AN ATTEMPT TO CLASSIFY EARTHWORMS. 211 



GoehlicVs drawing of the funnel of the nephridium of Lum- 

 bricus is wrong ; and in the various genera we find nephridia 

 with more and with less complicated convolutions of the tubule ; 

 for instance, Microchseta and Moniligaster or Ehino- 

 drilus. The character of the muscular region or '^duct" 

 also varies. 



In many cases it is, as in Lumbricus, a mere continua- 

 tion of the tube ; in other cases the muscular region is, 

 in proportion, very much larger, and the tube does not 

 enter it at its extremity, but at some point along its 

 side, so that the muscular region is produced as a 

 ''caecum,^' or bladder; and to some extent the families are 

 in part characterised by possessing either a simple " duct " 

 or a " caecum/^ 



The family Eudrilidse, for instance, all possess simple 

 nephridia ; the tube is comparatively short, and the duct simple 

 and in many cases ill-marked. In the accompanying diagrams 

 I have inserted the nephridia — so far as I have been able to 

 obtain information on the point — in order to show, first, the 

 presence or absence of a " caecum ;" and secondly, the somite 

 in which the series commence. 



In the family Rhinodrilidae all the genera have csecal 

 prolongations of the nephridial duct, more or less marked. 

 And frequently this caecum is less developed in the most 

 anterior than in the greater number of nephridia : for example, 

 Urobenus and Microchaeta; in the latter genus the 

 muscular portion attains the greatest relative size, and the 

 coiling of the tubule the greatest complexity to be found 

 amongst earthworms. In Rhinodrilus the more anterior 

 nephridia have a simple duct, those more posteriorly possess a 

 caecum. 



Plutellus is noticeable for the alternation, from somite to 

 somite of the position of the nephridiopore, which is placed 

 in front of the second or the fourth seta on each side, counting 

 from the most ventral seta. 



Perionyx saltans, A. G. B., presents a somewhat 

 similar condition, and according to Fletcher, certain species 



