as the stag-bettle, or the equally tough covering of Pulex irritans (or the flea), there are numerous species with delicate protecting hairs, or with appendages on the terminal portion of the abdominal segment, such as the pincers of an earwig, or the sting of a bee or wasp. Then there are protective resemblances in this order, marvellous cases of mimicry, warning colours, and recognition markings— all eminently protective to their possessors. Further details of this great group cannot be considered here. Lord Walsingham considers that only about 10 per cent. of all existing species have been described, and these are calculated to number 250,000. We may simply enumerate the better known forms-ants, wasps, bees, saw-flies, flies and fleas, butterflies and moths, beetles, dragon-flies, may-flies, white ants, crickets, grasshoppers, cockroaches, earwigs. The simple mention of the more or less familiar forms of insect life bring up before the mind a perfect wealth of contrivances for the protection of the bodies of their possessors.

In the Arthropoda (Crustacea, spiders), so called because of their pointed limbs, there is, instead of the calcareous skeleton of sea-urchins and the like, a chitinous external skeleton of the organic horny chitin, secreted by the integument. The immense variety of forms which this great family of animals exhibits will excite our admiration as showing the beautiful adaptation of their protecting structures for diverse environments-the hard carapace and armour of the limbs in crabs, lobsters, crayfish, to say nothing of acorn-shells, king crabs, hermit crabs, barnacles, shrimps, sandhoppers, water fleas among the smaller forms. The power possessed by the young among these Arthropoda of shedding their protective covering during growth is Nature's method of dealing with these young and stirring lower animals. The "jointed" young ones have a simple method of adapting their coats to their growing bodies and just shed their protecting "chiton" when it is too tight, remain quiet and in a temporarily timid state for a few days, no longer indulging in their favourite battles, and devote a little time to the secreting of a new "chiton" from their soft integument. They are then ready once more for the struggle of their life, offensive and defensive.

The Arachnida or spider family, in which hundreds of British forms alone of spiders are known, includes spiders, scorpions, mites, "harvestmen" and certain parasites.

In many the integument is not hardened for protection,

but most spiders have soft, flexible surfaces on the under and a harder chitinous covering on the upper part. Scorpions have a chitinous shell all over the body. In spiders the segments which represent the antennæ of insects are very efficient pincers, used for prehension. Scorpions have still more formidable nipping-claws, and have the power of stinging their prey by means of the tail, which is hooked. and has two poison-glands with minute canals opening into the tips. The spider's web must ever be borne in mind as a wonderful and beautiful method of protection devised for the double purpose of protection and supply of the animal's needs. Its formation and origin need not be here described. Centipedes and millipedes also possess a chitinous covering and glands in the integuments which secrete an acrid fluid for protection.

The remaining group of Invertebrates or non-chordate animals is the large sub-kingdom of Mollusca or soft-bodied animals. For us the interest centres on the shells, which almost all possess. They are aquatic, inhabiting sea and fresh water, and terrestrial. It is computed that 50,000 species of the former and less than half that number of the latter have been identified. The vast majority of Mollusca have shells consisting either of one piece shaped after diverse patterns, or of two valves, thus constituting the two main divisions of Mollusca, univalve or gastropod molluscs, and bivalve or lamellibranch molluscs-e.g., snails on the one hand and oysters on the other. The shell is in nearly all composed of calcareous matter mixed with a small amount of animal matter, and is formed by the outer layer of the "mantle," so called. This shell is essential to the life of the animal, and it cannot, in the convenient manner mentioned among Crustacea, shed its coat and form a fresh one. Injuries to the shell can be repaired, but no new one has ever been known to be produced. Shells are described as porcellanous from their dense white structure, horny, fibrous, or nacreous, such as those of the mother-of-pearl. In addition to the ordinary protection of the hard shell, there is in many a further protection of the shell itself. This "overcoat" of the molluscan shell is called the "periostracum,” and is a tough, smooth coating laid over the calcareous surface, efficiently protecting fresh water shells, in particular, from the eroding chemical action of the water, in which carbonic acid gas is dissolved. A past generation of men thought the discovery of copper coatings for the bottoms of ships a great

advance, which it truly was, on the old style of ships' bottoms, when the great seamen of old days would be obliged after a long voyage to spend weeks in "careening" the bottoms of their stout, rough little vessels that the surface might be freed from myriads of barnacles, seaweed, and such like. So the growth of knowledge produced copper bottoms, and in course of time this process was improved upon by the discovery of compositions to preserve the copper bottoms themselves. But here in a molluscan shell is this late discovery of man anticipated in an organic composition, formed from the shell itself, and reformed as required.

It only remains to remark upon the exceeding beauty of the colouring of many shells, connected with the presence of certain glands in the "mantle " of the mollusc. The colours may be white, red, green, yellow, olive, purple, slate blue, black, and marked with a marvellous symmetry. As to the forms of shells, there are those of cephalopods, such as cuttlefishes, argonauts, pearly nautilus, octopus, and a few more. Ammonites and Belemnites, among extinct forms, come under this division. Of these, all the pearly nautilus and Argonauta argo, with its shell used as a boat in which the mollusc swims near the surface, are the most beautiful and familiar forms. But the protection conferred on cuttlefish is very interesting, with the dorsal plate or cuttle-bone placed under the skin of the back so as to protect the animal against collisions as it swims backwards, as also the remarkable ink-bag which can be discharged by way of selfdefence against pursuers at the pleasure of the animal.

