[Illustration: Three specimens of _Arion ater_, showing tentacles,
breathing orifice, and slime gland.]
_Arion subfuscus_ (_i.e._ somewhat tawny). Smaller (2 to 3 inches)
than _A. ater_, grey or yellowish, with usually a dark stripe on each
side. Foot-sole white, and its fringe white with dark cross streaks.
Never very abundant.
_Arion minimus._--The smallest Arion: not an inch long. Grey or
yellowish. Feeds on fungi. Body wrinkled with microscopic spikes.
Common. The _young_ of _A. ater_ might be mistaken for it.
_Arion hortensis._--Grey with purple side bands. Foot-sole yellow. 1
to 1-1/2 inch in length. Generally found in gardens, as its name
indicates.
_Arion circumscriptus._--Very common in fields. A dark band down the
back, foot-sole white. Very "sluggish."
_Geomalacus maculosus_ (_i.e._ the spotted earth-mollusc).--Only found
in south-west Ireland. Probably a relic of the prehistoric time when
Ireland was joined to Portugal and Spain. Has a solid chalky shell
beneath the shield. Blackish with oval yellow spots. Feeds on lichens.
_Amalia gagates_ (_gagates_ is Greek for "jet").--Dark lead colour.
Foot-sole white. Length 2-1/2 inches. Local, and mainly near sea.
_Amalia Sowerbyi._--Brown, speckled with black. Foot-sole yellowish.
Length 2-1/2 inches. Local. Shell often very thick.
_Limax maximus._--Length 4 to 6 inches. Grey with two dark lateral
bands. Often found in cellars.
_Limax cinereo-niger._--Ashy-black. Very like _L. maximus_, but with a
sharp keel, and the sole paler in the middle than at the sides. Less
nocturnal and less fond of houses; chiefly found in forests on hills.
Local, and not common.
_Limax flavus._--Yellow, with a faint dark network of markings.
Tentacles blue. Sole cream. Length 4 inches. Only found in cellars and
near houses.
_Limax marginatus._--Semi-transparent. Grey, with two dark bands on
each side. Foot-sole with a dark line down the middle. Shell solid,
often a cube. Length 3 inches. Fond of tree climbing.
_Limax tenellus._--Yellow. Tentacles black. Mucus yellow. Found in
woods. Lives on fungi. Rare.
_Agriolimax agrestis._--The common field slug. Swarms everywhere. Its
milk-white slime is characteristic. Very variable in colour and
markings.
_Agriolimax lævis._--Slender. All chocolate brown. Length 3/4 inch.
Shell may be seen through the mantle. Active. Our smallest slug.
Usually found near ditches.
* * * * *
It may be useful here to give the chief differences between the genera
Arion, Amalia, Limax, and Agriolimax. The shield in the first two is
granulated, in the other concentrically striated. The breathing
orifice in Arion is in front of the centre of the mantle margin; in
the others behind. The shell is distinctly formed in all but Arion,
in which it is absent or represented by a few granules. Arion has no
dorsal keel. Amalia has one all down the back. In Limax and Agriolimax
it is confined to the caudal part. Other differences are only
discovered by dissection.
One may also here note that to preserve slugs is difficult, and the
best plan is to have a coloured drawing made of them when extended.
Otherwise they may be drowned in cold water, cleaned of slime with a
soft brush, and then preserved in glass tubes with diluted formalin or
alcohol. Or, after drowning, they may be skinned and the skins dried
on a card and varnished. Note also that most slugs have many
variations in colour and markings.
_Testacella haliotidea._--This genus of slugs forms a link between the
naked slugs with rudimentary shells within, and the snails which live
within their shells. The name _Testacella_, or little shell, was given
by Cuvier in 1800, because this slug has a small shell at the end of
the tail. Haliotidea means having a shell in the form of the marine
shell _Haliotis_, the meaning of which again is the ear-shaped
seashell, often called "Venus' Ear." It is subterranean in habit, and
lives on worms. It should be looked for on the surface on damp nights,
or is found when digging. Its length is 3 inches at most. Pale yellow
in colour. See the illustration on page 35.
_Testacella scutulum_ (a little shield).--Not so common as the former
species, and differing chiefly in anatomy.
_Testacella Maugei._--First found at Tenerife by M. Mauge. Reaches 4
inches in length. Deep brown in colour. Shell larger. Rarer and more
western in habitat than the other species.
