SEA ANEMONE. 239 



49. SEA ANEMONE (Tealia eras sic or nis). 



THE animal has been bisected vertically: and one of the halves thus 

 obtained has been suspended with the peristome or mouth-disc pointing to 

 the right, and the base of attachment or pedal disc to the left. The pre- 

 paration shows the chief features characteristic of the class Anthozoa, as 

 well as of the Actiniaria, to which suborder the Sea- Anemone belongs. 



The animal creeps about upon the base, which is here much contracted, 

 so that the free edge or limbus is scarcely discernible. At the limbus 

 the base passes into the wall or column, which is naturally more or less 

 straight but owing to muscular contraction is convex in this specimen. 

 The wall has a distinct margin where it passes in its turn into the peri- 

 stome which supports a marginal series of tentacles and has the mouth in 

 its centre. The tentacles are contracted to short conical stumps. In the 

 living animal they appear to be arranged in four circles, but are really dis- 

 posed in five. Of these the innermost contains forty tentacles ; the fourth 

 twenty; the third ten, and the two external circles five apiece. The area 

 of the peristome is naturally flat or even slightly concave. It has a slight 

 furrow concentric with the mouth, which may be seen on the surface of 

 the section to correspond with a round spot, the cut surface of a strong cir- 

 cumoral sphincter muscle. The mouth is naturally a long slit, the edges of 

 which are kept apposed, save at the two extremities or oral angles. The 

 margins of these angles are prominent, and the open spaces they border are 

 the pharyngeal or oesophageal grooves \h& gonidial canals of Gosse or si- 

 phonoglyphes of Hickson. These grooves or furrows are lined with long cilia 

 which create currents of water to, and perhaps from, the interior. They cannot 

 be seen here. The tube which leads inwards from the mouth is the oeso- 

 phagus or stomodaeum. Its lower edge is at some little distance from the 

 base, and is prolonged into two lappets which correspond to the oesophageal 

 grooves. Food passes down it into the central region of the coelenteric space. 

 This space extends outwards and upwards between the oesophagus and the 

 wall, and into the tentacles, at the tips of which it opens by a pore. But the 

 space in question, as may be seen here, is not a simple space : it is broken 

 up into a series of radial chambers by radial mesenteries or sarco-septa, one 

 of which is reflected at the lower part of the preparation. These mesente- 

 ries are attached above to the peristome, below to the pedal disc, and ex- 

 ternally to the wall, of which they are really processes. A certain number 

 of them are complete, i.e. are attached to the stomodaeum ; they are some- 

 times termed primary. The remainder fail to reach the stomodaeum and 

 are hence incomplete. Some fall short of reaching it by a little distance ; 