Next to Cephalopods come the bivalves, oysters, scallops. cockles, mussels, and razor-shells, too familiar to need description.

The largest division is that of Gastropods, such as snails, whelks, periwinkles, limpets and cowries, which inhabit fresh water lakes, rivers, salt water at all levels and in all regions, and the land.

Some of these have an internal skeleton, but the majority have an external skeleton, and some, such as slugs, none at all. They have spirally-coiled shells and are univalve as a rule, and nearly always they are coiled from right to left. To take one familiar example out of many as to efficient protection, we may remember the numerous and fruitless efforts made by us in the days of our youth to dislodge a well-grown limpet from its rocky home, and may thus gain an idea of the power of the muscle which retains it in

contact with the rock, and the efficient covering given by the strong little shell to the soft-bodied animal within.

The next class of animals is that of the fishes, lowest among chordate animals for we need hardly in this short sketch consider the so-called semivertebrates, lancelets, seasquirts, and sea-worms.

Below the true fishes is a class called Cyclostomata (lampreys or hag fishes), called also Marsipobranchii from their pouched gills, the hag fishes being not a little interesting as regards a singular form of protection they possess, viz., that of secreting enormous quantities of slimy mucus, which may even be so great as to interfere with fishing in their immediate neighbourhood.

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We have now to consider the various methods of protection among vertebrates, such as scales, spines, fur, hair, feathers, horns, poison-glands, possessed by all below man, according to their individual needs. There are five orders of fishes described, and a few only of these can be touched upon by way of illustration. The means of protection among fishes, generally speaking, consist of scales, teeth, and fins and fin-rays. Of scales there are three kinds, "ctenoid" or comblike (as to their hinder edge), " cycloid" or circular, and "placoid" or plate-like, these last being often composed of structures similar to those of the teeth, viz., dentine and enamel. The fin-rays are delicate bony rods supporting the fins. There is also as a rule in fishes a gill-cover or operculum" covering the gill-slits and gill-rays efficiently. The brains of fishes require protection to a great degree, and they obtain it in the delicately shaped and carefully welded bones of the skull (e.g., in the skull of a perch there are thirty-seven pairs of bones enumerated), which as a rule has a pointed, tapering shape, with obvious advantage conferred thereby in the rapid passage of the fish through the water—a shape advantageously imitated by man in the construction. of his ships. The same advantage in its rapid movement is obtained by the beautiful imbricated or overlapping arrangement of its scales with which we are familiar, and further assisted by the slimy abundant secretion of mucus. Fins are among the earliest of organs among Vertebrates, in which the beautiful double purpose of protection (offensive and defensive) and direction by one organ is supplied. Not only does the fish progress by means largely of its fins, but it at the same time steers and maintains its balanced position in the water with them, as is shown by the

experiment of cutting off the fins of one side, or of the two pectoral fins. The tail fin has this double purpose in a special manner, as if a steamer were propelled and steered at the same time by screw or rudder. The teeth of fishes are of great variety as to number, size, and arrangement, and contribute of course very largely to the protection and supply of food to the animal, especially the latter, and can be renewed indefinitely as a rule. We may notice the terrible armature of the sharks with their interlocking formation, and numerous rows of reserve-teeth which lie folded back behind those in use, also the great basking shark, sometimes 28 feet long (e.g., one caught at Shanklin), shows a remarkable development of denticles on the surface of its body, constituting very efficient mail armour, and otherwise rather devoid of protective structures.

Other more rare methods of protection among fishes can only be enumerated, e.g., the electric organs near the tail of the electric eel, found in the river sand lagoons of Brazil; the series of galvanic plates along the back of the torpedo, or electric ray; the strange modification into spines of the skin of the globe-fishes, capable of immense distension by means of air taken in through the gullet. When well filled with air it becomes nearly circular, the spines stick out at right angles to the surface, and the inflated globular creature floats along the surface of the water, and can afford to laugh at almost any hungry enemy; it is appropriately called the sea-hedgehog.

Again, some small fishes frequenting the coral reefs of the Pacific, called Scorpanoids, possess appendages of the skin causing them to resemble seaweeds, so that they are easily hidden. Some of these are justly feared because of their poisonous dorsal spines. The class of swordfishes forms a remarkable group of specialized animals, the well-known offensive weapon being a prolongation of the upper jaw. This well-armed warrior of the deep not being otherwise well protected, and having neither scales nor teeth-its active structures of offence or defence are sufficient to allow it to dispense with passive ones. Its great weapon can transfix a codfish or tunny, and even, by repeated stabs, a whale, and will even penetrate the strong timber of a ship. At the College of Surgeons Museum one may see a portion of the bow of a South Sea whaler with the end of a sword from one of these fishes embedded in it. At one blow the fish had lunged his sword through and transfixed 134 inches of solid timber. Another