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 cf irritants, 

 the polypes contract themselves, and by their contractions force out 

 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 submuscular 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, Man. d'Actinologie, p. 68. 



