II.— THE ENCHYTRAEIDAE.i 



By Paul S. Welch. 



Eight of the collections "contained mature enchytraeids representing six 

 species distributed among four genera. Immature specimens not permitting 

 specific identification were also present. Serious difficulties encountered in 

 connection with some of the material necessitated provisional identification of 

 two species. These difficulties were mainly due to incomplete, original descrip- 

 tions of arctic Eurasian species made many years ago when the Enchytraeidae 

 were little known and before the taxonomic importance of several anatomical 

 features was recognized. Since the original Eurasian specimens are not avail- 

 able, the descriptions and accompanying illustrations are the sole dependence, 

 thus preventing positive identifications, at least in some cases. For this reason, 

 brief anatomical descriptions of the representatives of each species treated in 

 this report have been included and it will be understood that they are based 

 exclusively upon the characters of the Canadian specimens. Characteristics of 

 immature specimens are listed only in case it is unlikely that they are juvenile 

 individuals of a species already discussed. 



Henlea nasuta (Eisen.) 



A collection of enchytraeids made July 7, 1915, from wet moss roots on a 

 tundra, Bernard harbour, Northwest Territories, contained two specimens, both 

 mature, and the posterior portion of another which exhibit the characters of 

 Henlea nasuta (Eisen.) 



Characteristics. — Length, 19.3 mm. Diameter, about 1.0 mm. Somites, 

 about 58. Colour of alcoholic specimens light brown. Prostomium small; 

 short; pointed. Setae 4-6 per bundle in ventral rows; 3-5 per bundle in lateral 

 rows; straight; inner ones of bundle slightly smaller. Clitellum well developed ; 

 on 12-fl3; continuous- around body. Lymphocytes scanty; ovoid to circular. 

 Peptonephridia present; one dorsal and one ventral strand; both arising from 

 digestive tract in 5; both in close contact with wall of latter; branches pro- 

 jecting into coelom in 6; ventral strand longer than dorsal, extending to 8. 

 Oesophagus expanding abruptly into intestine in 8. Two conspicuous intestinal 

 diverticula in 8, each opening independently by single opening into latero- 

 ventral part of the digestive tract; bag-shaped; reflected cephalad; slightly 

 flattened laterally; large central cavity with many deep folds of lining. Dorsal 

 blood-vessel arising in 8. Nephridia with small anteseptal and large postseptal 

 part; efferent duct arising from anterior ventral surface of latter. Spermiducal 

 funnel about 1§ times longer than wide. Sperm duct confined to 12. Penial 

 bulb of simple lumbricillid type; body of bulb composed of but one set of cells. 

 Spermathecae with no definite demarcation between duct and ampulla; few, 

 small, unicellular glands at ectal opening; duct about one-half as long as 

 ampulla; body of ampulla ovoid, decreasing entad into very fine tube above 

 digestive tract and uniting with similar tube from corresponding spermatheca 

 on opposite side of body to form common duct; apparently uniting with alimen- 

 tary canal in posterior part of 5. 



Distribution. — Henlea nasuta was originally described by Eisen (1879 : 20- 

 21) from specimens collected all along the Yenisei river, northern Siberia, at 

 localities varying from 60° 50' to 72° 40' n. lat. According to the synonymy 



'Contribution from the Entomological Laboratory, Kansas State Agricultural College, 

 No. 34. 



