124 
ON THE ORGANS OF RADIATED ANIMALS. 
“bodies with fluid, depends upon the tubular structure of their tentacula; and 
their protrusion to a greater or less extent, is regulated by the quantity of 
water injected from the respiratory chamber into the tentacular tube. In most 
of the Adinice that inhabit our shores, the tentacula are simple conical tubes ; 
but in some Tropical species, as Adinia alcyonidea , A. arborea , of the South 
Pacific, the body is about a foot in height, and the sixteen tentacula radiate to 
the distance of six inches from the oral disc, and have their surface tuberculated 
with ramified club-shaped expansions, and armed with numerous pedunculated 
suckers. With these musculo-sensitive prehensile instruments, abundantly 
coated with a poisonous tenacious mucous, these gigantic Adinice perceive, seize, 
and retain in their grasp molluscs, Crustacea, and fishes much larger than their 
own bodies. The muscular fibre forms a distinct system in this class, and its 
intimate union with the tegumentary membrane enables them to assume at 
pleasure the varied forms for which they are remarkable. Beneath the coriaceous 
skin we observe a plane of longitudinal fibres, intimately united with it, and 
which converge inferiorly to form the disc, by which these floriform beings attach 
themselves to the rocks. 
In a large errant species from the shores of the Mediterranean, Meckel found 
a second layer of muscular fibres, situated internally to the preceding, that took 
a transverse direction, and were loosely united to them. The strise seen on the 
surface of the bodies of Zoanthidce arise from the contraction of the muscular 
tunics, which corrugate the irritable integument, and thus give it an annulated 
and longitudinally contracted air. So perfect a development of the muscular 
system as that just described necessitates the existence of a regulating power by 
which the movement produced by the contractile fibres may be subjected to the 
control and direction of the will. Long ago Spix, in his minute dissections of 
Adinice , observed nodulated filaments among the muscular fibres of the pedal 
suckers, which he figured and described as the nervous system, consisting of a 
circular cord with three pairs of ganglia developed at equal intervals apart; from 
each a lash of six filaments branches off to supply the walls of the muscular sac. 
Later observers, however, have not been equally successful in detecting this 
arrangement; and indeed, were such found to be the case, it would in some 
measure be at variance with the general law that appears to regulate the dis¬ 
position of the nervous system in other cyclo-neurose classes. Some years ago, 
when dissecting Adinia equina , he observed a cord lying embedded in the 
muscular fibres of the oral sphincter, and took a circular course around the base 
of the purple-coloured tentacula: this he regarded as the circular nervous system 
of the animal. This filament has been likewise recently seen by Professor Jones, 
who says,— 44 It is more probable that the nervous system consists of a delicate 
thread, which we are pretty well convinced we have detected running round the 