[Illustration: _Testacella haliotidea._]
_Vitrina pellucida._--The Vitrinas in several ways afford a connecting
link between the slugs and snails, having the same tooth-formation and
mantle as the former, while the shell cannot contain the whole body.
As the name indicates, the shell is like a bubble of clear greenish
glass and very delicate. It is small, and found in damp places, coming
out mostly at night. Omnivorous, it is often found feeding on dead
worms, and, unlike nearly all our earth molluscs, can be found abroad
in winter.
_Vitrea (Polita) lucida._--This is the largest of our British
Hyaliniæ, which are difficult to distinguish. The body of this species
is cobalt blue, the apex of the shell is flat, its colour opaque, and
the last whorl more expanded than in others. All belong to the
sub-genus _Polita_, and have polished or glossy shells. All love shade
and moisture, and should be sought under stones or wood or in moss.
They only come out by day when it is wet, a habit they may have
acquired from their being a favourite food of birds, 416 having been
found in the crop of one nestling Stockdove; while various flies are
very destructive to them. This species prefers animal food, and is
more gregarious than others. Not common.
_Vitrea (Polita) cellaria._--The next largest species is the most
common of all. It is fond of cellars (whence its name), and I found it
under the stone lid of a manhole in the drain of S. Peter's Rectory,
Walworth--the only shell left in that part of London. It resembles the
previous species, but is smaller and has a broader and deeper suture
between the whorls, while the foot-sole is paler than the body.
_Vitrea (Polita) Rogersi._--Local. Found in dense woods. It is much
like both _H. cellaria_ and _H. alliaria_, and all three smell of
garlic, but the last is much smaller than the others. The tentacles
in the first are long, and in the third short; while in _Rogersi_ the
upper pair are long and the lower very short. It is also the most
glossy of all. If put in a box with other small shells it will clean
them by cannibalism.
_Vitrea (Polita) alliaria_, _i.e._ smelling of garlic.--Often confused
by quite good conchologists with the preceding species, but the body
is much darker, and the shell smaller and less white below than either
_cellaria_ or _helvetica_. The always present smell is said to protect
it from ants. Common, but local, and often a pest in greenhouses and
ferneries.
_Vitrea (Polita) nitidula._--Common. Less glossy. Marked expansion of
the last whorl as it nears the mouth.
_Vitrea (Polita) pura._--Like _nitidula_ but smaller, and edge of
mantle white instead of dark. More common in the north. Shell thin and
dull white.
_Vitrea (Polita) radiatula._--Never abundant. Striations on shell give
it a radiated appearance when magnified. Animal nearly black.
_Vitrea crystallina._--The smallest of the genus. Shell transparent,
pearly white. Umbilicus (_i.e._ the opening in the centre of the
underside showing the whorls) very narrow. Subterranean in habit.
Whorls, four; whereas _H. pura_ has five; also more compressed.
_Euconulus fulvus._--Distinctively pyramidal in shape. Small. Brown.
Common under rotten branches and moss in woods. Hardly hibernates.
_Zonitoides nitidus._--Chocolate-brown, with no white round the
umbilicus (as has _H. nitudula_). Larger than, but not unlike, _H.
radiatula_. Gregarious. Chiefly found by water; also in damp
hothouses. Amphibious.
_Zonitoides excavatus._--Its broad and deep umbilicus is quite
distinctive. Mainly British. Dislikes lime, and is most plentiful on
the coal measures.
We come now to the Helicidæ family and its genus Helix, in which there
are various sub-genera of which the name is given in brackets. The
shell in this genus can wholly contain the body; the tentacles are
always four; the shell conical, and rarely with a depressed spire. The
word "helix" is Greek, and means a coil.
_Helix (Gonyodiscus) rotundata._--Very common under stones, moss, etc.
Circular, flat, with a large open umbilicus. Horn colour with brown
markings.
_H. (Pyramidula) rupestris_, _i.e._ inhabiting rocks.--Small.
Gregarious. Dark brown. Mainly on exposed dry walls and cliffs.
_H. (Punctum) pygmæum._--Very small. Yellowish brown and glossy shell.
Mainly on moist dead leaves. Not unlike _H. rupestris_ except as to
habitat.
_H. (Acanthinula) lamellata._--Small. Horn-colour. Epidermis raised
into lamellæ or ridges in the line of growth. Mainly northern.
Frequents dead leaves, especially beech and holly.
_H. (Acanthinula) aculeata._--More common than the former; which it
resembles in habitat. Differs chiefly by the ridges being produced
into spines.
