Marine biology -- Great Britain; Seashore; Seashore biology
If the Beroe is left out of water for some time, the water which forms
such a large proportion of its body evaporates, leaving an almost
imperceptible residue of solid matter; and if left in water after it is
dead, its substance rapidly dissolves away, leaving not the slightest
trace of its presence. There seems to be no satisfactory way of
preserving this beautiful form of animal life. If placed in strong
spirit the water is rapidly extracted from its body, and its animal
substance shrivelled to a minute, shapeless mass; while in weak spirit
and in other fluid preservatives it becomes more or less distorted, and
deprived of its beautiful transparency, or else it disappears
altogether.
We now come to the great favourites among the cœlenterates--the
beautiful anemones-the animated flowers of the ocean, remarkable not
only for their lovely flower-like forms, but also for the great variety
of colour and of habits which they display. These, together with the
corals, form the division of the cœlenterates known as the
_Zoantharia_, characterised by the possession of simple tentacles, the
number of which is a multiple of either five or six. The latter differ
from the former mainly in the power of secreting a calcareous skeleton
which remains attached by its base after the animal substance has
decayed.
The expanded anemone exhibits a more or less cylindrical body, attached
by a suctorial base to a rock or some other object, and a broad circular
disc above. In the centre of this disc is the mouth, surrounded by the
tentacles, often very numerous, and arranged in one or more whorls. When
the animal is inactive the tentacles are usually completely withdrawn,
and the body contracted into a semiglobular or pear-shaped mass which is
very firm to the touch.
The general internal structure of an anemone may be made out by simple
dissections, and the examination conducted with the specimen submerged
in water. A longitudinal section will show that the body is a double
tube, the outer being formed by the body-wall, and the inner by the
wall of the stomach. Thus there is a body-cavity distinct from that of
the stomach, but the two will be seen to communicate below, since the
stomach-wall does not extend as far down as the base. It will be seen,
too, that the body-wall is made up of two distinct layers--an outer
one, that is continued inward at the mouth to form the inner wall of the
stomach, and an inner one that lines the whole of the body-cavity. The
latter contains the muscular elements that enable the anemone to
contract its body.
When the animal is expanded, the whole interior is filled with sea
water, as are also the tentacles, which are hollow tubes, really
extensions of the body-cavity, and formed by prolongations of the same
two layers that constitute the body-wall. As it contracts this water is
expelled, partly through the mouth, and partly through small openings
that exist at the tips of the tentacles.
Public-domain text, read in full here on John Shaqi.
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