22 GUSTAF EISKN, ON THE ARCTIC OLIGOCHiETA. 



which they differ consiclerably. The principal one is the supra-oesophagial ganglion, 

 the sliape of which seems to be constant, at least to judge from the few specimens I 

 have had occasion to dissect. 



In A. affinis there is no ring round the interiör opening of the efferent vesicle. 

 As to its nature in A. nasutus I hesitate very much. At first it seemed to me as 

 if it consisted of a härd chitinous layer, being of a different brown colour from the 

 rest of the vesicle, but I am now more inclined to believe it to be composed of the 

 tails of the spermatozoa, which are bent över and adhering to each other, either per- 

 manently or temporarily. I am led to this opinion partly because I never have found 

 a bundle of spermatozoa projecting as usual from the opening of the vesicle, as is the 

 case with most of the species, partly also because the ring itself very much resembles 

 a thick layer of adhering tails of spermatozoa. Fig. 10. f and g represent correctly the. 

 appearance of said walls, the former showing the vesicle from the side, the latter from 

 the top. 



The largest specimens of A. nasutus are by far the largest ones of the whole 

 genus Enchytrceus, and may easily be mistaken for true Lumbtici. Their front lobes 

 are very narrow and of a peculiar shape readily characterizing the species. 



9. Archienchytrseus profugus n. sp. 

 Pl. VII. Fig. 12. 



Syn.: 1872. Ei tel iy trams Pagenstecheri Ratzel, according to Eisen in Öfv. K. Sv. Vet. 

 Akad. Förhandl. N:o 1. p. 122. 



The supra-oesophagial ganglion is square and its postenor emargination shallow 

 (hg. 12. b). 



The receptaele consists of a short tube furnished at the top with a somewhat 

 shorter, eggshaped receptaele proper. The tube itself is surrounded along its whole 

 length by numerous glands (fig. 12. c). 



The vesicle of the efferent duet is square and the penis is of nearly the same 

 size as the vesicle itself (hg. 12. d). 



The segmental organs have the onter duet somewhat longer than the middle lobc, 

 but the inner duet or tube is very short, resembling those of N. Vejdovskyi and Stux- 

 bergii (fig. 34). 



The ovaries are small and situated in the ll ,h and 12 tk segments. 



The testes are deeply lobed, the lobes varying in size and form, being in some 

 specimens larger, in others smaller; always in the segments 9 and 10 (fig. 54 and 

 fig. 12. e, f, g and h). 



The spines are of the same length in each fasciele, 8, 9, 9, 8. 



The length of the body about 18 in. in. 



Its width about 1 m. m. 



The number of segments about 50. 



The colour is whitish or milky. 



