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[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.


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