the british - Corning Museum of Glass

xxiv INTRODUCTION.
what irregular in form. (4.) Cnidæ, in greater or less
abundance, according to the species. As the craspedum
flattens under pressure, these are crowded at the edges, and
are seen to be arranged, more or less distinctly, side by
side; their long axes set at right angles to the axis of the
craspedum, and their emitting extremities either close to its
edge, or projecting from it. The more dense their aggregation,
the more definitely is this arrangement maintained;
doubtless because displacement of their original position is
more readily effected by the flattening action of the compressorium,
when the cnidœ are more loosely scattered in
the fluid sarcode. The peritoneal membrane which invests
the whole is richly ciliated on its entire surface. (Plate XI.
The Acontia. Certain species of the Zoophytes under
consideration have the faculty of shooting forth from the
mouth, as well as from minute orifices scattered over the
surface of the body, 'slender flexible filaments, usually of
an opaque white hue, but sometimes, as in Adamsia
palliata, of a brilliant lilac tint. In some instances, as in
Sagartia parasitica, S. miniata, and Adamsia palliata, these
threads are protruded in great profusion, coiled up in
irregular spirals, and forming tangled masses that resemble
bundles of sewing cotton. It appears to be a means of
defence; and any of the species just mentioned may
readily be excited to display these weapons by a slight
irritation of the surface of the body. The slightest touch
is usually a sufficient stimulus to the extension, which will
often continue to proceed for some time, the filaments
shooting forth from various points with great force and
rapidity. They have a strongly adhesive power, which,
however, is not dependent on any superficial viscosity, but
on the projectile power of the contained cnidœ, of which I
shall presently speak.
If we carefully watch one of these threads, we shall
perceive that after a time it is gradually withdrawn again
into the body, by the orifice at which it was protruded. In
the case of S. parasitica, a large species, these filaments,
which I designate by the term acontia, sometimes extend
six inches from the body, in a straight line. Yet in a few
minutes the whole has disappeared. It is gradually corrugated
into small irregular coils, at the end which is
attached to the animal; and these little coils are, one after