CORALLINE. 229 
The arms of the polyps are at times subject to violent agitation : 
the tentacula become much excited. If this excitement continues, 
the tentacula can be seen to fold and roll themselves up, as shown 
in Fig. 86. If we look at the expanded disc, we see that the eight 
tentacula are attached to the body, around a space nearly circular, 
in the middle of which rises a small protuberance, the summit of 
which is occupied by a small slit forming two rounded lips. This is 
Fig.8s. Fig. 86. 
Coral Polyp (Lacaze-Duthiers). Another form of Coral Polyp (Lacaze-Duthiers). 
the mouth of the polyp, the form each assumes is very variable, but 
it is well represented in Fig. 86, where the mouth is well seen. 
A cylindrical tube connected with the mouth represents the 
cesophagus or gullet; but all other portions of the digestive canal 
are very rudimentary. The cesophagus connects the general cavity 
of the body with the exterior world, and looks as if it were suspended 
in the middle of the body by certain folds, which issue with perfect 
symmetry from eight points of its circumference. The folds which 
thus fix the cesophagus form a series of cells, above each of which it 
attaches itself, and supports an arm or tentaculum.. 
