206 Studies in Enchytraeid Worms 



certain special cells on the outer surface of the intestine. As a rule 

 these cells commence about the fifth segment, and extend to the posterior 

 extremity of the body, save that it is no unusual thing for their number 

 to be greatly reduced in the region of the girdle. In this respect Henlea 

 fragilis shows a decided departure from the rule, and the absence of 

 chloragogen cells from the first twenty to five-and-twenty segments 

 is a marked characteristic. I have not. found them in any instance 

 in front of segment 20. We may now sum up the main points. 



Definition of Henlea fragilis. 



Length about 15 mm. Segments 55 to 60. Setae 4 to 8, the inner- 

 most in each bundle usually the shortest. Girdle extending over 

 one-third of segment 11, the whole of the 12th segment and two-thirds 

 of segment 13. Brain slightly longer than broad ; spermathecae without 

 glands or diverticula. Three pairs of septal glands; one pair of oeso- 

 phageal in segment 8, behind which, in the same segment, the dorsal 

 vessel arises. Nephridia with small anteseptal portion ; duct imme- 

 diately behind the septum as long as the postseptal. Sperm funnels 

 only slightly longer than broad, the duct not centrally placed, penial 

 bulb of moderate dimensions of the lumbricillid type. Coelomic 

 corpuscles large, broadly elliptical; chloragogen cells commencing 

 behind the 20th segment. Salivary glands present, one dorsal, the 

 other ventral, attached to the epithelium of the intestine in segments 

 4 to 7, branched at the ends. 



Observations made on a large Dumber of specimens in various 

 stages of development show the following among other points of 

 interest : 



(1) The number of setae seems to increase with age. 



(2) The ampulla of the spermatheca appears to enlarge as the 

 adult stage is reached. 



(3) The brain tends to become convex posteriorly as the worm 

 grows older. 



(4) The salivary glands undergo modification as the animal 

 develops. 



Systematic position of Henlea fragilis. 



It is not an easy matter to assign to this species of Henlea its 

 rightful place. We have agreed, however, for the present, to eliminate 

 all species which do not possess oesophageal glands (Henleanella), as 

 well as those species (Hcnleana) whose dorsal vessel is of intraclitellar 



