38 EISEN 



but they are certainly situated in the center of the windings, and do 

 not connect either immediately with the nephrostome, nor with the 

 posterior duct. There are at least 19 nuclei in a nephridium, not 

 counting the row situated transversely in the nephrostome. 



MESENCHYTR^US VEG^ sp. nov. 

 pi. Ill, figs. I and 2; text-fig. 15. 

 Definition. — Length 20 mm., width about i mm. Somites ^c^. 

 Prostomium pointed. Setae sigmoid ; ventrals : 7, 8, 8, 8, 8, 9, 7, 7, 7, 



8, 7, o, 6, 6, 6 5, 5, 4, 4, 3 ; laterals : 5, 5, 5, 5, 6, 5, 4, 4, 4, 4, 



o, 4, 3, 3. Sexual papillae not prominent. Brain broader than long, 

 anteriorly and posteriorly emarginated. Intestine with chloragogen 

 cells. Spermatheca very large, extending through several somites, 

 connecting with the intestine by a very narrow duct in VII or VIII ; 

 two diverticles ; the ampulla inflated, sig- 

 moid, tapering to the apex. Sperm-ducts 

 narrow and comparatively long. Atrium 

 and penis, which are wide, connected by a 

 narrow part. About 12 to 14 atrial glands 

 opening in the atrium in the same horizontal 

 plane. Penial bulb with one kind of gland, 

 Fig. 15. MesenchytrcBus ^bout four or five in the same plane. No 

 ^^'^' accessory glands. A thin but dense layer of 



pigment in the peritoneal membrane. No other pigment. Color of 

 the single specimen dark yellow. 



Locality. — Port Clarence, Alaska. Collected by Dr. Anton Stux- 

 berg, July 27, 1878, Vega Expedition. Owing to the fact that the 

 collection contains only a single specimen of this species, the descrip- 

 tion is necessarily meager. The characteristics, however, are so 

 prominent that the species cannot be confounded with any others so 

 far known. 



Spermathecce (p1. hi, fig. 2). — The most characteristic feature con- 

 cerns the spermathecae. As the accompanying figure fully illustrates 

 the structure of these organs no further description is necessary. 

 Their structure places this species in the same group as M. harrimani 

 and M. setchelh., in wdiich species the spermathecae are unusvially 

 large, connecting with the intestine in a somite posterior to V. These 

 species are all characterized by the inflated distal part of the sperma- 

 thecal ampulla. 



Spermiducal apparatus (p1. hi, fig. i). — Penial structure and 

 atrium characterized by the narrow part connecting them ; narrow 



