1116 DR. J. STEPHENSON OIN THE OLIGOCH^TA OF THE 



and fewer will be seen in any transverse section. Still diminishing 

 the width of the lumen, two cells, and finally one single cell, will 

 go all round the lumen — i. e., only one cell will be seen in any given 

 transverse section of the tube, and the lumen will be described as 

 intracellular. There is thus really no reason for assuming the 

 nephridial nature of these tubules of the Euchytrseidse, and in my 

 opinion they should not be called nephridia. 



The third group of structures — the bulb- like organs — are even 

 more unlike nephridia; nor, except for their assumed connection 

 with the tubular organs first described, could it ever be supposed 

 that they were nephi-idial. It is possible that they are, as has 

 been suggested, vestigial remains of the tubules ; they are con- 

 nected to the same dorsal diverticulum of the alimentary canal as 

 these. In Enchijtrams albidics, however, I find, along with the 

 typical tubules, and just in front of and lying against the narrov;' 

 proximal part of these, rather indefinite groups of cells somewhat 

 similar to the bulb-like organs. To establish the homology of the 

 bulb-like oi^gans with the tubules it would be necessary to ascer- 

 tain definitely whether they do or do not occur along vrith these, 

 and whether or not intermediate forms exist. 



The second group of organs, then — the dorsal and venti-al 

 " peptonephridia" of the genus Henlea, — may provisionally be 

 taken to be nephridia. But there is no evidence whatever of 

 their digestive function, and I propose for them the name 

 oesophageal nephridia. 



The first group — the sinuous tubules — are quite possibly not 

 nephridia at all. Since the alternative nH,me salivari/ glands has 

 long been in use for them, I would reject the name peptonephridia 

 in favour of this. 



The third group — the solid bulb-like organs — do not seem to be 

 nephridial, and their function, if they have one, is quite unknown. 

 I propose a purel}^ descriptive term, the postphavT/ngeal bulbs, as 

 most suitable for them. 



The Genus Henlea. 



Henlea is a large genus, and contains species showing a wide 

 varietj^ of structure. Characteristic of a number of species are 

 the oesophageal sacs in or about segm. viii. ; and the question 

 arises whether the presence or absence of these sacs should not be 

 made the basis of a separation into two genera, or at least sub- 

 genera.. 



This course has already been proposed by Friend (7, 8) — forms 

 with oesophageal diverticula to be called Henlea, those without to 

 receive the name Henleanella. In the second of the papers just 

 referred to, Friend remarks that it would be advisable to make a 

 third group for those species in which the alimentary tube dilates 

 gradually to form the intestine. In a subsequent paper (9) 

 Friend proposes a different criterion for the third group, viz., the' 

 origin of the dorsal vessel in the region of the clitellum (in most 



