4 GENERAL DESCRIPTION 



which is next to the centre ; its BACK (jjostica), that which 

 is next to the margin ; its right and left sides (latus 

 dextrum, I. sinistrum), those which depend upon these 

 indications. Each tentacle has a foot (radix) and a tip 

 (apex). 



5. The Mouth (Os). 



The entrance to the stomach is placed, as has been stated 

 above, in the centre of the disk. It is surrounded by a 

 generally thickened LIP (labium), which is sometimes 

 elevated on a cone (colliculus) , and sometimes level. The 

 LIP may be SMOOTH (Iceve), or FURROWED (sulcatum) ; at 

 each of two opposite points, — the mouth-angles (gonidia), 

 — there are placed two tubercles (lentigines) , between which 

 opens an imperfect tube or groove formed by the approxi- 

 mation of two cartilaginous bands : these grooves, one at 

 each mouth-angle, may be termed GONIDIAL grooves 

 (canales gonidiales). Their function appears to be that of 

 oviducts. (In Actinoloba, there is but a single mouth- 

 angle, and a single groove).* From the lip descends 

 into the cavity of the body a membranous veil, much 

 gathered into folds, but free at the lower edge, like a sack 

 without a bottom ; this is the stomach (stomachus), of 

 which the portion immediately below the lip may be 

 conveniently termed the throat (gula). 



6. The Cavity (Venter). 



The whole of the region included between the walls of 

 the column and the stomach-wall, and between the free 

 edge of the stomach and the base, may be indicated by 

 this term. It is divided into imperfect chambers by 



* In Actinopsis, a singular form recently described by Messrs. Danielssen 

 and Koren from the Norwegian coast, the gonidial tubercles are prolonged 

 into a pair of long and rigid semi-cylinders, the sides of which are bent 

 downwards, and the tips of which are cleft. 



