ACTINIA. 121 
III.—ACTINIA. 
PHYLUM CQ@LENTERATA. 
Cuass SCYPHOZOA. 
SuB-CLAss ACTINOZOA, 
ORDER HEXACTINIA. 
Fig. 54.—AcTINIA MESEMBRYANTHEMUM, 
On the left is an expanded individual with viviparous young escaping from mouth. 
On the right is a partially contracted specimen. 
Actinia mesembryanthemum is a common marine 
organism found between tide-marks. It is, at least ex- 
ternally, axo-symmetric and cylindrical-in shape; 
when expanded it may be about two inches 
long. The base or aboral end is attached to 
a foreign body, such as a rock, and the oral end has a 
ring of numerous short ¢extac/es surrounding a flat peristome, 
in the centre of which is situated the mouth. The exterior 
of the body is smooth and of various shades of brown and 
green, matching its surroundings The body often has 
particles of sand and fragments of shell adhering to it, 
which assist in hiding the animal. On stimulation the 
tentacles are withdrawn into the peristome, and the whole 
animal assumes a rounded and contracted form. So far 
External 
Features. 
