NOTES ON SOME OF THE POLYCH^TA. 347 



ventral vessel is covered by large epithelial cells, which , 

 on its under aspect become aggregated into a plate with 

 lateral ridges, forming the genital gland (PI. VII, fig. 2). 

 From these ridges the ova (or spermatozoa) are budded 

 off into the coelome.* The alimentary canal shews very 

 well the relationship of the intestinal caeca to the intestine 

 itself. Prolongations of these caeca are carried up into 

 the dorsal protuberances (PI. VII, figs. 1 and 5). Like 

 Bourne, I have not discovered any communication between 

 the scale cavity and the body cavity ; the epithelium cover- 

 ing the surface of the knob is entire, even over the attach- 

 ment of the muscle. Moreover, the epithelial cells bearing the 

 cilia on the *' branchiae " are quite as large as anywhere else, 

 and there are bands of muscle and connective tissue between 

 the superficial epithelium and the wall of the caecum. The 

 intestine is lined by columnar ciliated epithelium in one or 

 more layers. The epithelial layer is frequently folded, but 

 the folds do not affect the muscular wall. The folds are 

 epithelial only ; the muscular wall is extremely thin, con- 

 sisting of a very few fibres, arranged, the inner layer 

 circularly, the outer longitudinal. The caeca open into the 

 alimentary canal by funnel-shaped openings. The funnel is 

 lined by columnar ciliated epithelium, the cilia being very 

 long and pointing towards the cavity of the intestine (PL VII, 

 fig. 5). The caeca are branched and send prolongations 

 into the dorsal protuberances, as above stated. The funnel 

 has a layer of circular muscle, slightly thicker than that 

 forming the body wall of the intestine. The cells lining 

 the caeca are glandular and secretory (PI. VII, fig. 5), and 

 frequently shew clear superficial portions which often contain 

 concretions. I can scarcely agree with Haswell in considering 

 that intestinal respiration goes on to any great extent, at 



* See Haswell, *' Monograph on the Australian Aphroditida," Proc. 

 Linn. Soc, N.S.W., vol. vii. 



