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OUR BRITISH SNAILS

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.

PAGE

Body of snail and of slug 23

Some of our smaller shells 47

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. Secondly, one must learn to observe the difference 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."

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.

You would note, however, in this wall-case that the species are not many , 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.

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.

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.

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.

"I differ from the Gasteropoda 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.

Now let us enumerate the species of land and freshwater shells to be found, in England, and most of them in Ireland or Scotland.

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.

We come now to the Helicidae 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.

We come now to the Pupa family and its genus Buliminus and its sub-genus Ena. It is represented by:--

The genus Vertigo contains shells even smaller than the Pupae, about the size of a pin's head.

In the family Stenogyra we have three genera, Azeca, Cochlicopa, and Caecilioides .

I may notice here two other land shells, although they scientifically are grouped amongst the fluviatile Gasteropoda.

The Family Succinea really ranks with the land shells, as belonging to the sub-order Pulmonata or lung-breathing molluscs. It is, however, amphibious, and hibernates in the mud at the bottom of a ditch.

We now come to the freshwater shells, which we capture best by means of a perforated scoop, whether they are on the waterweeds or hidden in the sand or mud of the bottom.

It may be noted that all freshwater shells are greenish-brown which is an excellent protective colouring as rendering them less visible among water weeds to the fish, which devour them greedily.

The sub-family Physa has two genera, Aplecta and Physa.

The sub-order Pectinibranchiata contains the genera Neritina, Paludina, and Valvata, in all of which there are two tentacles with eye at the base, and an operculum to the shell.

We now come to the bivalve shells with leaf-like gills. The Unionidae contain two genera, Unio and Anodonta, commonly called freshwater mussels.

In the next family are two genera, Sphaerium and Pisidium.

As to the arrangement of shells in a collection before a regular cabinet is obtained, the tinier shells may be kept in small glass tubes with corks , and the medium sized ones in the trays of common matchboxes, these being arranged in large shallow glass-covered trays which can be obtained from any cardboard boxmaker at a small cost, and several of these, stored one above the other, form an excellent substitute for a more costly cabinet. In all cases the name, and the place where the shells were found, should be written on a small slip of card placed in the tube or tray. It is not well in most cases to fasten the shells on card, but if this is done gum tragacanth is best. The collection should be kept free from damp and from dust.

HINTS FOR COLLECTING AND PRESERVING SHELLS OF MOLLUSCS.

The following notes supply a few general rules as to finding and preserving shells:--

Of Shell-bearing Molluscs there are three classes--Marine, Freshwater, and Land. The first two include Univalves and Bivalves, the last only Univalves.

Limpets, etc., should be detached with a thin blade passed quickly under the shell, taking care not to break the edges. Small shells on and in seaweed, and limpets, etc., adhering to stones will drop off and sink to the bottom in a vessel of cold fresh water.

The smallest shells, especially of land species, and young imperfect shells should be collected.

All solid shells may be wrapped in one or two folds of paper of any kind. Fragile and minute shells should be put, generally separately, into a box or bottle--with or without cotton, as required. Such packets may be heaped up in any box, heavy shells at the bottom, without pressure, and any blank filled at the top with paper or other elastic material. Sawdust injures the lustre of many species.

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