Chapter III: Preface (3)

The fresh-water mussels found in the Ohio and other rivers and streams are pearl producers. Very valuable gems have been taken from them in various states, and the fresh-water pearl fishery of the United States is of considerable importance. A fresh-water pearl found in New Jersey was valued at $2000, and one taken from a stream in Scotland brought $50,000.

The vast number of shells and the varieties of each kind can hardly be realized by those who have not examined a well-equipped collection. Over four thousand species of the mussel are known, and hundreds of species of almost every shell exist in various streams and seas. The shells range from minute specimens hardly visible to giants weighing several hundred pounds, one of the latter being the huge clam, Tridacna (Fig. 88), found in the equatorial Pacific. There are several species, and in the largest each valve weighs about two hundred and fifty pounds. The animal itself weighs thirty pounds, and affords a meal to forty or fifty men. The shell, by means of its foot, buries itself in the soft rock of the regions in which it lives. With its valves partly open it resembles a huge sea anemone; but it closes them at the slightest alarm. Large fishes, and even natives, it is said, have been trapped by this giant, whose jawlike valves, with three huge teeth, grip the fin of a fish or the foot of an unfortunate wader with a vicelike grasp. The byssus or anchor of this huge shell is so thick and tenacious that it is severed only with great difficulty and labor. The shells are valuable as ornaments, large numbers being sent to various countries for this purpose. The giant never moves, and in this respect is a sharp contrast to the little donax, so common on our various shores and in France, which leaps along the muddy flats by convulsive movements of its fleshy foot.

The common razor clam, of which sixty or more species are known, by means of its foot (Fig. 89) digs a deep burrow which is filled with water even at low tide. The shell is often found at the entrance, but at the slightest alarm it dashes deep down into its den, to be caught only by persistent digging.

The odd shapes assumed by many bivalves is well illustrated in the hammer oyster (Fig. 90) and the pholas. The latter illustrates the power of the most insignificant animals, as by means of its foot this little shell burrows into the hardest granite. It is invariably found there and imprisoned; for when it reaches the interior of a stone, it grows and enlarges, leaving but a small opening for the siphons. It is supposed by some that the pholas possesses some secretions by which it dissolves the stone, and by others that it wears away the rock by using its shell as a file. In any event the shell is known to contain aragonite, a very hard substance. In the pillar of the temple of Serapis, Italy, the holes made by this shell are seen.

Perhaps the most remarkable feature of the pholas is its power as a light giver. It emits a delicate blue light, dead or alive. One placed in a glass of milk has been used as a lamp, illuminating the faces near it. Another placed in honey retained its phosphorescence for over a year. The little pholas is found all over the world, more than eighty different species being known.

The teredo or shipworm (Fig. 91) is called a worm because it secretes a limy shell, but it is really a bivalve shell open at both ends, a shell which with one exception causes more destruction than all other marine animals combined. Instinctively it bores into wood, forming an irregular tunnel and lining it with a delicate coating of carbonate of lime. Some years ago I visited on the outer Florida Reef, an old wreck which was newly buried in the sand and partly exposed at low tide. The timbers of the vessel looked strong and able to stand many a storm, yet with a blow of my hand I broke through the planking. The interior was completely honeycombed by the teredo, so that it was a maze of tubes. At this place the life of a pile of yellow pine was a year and a half; in other words, after being exposed to the teredo for this length of time, it was useless. On the Pacific, at Avalon Bay, the piles last about two years, being rapidly destroyed, even though soaked in various poisonous fluids and coated with tar. Many thousands of dollars have been expended in experiments with devices to outwit the teredo, but without avail, and they are the greatest menace to navigation and piers to-day, making their way into hulls, despite the copper sheathing. In the mud banks of the waters of Sumatra, teredos are found which attain a length of six feet, with tubes four inches in diameter.

The shells are famous for their beauty, the polished valves and their marvelous tints presenting attractive combinations. The common mactra (Fig. 92), the cockle (Fig. 93) with its deep radiations, the gorgeous pectens of the South, the splendid pearl-bearing shells, all tell a wonderful story of the resources of nature, and emphasize the fact that the smallest and most inconspicuous animals vie with the larger forms in beauty of shape and color.

XII. THE UNIVALVES

The shells which have been noticed in the preceding chapter belonged literally to the stay-at-homes of the family. They rarely wander far, and many, as we have seen, never leave the place which the young shell first selected as its home. What are known as the univalves, the mollusks with one shell, or perhaps no shell at all, are the reverse of this, being in many instances travelers, wandering here and there. This suggests that they have more highly organized locomotive organs. Those shown on the upper part of Figure 94 are univalves, and if we make a section of a univalve (Fig. 95), we see that the shell is much more complicated than in the previous forms. The univalve has a shell-secreting mantle and organs resembling those of the bivalves, only differently placed. This marvelous mantle performs some singular feats, judging from the spines found on many shells. To make these, the mantle must have been thrown outward and upward, forming a tube in which the spine was secreted.