_H. (Vallonia) pulchella._--Tiny. White. Mouth trumpet-shaped.
Umbilicus wide. Under stones and at the roots of grass. Its variety
_costata_ (which some make a separate species) is strongly ribbed.
_H. (Helicigona) lapicida._--Circular, flattened, dark brown, strong
white reflected rim to mouth. Large umbilicus. Marked keel, which
distinguishes it from all other British land shells. Chiefly on chalk
soils. Often on beech tree trunks.
_H. (Gonostoma) obvoluta._--Common abroad, but confined in England to
a few spots in Sussex and Hants. Circular, flat above, mouth
triangular, with a strong pinkish-white rim with three denticles.
_H. (Pomatia) pomatia._--Described earlier. Found in Hants, Sussex,
Kent, Surrey, Oxford, Gloucester, and Bedfordshire; but very local.
Elsewhere it may well be an escape from captivity, or the remains of
an attempt (always unsuccessful) to establish a colony. Box Hill and
Caterham are two good localities for Londoners. In Kent it has two
centres, Charing and Shoreham with their contiguous parishes, but
there is a great gap between them, and it is absent from places on the
same chalk ridge which are identical in soil and vegetation.
_H. (Cryptomphalus) aspersa._--The sub-generic name means that the
umbilicus is hidden in adult shells by a fold of the pillar lip; the
specific name means sprinkled (with brown blotches); but it may be a
slip of the pen, for _aspera_, or rough, from the rough shagreening of
its surface. Five banded, like so many of the Helicidæ, but usually
the second and third band unite. No umbilicus. The variety _exalbida_
(chiefly found in Kent and the West) is straw colour and somewhat
transparent. Commonly sold for food on the Continent as well as
_pomatia_, which is cultivated in "snail-farms," but not native in
Germany or Switzerland, and in France chiefly found in the coast
departments. Insipid; but as nourishing as calf's-foot jelly. Fond of
gardens (whence its common name), but not of gardeners. As most
animals are marvellously gifted with a knowledge of what food to eat
and what to avoid, it is curious that _aspersa_ will eat voraciously
the leaves of the spindle-tree, though this soon poisons them. It is
said also that they share with cows and horses the ignorance that the
leaves of the yew should be avoided on pain of sickness or even of
death.
_H. (Cepæa) nemoralis._--As already stated, this is the most
brilliantly and variously coloured and diversely banded of all our
English land shells with the exception of its very close connection
_H. (Tachea) hortensis_. It is happily very common, and so the
attention of beginners should first be directed to this. Thrushes and
mice are its great enemies, the former smashing it on some stone which
may be found surrounded by the broken shells. The "mouth" or peristome
is normally black, the shell larger and stouter than _hortensis_, in
which the mouth is white. When a white-mouthed _nemoralis_ or
dark-mouthed _hortensis_ (both rare) is found, the shape of the
internal flinty dart at once distinguishes them. In some places both
live together: in most one is found and not the other. _Nemoralis_ is
fond of sand-hills by the coast, but is chiefly a hedge-snail, and the
edges of main roads are preferred because of the greater variety of
food, because the traffic scares away their bird enemies, and because
the dust gives them abundance of already prepared material for their
shells. When, however, the collector comes to a wayside cottage where
fowls are kept he need not waste his time in looking for snails in the
neighbouring hedge. The more the chicken industry extends and the more
the Bird Protection Acts operates, the worse it is for collectors of
snails. The banding is probably protective, as in the case of the
tiger and the zebra, and renders the shell less visible.
_Helix (Cepæa) hortensis._--Rarely found in gardens in spite of its
specific name. A hedge-snail. White forms not uncommon, though almost
unknown in _nemoralis_. Though the weaker form, the coalescence of the
five bands into one broad one is more common here than in _nemoralis_.
Also the variety with only one band, and that on the periphery, is
very common in _nemoralis_ and rare in _hortensis_. It is more
dependent on shade and moisture than its congener. Smells of garlic
when immersed in boiling water to be killed. _Hortensis_ is a more
northern, and _nemoralis_ a more southern, shell by origin and
distribution. There are 89 possible band variations in any normally
five-banded shell, and all have been noted in the case of _nemoralis_,
but in _hortensis_ only 61. They are distinguished, for purposes of
record and exchange, by numbers. Thus the type is 12345, the usual
one-banded variety 00300, the common coalescence of the second and
third band is 1(23)45, and when all bands unite (12345). The
unicolourous or bandless variations would be 00000.
