Coral assumes a variety of shapes, imitating-almost all forms of vegetation on the land.
Most of the coral-producing polyps are confined to the tropical parts of the ocean. A few kinds live in temperate waters. Dana's Astrangia lives and flourishes in Long Island Sound, where it occurs in little clusters upon stones and shells.
The visitor to the sea-shore will hardly fail to find among the growing sea-weeds little plant-like clusters like the one represented by Fig. 9. This is a cluster of hydroids, and its life-history is very interesting. The beginner may well be pardoned if he mistake these little clusters for plants, but they are indeed animals. From each little branch there arise buds (Fig. 10), which enlarge, till at length they become detached, float away, and grow into the beautiful jelly-fishes known as Sarsia or Coryne; it has been called by both names, the latter name meaning a club, and the former coming from Sars, the distinguished Norwegian naturalist, who was one of their earliest investigators.
Other hydroids, called Campanularians, will be found among sea-weeds. Here the minute jelly-fishes are formed in little bell-shaped organs (Fig. 12). At length they drop out into the water and become free jelly-fishes similar to Tiaropisis (Fig. 14).
|Fig. 12.—Campanularian (Obelia commissuralis, McCready). The hydro-medusæ in the cups drop out and become free Medusæ, or jelly-fishes, similar to Fig. 14.||Fig. 13.—Tubularia Couthougi (Agassiz). m, Medusæ; ct, coronal tentacles; p, proboscis.|
|Fig. 14.—Campanularian (Tiaropsis diademata, Agassiz).|
The visitor will find other hydroids, which appear like miniature trees with all their foliage crowded to the top, and from beneath which there hang bunches, as it were, of grapes or other fruit. Such is Tu-