In the univalves a distinct head is seen (Fig. 98) with tentacles and prominent eyes. The foot is now elaborated into a huge sucking, clinging, disklike organ. In the whelk it is as long as the shell, the latter being perched high above it, presenting a remarkable spectacle as it moves along the sandy floor of the ocean. On the head are two tentacles, feelers or sense organs, and sometimes the eyes are mounted on tall stalks, that the shell may have a wide range of vision. A siphon, such as we have seen in the clam, is present and extended upward and forward. It protrudes from a canal formed in the shell for the purpose, and is often very long. If the whelk (Fig. 99) is disturbed, it suddenly withdraws its body, including the enormous colored foot; and if the shell is picked up, the entrance is found securely closed by a horny door called the operculum, which is attached to the foot (Fig. 99). This door takes many shapes. In the beautiful conch it is saber-shaped, and is used to dig into the sand, or, as a lever, to force the conch along by a series of jerks. In other shells it is apparently made of porcelain, hard and highly polished. It is well known as the "eye stone" of popular fancy.

Many of the univalves are flesh eaters, preying upon others of their kind. They have a remarkable tongue (Fig. 96) for the purpose, in fact, the teeth are upon the tongue in sawlike rows. The tongue, which is called the lingual ribbon, is ribbon shaped, long and slender, and is really a soft, pliable saw with which the animal bores into the hardest shells of the helpless clams. In strolling alongshore a large majority of the "dead" clam shells found bleaching in the sun, where they have been washed by the sea, will be seen to contain a circular hole of perfect symmetry (Fig. 97). This has been made by the boring, sawlike tongue of a univalve, which, after gaining an entrance into the tightly locked shell, deliberately sucked it out. It is interesting to note the location of this hole, which is invariably over the softest and plumpest part of the victim, near the lungs, showing that the cannibalistic univalve is very clever in its mode of attack.

While the oyster deposits vast quantities of eggs, which float out into the water to be destroyed by other animals, many of the univalves protect their eggs in remarkable cases. I have often found on the Florida Reef strings (Fig. 98) of singular objects which resembled sections of a yellowish cylinder connected by a little cord. Each section is an egg case, or capsule, and contains many shells, the entire chain being two or three feet in length. This becomes tangled in the coral or seaweed, and holds the young shells, all of which escape through a little door in each section.

Other shells, as the whelk (Fig. 99), deposit their egg cases in heaps or mounds. They are soft and spongelike, and are often mistaken for sponges when divested of their shells and cast ashore. Perhaps the best-known egg case is that of the common Natica, which forms a singular object called the "sand collar" (Fig. 100). The animal molds this collar out of fine sand with its foot, and deposits its eggs in the interior, all being cemented or glued together in a solid mass. We shall find that certain birds deposit their eggs in the nests of others, so saving the wearying process of hatching. A certain shell, called Nassa, has a similar habit. At times it deposits its eggs on the collar nest of the Natica.

Among the myriads of shells which we may select to illustrate the various interesting types, shapes, and kinds, are the Chitons (Fig. 101). Their shells are made up of many plates resembling the plates of a hawkbill turtle. Many live in holes in the rocks, and all have a very large, sucking, disklike foot which clings to the rocks with great tenacity. Resembling them somewhat are the limpets. These are interesting and beautiful shells, especially when polished, forming attractive domes marvelously tinted and colored. Some are called keyhole limpets (Fig. 102), from the fact that they have a keyhole-like opening in the top. They range in size from very minute forms to giants a foot in length.

Among the most beautiful of all shells, and at the same time the most common in tropic and semitropic seas, are the abalones. They are also called ear shells. They have an enormous foot that covers the entire lower surface, being a remarkably powerful organ. Instances have been known where Chinese abalone hunters have tried to pry off the shell from a rock with their hands, and have had their fingers caught and held as though by a vice.

The Haliotis is very common on the shores of the southern Californian islands. In some localities every rock is covered with them, and in places where the black abalone is common, I have found them piled one upon the other. There are two hundred species living. Every tint, color, or tone known in the scale of color, or its combinations, is flashed from these marvelous shells, which, if rare, would be counted among the most beautiful of all natural productions. On the Californian coast they are collected in large numbers, and when polished are converted into buttons and a thousand and one other objects. The meat, which is of excellent quality, is sold in large quantities to the Chinese. Thousands of the shells are bought by tourists, the outside being richly polished. From the ancient graves or Indian mounds of the Californian islands I have taken quantities, especially the large kind known as the red abalone, showing that they were used by the ancient inhabitants. In all of these islands heaps and piles of abalones are found far from the water. By stopping up the holes in the shell with asphaltum, which drifts ashore here, the natives had an excellent dish, or bailer. They cut the shell into earrings and ornaments of many kinds, and most of their fishhooks were evolved from this beautiful shell, which also supplied a large proportion of their food.

