Page:Popular Science Monthly Volume 13.djvu/329

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tion of an inch in diameter. Our most common kinds are from one to two inches, and expand from two to four inches. Some of the tropical kinds are a foot in diameter.

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Fig. 5.—Cluster of Coral-Polyps (Asteroides calycularis, Milne-Edwards)—in various stages of expansion. Fig. 6.—Dead Coral (Asteroides calycularis, Milne-Edwards.)—The coral of Fig. 5.
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Fig. 7.—Madrepore Coral (Madrepora aspera, Dana). Right-hand branches alive; the left, dead.

The sea-anemones, whether in their natural home or in the aquarium, are exceedingly interesting objects; and in the latter place we can study them to the best advantage. Carefully remove a dozen of them

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Fig. 8.—Dana's Astrangia (Astrangia Danæ, Agassiz): c, a growing cluster; a, a single polyp enlarged; b, the dead coral.