260 J. H. ASHWOIITH. 



receives a large number of fine vessels (or lacunae; see below, 

 p. 201) from the walls of the stomach and intestine. Near 

 the anterior end of the stomach tlie dorsal vessel presents a 

 well-marked enlargement, which is apparently constant, as it 

 is present in the other specimens examined. In my largest 

 example tliis swelling, whicb, following Danielssen, we may 

 call the blood-reservoir, is 7 mm. long and 1'2 mm. thick in 

 its widest part. Anterior to this the dorsal vessel resumes 

 its normal diameter for a length of about 4 — 5 mm. and then 

 abruptly dilates into a conical bulb, which Danielssen named 

 the heart, about 1*5 mm. in diameter. The vessel then nar- 

 rows to its previous size, and gives off four pairs of stout 

 afferent vessels which run along the corresponding dia- 

 phragms to the gills. On reaching the pharynx the dorsal 

 vessel divides into two branches, which soon break up 

 into smaller vessels supplying the pharynx, buccal mass, 

 brain, etc. 



The ventral vessel arises near the mouth, by the union of 

 small vessels from the prostomium and peristomium. It runs 

 along the whole length of the animal jnst above the nerve- 

 cord. Soon after its origin it receives four pairs of efferent 

 branchial vessels, and thus becomes almost at once a thick 

 trunk. In each of the post-branchial segments the venti'al 

 vessel gives off a pair of slender vessels suppl3ang the 

 nephridia, setal sacs, and neighbouring tissues. Besides 

 these paired branches the ventral vessel gives off to the 

 stomach six median vessels, the first of which is situated 

 just behind the fourth diaphragm, and the last at the level 

 of the thirteenth setae. In the posterior portion of the 

 animal, behind the twentieth segment, the ventral vessel 

 bears a large number of short, blind, usually curved out- 

 growths, which are covered with a layer of cells, probably 

 chlorogogenous, and corresponding to the similar tissue 

 clothing the blind outgrowths of the ventral vessel of 

 Arenicola marina (Gamble and Ashworth, 1898, pi. 2, 



fig- 5)- 



Along the whole length of the intestine there is a pair of 



