10 A Canadian Arctic Expedition, 1 913-1 S 



given by Michaelsen (1900 : 69), it was later reported under other names from 

 Solowetski island in the White sea, Denmark, Germany, Bohemia, France, and 

 Italy. 



Henlea tenella (Eisen.) 



Two mature enchytraeids belonging to the genus Henlea were collected 

 under old driftwood logs on the tundra at Collinson point, Alaska, September 

 27, 1913. These specimens agree in so many particulars with the description 

 of Henlea (Archienchytraeus) tenella (Eisen) that they are placed provisionally 

 under that name. Unfortunately, the description of this species, like many of 

 the older ones, is very brief, indefinite with respect to some features, and entirely 

 lacking in information concerning certain important anatomical characters. In 

 order to facilitate future revision, the principal characters of the specimens 

 studied are given below. 



CHARACTERISTICS. Length, 10 8-12 mm. Diameter, in region of clitellum, 

 about 0-42 mm. Somites, 52-53. Colour of alcoholic specimens uniformly 

 dark brown. Prostomium short; very blunt; rounded; smooth. Setae almost 

 straight; inner ones of bundle slightly smaller than outer; 2-5 per bundle in 

 lateral rows, usually 3-5; 2-6 per bundle in ventral rows, usually 4-6; number 

 per bundle decreasing at posterior end of body. Clitellum only slightly devel- 

 oped; inconspicuous; on 12-13; diameter of body slightly or not at all greater 

 at clitellum than at adjacent somites; continuous around body. Lymphocytes 

 scanty; elliptical; variable in size. Brain 0-19 mm. long, 0-12 mm. wide; 

 depressed; lateral margins slightly divergent caudad; posterior margin deeply 

 emarginate; anterior margin slightly concave; one pair supporting strands from 

 apices of posterior lobes, another pair from latero-posterior margins-, both pairs 

 extending caudo-laterad to body-wall. One pair of diminutive peptonephridia 

 in 5 on ventral side of digestive tract; slightly branching. Chloragog cells in 

 dense layer about digestive tract for its whole length. Oesophagus expanding 

 abruptly into intestine in 8. Intestinal diverticulum in 8; entirely surrounding 

 digestive tract; conspicuous in transverse section; tubular in structure, tubules 

 uniting with intestine in posterior part of 8. Origin of dorsal blood-vessel in 

 posterior part of 8 or beginning of 9. Nephridia with small, anteseptal part; 

 postseptal part large, compressed; efferent duct as long as postseptal part, 

 arising from ventral surface of latter near septum. Spermiducal funnel small; 

 somewhat cylindrical; expanded near middle; length about twice maximum 

 diameter. Sperm duct much contorted; confined to 12. Penial bulb small; 

 of lumbricillid type; body of organ with but one set of cells. Spermathecae 

 very small and simple; wall thinned to form ampulla without increasing diameter 

 externally; no diverticula; inconspicuous glands at ectal opening of duct; 

 spermathecae uniting dorsad of digestive tract to form small, common tube; 

 latter connecting with lumen of digestive tract; ental portions of spermathecae 

 very slender. 



DISCUSSION AND DESCRIPTION. 



When compared with the original description of Henlea tenella (Eisen, 

 1879 : 17), differences appear in the number of setae per bundle, the length and 

 breadth of the brain, and the shape of the spermiducal funnel, but these disagree- 

 ments are minor and cannot be regarded as having any particular importance. 

 It is not known whether the original material from which Henlea tenella was 

 described had an intestinal diverticulum, penial bulbs, and dorsal blood-vessel 

 of the kinds herein described for the Collinson point specimens or not and an 

 element of uncertainty thus exists in the identification. For the purpose of this 

 report none of the anatomical features demand special mention except the 

 intestinal diverticulum, the penial bulb, and the spermathecea. 



