Corals and coral islands.

ACTINILA AND OTHER AUTINO1D POLYPS.

25

the Actinia, according to Dr. Stimpson, never being seen
except upon the crab's back, and the crab never without its
Actinia. The fact shows an instinctive liking on the part of
the Actinia for a Dorippe courser, and for the roving life
thus afforded it. And the crab is undoubtedly conscious that
he is carrying his fortress about with him. It is not a solitary case; for there are many others of Actiniae attaching
themselves to loconotives-to the claws or backs of crabs, or
to shells in possession of soldier crabs, or to a Medusa; and
frequently each Actinia has its special favorite, proving an
inherited instinctive preference for rapid change of place, and
for just that kind of change, or range of conditions, which the
preferred commnensal provides. Prof: Verrill has an interest.
ing article on this subject, with especial reference to crustaceans, in the third volume of the American Naturalist.
Species living in sand are often unattached; and then the
base is rounded or tapering, and sometimes balloon-sllaped;
some of' theln are long and almost worm-like, and even burrow
like worms.
The following are figures of three species: one, figure 3,
exhibiting simply the tentacles and disk of the Actinia. the
only parts visible above the sand; the others showing the
whole body removed from the sand, and consequently a little
out of shape. They are from Gosse's "British Sea-Anemnones," in which they are given with the natural colors.
Figure 1 represents the Peachia hastata of Gosse, a beautiful
species having twelve large tentacles; fig. 2, the Edwardsia
callimorplia G.; fig. 3, Halocampa chrysanthellum G. Most
of these sand-dwellers bury themselves like the Halocampa,
and often hide all the disk but the mouth. The Edwardsia
is peculiar in having, above the hollow bladder-like basal
portion, a firm opaque exterior to the body, making for it