456 On the Structure q/Magelona. 



considered to belong to the genus Magelona, Fritz Miiller, 



at St. Vaast la Hougue. In its youngest condition it presents 

 a somewhat club-shaped appearance — broad in front and 

 rather narrowed posteriorly. The anterior end has an open 

 ciliated funnel, then follows about tw^enty segments, each 

 with a ciliated ring, while posteriorly the abruptly truncated 

 tail has a ring of long cilia round the anus. In addition to 

 the cilia on the funnel the anterior end bears a tuft at each 

 side (doubtless homologous with the lateral cephalic pencil 

 in the Nemerteans), besides a papilla armed with a tuft of 

 bristles nearly as long as the body, after the manner of the 

 young Polydora. The alimentary canal proceeds straight 

 from mouth to anus. The next stage shows a heart-shajjed 

 snout with four eyes^ and at the base between it and the 

 body-collar a pair of short tentacles with brown bars (whicii 

 differ quite from the dark pigment-bars of the tentacles in 

 Magdona) on the anterior border near the tip, and a series 

 of palpocils ; while internally is a cavity containing a csecal 

 blood-vessel (according to the type M. Claparede states he 

 usually found in the Spionidae), with corpusculated blood. 

 The first body-segment still bears at each side the tuft of 

 long larval bristles, and is succeeded by eight distinct bristle- 

 bundles. The ninth segment carries a row of hooks on each 

 side. A simple pyriform anal papilla terminates the body. 

 The alimentary canal is differentiated anteriorly into a 

 muscular oesophagus, and the mouth closely approaches that 

 of Magelona. Behind the oesophagus the canal exhibits two 

 short glandular diverticula and then proceeds in the usual 

 moniliform manner to the anus. The body is tinted with 

 various brownish transverse bands. In this condition the 

 flattened spatulate snout has a considerable resemblance to 

 that in Magelona^ but the subsequent stage shows less 

 affinity, for the long tentacles have slender palpocils, wliich 

 differ in character and arrangement from those in the British 

 form. Moreover, the cephalic region has greatly diminished, 

 its shape being that of a short truncated cone, with four eyes 

 arranged in a transverse manner at the base. The first 

 segment of the body retains the long larval bristles, but the 

 succeeding segments to the eighth have lost their shorter 

 temporary bristles. From the ninth segment backward, 

 however, four or five pairs of longer and stronger bristles 

 occur, in association with the rows of hooks (which conform 

 in structure to the Spio type). The blood is bluish. The 

 posterior end has the form of a peculiar hoof-shaped process 

 furnished with small papillae. 



The fragmentary state, therefore, in which our knowledge 



