JAPANESE PALOLO, CERATOCEPHALE OSAWAI, N. SP. 25 



shaped bristles are found together with the ordinary bristles, but 

 in the more posterior segments, the latter disappear altogether. 

 Only exceptionally are a few ordinary or setose bristles again 

 found in both the dorsal and the ventral rami in the last one 

 or two abdominal segments. 



The paddle-shaped bristle (PI. IL, figs. 19 and 20) consists 

 of a shaft, which shows regular transverse striations, and of a 

 blade, which is very finely serrated on one edge. It remains 

 the same in form throughout the same individual but differs 

 somewhat according to sexes. The body-region in which the 

 above mentioned transition in the character of bristles, from the 

 setose to the paddle-shaped, occurs, — that is, approximately the 

 boundary between the thoracic and the abdominal parts, — nearly 

 coincides with that region of atocous worms in which the falcate 

 bristles become replaced by the setose. 



The Hindmost Segment. — In external appearance the hind- 

 most segment of the epitocous worm is just like any of those 

 which precede it. Its parapodia are directed postero-laterally, 

 and of course no anal cirri are present. Examined in longitudinal 

 sections, the hypodermis of this segment is seen to be greatly 

 thickened, especially in the dorsal part. At the posterior end 

 of the segment it is four times or more as thick as at the anterior 

 end or in any other segment. Further, the hypodermis can be 

 distinctly made out as being discontinuous with the wall of the 

 intestine, in contrast to the condition in the hind end of atocous 

 worms, in which the hypodermis cells pass gradually and con- 

 tinuously into the cells of the intestinal wall at the anus. The 

 epithelial cells of the intestine in the hind end of epitocous 

 worms present some signs of atrophy, in that the cell-outlines 