On the Florida Reef the great conchs (Fig. 103) are very common. They live on the sandy floor of the lagoons, hitching themselves slowly along by their long-pointed, saberlike operculums. This is the conch of commerce, in which appears the most delicate of all pink colors, and which is the source of the rare pink pearls. In the same locality, but in deeper water, is found the Queen conch (Fig. 104), which is cut into medallions and cameos. The beautiful Cypræa (Fig. 105), of which many varieties are known, are called micramocks in Florida, and cowries elsewhere. Their luster and natural polish often excite wonder, for they commonly live concealed in the rough portions of dead coral branches, where they would easily become scratched. The cowry, however, is protected by a remarkable mantle which covers the entire shell, thus keeping its pianolike surface as smooth as a mirror. Many cowries are beautifully striped; some are spotted with dark spots on a white background; some are yellow; others are red or old gold, every tint and color seemingly being employed by nature in painting these gems of the sea. Few other shells have been so universally esteemed by all nations. Among certain African tribes they are used as money, and not many years ago collections of cowries were made with all the ardor that actuated the tulip collectors, thousands of dollars being paid for single shells, as the orange cowry.

The cone shells (Fig. 106) represent a beautiful group, spotted like leopards, striped like the tiger, black, red, yellow. Some shells are very pointed, like the augur shell (Fig. 107). Some have an extraordinarily long projection for the siphon, as the spindle shell (Fig. 108). In some the opening is very small, as the cone shells, while in others it is immense, and protected by a large, doorlike operculum. The Bulimas is a famous nest builder. Bulla is interesting from the lightness and delicacy of the shell and its rich neutral browns.

Among the very familiar shells are the land snails (Fig. 109), common in every garden and raised and sold in France and Italy as table delicacies. Closely allied to them are the slugs, which bear upon their backs, beneath the skin, a delicate, scale-like shell. On the island of San Clemente, fifty miles off the coast of California, I found an extensive sandy plain which was so thickly strewn with the white, bleached snail shells that I could hardly step without crushing several. The verdure had died, and the snails were doubtless killed by the direct rays of the sun.

These interesting animals are called pulmonates because they breathe air directly.

The slugs (Fig. 110) have many peculiar characteristics. If the long tentacles on the short eye stalk are destroyed, the snail will reproduce them. In winter the snails descend into the ground, or hide themselves away, literally sealing themselves in their shells by closing the door firmly, and there hibernate until spring, neither eating nor drinking, and hardly breathing during this time; if placed in a cold storage box, they will remain several years in this state.

Some of the snails of Africa are six inches across, and the eggs are an inch in length. Semper found a little snail in the Philippines, which when caught by the foot or "tail" throws it off as a lizard jerks off its tail. This is not a great hardship, as the tail is soon renewed. In a collection of shells which came from France some years ago I found several snails of different colors which were joined one to the other. The collector had cut the top from an empty brown snail and placed a living snail with a yellow shell upon it, tying the two together. The snail, supposing that its shell had been broken, immediately began to repair the wound, and closed up the breach with its shell-secreting mantle, so that the two shells became one.

In floating on the borders of the Sargasso Sea, the vast sea of weeds in the South Atlantic, I found numbers of a beautiful sea slug (Fig. 111) which so resembled the weeds in shape and color, a rich olive green, that it was almost impossible to distinguish it, except when very close to the surface. They have attractive names, as Doris, Tritonia, Æolis, and Aplysia, and are among the wonders of the great belts of kelp which surround the continent. I once found a slug at Santa Catalina which was a vivid, almost iridescent purple; another was yellow; but the most interesting was Aplysia, a giant two feet long, which I kept in an aquarium. It weighed nearly eight pounds, could lengthen itself out to a distance of nearly three feet, or contract into a dark, olive-hued ball, scarcely six inches across. It took sea lettuce from my hand, eating with avidity, and when disturbed emitted a purple ink which filled the water and hid the monster "sea hare" from view. It laid its eggs on the sides of the tank in long chains, but if not well fed, exhibited a decided cannibalistic tendency, devouring its own progeny. This animal had an enormous foot by which it crept rapidly along, and it invariably protected itself by imitating the color of the bottom upon which it rested.

One of the most interesting slugs is the Onchidium (Fig. 112). According to the naturalist Semper, it has upon its back numerous eyes, which enable it to see from above. It is a mud-loving form, common in our new provinces, the Philippines, where the heat is intense and the water warm. One of the land slugs, Limax noctiluca, emits light; and the eggs of another, Arion, have been noticed to be luminous for nearly two weeks after being deposited.

Nearly all these shells are slow-moving animals, but there are others, the pteropods (Fig. 113), which are swimmers. The veritable fairy craft of the sea, they are housed in shells of dainty structure and moving by singular winglike fins, which give them the name of ocean butterflies. They have the property of phosphorescence to a remarkable degree. Cleodora (Fig. 113, _D_) emits a soft light which gleams through the delicate shell like a light in a lantern. In swimming it moves its fins up and down very much like a butterfly, so that they touch at the top. As delicate and dainty as this little creature is, it has a marvelous arrangement for seizing prey, each tentacle having about three thousand transparent cylinders, each of which contains twenty stalked suckers. As there are six tentacles on each sucker, Cleodora can grasp its prey with three hundred thousand hands. Equally dainty in its way is the sea snail, Ianthina, a violet shell of great delicacy, whose foot develops a raft which resembles a mass of soap bubbles, so the violet snail floats upon the surface of tropical and semi-tropical seas. I have seen the shores of the keys of the Florida Reef lined with an undulating ribbon of these shells after a storm. When touched they emit a rich violet ink which lasts a long time as a stain. A small species of Ianthina is found in the winter on the southern Californian shores, and beneath the attractive float will be found the eggs.

