Fig. 135.—Goose barnacles.
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.
Fig. 136.—The barnacle: A, from above; B, section from the side.
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.
Fig. 137.—Water fleas: 1, Cyclops, showing egg pouches; 2, Cypris; 3, Daphnia.
Fig. 138.—A parasite of a fresh-water fish (CyprinÆ):
1, larva, as it leaves the egg;
2, larva, more advanced;
3, adult female, showing the egg sacs. (Nordmann.)
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.
Fig. 139.—Brine shrimps: a, Branchipus; b, Artemis.
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.
Fig. 141.—Sand flea (Talitrus).
Fig. 142.—Arcturus longicornis, enlarged.
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.
Fig. 143.—Mantis shrimp (Squilla).
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.
Fig. 144.—Common lobster.
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.
Fig. 145.—Crayfish or spiny lobster.
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.
Fig. 146.—A, prawn; B, claw enlarged.
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.
