Oligochaeta 15 A 



DISTRIBUTION. Thus far Enchytraeus hyalinus has been definitely known 

 only from Nova Zembla. The habitat of the original specimens is not given. 

 Friend (1912 : 222-223) has described, apparently with some hesitation, a variety 

 of hyalinus under the name densus from specimens existing under inland con- 

 ditions in England. The brief description of this variety corresponds closely 

 with that given above for the North American forms, with the exception of the 

 spermathecae. The structure of the penial bulb is not described and no com- 

 parison is possible. Until this variety densus is more certainly and more com- 

 pletely described, the writer- prefers to leave this arctic American variety without 

 a name. 



Mesenchytraeus johanseni, n. sp. 



As mentioned before, the collection made July 15, 1916, from moss roots 

 on Pihumalerksiak island (Cockburn point), Northwest Territories, contained 

 enchytraeids other than Henlea sp. and Enchytraeus hyalinus var. About ten 

 of the specimens show characters of the genus Mesenchytraeus. All of these 

 specimens which were sectioned proved to be representatives of a new species 

 of Mesenchytraeus, which is named in honour of the collector. 



DEFINITION. Length, 12-14 mm. Diameter, about 0-7 mm. Somites, 

 55-57. Colour " white " according to field notes accompanying specimens; 

 light yellowish in alcohol. Prostomium blunt; smooth; rounded. Head pore 

 near tip of prostomium. Setae sigmoid; similar in size; 3-5 in ventral rows, 

 2-4 in lateral rows, fewer at extremities. Clitellum well developed; on f 11-13. 

 Lymphocytes scanty; ovoid. Dorsal blood-vessel arising in 22-23; cardiac 

 body present. Chloragog cells with heavy load of brownish-black pigment. 

 Nephridia with typical mesenchytraeid structure; anteseptal part small; post- 

 septal region large; efferent duct arising from ventral part of latter near septum. 

 Spermiducal funnel about one and one-half times longer than wide. Sperm ducts 

 elongate, extending caudad to 16 within ovisac; much contorted. Testes 

 massive; undivided. Sperm sac present; single; extending caudad to 

 16; within ovisac; bifurcating at posterior end. Ovisac present; extending 

 caudad to 16; bifurcating at posterior end. Penial bulb of mesenchytraeid 

 type; small; atrium present, largely within body of bulb, about five irregular 

 atrial glands extending into coelom; no accessory glands observed. One pair 

 spermathecae; few unicellular glands at'ectal opening; no distinctly differen- 

 tiated ampulla, body of organ and duct of about same diameter; each sperma- 

 theca joining digestive tract very near mid-ventral line in posterior part of 5; 

 each with two long, slender diverticula extending dorsad over alimentary canal. 



The above description is based upon a careful study of three mature speci- 

 mens. This species exhibits some resemblances to Mesenchytraeus solifugus 

 (Emery), but lack of agreement appears in such features as the amount of pig- 

 mentation, place of origin of the dorsal blood-vessel, number of atrial glands, 

 and presence or absence of accessory glands. 



Lumbricillus lineatus (Mull.) 



One specimen belonging to the genus Lumbricillus was collected under 

 sea-weed on the beach at Bernard harbour, Northwest Territories, June 12, 1916. 

 The posterior part of the body of the worm was badly deteriorated but fortu- 

 nately the anterior 19-20 somites were in a fair state of preservation and thus 

 specific identification was possible. The specimen lacked a little of being 

 completely sexually mature but the development of the various organs was 

 sufficiently completed to make it evident that the worm is Lumbricillus lineatus 

 (Mull.). 



