312 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Figs. 7, 8. Nereis pelagica. Dorsal and ventral 

 aspects of the anterior end for comparison with the two 

 preceding figures of Arenicola. 



Fig. 7. Dorsal aspect. Prostomium with pair of 

 tentacles, pair of much stouter palps and four eyes, the 

 peristomium bearing on each side four cirri (the basal 

 portions only are shown on the left), the first and second 

 body segments with their parapodia. x 6. 



Fig. 8. Ventral aspect. Note prostomium with ten- 

 tacles and palps, peristomium bearing mouth on anterior 

 margin, the first and second body segments with their 

 parapodia. The structure at the base of the palps is part 

 of the peristomium forming the upper lip. x 6. 



Fig. 9. Nereis pelagica. A parapodium, from the 

 74th chEetigerous segment, divided distally into bilobed 

 notopodium and neuropodium, each of which bears a 

 sensory cirrus, an aciculum and a bundle of setae (jointed) 

 situated in a setal sac, the lips of which are well seen in 

 the neuropodium. x 20. 



Fig. 10. The seventh notopodium and the small and 

 simple first right gill of the Laminarian specimen shown 

 in fig. 1. Compare with fig. 19. x 6. 



Plate II. 



Fig. 11. Three notopodial setse from a post-larval 

 specimen 4*35 mm. long. Most of the setse are of the type 

 shown in fig. 11C ( x 800), but in each notopodium there 

 is one seta of the kind shown in figs. HA, 11B. ( x 1,000.) 



Fig. 12. Distal fourth of a seta (7*5 mm. long) from 

 a Laminarian specimen 250 mm. long. x 80. 



Fig. 13. A portion of same seta (from the region 

 marked + ) more highly magnified. On the left the 

 broad lamina, with its finely dentate margin, is shown. 

 x 800. 



