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POPULAR SCIENCE REVIEW. 
attention is the ample gelatinous disc, the mass of u blubber,” 
as it appears when cast upon the sands — the contractile bell, or 
swimming-organ, of more or less transparency and most grace- 
ful proportions, by whose rhythmical movement the living 
Medusa is propelled through the water. This is both the loco- 
motive organ and the float on which are suspended the various 
organs of prehension and digestion. It varies in form, though 
scarcely in grace, but is commonly a glassy hemisphere with 
lobed or sinuated margin, from which in many cases depend 
a multitude of fringe-like filaments, or a smaller number of 
long extensile arms (vide Plate LXX. fig. 10). These tentacular 
appendages are sensitive feelers, cast about in all directions in 
quest of prey, and also fishing-lines by means of which it is 
arrested and dragged towards the mouth. In some species 
they are present in enormous numbers, and are capable of ex- 
trordinary elongation. The gigantic Cyancea arctica , which 
sometimes attains a diameter of 7\ feet, has these organs dis- 
posed in eight bunches round the margin of its disc — tangled 
masses of interlacing threads, in constant motion, which can be ex- 
tended to a length of more than 1 20 feet ! * When it is remem- 
bered that this formidable offensive apparatus is endowed with 
the power of stinging violently, that these extensile filaments, 
which can be shot out to such amazing distances, are poison- 
ous and paralyse as well as grasp, we may form some idea of 
the terrors that wait upon this floating mass of jelly. 
Round the margin of the disc are ranged certain organs of 
vision, which may be regarded as the equivalent of the eye in 
more highly organised beings (Plate LXX. fig. 9a). Each of 
them consists of a spherical cluster of lenses, borne on a peduncle, 
and usually more or less protected by a hood-like covering. 
Professor H. J. Clark, who has carefully studied the intimate 
structure of these bodies — who has actually taken out the minute 
lenses and turned them about, so as to trace the curvature of 
the face — is of opinion that we have in them a all the elements 
of an optical apparatus sufficient to produce a distinct image.” 
At any rate, there can be little doubt that they are light- 
perceiving organs, and serve in some way or other to direct the 
creature in its course. Agassiz remarks that “ there can be no 
doubt that these animals perceive what is going on about them, 
and that they are very sensitive to changes in the condition of 
the atmosphere Even accidental disturbances are perceived 
by them, for when approached, however carefully, the change 
of their course, or the unusual rapidity with which they sink, 
show plainly that they are making the utmost efforts to escape. 
.... When approached with a dip-net it is evident, from the 
A. Agassiz, in his u Catalogue of North- American Medusae.’ 
