4 GENERAL DESCRIPTION 



which is next to the centre; its back {postica), 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 {sidcatum) ; 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. 



