Fig. 78.—A group of tube-secreting worms (Serpulæ).
One of the most familiar forms is Serpula (Fig. 78), whose tubes wind in and out in every direction. No garden of pansies gives a greater variety of tints than did a mass of these radiant creatures that I found on a floating spar in the Pacific at Avalon Bay. But touch these "flowers" or jar them and they disappear like magic, leaving a hole closed by a little door, which is formed by a part of the worm that thus defies all intruders.
XI. THE TWO-VALVED SHELLS
Fig. 79.—The oyster: A, muscle; B, mantle; C, gills; D, labial palpi; E, hinge; F, mouth; G, liver and stomach; H, heart.
The beautiful objects which we know as shells, and which form ornaments in many a home far distant from the sea, are the coverings of a group of animals called mollusks. They are found in all seas, many upon land, and in fresh-water streams, and are among the most attractive of all natural objects, so much so that many persons devote their entire lives to their collection, and many others much time to the study of their habits. It is rare to find a new shell, so well have these shell hunters searched the waters of the world. Such collections, especially if complete, are very valuable, and many of the great museums have paid thousands of dollars for them.
