The Living Animals of the World, Volume II: Birds, Reptiles and Amphibians, Fishes, Jointed Animals, Molluscs, etc.
Nor must we omit to notice the use of flies as articles of food for man or useful animals. Many persons are very fond of cheese-hoppers, which are really the maggots of a : " The Rev. A. E.small fly; and we read in Kirby's " Textbook of Entomology," page 92 Eaton informs me that he believes that two species of Ephemeridce (May-flies) form a portion of the so-called ' Kungu Cake,' manufactured by the natives of South Africa of gnats, arid probably any other insects which can be obtained in sufficient abundance." "Gentles," which are the maggots of flies, are used by anglers for ground-bait.
Photo by W. Saville-Kent, F.Z.S., Milford-on-Sea.
PORTION OF INSHORE CORAL REEF AT THURSDAY ISLAND, TORRES STRAITS.
In the foreground are hemispherical masses of so-called Brain-Stone and Star-Corals. In the background the rocks are encrusted with various species of soft-fleshed corals, allied to the familiar “Dead Men’s Fingers” of the British Seas.
UNIV. OF
CALIFORNIA
UNIV. OF
CALIFORNIA
BOOK VI. SHELL-FISH, LAMP-SHELLS, SEA-URCHINS,
STAR-FISHES, MOSS-ANIMALS, WORMS, CORALS,
JELLY-FISHES, AND SPONGES.
BY W. SAVILLE-KENT, F.L.S., F.Z.S.
CHAPTER I.
SHELL-FISH, OR MOLLUSCS.
Molluscan Group or Sub-kingdom represents one, if not the most important, of the invertebrate sections THE of living animals with relation both to its numbers and variety and in its commercial and economic utility to mankind. In its ranks are included all those animals generally known as Shell-fish, and familiar to the nonscientific in the shape of Oysters, Mussels, Whelks, Peri-winkles, and the innumerable varieties of gorgeous or delicately tinted shells of tropical seas.
Collectively, Molluscs differ from all such invertebrate in that they groups as Insects, Crustaceans, and Worms possess neither jointed limbs nor jointed bodies, their body-substance being enclosed by a more or less distinct muscular sac, or integument, technically known as the " mantle." Molluscs possess no internal skeleton; but for the protection of their soft and otherwise defenceless bodies the mantle is among the great majority of species Photo by W. Saville-Kent, F.Z.S., Milford-on-Sea. endowed with the property of secreting a more or less AN OCTOPUS CROUCHING IN A ROCK-POOL. indurated calcareous shell, within which, when danger Green shore-crabs constitute the chief food of the threatens, the creature can entirely withdraw. In some octopus. species the shell secreted is relatively small, and serves only as a protective shield to especially vital areas; while in a third very considerable assemblage a shell is altogether absent. The minute yet technically recognisable structural differences between the shells of even the most closely allied specific forms, and the wider and distinctly evident "divergences that separate the more remotely connected varieties, furnish the basis for their classification and nomenclature by the systematic conchologist. Molluscan shells, being so extensively preserved in the fossil state, furnish the geologist with invaluable data for his determination of the age and respective relationship of the Photo by W. Saville-Kent, F.Z.S., Milford-on-Sea, fossil-bearing strata of the earth's crust. AN OCTOPUS ON ITS BACK AT BAY, LEFT Having no jointed limbs, molluscs are dependent upon HIGH AND DRY BY THE RETREATING TIDE. some other mechanical adaptation for their powers of loco-can the attitude use its many- In this octopus motion. This, in the majority of species, is represented by beak its formidable tentacles and parrot-like suckered a modification of the lower surface of the animal's body, as defensive weapons. 737 93
of the World738 The Living Animals
which is so richly supplied with muscular tissues as to constitute an effective creeping-base. As a locomotive organ this muscular area is usually known as the "foot." Of living molluscs some 50,000 distinct species have been recorded. The great majority of these organisms are, as is well known, marine. A very considerable number, however, are inhabitants of fresh-water; while a yet smaller proportion, like the Slugs and Snails and their allies, are especially adapted for a terrestrial existence. Excepting two relatively small and inconspicuous groups, the great natural division or sub-kingdom of Molluscs is separated by systematic zoologists into three main sections or classes. The
Photo by W. Saeille-Kent, F.Z. $.] [Milford-on-Sca. OCTOPODS. A blue-spotted West Australian species.