XIII. THE CUTTLEFISHES

In the great libraries of the country will be found books dating back to the last two centuries, many of which contain cuts and descriptions of frightful animals resembling huge spiders, called krakens, or devilfishes. They are represented climbing over ships, and hauling them down. One is described as so huge that the crew of a vessel landed upon it, not discovering that it was not an island until they had built a fire, when the supposed island, really a kraken, sank beneath them. These are tales of romancers, but it is interesting to know that they are based upon a slight foundation of fact. Devilfishes have been discovered in various seas, which weighed several hundred pounds, and whose length ranged from fifty to seventy or more feet. Such an animal is the giant squid (Fig. 115), which is a very timid animal, and though it might overturn a small boat, it is not likely to make the attempt.

These animals are called cephalopods because their feet are attached to the head; in other words, they are head-footed. The typical squid or cuttlefish has a barrel-shaped body, and a tail resembling an arrowhead. Its head is separated from the body by a seeming neck, and is provided with two immense eyes (Fig. 116). Projecting forward are two long, slender arms, and eight shorter ones, which in the giant squid are from six to ten feet in length. These are armed with peculiar suckers (Fig. 117), each of which is extremely powerful. In a specimen six feet long, which I kept for an hour alive in a large tank, some idea of the strength of a squid could be obtained. It fastened its eight arms to the tank, and with all the force I could bring to bear I was unable to tear them off. Besides the eight short arms there are two long ones.

In a specimen of the giant squid which I handled and measured, the long arms were about thirty feet in length. The ends were enlarged with paddlelike organs, and bore a group of suckers. The object of the long arms is to serve as graspers. They are kept near the body, coiled up, and can be shot out with remarkable velocity, grasping a fish like two hands with gigantic arms. They haul the prey to the short arms, when hundreds of sucking disks hold the victim that is now pressed to the remarkable mouth. This lies between the base of the arms, and in color and appearance is almost exactly like the beak of a parrot, with the exception that the under bill fits over the upper (Fig. 118). These bills almost invariably nip the struggling fish over the vertebra or back bone, severing it at once, and ending the struggle. The tongue of the squid is a ribbon with teeth upon it. Such an armament alone is sufficient to attract attention to the animal, but it has still another feature which adds to its interest as a weird and disagreeable creature. The squid has a siphon which terminates in a tube, opening beneath the head. Into this an ink bag opens (Fig. 119). In swimming, the squid rarely if ever rests upon the bottom, but takes in water around the edge of the mantle and ejects it with more or less force from the siphon, and thus the squid is driven along, tail foremost. When alarmed its movements are very rapid. If in danger, the squid pours an inky secretion, which is the sepia of commerce, into the siphon, and the secretion is swept out into the water in a cloud which spreads rapidly, to the confusion of any following enemy.

The squid has a shell, but it is very small, and internal. It is called the pen, and that of some species is the cuttlefish bone of commerce (Fig. 120). In specimens six or seven feet long, taken at Santa Catalina, California, the pen was fifteen inches long and glasslike--a perfect pen in shape. Such is this peculiar creature, and if we add that it can change its color from very dark brown to almost white, adapting it to the color of the bottom over which it rests, we can form some idea of one of the strangest of all animals. They deposit eggs in clusters.

The squids range in size from gigantic specimens seventy or more feet in length to the minute Cranchia, which is luminous at times. Some have no tails, some only the suggestion of a tail, some have very pointed ones, some very broad ones. In specimens of the little Cranchia which I observed the head was very small and the body long in proportion. One form appears to have side winglike fins. The large squids live in the deep sea, and most of the specimens known have been taken from the deep fjords of Newfoundland, which appears to be a favorite locality for them. They doubtless live everywhere in the deep seas, as they are almost invariably found in the stomach of the sperm whale, evidently constituting a favorite food of this giant-toothed whale.

The squids live mainly upon fishes, and are very skillful in taking them, poising like a cat, near the bottom, creeping upon a school of sardines,--all the time simulating the color of the bottom, and almost invisible but for their large, dark eyes standing out,--then suddenly darting tail first into the school, flinging the long arms at the flying fishes, and almost always catching one, which is dragged up to the parrotlike bill and dismembered. In the six and seven foot squids taken at Santa Catalina the stomachs were filled with seaweed, showing that at least some of these animals are vegetarians.

On all tropical shores is found a beautiful coiled shell, the Spirula, with little pearly septa dividing it. I have seen a windrow of these shells a mile long, but never found the animal and shell together, so easily are they disconnected. It is the smallest and the most beautiful of all the cephalopods.

