28 GUSTAF EISEN, ON THE ARCTIC OLIGOCIL^ETA. 



The length of the body about 10 — 20 in. m. 



The width of the same 0,5 m. m. 



The number of segments about 64, hardly defined at all. 



The three last ones are destitute of spines, and narrower but longer than the 

 preceding ones (fig. 21, d). 



Habitat. This species has a very wide range of distribution, perhaps more so 

 than any one of the other species described here. It is found in the following loca- 

 lities: Matotschkin 73° 20', Besimenaja 72° 50', Dicksons harbour 7o° 25', Jefremow Ka- 

 men 72° 40', Mesenkin 71° 20', Dudino 69° 15', Werschininskoj 69° 5', Potapovskoj 68° 

 55', Chantoiskoj 68° 5', Troitskoj 65° 45', Surgutskoj 62° 50', and Vorogova Selö 60° 50'. 

 The last named is the most southern locality, but it seems very likely that this species 

 inhabits the whole country visited by the expedition. 



Of this species two forms, at least what regards their external appearance, are 

 very frequent, and apparently inhabit the same localities. One form is long and 

 narrow, say 15 — 20 m. m. long, by 0,5 m. m. broad, and translucent or nearly so, the 

 internal organs being seen through the epidermis. The other is also long, but much 

 broader, say 15 — 20 millim. long by 1 millim. wide, the epidermis being opaque 

 and the colour milkish white, preventing the internal organs to be seen through the 

 integument. But as I have as yet not succeeded in finding any anatomical differences 

 whatever, I do not hesitate in the least to consider both forms as belonging to one 

 species, for which I propose the above name, alluding to the extreme hardness of the 

 cuticle, both in the translucent and the opaque forms. 



Together Avith the two following this species forms a natural subdivision charac- 

 terized by both the anterior and posterior margins of the cerebral ganglion being con- 

 vex, which places them, according to my opinion, on a higher degree of development 

 compared with any other Enckytrceidw hitherto described. 



6. Neoenchytraeus dxirus n. sp. 

 Pl. XII. Fig. 23. 



The supra-cesophagial ganglion is nearly triangulär, being broadest behind. Its 

 anterior margin is convex (fig. 23, f and g). 



The receptacle is furnished near the top with several bladderlike follicles consti- 

 tuting the receptacle proper (fig. 23, h). 



The vesicle of the efferent duct is oval, and the penis is nearly as large as the 

 vesicle itself (fig. 23, s). 



The inner duct of the segmental organs is nearly as broad as the middle lobe, 

 but not so long. The outer duct is long and narrow or about 2 l /s times longer than 

 the middle lobe, but many times narrower (fig. 41). 



The perigastric cells are of two kinds, one is opaque, furnished with nucleus and 

 cell contents and of round or oval or elliptical form. The other kind, the most com- 

 mon one, is much larger, circular or irregular, destitute of any cell-contents whatever, 

 except a well defined nucleus (fig. 23 q and r). 