particular modification of the locomotive organ, or foot, serves, on the one hand, to readily distinguish the first or most highly organised group from the second or central class; while the third or lowest one is as clearly separated from the second and first by the character of the shell. The first and most highly developed section includes such species as the Octopus, the Cuttle-fish, the Squid, and the several varieties of Nautiluses; to the second or central group are referred all the marine and terrestrial Slugs and Snails with their innumerable modifications; while the third and lowest group comprises all the double-shelled or bivalve forms, such as Oysters and Mussels. In the OCTOPUS and its allies the creeping-base, or foot, is prolonged round its margin into eight or more arm-like extensions. The anterior of these in the earlier phases of their development grow round and enclose the mouth, which consequently opens upon the centre of the locomotive surface. The arms of the octopus and other forms are in most instances provided throughout their length with complex sucking-disks, wherewith their Photo by W. Saville-Kent, F.Z.S.] [Milford-on-Sea; owners can seize and retain their prey - or
A TASMANIAN SQUID, OR CUTTLE-FISH. walk with ease and celerity over the smoothest Giant species of squids have been recorded in which the shorter perpendicular or overhanging rock-surfaces. tentacles its class, possesses measured 12 feet, and the two longer ones as much as 30 or 40 The octopus, as the type offeet in length.
Shellfish, or Molluscs 739
yet another most effective locomotive organ. This is the so-called funnel, or siphuncle, a membranous tube connected with the capacious gill-cavity which is formed by a folding of the in through themantle on the under-surface. When at rest or moving leisurely, the water taken pocket-like entrance to this cavity is discharged through the funnel without any particular effort. The animal can, however, at will leave go its attachment to the rocks, and propel itself swiftly through water by successive forcible expulsions of the water through the funnel. left, the creature can also direct itsBy directing the aperture of the funnel to the right or its translation is necessarilycourse in whatever direction it desires. When thus swimming, backwards. Another notable feature of the octopus is the "ink-bag," a huge gland secreting an inky-black fluid, which, as produced by the common cuttle-fish, constitutes the sepia of commerce. The contents of the ink-bag are discharged through the funnel at the will of the animal; as soon as the ink is brought into contact with the water, it becomes distributed through it in the form of a thick cloud, under cover of which the mollusc makes good its escape from any attacking enemy.
The octopus in British seas by no means attains to its maximum growth. Examples with arms from 2 to 2 feet in length are accounted large specimens. In Mediterranean waters, however, these dimensions are much exceeded, individuals with arms 5 feet long, which are capable of covering a circular area no less than 10 feet in diameter with their fully extended appendages, being frequently recorded. In the West Indies, on the North-west American coast, . creatures.and also in Chinese seas, similar, if not larger dimensions are attained by these That these monster octopods, or " devil-fish," as they are sometimes designated, prove a source life has been abundantly demonstrated. Lurking, as is their custom,of danger to human among rock-crevices, they seize hold of any moving object which approaches within reach of their extended arms. Bathers in this manner have been seized and drowned, it being impossible for even the strongest swimmer to free himself from the clutches of one of these animals, which, while retaining a firm hold on the rocks with a portion of its hundred-suckered arms, has entwined the others around its victim.
