14 A 



Canadian Arctic Expedition, 1913-1$ 



colour of the living specimens. An inspection of this collection indicated that 

 more than one species was represented, and this was confirmed by subsequent 

 examination of cleared specimens and serial sections of selected individuals. 

 Not all of the material was sectioned and, since specific identification depends 

 upon such procedure, the identity of many of the worms was judged from t In- 

 external examination of cleared specimens and a comparison of the results with 

 those obtained by a study of the sectioned specimens. Most of this collection 

 belongs to a variety of Enchytraeus hyalinus (Eisen). The other species repre- 

 sented (Henlea sp. (a) and Mesenchytraeus johanseni n. sp.) are referred to 

 elsewhere. Unfortunately, the original description of hyalinus is meagre, 

 certain important structural features being unmentioned. 



CHARACTERISTICS. Length, about 11 mm. Maximum diameter, about 

 0-5 mm. Somites, about 50. . Colour " white " according to collection record; 

 alcoholic specimens yellowish brown. Setae straight; those of a bundle equal 

 in size; 2-3 in lateral bundles, mostly 3; almost inyariably 3 in ventral bundles, 

 except in immediate vicinity of extremities. Clitellum on 12-13; moderate in 

 size; incomplete on mid-ventral surface. Prostomium blunt; rounded; smooth. 

 Lymphocytes sparse; small; ovoid to circular. Brain about 1-8 times longer 

 than wide; lateral margins divergent caudad; anterior margin very slightly 

 concave; posterior margin straight or very shallowly concave; nearly circular 

 in transverse section through middle. One pair peptonephridia arising from 

 mid-dorsal part of oesophagus in 4; strands arising independently but almost in 

 contact; unbranched; thick-walled; somewhat contorted; each strand extend- 

 ing ventro-laterad from point of origin; thin-walled, somewhat spherical expan- 

 sion in middle of length of each organ, walls differing in structure from adjacent 

 ones; both organs confined to 4. Dorsal blood-vessel arising in 14. Anteseptal 

 part of nephridia small, comprising little more than mere nephrostome; post- 

 septal part large, efferent duct arising from posterior end of postseptal part. 

 Spermiducal funnel about three times longer than wide; sperm duct short, 

 confined to 12. Penial bulb of the typical enchytraeid type as defined by Eisen 

 (1905 :7-8); consisting of separate and distinct sets of glands, each opening 

 independently on surface of body; mainly composed of two well-developed, 

 multi-cellular, spherical glands or " cushions " on each side of body, arranged 

 in longitudinal sequence and close together but not in contact; sperm duct 

 opening to exterior independently of anterior gland on its ectal side; cells in 

 glands apparently all of same kind. 



DISCUSSION AND DESCRIPTION. 



When compared in detail with the original description of Enchytraeus 

 hyalinus. (Eisen) (1879 : 26-27), it is noted that the correspondence is very close 

 for all of those features mentioned, with the exception of the form of the sperma- 

 thecae. It appears that the specimens from Nova Zembla on which the original 

 description was based had spermathecae which showed an atrium-like enlarge- 

 ment of the duct. No such enlargement appears in the spermathecae of the Can- 

 adian specimens. There is some resemblance to the spermathecae in Enchytraeus 

 marinus as described by Moore (1902 : 80-82). 



LYMPHOCYTES. The original description also states that no " perigastric 

 cells " (lymphocytes) are present in the Nova Zembla material. If such obser- 

 vation was correct, another difference appears since lymphocytes do occur in 

 the specimens from northern Canada. 



DEVELOPING OVA. Masses of developing ova occurred in the usual position 

 in 12. In addition, ova were observed in the body-cavity scattered at' intervals 

 from 29 to 42 inclusive. The remoteness from the oviducal pores makes it 

 doubtful if such ova ever pass to the exterior. 



