Functions of the Limnoria Terebrans, 321 



close to one another, near the median line ; the inferior are more 

 widely separated, and therefore more external, than the others. 

 Each superior antenna (Fig. 6.) is composed of four articula- 

 tions, and bears at its point several long bristles. The lower 

 ones (Fig. 7.) have five articulations, and only a few short bris- 

 tles. They are somewhat longer than the others. The eyes 

 are placed on the sides of the head, a little anterior to the extremi- 

 ties of its longest transverse diameter. Viewed with low magni- 

 fying powers, they appear to be only simple, circular, convex, 

 corneal, through which a deep black colour is transmitted ; but, 

 with high powers, they are seen to be compound eyes ; each 

 cornea being formed of eight circular portions, seven set round 

 the circumference, and one in the centre. They project very 

 little beyond the general level of the contiguous surface. The 

 deep black colour, which is remarkable in the eye even of the 

 foetus, appears to be owing to a choroid coat common to all the 

 corneae. The position and external appearance of the eye are 

 represented in Fig. 8. It is uncertain whether we ought to re- 

 gard the caudal styles as organs of sensation. But their situa- 

 tion and structure make it not improbable that they are used as 

 feelers *. They are attached to the ventral surface of the ter- 

 minal edge of the last segment. There are two styles on either 

 side, arising from a common peduncle. One, which projects 

 laterally, is short, and composed of three or four articulations ; 

 the other projects behind, has two articulations, and several long 

 bristles. (Fig. 1.) 



The organs of digestion, which have been satisfactorily made 

 out and traced, are, two pairs of jaws, a pair of strong mandi- 

 bles, four tubiform organs connected with the oesophagus, a 

 stomach, and intestine. The general arrangement of the jaws 

 and mandibles, and their connexion with the head, will be best 

 understood by reference to Figs. 2 and 8. The two pairs of 

 jaws are represented in connexion in Fig. 9, and the inner pair 

 detached in Fig. 10. The jaws are articulated with the corse- 

 let at its inferior and posterior edge, and their muscles arise 

 within the head. The external jaws have each two articula- 

 tions, one of which is placed laterally, and does not enter into 



• The correctness of this view, may, perhaps, bq. doubted when it is consi- 

 dered, that, in some onisci, a thick fluid has been seen issuing from the cau- 

 dal styles. 



