PACIFIC COAST OLIGOCHiETA. 81 



The glaiulular part of the prostate which commences at the anterior bend of 

 the organ consists of two or possibly of three layers. The inner lining consists of only 

 one layer of eiiithelial cells with ovoid nuclei. These long cells appear to be sur- 

 rounded by a narrow zone of fibrous or perhaps muscular tissue with few nuclei. 

 But by far the greatest part of the prostate consists of fibrous tissue with numerous 

 small roundish nuclei, with here and there a cell being visible, and with a few cells 

 of a glandular appearance (fig. 68), especially toward the circumference. In cross- 

 section the anterior part of this prostate is triangular in outline, while the muscular 

 part is always circular, and in size always thicker. The very narrow part of the 

 prostate which j)enetrates the body-wall is strongly muscular of the same general 

 structure as the free muscular part. The general structure of the prostate appears 

 similar to the one of Pontodriliis hesperidum as described by Beddard. He has 

 pointed out the absence of a regular layer of glandular cells in the prostate of that 

 species, and it is possible that this construction of this organ which thus ap- 

 proaches that of Ocnerodrilidfe, is not a species but a generic character, if it does not 

 prove to be of even greater value. 



Vascular system. There are a dorsal and ventral vessel, but no subneural, nor 

 any subintestinal vessel, and no thyphlosole. The two main vessels are connected 

 with hearts in x, xi, xii, xiii, the most posterior one of which is found in somite xiii, 

 immediately in front of the sacculated intestine. This heart is the largest, the others 

 gradually decrease in size forward. The posterior part of these vessels are entirely 

 free of brown cells. The ventral vessel is forked in somite ix in two parallel 

 lateral vessels, there being no central vessel left. These two branches are always of 

 unequal size, both being situated immediately under the oesophagus (fig. 04 v. v.) In 

 the somites anterior to x, these branches of the ventral are connected by laterals with 

 the dorsal vessel. In one specimen the ventral fork commenced in xii (fig. 64). 



Between the dorsal vessel and the ventral forks there are connecting vessels, 

 one pair in each of the somites v, vi, vii, viii and ix. To the ventral parts of these 

 connecting vessels are attached oblong glands, wiiich again are surrounded by a coat- 

 ing of globular brown cells. These glands do not extend clear to the dorsal vessel, 

 but end laterally before reaching it. The nature of the glandular cells appear the 

 same as those of the pharynx, staining in exactly the same way. The cells of these 

 septal glands are more numerous in the anterior somites, gradually diminishing 

 posteriorly, while the opposite is the case with the free round cells which are more 

 numerous in the posterior glands (figs. 29 gl. and 71 (jl.) 



Nephridia (figs. 71 and 72). These organs commence in somite xiii, or in the 

 same somite as the ovaries. The first two anterior nephridia are furnished with a 

 .smaller covering of peritoneal cells, but already in xvi do the nephridia attain their 

 full size, as in all posterior somites. 



The nephridia are built upon the same general princijjles as those of Argilo- 

 philus, Deltania, Ocnerodrilus and Phrenicodrilus, as well as of Lumbricus as shown 

 by Benham. We find here the corresponding ducts, canals, lobes, etc., and a gen- 