The familiar devilfish or octopus (Fig. 122) is another form, a bottom lover, found among the rocks, rarely attempting to swim. It has a round, baglike body, often covered with soft, fleshy spines; two fiery green eyes, which always seem to emit a baneful light; eight sucker-lined arms, which can be thrown in any direction, and the beak and ink bag noticed in the squid, but no pen or shell. The octopus lives in dens or crevices in the rocks, and ranges in size from specimens a foot or two across to giants with arms having a radial spread of nearly thirty feet (Fig. 123). These large individuals are found along the Pacific coast from California to Alaska, and when caught generally make a desperate struggle for liberty and display a vast amount of strength. I once kept a number in a tank, which were two or three feet across, and when they had grasped firmly it was almost impossible to wrench them from the glass. They differed much in temper. Some would apparently play with my hand, tapping it with their tentacles, or gripping it gently. Others would crouch like miniature tigers, quivering with rage, and with green eyes shining, would spring upon it and attempt to smother it with their arms--a most disagreeable sensation, especially when it was almost impossible to remove the hand from the uncanny grasp without lacerating their flesh. One large octopus in this family, when it obtained a grip, would hold my hand firmly; hence I concluded that a specimen thirty feet across, similar to those represented by casts in the Yale and National Museums, might easily overcome a man. Yet the octopus is a very timid animal in the open water. I rarely caught them either in Florida or California, unless they were cornered, and they never attempted to bite. But I seized one in the coral, and it wound about my arm so tightly that I was obliged to wrench away twenty or more pounds of branch coral, before I could release it without laceration. When attacked the octopus changes color with great rapidity from black to gray, and when enraged it often has the appearance of a leopard. Then it hurls a cloud of ink into the water, and endeavors to slink away under this cover, gliding through crevices that would seem entirely too small to admit so large an animal.

The octopus swims when forced to do so, using a weblike membrane which is seen to connect the base of the eight arms or by forcing water from its siphon. These arms, when extended, give the octopus a faint resemblance to an umbrella without a handle, and with very long supports. The octopus preys upon very small animals, particularly crabs. I have lain among the bowlders on the shores of the Californian islands and watched the octopus hunting. They selected the flood tide and crept near the shore, moving along slowly, on the watch for a species of Grapsus very common here, a land crab which occasionally enters the water. The crabs crept down to the water's edge, and often entered, and in this moment of incaution were pounced upon by the disagreeable creature so well named the devilfish. Sometimes they were caught at the very edge; a long, livid tentacle would come shooting out of the water like a flame and seize the victim. Despite its struggles, it was soon hauled in, the octopus immediately covering it with its umbrellalike bag, doubtless bringing its nippers into play. I have seen an octopus dash out of water two or three feet and scramble up the dry rocks with remarkable speed after an escaping crab. At these times the octopus can be caught by seizing it quickly, but some experience is required before one can grasp a large octopus and retain the hold, so disagreeable is the sensation of the snakelike tentacles winding about hand and arm. The very appearance of the octopus is like a horrible dream, and so intensely repulsive is the animal that in an actual test not one person in fifty who passed a tank containing an octopus with arms a foot long and a hideous striped body, could be induced to touch the animal, though assured that it was absolutely harmless and would merely squeeze the hand.

While the devilfish is the type of all that is hideous and repulsive in nature, it has a near relative, the paper nautilus, which is a very dainty and beautiful creature. It appears to be an octopus which lives in a shell. The argonaut, as it is called, has eight short arms, the upper pair being largely developed at their tips, forming fanlike or saillike organs. It was formerly believed that these were really sails, held aloft to catch the breeze to blow the fairy argonaut along. So fixed in the public mind was this erroneous belief that illustrations in various works otherwise correct, display the argonaut in this incorrect position. The animal is the female, which, to protect and carry its eggs, is provided with a dainty shell which it secretes, but is not attached to, and would lose were it not for the two large-ended tentacles with which it grasps the beak of the shell (Fig. 124). These arms also bear the shell-making and repairing glands. The argonaut can crawl upon the rocks at the bottom, swim through the water, forced along by its siphon stream, or float calmly at the surface. About nine species are known; generally in some tropical waters. Every year a few are found stranded upon Santa Catalina Island, California.

In many of the fossil deposits are found gigantic shells resembling the wheels of a cart, and enormously heavy. These are ammonites (Figs. 125, 126), and ancestors of the nautilus (Fig. 127), another member of this wonderful family of animals, with feet attached to their heads. It has a shell of radiant pearl, divided, like the little Spirula, by pearly septa or partitions, into rooms or chambers (_C_) all of which surround a small tube (_s_) called the siphuncle. This contains a long, fleshy pedicel, hence the nautilus is attached to its shell and can not leave it. The shell chambers are filled with gas, and the animal has the power to change its specific gravity, to float or rise. The nautilus forces itself along by a current from its siphon, and in a general way resembles others of the group. It has no ink bag, and its eye is not the striking object seen in the other forms. It is merely an elevation bearing a minute hole which leads into the globe of the eye, which during the life of the nautilus is filled with water. According to Doctor Hensen, in place of a refracting lens and a cornea, the animal has an arrangement for forming an image on the principle of a pin-hole camera. We might imagine the nautilus easy to capture; but it is very timid and rarely caught. Instead of eight or ten arms the nautilus has ninety-four. The shell is a beautiful object when cleaned and polished, being a vase of pearl of a chaste and elegant design, often copied, and in great demand by native artisans who carve and engrave it, and mount it in gold and silver. The nautilus, aside from its beauty, is a most interesting animal, being the last or almost the last of its race of fifteen hundred species, which have lived in former periods of the earth. Only two are still alive, and these in all probability are doomed to extinction.

