FLUMCLARIAXS. 
233 
The sarcothecae, so far as their amoeboid element is con- 
cerned , are peculiar to the Plumularian family. But beyond 
its limits we meet with some curious structures, which remind 
us of the apparatus of thread-cells, with which they are also 
furnished. Thus in a most interesting form ( Lafceina ) ob- 
tained from great depths by the distinguished Norwegian 
biologist, Sars, the creeping stem gives origin to a multitude 
of slender tubular cases, each of which incloses a thread of 
sarcode, terminating above in an enlarged capitulum, in which 
a number of thread-cells are immersed. A small orifice at 
the summit of the horny tube, protecting this curious piece of 
structure, gives a passage to the thread-like darts, which are 
emitted from the cells. These defensive zooids, if such be 
their nature, are thickly distributed amongst the polypites, 
which are completely environed by their strange protectors. 
They remind us forcibly of “ calicetti ” deprived of their 
extensile lobes. Another appendage of still more extraordinary 
character occurs in the genus Opkiodes , and marks an advance on 
the primitive structures I have been describing. And it is a 
fact of no little interest that an appendage strictly identical 
with this is met with on a Plumularian lately obtained from 
great depths off the coast of Norway,* occupying, as it seems, 
the place of the ordinary sarcothecae, which are wanting. 
This appendage (PI. CXI., fig. 6) is a tentaculoid organ of very 
snake-like appearance, attached below to the common flesh of the 
zoophyte, and terminating above in an enlarged head, bearing 
numerous thread-cells, from which long, barbed threads are 
emitted. It is very extensile, and capable of the most vigorous 
movements. The base is protected by a small chitinous cup, but 
the main trunk is naked. One or two of these strange organs are 
always stationed like watchful sentinels near each calycle, around 
which they execute the most energetic movements, twisting 
themselves in all directions, and casting forth their lasso-like 
threads. Their appearance in a Plumularian, as a substitute 
for the usual 66 calicetti,” is significant ; they are probably an 
advanced modification of the simpler structure. Their occur- 
rence in identical form on two species belonging to different 
families is certainly remarkable, and points probably to a 
common ancestor from which both are descended. 
I cannot pursue the history of these curious structures 
further, but merely remark that they seem to replace the more 
primitive forms, with which the protoplasmic movements are 
associated, and which, so far as we know, are absolutely confined 
to the Plumularian family. 
- * This is the exceptional Plumularian ( Ophionema mihi) to which I hav 
referred before. 
