H. Friend 107 



species, though it is very difficult, in the light of the most recent 

 research, to define the genus. The brain, to which no allusion has 

 been made in any of the foregoing diagnoses, is usually of quite a 

 definite type, being as a rule hardly longer than broad, and more or 

 less concave behind. The spermathecae vary ; salivary glands (pepto- 

 nephridia) may be present or absent, as may also the oesophageal glands. 

 The setae may be of the Fridericia type, i.e. shortest in the middle of 

 each bundle, or of equal length, and the oesophagus may or may not 

 go sharply into the intestine. Sometimes there are glands at the 

 ectal opening of the spermathecae in the intersegmental groove 4/5, 

 at other times they are absent. The coelomic corpuscles may be 

 discoid, as in the assumed type, or irregularly shaped; the salivary 

 glands may or may not open into the intestine, while their position 

 varies greatly. Sometimes they are dorso-lateral, at other times they 

 are ventrally placed, while in a third group one gland is dorsal and 

 the other ventral. Once again the dorsal vessel may arise in segments 

 7, 8 or 9, in which case we usually find the oesophageal glands near its 

 point of origin, where also the oesophagus suddenly merges in the 

 intestine; or the vessel may originate in or near the clitellum, the 

 oesophageal glands being in this case wanting, while the oesophagus 

 passes gradually into the intestine. When the oesophageal glands 

 are present there may be only one (Henlea moderata Welch), or we 

 may find a pair (Henlea nasuta Eisen). In at least one instance (Henlea 

 ventriculosa D'Ud.) they number four (or two pairs). 



Welch has well observed that "Taking the genus as a whole, there 

 is a remarkable variation in the different organs. Henlea puteana 

 Vejdovsky is unique in having two pairs of spermathecae. The species 

 of the genus can be grouped in one of several ways according to the 

 criteria, which may be the character of the setae, the presence or absence 

 of intestinal diverticula (Darmtaschen or oesophageal glands), the 

 presence or absence of peptonephridia (salivary glands), the place of 

 origin of the dorsal vessel, or the presence or absence of diverticula 1 

 on the spermathecae." The nearest allies are Buchholzia and Bryo- 

 drilus. A newly described American species (Henlea moderata Welch) 

 with its solitary oesophageal gland brings us very near to these genera, 

 which are also closely approached by other species in other directions. 



As a step towards a more satisfactory definition I suggested some 

 time ago (4) that it would be well to form at least two groups, calling 



1 The original reads "ampullae," but what we call "diverticula" are clearly intended. 



