1905.] NATURAL SCIENCES OF PHILADELPHIA. 385 



in Monopylephorus, and the somites are more elongated but similarly 

 ringed. In mature examples the clitellum is developed on X, XI, XII 

 and for a short distance on XIII. A pair of spermathecal pores 

 occurs far forw^ard on X just behind the furrow ^, and in line with the 

 ventral sets?, the male pores occupy the place of the ventral setae or 

 a little behind on XI, and the ovipores are minute slits in the furrow ^^. 



In young worms the color is pinkish, but in larger ones becomes deep 

 brownish or purplish-red, often very dark, and in mature worms always 

 very much darker than in Monopijlephorus cjlaber, a difference which is 

 probably due chiefly to the fact that the deep color of the chlorogogue 

 cells is untempered by the whiteness imparted by great numbers of 

 peritoneal corpuscles. 



The setfe are of two forms, one kind being hooked and bifid and the 

 other capillary and of very characteristic form. Both occur in the 

 dorsal bundles. In preclitellar somites there are usually 2 or 3 or 

 rarely even 4 of the former, with 1 or 2 or occasionally 3 of the latter 

 alternating with, or 1 on the ventral side of each of, the hooked ones. 

 Bundles of the middle region contain 2 hooked and 1 capillary seta, 

 and those of the posterior region 1 of each. Normally every dorsal 

 bundle except a few at the posterior end contains capillary setge, but 

 they are easily detached, and in some specimens fully formed ones are 

 absent from as many as one-half or more of the bundles, ^^^len more 

 than one is present they are usually of unequal lengths, the longest much 

 exceeding the diameter of the body. They are very slender and taper 

 regularly to the end, toward which they exhibit 2 or 3 very slight but 

 distinct spiral turns (fig. 11). Possibly this region may be slightly 

 flattened, though this appearance may be due to the lights and shadows 

 caused by the spiral turns. The short hooked setaj (fig. 9) are always 

 bifid, with the distal process decidedly longer unless worn or broken, 

 which is seldom the case. Ventral bundles contain hooked setae only 

 which are quite similar in form to those of the dorsal bundles but some- 

 what larger; those of anterior bundles of both rows are larger than the 

 posterior. Anteriorly the ventral bundles usually contain 3, in the 

 middle region 2. and posteriorly 1. As usual the ventral bundles are 

 wanting on XI, but those of X are not modified as copulatory "setae. 



The vascular system of this species is remarkably like that of Mono- 

 pijlephorus glaher, presenting a similar valvular dorsal vessel, chambered 

 and valvular lateral trunks, complex integumental plexus, and similar 

 mode of branching. As distinctive characters it presents a finer and 

 more numerously l^ranched integumental plexus, with a more conspicu- 

 ous longitudinal intersegmented trunk, and a greater number of sets 