_H. (Arianta) arbustorum._--Local. Usually found in hedges and by
ditches on chalk and limestone. Shell globose, brown or yellow, with a
check or willow leaf pattern, and a single dark band on the periphery.
Lip strong and white. Animal usually nearly black. Very fond of
moisture. Anatomically related to _A. lapicida_, but no external
resemblance.
_Helix (Theba) cantiana._--First observed in Kent (where it is
especially fine and abundant), whence its specific name, but generally
dispersed in South and East England. A dull, creamy white shell with a
pink tinge, sometimes becoming partially or wholly reddish.
_Helix (Theba) cartusiana_ (first noticed near a Carthusian
monastery). Much resembles _cantiana_, but is much smaller and more
smooth. Chiefly found on the downs of Kent and Sussex. Used to be
common on Deal sand-hills--now devastated by golf! The tint in this is
brown, in the former red.
_H. (Hygromia) rufescens._--A flattish, dark brown shell, abundant in
the south of England, and not rare elsewhere. Has a semi-lunar mouth
with a white internal rib. In gardens seems to prefer violet beds.
_H. (Hygromia) hispida_, _i.e._ hairy.--These hairs are deciduous, and
the hairless variety used to be considered a separate species under
the name of _concinna_ (_i.e._ neat), but would now be the variety
_depilata_, or bald. Broad and deep umbilicus. Common, except in
Ireland. Usually associates with _H. rufescens_ in moist places.
_H. (Hygromia) granulata_ is also hairy with white silky bristles.
Yellowish in colour. Shell thin. Local, but abundant where found. Its
umbilicus is very small. It falls from its food plants at the least
shake.
_H. (Hygromia) revelata._--Scantily haired. Globular thin shell. Pale
green. Mainly found in Cornwall and South Devon. In cold or dry
weather it buries itself rather deeply.
_H. (Hygromia) fusca._--Very thin, glossy, brown shell. Local. Hardy,
and even active in frost. Chiefly found on nettles, which many shells
like as food, though avoiding the commonly associated horehound.
_H. (Euparypha) pisana._--First noticed at Pisa. Somewhat like
_Helicella virgata_, but larger, sub-globular, and solid shell,
yellowish-white with dark lines or bands. Aperture or mouth yellowish
or rosy. Most common in Portugal and Morocco, and all round the
Mediterranean, dry places, especially near the sea. In England chiefly
confined to Tenby and other parts of Pembrokeshire; also in the
Channel Islands. Varies much in tint and markings. Swarms where found;
it loves sun and heat. Seems to lend itself better to colonization
than most species.
_H. (Helicella) itala._--So named by Linnæus, who probably received it
first from Italy. Shell almost circular, flat. Umbilicus very large
and open. Common on heaths and downs, especially near the sea.
_H. (Candidula) caperata._--(The specific name means wrinkled, like a
goat's horn.) Careless of heat or cold. Distinguished from the young
of _H. virgata_ by being more depressed, having a larger umbilicus,
regular and strong striation, and round mouth with white internal rib.
Found under stones and on grass. Common.
[Illustration: _Helicella virgata_ at rest on thistle, natural size.]
_H. (Heliomanes) virgata_ (_i.e._ striped).--A very variable shell.
See the illustration above of some at rest on thistles. Local, but
very abundant where found. Whitish shell with dark bands, but a
yellowish and a white variety usually is found with the type. The most
beautiful variety, _radiata_, is chiefly found in Romney Marsh, and
from Hythe to Rye.
_H. (Turricola) terrestris._--A Mediterranean species, well
established since 1890, in one spot near Dover. A pyramidal shell,
greyish, with one dark band on each whorl.
_H. (Cochlicella) barbara_ (_i.e._ foreign).--Long, conical, whitish,
with one dark band. By the sea-coast. In shape somewhat like a
Buliminus.
We come now to the Pupa family and its genus Buliminus and its
sub-genus Ena. It is represented by:--
_Ena montana._--A local and southern shell, conical, slightly glossy,
brown. Lip white and deflected. Commonly found on the holes of
smooth-barked trees, and it closely resembles the small knobs on beech
trunks.
_Ena obscura._--Like the former, but much smaller, and found nearly
everywhere in England and Wales. Found in hedgebanks, or on beech
trunks. Its specific name is derived from its habit of covering itself
with a coating of earth, and so becoming inconspicuous.