XIV. THE CRUSTACEANS

Among all the animals few are more interesting and whimsical than the crabs and lobsters. They have jointed legs, feelers and claws in pairs, living in a shell which they cast like an overcoat when they outgrow it, and have bodies which are made up of hard, tough, limy rings or segments (Fig. 128). The crustaceans are found in all waters, fresh and salt, and on land. They abound in the greatest variety, and range in size from specimens almost invisible to the naked eye to forms with a radial spread of over twenty feet.

During a recent visit to the outlying islands of the Texan coast, I found these extensive regions populated by vast hordes of white or yellowish land crabs, which paraded the beaches and climbed over the dunes in such numbers that the eyes could not be raised without seeing a dozen or more. They were so familiar and tame that several large individuals had burrows by the side of the walk which led from the hotel, and readily took bread thrown to them.

On the keys of the Florida Reef the "spirit crabs," as they are called, are equally common. Pretending to be asleep, I have often watched them cautiously approaching, led by their curiosity to see what strange object this was that had washed ashore. If I remained perfectly quiet, they would gather in dozens, and numbers of little hermits would crawl over me, to drop off at the slightest alarm. In the water were countless other forms.

Wherever we go, from the ocean to the interior, we shall find some members of this interesting family. On almost any seashore we shall find a crab or crayfish, from which some idea of the structure of these animals can be obtained (Fig. 129). We see that there are two distinct regions, the head portion and the tail. The first mentioned is hard and in one general piece; the latter is made up of joints or rings. Everything about this curious animal is jointed. Turning it over (Fig. 130), we see that it has five legs on each side, all jointed. The first pair are large biting claws, and in some species others are biters. Even the eyes are upon stalks and jointed, and about them are two sets of feelers, whips, or antennæ--one large and one small pair--which the animal holds out before it as a blind man does a cane. The mouth is made up of many curious organs for separating and grinding food.

Some idea of the various internal organs of the crustaceans may be obtained in Figure 131. The breathing organs are conspicuous, curled up like plumes on each side of the crayfish and attached to the base of the legs. Water enters the shell under the edge, back of the great claws, and is swept along over them by a little organ called the gill bailer, the gills taking up oxygen from the water, which in turn is absorbed by the colorless blood. The brain is very small, and nerves can be seen passing from it to the various organs. The ears are situated at the base of the small or first antennæ, and are little sacks on the upper side containing a thick fluid in which are floating minute grains of sand. The tail portion is made up of a number of rings or segments, and is provided with small swimmerets. At the extreme end are seen five paddlelike or fanlike organs (Fig. 132), which constitute a most important swimming organ to the lobsters and crayfishes, by the violently flapping of which they dash away backward. In color the crayfish is yellowish brown or greenish. When alive it presents (Fig. 133) an attractive appearance.

The crustaceans deposit eggs which they carry about with them attached to the swimmerets, and resembling minute bunches of grapes. When first hatched (Fig. 134) the young crustaceans are totally unlike the parent in appearance, passing through several stages before they reach the adult form. When the crustacean grows too large for its shell, what are known as casting hairs appear on the inner side, which push the shell upward.

I have watched this process in the California sea crayfish, and it is generally accomplished at night. The flesh of the animal appears to become very watery and soft at this time. Finally the animal bursts the shell and by a slow and convulsive effort drags the flesh from claws, eyes, swimmerets, and antennæ, and escapes through the upper portion of the division between the head and tail, and presto! we have two animals; one flabby and very nervous, the other the deserted shell, yet seemingly alive. The crayfish is very helpless now, and secretes itself for several days until the new skin hardens, when it appears in a freshly colored coat of yellow and black.

XV. FROM BARNACLES TO LOBSTERS

In strolling along the shore one may often find pieces of wood washed in by the combing waves, which are covered with white and blue-tinted objects, resembling dates (Fig. 135). They have long, fleshy stems, and appear to have a number of plates or shells, and are by many considered shells. Other floating matter will be found covered with small white objects (Fig. 136), and many of the rocks alongshore are so completely encrusted by them that the surface of the rock is concealed. On the backs of whales are found similar objects, often three inches across and two inches high. These are barnacles, cousins of the crabs, which secrete multivalve shells and are anchored to various floating or submerged objects. They are crustaceans which are attached to the bottom by their antennæ.

If the shell of a barnacle is carefully observed, fluffy, feathery objects may be seen coming out with regular motion. These are the feet of the crustacean, which in the barnacles are modified into food catchers, grasping at the minute animals contained in the water. What are called goose barnacles have long stems, and the old writers considered them young geese which grew on trees and finally fell into the water. I have found a goose barnacle in the mouth of a large sunfish, so placed that the barnacle swung clear of the curious teeth of the fish. They are also found on the feathers of penguins in the South Pacific. Every floating timber or wreck at sea is covered with the curious, long-stemmed creatures. The barnacles deposit eggs, and the young are at first free swimming, but soon acquire a shell, seek the bottom, or some floating object, and become fixtures for life.

