Natural History of British Zoophytes. 239 
nic, passes into the tentacula with whose cavity the canals are con- 
tinuous, and by means of small apertures in the sides of the hollow 
tentacula, the water penetrates and unfolds the cilia, with which 
these tentacula are fringed. By the distension from the water thus 
introduced, the body of the polype and its tentacula are forced be- 
yond the surface, and every organ fully displayed. Another portion 
of the water in the abdominal cavity passes into the tube continuous 
with it, fills it and the others in connection with it, and by means 
of holes in their parietes finds access into the intermediate capillary 
net-work, so that the whole mass is permeated with the fluid, and 
all and every portion distended to a bulk which may be more than 
double of that which it had previous to the introduction of the 
fluid, and which it resumes when, from the application of irritants, 
the polypes contract themselves, and by their contractions force eut 
all the imbibed water. The tortuous filaments suspended from the 
base of the stomach have been generally taken for ovaries, but the 
observations of Dr Grant and M. Edwards seem to have disproved 
this opinion. The latter of these eminent naturalists believes them 
to be analogous to the biliary canals of insects. * 
The affinity in structure between the asteroid zoophytes and 
those which we name helianthoid, from their resemblance to some 
compound flowers, is evident, although in the latter there is a still 
further recession from the simplicity of polype anatomy. We find 
in them a mucous coat covering the surface, beneath it a layer of 
transverse stibmuscular fibres, while the body is supported by nu- 
merous strong cartilaginous lamellae arranged in longitudinal paral- 
lelism. Each of the lamellae is attached inferiorly to the circular 
layer which constitutes the base of the animal, and divides into 
three fascicles, one which goes to the stomach and to the rim of the 
oral aperture, another to the roots of the tentacula, and the third 
is prolonged to the outer labial border, where it is bent back to form 
its free margin. t The stomach has its distinct and proper parietes; 
there are special organs for the developement of the reproductive 
gemmae ; and even some traces, as is asserted, of a nervous system ; 
while the numerous tentacula are perforated like canals, in order 
that the water of respiration may be introduced into the interior, 
and the nutritive fluids more thoroughly influenced by its oxygen. 
It has been mentioned already that there is no proper circula- 
tion no movement of a fluid analogous to blood in appropriate ves- 
* Ann. des Sc. Nat. iv. 331 ; an 1835. 
f Blainville, Mmi. d'Actinologie, p. 68. 
