236 CALIFORNIA ACADEMY OF SCIENCES. 



pouch is of the same general structure, and as far as I 

 can see varies only slightly as to form and number of 

 parellel blood vessels. The description given here of 

 the pouch in Oaierodrilus Beddardi may therefore in a 

 general way be applied to those of the other species 

 too, Ocnerodrilus occidentalis has of all species the 

 simplest diverticala furnished with the least number of 

 blood vessels. 



The pouch contains only one single room, widest at the 

 middle, or near the middle, and tapering towards both 

 ends, but especially so towards the distal end. But this 

 interior cavity of the pouch does not exactly correspond 

 in form to the exterior form of the organ, which tapers 

 more towards the distal end than the inner cavity does 

 (fig. 12). The wall of the pouch is traversed longitu- 

 dinally by a number of ridges consisting of blood vessels, 

 which lie close enough to almost touch each other, but 

 which do not anastomose (tig. 20). They collect in the 

 distal end (fig. 20, c. I. v.) and emerge as one single 

 vessel (c. I. v.), the lateral vascular blood vessel which 

 longitudinally traverses the body (fig. i, /. v) from the 

 pouch towards the prostomium and somite i. The 

 distal end of the pouch is directed forward and down- 

 ward, resting heavily on the anterior septum between 

 somites viii and ix, pressing the septum forward. The 

 longitudinal blood vessels originate from a single stout 

 blood vessel in the tubular intestines. This vessel does 

 not appear to emanate directly from the dorsal vessel 

 above it, as I have not been able to see a direct connec- 

 tion, but it comes apparently from a very short sub-dorsal 

 vessel which connects the two hearts in somites x and xi, 

 and which is partially or entirely covered by the intestine. 

 This vessel, first described by Beddard, does not exist in 

 all species, but owing to its fragility it is difficult to de- 

 termine its presence except in live specimens. 