Many of the crustaceans are so small that but few persons ever see them. Such is Cyclops (Fig. 137), a minute creature seen distinctly only under a microscope, yet swimming in fresh water and readily recognized by its egg pouches, one on either side of the tail. The eggs hatch out into singular little objects, having very little resemblance to the parent. The Cyclops and others are very tenacious of life. When pools and streams dry up and remain so for months, they lie dormant, coming to life again with the return of the water. Many of this group are parasites upon fishes, as the Lernæidæ (Fig. 138), which appear like streamers on the sides of carp and other fishes. These parasites, deeply embedded, live upon the fish.

Some of these minute crustaceans are almost exact in their resemblance to shells, as Estheria which has a bivalve shell. But perhaps the most remarkable creature is Artemis, the brine shrimp (Fig. 139), which lives in brine that would be deadly to almost any other animal. A strange experiment has been made with this little creature; thus if the brine is very strong its form resembles _a_, but if the brine is diluted, it changes to _b_, a very different animal, so different that it has been given another name. Many shrimps seem to prefer extreme cold. The Apus (Fig. 140), withstands freezing, and hatches readily in the icy water of the far north. This little creature has forty-seven segments and one hundred and twenty legs. The fairy shrimp is a dainty and beautiful crustacean with a marvelous array of leaflike feet which also serve as breathing organs.

In the summer, while strolling alongshore, one may find that every piece of seaweed or rock when turned over affords concealment to myriads of "sand fleas" which belong to a group of crustaceans having fourteen feet. The sand fleas, true to their name, are remarkable jumpers, darting in all directions and looking very much like an ordinary flea (Fig. 141). They are valuable scavengers, eating all kinds of refuse matter. They have the most bizarre shapes, and many, as Arcturus, resemble twigs or pieces of seaweed, extremely difficult to see and doubtless owe their immunity from attack to this cause. This Arcturus (Fig. 142) is not only a remarkable mimic, but carries its young upon its back. Idotea is a common form about piers, while the little Gammarus may be caught with almost every haul of a very fine net. At times one known as Podocerus builds a singular nest for its better security, and one of the giants of the tribe has eyes so huge that they are made up of facets and entirely cover the head.

One of these crustaceans, Limnoria, is among the most destructive of all animals to the work of man. On the Pacific coast they vie with the teredo, and on the coast of southern California are the chief aggressors, the life of a prepared pile being less than two years. The little creatures completely perforate it, so that the wood literally falls in pieces, being so closely filled with circular borings that the entire interior of the pile seems to have disappeared.

One of the most beautiful of all the crustaceans, in my estimation, is the mantis shrimp, or Squilla (Fig. 143), which I have kept alive. It is found in deep and shallow water, and is a most remarkable creature both in shape and color. Its head is ornamented with beautifully tinted antennæ, vivid blues, greens, and yellows predominating. Its claws are sharp pointed, and deadly weapons when used against its prey. The finlets are richly tinted and in such rapid motion that they appear to be a mass of revolving wheels, so that the Squilla resembles some strange product of the imagination rather than a living animal. Its young are even more remarkable.

One of the best-known groups of crustaceans is represented by those with ten feet, of which the common lobster (Fig. 144) is a familiar example. In this instance the first pair of legs are developed into enormous biting claws; yet when the lobster sheds its skin all the flesh in the large claws is drawn through the very small joint. The lobster is a product of the colder waters of the North Atlantic, not being known on the Pacific slope, although attempts have been made to introduce it there. South of Long Island Sound it is very rare, and despite the stringent laws for its preservation, is rapidly being exterminated. Lobsters are caught in traps, called lobster pots, which are lowered into the kelp and seaweed. Twenty years ago the annual catch for the state of Maine was nearly fifteen million pounds, valued at $250,000. It is far less to-day. The lobster sometimes attains a weight of fifty pounds; but specimens weighing four or five pounds are now rare, due to overcatching, and the destruction of the undersized young. The color of the animal when alive is a dark green. The familiar red hue is the result of cooking. The eggs of the lobster are laid in March, and are masses of green spheres which are carried about by the female attached to her swimmerets.

In southern waters and on the Pacific coast, the place of the lobster is taken by the crayfish, or spiny lobster (Fig. 145). The resemblance to the lobster is almost exact with this exception: instead of large biting claws, the latter are but slightly larger than the ordinary claws, ending with a sharp point, while the antennæ or feelers are enlarged to an extraordinary degree, becoming highly serrated and defensive organs in every sense. The Florida crayfish is a rich reddish yellow, mottled color, while the California form is a greenish yellow. On the Florida Reef almost every coral branch or coral head hides a crayfish, the whips being seen waving to and fro. This is their day retreat, but at night they wander forth to feed in the luxuriant pastures of Algæ, or seaweeds, of various kinds found in the lagoons. By going out early in the morning, before sunrise, I have often surprised the crayfishes, the bottom being covered with them, massive fellows weighing eight or ten pounds. They are not so delicate in flavor as the lobster, but are very valuable as bait. The lobster and the Pacific crayfish are both canned, the industry being an important one.

