Page:Popular Science Monthly Volume 13.djvu/330

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THE POPULAR SCIENCE MONTHLY.

from the rocks; lay them in your basket, with plenty of wet sea-weeds; break from the rock some fragments with the sea-weeds still growing upon them; on your return to your studio put the whole into your aquarium, well supplied with pure sea-water. At first, the sea-anemones will appear like so many mere lumps of soft flesh, without definite form. But leave them there for a night; and, when you look again, you will find each one has established itself, and has expanded into a thing of beauty.

Those polyps which form the beautiful clusters of coral that adorn our mantels and museums, and which build up the vast coral-reefs and islands, differ in only one important respect from the sea-anemones.

PSM V13 D330 Sarsia mirabilis.jpg
Fig. 9.Sarsia (Coryne) mirabilis (Agassiz). Cluster of Hydroids growing on sea-weeds. Fig. 11.Sarsia (Coryne) mirabilis (Agassiz). Adult, Massachusetts Bay.
Fig. 10.—Single individual of Fig. 9 enlarged, showing a b just ready to become free jelly-fishes or Medusæ; Fig. 11, c, young bud.

The sea-anemones are wholly soft; they secrete no skeleton, or only the merest particles of hard matter. On the other hand, the coral-producing polyps secrete a stony skeleton. The old notion that coral is something built by an insect is entirely erroneous. The coral-producing animal is in no sense an insect, nor does it toil to build the clusters and reefs of coral which it forms. The coral-polyp lives and eats, and the getting of its food is the only labor of its life.