the british - Corning Museum of Glass

xxxvi INTRODUCTION.
lining membrane of high contractile power, lessened, on
irritation, the volume of the cavity, and forced out the
wire.
The cnida is filled, however, with a fluid. This is very
distinctly seen, occupying the cavity, when from any impediment,
such as above described, the wire flies out
fitfully—waves, and similar motions, passing from wall to
wall: sometimes, even before any portion of the wire has
escaped, the whole mass of tangled coils is seen to move
irregularly from side to side, within the capsule, from the
operation of some intestine cause. The emission itself is a
process of injection; for I have many times seen floating
atoms driven forcibly along the interior of the ecthorœum,
sometimes swiftly, and sometimes more deliberately.
Nothing that I have seen, would lead me to conclude that
the wall of the cnida is ciliated.
I consider, then, that this fluid, holding organic corpuscles
in suspension, is endowed with a high degree of
expansibility; that, in the state of repose, it is in a condition
of compression, by the inversion of the ecthorœum;
and that, on the excitement of a suitable stimulus, it
forcibly exerts its expansile power, distending, and consequently
projecting, the tubular ecthorœum,—the only part
of the wall that will yield without actual rupture.
The cnidœ cannot, I think, be regarded in the light of
cells, since they are but the contents of other vesicles,
which thus present a higher claim to the character of cellwall.
In the craspeda of S. parasitica, may be seen many
of the chambered cnidœ, bearing this outer envelope,
which, without determining anything concerning its nature,
I shall distinguish as the peribola. Many of the cnidœ have
ruptured their investing membrane, which gives way at no
special point, sometimes at the anterior end, sometimes at
the posterior, and as frequently, all down the side. The
peribola thus ruptured, may be seen in many instances still
hanging about the cnida, while others are quite free from
any remains of it, and in some cases I have seen the cnida
still enveloped in its peribola, unruptured.
The peribola I have seen investing, and hanging around
the cnidœ of the spiral and globate kinds, and this circumstance
has afforded me an additional ground for presuming the
latter to belong to this category of organs (figs. 11, 12, g).
It appears necessary that the cnida should set itself free