XXXIV 
INTRODUCTION. 
until after many observations that I detected them, in an 
example from T. crassicornis, which had discharged about 
half of the wire ; 1 have not seen the slightest sign of arma- 
ture on the cethormim. So far as my investigations go, 
these spiral cnidce are confined to the walls of the tentacles, 
in which, however, they are the dominant form. 
(4.) Olohate Cnidce [cnidce globatce) ? In the acontiiim 
of T. parasitica flattened under pressure, and finally ex- 
pressed 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 pro- 
trusion above spoken of. I am not at all sure that these 
vesicles are consimilar in function with the true cnidce ; 
and I am still more doubtful about the bacillar bodies 
found in the acontioid filaments of T. crassicornis. 
In the indubitable cnidce, — those which I have distin- 
guished as (1) Chambered and (2) Tangled, — the emission 
of the ecthorceiim is a process of distinct eversion. This is 
not a solid but a tubular prolongation of the walls of the 
cnidce, turned in, during its primal condition, like the finger 
of a glove drawn into the cavity. Some of the observa- 
tions 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 occuiTed to me, all 
proving the same fact. In the discharge of the ecthorceiim 
of the tangled cnidce, 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, wnile the tips go on lengthening : the tiio 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 cnidce of Caryophyllia, I 
