TYPES OF CCELENTERA A SEA-ANEMONE. 161 



complete," i.e. do not extend so far inwards. The./> ^ 



mesenteries are attached to the oral disc above, to the side 



of the gullet, and to the base, and all the mesenteries are 



ingrowths of the body wall. The cavity of the anemone 



is thus divided into a number (some multiple of six) of 



radial chambers. These are in communication at the base, 



so that food particles 



from the gullet may pass 



into any of the chambers 



between the partitions. 



Moreover, each partition 



is perforated, not far from 



the mouth, by a pore, 



besides which there is 



often another nearer the 



body wall. The tentacles 



are continuous with the 



cavities between the mes- 



enteries, and thus all the 



parts of the body are in 



communication. The 



mouth is usually a longi- 



tudinal slit, and its two 



corners are often richly 



ciliated. The gullet is 



marked with longitudinal 



grooves, two of which, 



the " siphonoglyphes," 



correspond to the corners 



of the mouth, and are 



especially broad and 



deep. Along these two 



grooves, and by these two 



FJG. 79. 



anemone. 



Vertical section of a sea- 

 After Andres. 



/., Tentacles; <?., mouth; a?s., oesophagus 

 c.yC'., apertures through a mesentery; ., a'. 

 acontia; ^., genital organs on mesentery 

 m.f., mesenteric filaments ; m.l., longitudina 

 muscles; s., primary septum or mesentery 

 s f . ) secondary septum; /'., tertiary septum 

 ., basal disc. 



corners, food particles 

 usually pass in; but in 

 some, one side is an incurrent, the other an excurrent 

 channel. Occasionally only one corner of the mouth 

 and side of the gullet is thus modified. The gullet 

 often extends far down into the cavity of the anemone. It 

 admits of a certain amount of extrusion. The mesenteries 

 bear (a) mesenteric filaments; (ft) retractor muscles; (c) 