The prawns (Fig. 146) and shrimps are well known and valuable members of this group, swarming in the same waters, and among the most graceful of the tribe. Many are absolutely transparent, the large black eyes alone being seen. The chameleon shrimp is noted for its rapid changes of color, green, brown, and reddish hues following each other over its crystallike body. In the deeper waters marvelous shrimps have been found, nearly all a dazzling red. Some of the East Indian shrimps are giants two feet in length. In England horses are employed to catch shrimps. A large dragnet is set in shallow water to which the horse is fastened, the fisherman, mounted, driving the animal over the shallow flats, hauling the nets inshore.

One of the most interesting of these ten-footed crustaceans is the blind crayfish of Mammoth Cave. It is found also in various subterranean streams of the country. The eyestalk of these little creatures is all that remains to tell the story of what was once an eye, and they live and thrive in perfect darkness. The ordinary crayfish of Western streams has a peculiar habit of burrowing, which at times has occasioned great damage in undermining dikes and dams. I once came upon a remarkable crayfish community in Indiana. There had been a flood the day previous, and every log in the neighborhood and the piers of the bridge were covered with crayfish which, in this locality at least, appeared to be endeavoring to escape from too much water. On all sides, some yards from the creek and high above it, the ground was raised into small heaps six or eight inches across, each, as I discovered, being the home of a crayfish, and as far as the eye could see on the prairie were these mounds and heaps, suggestive of the vast numbers of these little animals in this vicinity.

XVI. THE CRABS

Of all the crustaceans, the crabs are the most singular and certainly the most intelligent. Rapid in movement, good swimmers, alert, garbed in extraordinary colors, often in stolen homes, they attract attention at once and are the harlequins and clowns of the animal kingdom. The crabs are distinguished from the rest of the group principally by their very short tails. Their bodies are round, elongated, or oval. They are found almost everywhere, from the deep sea, where they occupy shells and sometimes drag about a luminous sea anemone, to every beach. It is in or near the tropics that the most remarkable crabs are seen.

During a visit to the islands off the coast of Texas, I once found a remarkable crab community. The islands were flat sand banks just above the surface, blown and washed up by the sea, with here and there sand dunes and shrubs, and again vast stretches of sand inhabited only by crabs. The latter were all of one kind, a pale gray, so mimicking the sand in color that it was almost impossible to distinguish one from the other. There were legions of them, the sand in places being fairly riddled with their burrows, into which they darted with inconceivable rapidity. As I walked along the sands they ran ahead in rapidly increasing numbers, then divided and were so quick of foot that it was impossible to run them down. This vast army of crabs was the sanitary corps of the island, devouring every dead fish that came ashore and other animal matter of all kinds.

At Garden Key, Florida, these crabs were found in swarms, rarely entering the water except when driven, and never venturing far from the reach of the highest waves at high tide. They had long, stalked eyes, which seem to follow every movement, and were very comical and interesting creatures to watch and study. On the keys covered with bay cedars were other land crabs (Fig. 147), colored rich red and purple. These crabs lived among the cactuses and bay cedar bushes. When climbing on the former their resemblance in shape and color to the purple fruit was remarkable, and if the crab remained quiet, it was almost impossible to distinguish it. In these bushes a tern, the noddy, had built its rude brush nest, and the young bird and the food brought it by the parents were the objects of marked attention on the part of not only the purple-backed crab but a hungry, starving horde of hermit crabs which climbed the tree and snatched the bits of fish from the young birds, despite the presence of their mother. By crawling beneath the thick brush in heat which was almost suffocating, I watched numbers of these foraging expeditions on the part of the crabs, and I think it possible that some of the larger crabs finally carried off the young birds. This was not an impossible feat, as Professor Mosely, of the _Challenger_ deep-sea dredging expedition, observed the same crab or a very near relative, carry off young birds at St. Paul's Rocks. At Ascension he saw the doughty land crabs stealing young rabbits, dragging them from their holes by main force and devouring them. This crab with gorgeous colors was not very fleet of foot, and when I rose up suddenly in the cactus by a nest they would draw in their legs and cling to a branch, mimicking ripe fruit. The hermits would do the same, and fall to the ground in a shower.

An interesting crab found here is known as Grapsus, also a predatory creature with unequaled courage, preying upon every living thing that it can attack with safety. It is richly colored red and white; its legs are long; it is a racer along the sands, impossible to capture. On the West African coast these crabs, or a near relative, are very large, and so swift that they have been used in sport, horsemen following them at full speed as game.

The ordinary crab of the Eastern shore is highly valued, and vast numbers are shipped from Fort Monroe in Virginia to the northern cities. The trade in "soft shells" is even more important. The latter are caught in various ways. An old colored man of my acquaintance used to tread for them on the mud flats with his bare feet; but he confessed that it was a disagreeable business, as sometimes he stepped on "hard shells" by mistake and was badly bitten.

The English edible crab is of large size and always in demand, resembling the edible crab of the Pacific, which is also very large and greatly esteemed.