XV. FROM BARNACLES TO LOBSTERS
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.