the british - Corning Museum of Glass

xxxiv
INTRODUCTION.
until after many observations that I detected them, in an
example from T. crassicornis, which had discharged about
half of the wire; I have not seen the slightest sign of armature
on the cethorœum. So far as my investigations go,
these spiral cnidœ are confined to the walls of the tentacles,
in which, however, they are the dominant form.
(4.) Globate Cnidœ (cnidœ globatœ) ? In the acontium
of T. parasitica flattened under pressure, and finally expressed
from its substance, are numerous more or less
globose or ovate vesicles, which' gradually push out a
cylindrical protuberance at each end, sometimes to a length
equal to that of the original form (figs. 11, 12). These
vesicles appear filled with a fluid of different refractive
power from that of the clear sarcode in which they are
lodged; but no sign of contained thread have I been able
to detect, nor have I seen any discharge beyond the protrusion
above spoken of. I am not at all sure that these
vesicles are consimilar in function with the true cnidœ;
and I am still more doubtful about the bacillar bodies
ound in the acontioϊd filaments of T. crassicornis.
In the indubitable cnidœ,—those which I have distinguished
as (1) Chambered and (2) Tangled,—the emission
of the ecthorœum is a process of distinct eversion. This is
not a solid but a tubular prolongation of the walls of the
cnidœ, turned in, during its primal condition, like the finger
of a glove drawn into the cavity. Some of the observations
on which I ground this conclusion I have already
published, but it may not be impertinent to repeat them
here, with others which have since occurred to me, all
proving the same fact. In the discharge of the ecthorœum
of the tangled cnidœ, it frequently runs out, not in a right
line, but in a spiral form; whenever this is the case, each
band of the spire is made, and stereotyped, so to speak, in
succession, while the tips go on lengthening: the tip only
progresses, the whole of the portion actually discharged
remains perfectly fixed; which could not be on any other
supposition than that of evolution. In the discharge of the
chambered kind, the ventricose or basal portion first
appears; the lower barbs fly out before the upper ones,
and all are fully expanded before the attenuated portion
begins to lengthen. This again is consistent only with the
fact of the evolution of the whole. On several occasions of
observation on the chambered cnidœ of Caryophyllia, I