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.