Corals and coral islands.

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CORALS AND CORAL ISLANDS.

of a septum, mesenteric in character, at or near the outer margin. They have the aspect of a pulpy mass, or look like clusters of ovules. The ova have no chance for escape except
through the stomach and mouth. They are covered with vibratile cilia, and rove about free for a while. As the development of the embryo goes forward, a depression begins at one
end, which deepens and becomes a stomach, with the entrance
to it as a mouth. Concurrently, septa grow out from the inner
wall, and a few tentacles commence to rise around the mouth.
Not unfrequently, the young has already some of its tentacles
before it leaves the parent. There is at first but a single row
of tentacles; the number increases with the size until the full
adult limit is reached, the newer series being successively the
outer.
In the budding process, which is of rare occurrence, Actinise grow young ones on their sides near the margin of the
base. A protuberance begins to rise and soon shows a mouth,
and then becomes surrounded by tentacles; and, thus begun,
the new Actinia continues to grow, usually until its tentacles
have doubled their number, when finally it separates from the
parent, an independent animal. At times, as Prof. H. James
Clark has observed, small pieces of the base of an Actinia separate by a natural process before a trace of a tentacle has appeared, and in this case "they do not at first show any signs
of activity, but on the contrary, remain for a long time in a
quiet state, having the appearance of artificially separated
pieces, seeming to be undergoing, as in the latter, a recuperative process after the shock of a separation." After a while
they commence to develop and grow into perfect individuals.
Prof. Verrill mentions the case of an Actinia from Puget's
Sound (the Epiactis prolifera, V.) which had three rows of
young individuals attached to it around the middle of its