270 



POLYNOID^l 



occurs, and by which the nerve-supply to the cells and protoplasmic contents of the 

 sensitive organs takes place. He also notes that the muscular fibres show no strias, 

 either transverse or longitudinal, and that the elytras, after Haswell's description, have a 

 double cuticle superiorly and inferiorly, two layers of cells, and an intermediate fibrous 

 layer. They contain no cavity, but have a nervous plexus. They are evidently organs 

 of considerable sensibility. Amongst other interesting points he refers to the nerve- 

 supply of the palpi and dorsal cirri with their ganglia near the base of the terminal 

 division, the nerve-trunk in each breaking up into a tuft of cells in this region. 



Family III. — Polynoid^. 



Body more or less elongate; no facial tubercle, convex cephalic lobe; the base of 

 the tentacle arising from the middle anteriorly ; two lateral tentacles ; four eyes ; palpi 

 elongate. Peristomium, bearing the first foot, with long dorsal and ventral cirri, 

 and the ventral cirrus of the next segment long. Pharynx exsertile, muscular, 



Fig. 19. 



Alimentary apparatus of Harmothoe imbricata. — A. W. 



cylindrical, with papillae round the margin ; horny jaws. Intestinal casca shorter than 

 in the Aphroditidde, slightly branched; first foot bearing only a few minute bristles 



