I06 CALIFORmA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



valves, enabling the typhlosole to discharge superfluous 

 blood into the intestine. The advantage of such canals is 

 apparent in a typhlosole of such large dimensions as that of 

 Pontoscolex. 



Chloragogen Cells. — (figs. 24, 26, 37.) The chloragogen 

 cells of the dorsal vessel are of a different structure from 

 those of the intestine. They lack the granules possessed 

 by the latter and they stain less intensely with aniline stains, 

 such as eosin. The chloragogen cells of the intestine are 

 much longer on the dorsal side, gradually diminishing later- 

 ally. The long dorsal cells are separated from each other 

 by very narrow interstitial cells with narrow nuclei (fig. 37 

 a). Further down the sides of the intestine no such inter- 

 stitial cells are found. 



Corresponding to the long dorsal chloragogen cells we 

 find similarly very long epithelial cells on the opposite and 

 inner side of the intestine (fig. 36) ; they are, however, 

 slightly shorter than the chloragogen cells. Laterally the 

 epithelial cells narrow down in the same way as the chlora- 

 gogen cells on the opposite side of the blood-sinus. 



Vascular System. — The dorsal vessel is much enlarged, 

 occupying about one-fifth of the body-cavity in somites XI 

 to XVII, though even posterior to the latter segment it is of 

 considerable size and of nearly the same thickness. The 

 dorsal vessel is not strictly double, as for instance in Ponto- 

 scolex hawaiiensis Beddard, but it may be said to be rudi- 

 mentary double. By this I mean that cross-sections show 

 that in certain places, probably in the center of the somites, 

 the vessel is divided through the center by an upright bar, 

 which undoubtedly represents a diaphragm dividing the 

 vessel longitudinally. After entering somite X the dorsal 

 vessel narrows down. The supraintestinal vessel is enlarged 

 in two or three somites, the enlargement beginning just in 

 front of the sacculated intestine in XVII and extending for- 

 ward as far as XII, at which point it becomes much narrower. 



There are two pairs of hearts in XI and XII, both con- 

 nected with the supraintestinal vessel. There is considerable 

 difficulty connected with the counting of the septa, owing 



