766 J. H. ASHWORTH. 



There are sparsely scattered greenish-brown pigment cells 

 in tlie epidermis. 



The conical prostominm bears from two to fonr small 

 brownisli-red eyes on each side (fig. 18). It is followed by a 

 region divided into two by a faint groove (figs. 18, 19). 

 The anterior portion of this region is the true poristomial 

 segment, and in the lai'gest specimen is itself encircled by a 

 groove, which subdivides it into two annul i. 'J'he posterior 

 part of the region above named corresponds to the segment 

 bearing the minute vestigial seta in the ' post-larvae of 

 A. marina (Benham, 1893, p. 49). There is no trace of setae 

 in this segment in the post-larva3 now under consideration. 

 In adults (see fig. 20) the region between the prostomium 

 and first chaetigerous segment is divided into four rings 

 (see p. 741), in the third of which the oesophageal connec- 

 tives unite. By comparison with these post-larvre, it is seen 

 that the first two rings of the adult belong to the peristo- 

 mium and the other two to the first true body-somite, which, 

 in Arenicola, has lost its setae and has become fused with 

 the peristomium. 



There are nineteen chaetigerous segments, in each of which 

 crotchets and setse may be clearly distinguished. There are 

 two kinds of seta3 present in the notopodia. The moi'e 

 numerous and longer ones are very similar to those of the 

 adult (fig. 3). They are about 0'3 mm. long, and bear a 

 lamina along about half their length, "^^rhe shorter seta3, about 

 0"25 mm. long, are obviously laminate for a short distance on 

 both sides (figs. 4, 5). They are almost lanceolate in shape, 

 and drawn out into long, slender tips. Only one of these 

 setas is usually present in each notopodium, in which there 

 are two to four setae altogether. There is a tendency, more 

 marked in the lanceolate setae, for the lamina to break up, 

 from the edge inwards, into fine, pointed teeth (figs. 4, 6). 



The crotchets are 0*07 to 0*08 mm. long, and arc distinguished 

 })y the presence of a thickening, forming an encircling ridge 

 upon the shaft of the chaeta (fig. 10). This ridge lies just 

 below the level of the epidermis. As described on p. 756, 



