SQUIRTS, POLYPS, AND JELLY-FISHES. 61 
all the animals of the class we are now considering 
the extremities of the tentacles are provided with 
peculiar ‘ nettle-cells,’ which by a special arrange- 
ment can discharge from their interiors small barbed 
bodies or styles useful as weapons of both offence 
and defence. In Pennaria nettle-cells similar to 
those of the tentacles are also contained in the 
axis of the body, but what their function is in 
this position remains untold. 
Many of the wrecks that appear on our coast 
bring to us bunches of slender hollow tubes, meas- 
uring as much as three or four inches in height, in 
each of which lived at one time a delicate polyp. 
Possibly your cluster is still alive, in which case 
many of the tiny creatures will be seen expanded 
at the summits of the tubes, their double circle of 
tentacles spread out in the form of a double coronet 
(Pl. 4, Fig. 13). Hanging from some of these, 
like bunches of grapes, are the reproductive buds, 
which ultimately detach themselves and, medusa- 
like, swim about in the open sea. It is not gener- 
ally known that a large number of ordinary jelly- 
pads or jelly-fishes, whose graceful movements on 
the oceanic surface have from time immemorial 
challenged the admiration of the intelligent ob- 
server, are the products of tiny fixed colonies such 
as we have been considering. The discovery of 
this fact—of the dual existence led by these lower 
organisms—is one of the most surprising in the 
entire range of zoological investigation, and one 
that cannot but carry with it an impressive lesson 
of the wonderful resources of the world of nature. 
6 