The natural food of the octopus are crabs, lobsters, and their like; and in places like the Channel Islands, where the tide retires very low, leaving the rock-fissures inhabited by the molluscs more or less exposed, their presence may be often foretold by the accumulation of empty, broken-up crab-shells around the entrances^to their retreats. In common with other members of its tribe, the octopus is furnished with a strong, horny, parrot-like beak, wherewith it can with ease break through the shells of its accustomed food. The year 1900 was remarkable for the extraordinary abundance of the octopus on the English south coast, the result of their collective depredations very seriously affecting the local crab and lobster fisheries. The pots laid down over-night, in place of yielding the following morning their customary quota of marketable crustaceans, were more often than otherwise found to contain nothing but broken-up shells and a loathsome "devil-fish."
The SQUIDS and CUTTLE-FISHES, with their large lustrous eyes, are especially adapted for an open sea life, and for this purpose are furnished with lateral fin-like membranous expansions. A photo ^ w samiie-Kcnt, F.Z.S.] more important structural distinction is their SHELL OF THE PEARLY NAUTILUS. possession of two supplementary appendages, which. The inner lining of this shell is brilliantly iridescent.
of the World740 The Living Animals
usually retracted within special pouches when not in use, can be shot out to a length at least twice that of the eight ordinary arms. Both the cuttle-fish and the squid, or calamary, are also the possessors of an internal calcareous or horny shell which underlies and strengthens the upper-surface. The cuttle-bone used as a dentifrice and ink-eraser is the product of the first-named it is mollusc. The Ten-armed group, as named, with reference to the two supplementary arms, ten in all, possessed by its members, is notable for including species whose dimensions not only exceed those of any other invertebrate type, but whose fully extended length rivals that of the largest vertebrates. Giant squids, or calamaries, have been taken off the coast of Newfoundland, yielding, with their tentacular arms extended, flioto by W. Saville-Kent, F.Z.S.] [Milford-on-Sea. a linear measurement of over 50 feet, asso-
SHELL OF THE ARGOKAUT, OE PAPER-NAUTILUS. ciated with an estimated weight of as much The female animal only possesses a shell, and uses it as a cradle for her as 1,000 Ibs. There can be no doubt that eggs and young. these giant squids have in many instances furnished the basis of the oft-recurrent sea-serpent stories, more especially on those occasions where the supposed marine reptile and a whale have been reported as seen engaged in combat. As a matter of fact the sperm-whales habitually feed on deep-sea squids, and have been known, when mortally wounded, to vomit forth detached portions of these gigantic molluscs. The long tentacular arms of one of these monsters, thrown around the whale with which it had entered upon a death-struggle, might at a little distance be easily mistaken for some huge snake-like organism. The various species of NAUTILUS, including the so-called " Paper " and " Pearly " species, belong likewise to this group of Molluscs. In the former case, however, it is only the female animal which secretes a shell, and this is used as a cradle wherein she deposits her eggs and it is technicallyrears her young. The pretty romance of the PAPER-NAUTILUS, or ARGONAUT, as termed, floating on the sun-lit waves with spreading sails and an even keel, has unfortunately been entirely dissipated by the penetrating search-light of modern science. The animal only floats on the surface when ill, or when torn from its customary pasture-fields by abnormal storms, otherwise it creeps about the sea-bottom, or disports itself in the sub-marine grottoes like an ordinary octopus, with which, in point of fact, the shell-less male agrees in all essential details. The shell-cradle of the paper-nautilus is not vitally connected with the body of the animal, as is that of the pearly species and all ordinary shell-fish. It is freely detachable from the body, and' during life is grasped and held closely to it by the expanded extremities of the two lateral tentacles by,which the delicate shell is mainly secreted. , the great bulk of Simple-shelled Molluscs, of which it is The next group comprises impossible in these pages to give more than a brief enumeration of some of the most is usually awarded the first place on the list,prominent. The Lung-breathing section, which includes the familiar GARDEN-SNAILS, the SHELL-LESS SLUGS, the FRESH-WATER SNAILS which come to the surface to breathe, and many distinct terrestrial species. The largest living representative of this group is the huge LAND-SNAIL of tropical West Africa, sometimes known as the AGATE- SNAIL, the shell of which is not infrequently as much as 7i inches long.