OXFORD UNIVERSITY SPITSBERGKN EXPEDITION. 1117 



species the dorsal vessel arises considerably in front of the 

 clitellum) ; this third group to be called Ilenleana. These divisions 

 are apparently conceived as subgenera (cei.'tainly so in the first 

 two papers). 



Friend's suggestion as regards the oesophageal diverticula seems 

 particularly useful. But it is illogical and inconvenient to have 

 a double or triple principle for the simultaneous division of a 

 group; the subgroups will not be mutually exclusive. What, for 

 example, would become of a form with both cesophageal diver- 

 ticula and a posterior origin of the dorsal vessel — at the same 

 time a Henlea and a Heuleana ; oi', for that matter, of one with a 

 posterior origin of the dorsal vessel and no diverticula — both 

 a Heuleana and a Henleanella% 



In 1910 Cejka (3) established a genus Hepatogaster for two 

 species which are obviously nearly related to Henlea, tlie chief dis- 

 tinctive characters being the gradual dilatation of the oesophagus 

 to form the intestine, the presence of a mass of tubules closely 

 surrounding the alimentary tube in segm. viii., and of character- 

 istic longitudinal canals in the epithelium of the hinder end of 

 the digestive tract. The value of the first distinction is doubtful, 

 e. g. in Henlea heleotro'phxijS I am not certain whether or not the 

 intestine can be said to arise as a sudden dilatation of the 

 alimentary tube ; at first 1 thought not, but later I altered this 

 in my notes by adding the words " this might be called a sudden 

 widening, and so would agree with the diagnosis of Henlea." 

 Tiie second of Cajka's points of distinction occurs also in Henlea 

 tithulifera Welch and H. moderata Welch ; while, as Welch 

 remarks (23), the value of the third distinction as a generic 

 character remains to be demonstrated. Welch retains the genus, 

 though with some doubt, Delphy (5) also considers it as distinct. 



The oesophageal diverticula of Henlea, when present, may have 

 walls which are fairly smooth and even, or which are variously 

 folded; and I regard the "tubuliferous" condition of H. tubu- 

 lifera, etc., and of HejKctogaster, as simply a higher degree of this 

 folding, followed by fusion between the adjacent folds and 

 between the two sacs above and below the alimentary tube. A.n 

 intermediate condition is that of H. nasuta as described by 

 Michaelsen (10, cf. especially pi. fig. 1), where the folding of the 

 walls is veiy considerable, and there is only a very small central 

 free space, but the two sacs are not fused above and below the 

 oesophagus. The difiierence between Henlea and Hepatogaster 

 seems, in fact, to be less than that between Henleanella without 

 sacs and Henlea with them. 



For the present, then, 1 would retain the genus Henlea, but I 

 would recognize three subgenera : — 



(1) Henleanella, with no oesophageal diverticula. 



( 2) Henlea, with oesophageal sacs. 



(3) Hepatogaster, with a mass of tubules surrounding the 



alimentary tube and taking the place of the sacs. 

 I would disreo-ard the sudden or g-radual widening of the tube 



