530 OLIGOCHAETA 



exceptions are A. annectens and its near ally, A. paludosus a species which recalls 

 in some particulars the genus Octochaetus. It is indeed a question whether they 

 should not be incorporated in that genus. 



The following are the points in which the two species in question resemble the 

 genus Octochaetus: 



(1) The great prominence of the papillae bearing the atrial pores. 



(2) The completely double dorsal vessel 1 . 



(3) The presence of an anterior peptonephridium. 



(4) The attachment of the gonads to the posterior wall of the segment. 



The arrangement of the setae is also somewhat similar, but as in species which 

 are undoubtedly members of the genus Acanthodrilus (s. s.), such as A. georgianus, 

 &c., the setae are disposed in the same fashion, the resemblance is obviously of less 

 weight. In the two species above-mentioned the nephridia are paired, as in other 

 Acanthodrilus; but the muscular end sac so universal in Acanthodrilus is here 

 absent. There is thus a slight approximation to the diffuse nephridia of Octochaetus. 

 A final indication of affinity between A. annectens and A. paludosus on the one hand 

 and the genus Octochaetus is possibly afforded by the sperm-ducts which run in the 

 thickness of the body- walls. But as this also occurs in A . communis the resemblance 

 is perhaps less noteworthy. 



The table printed on pp. 532 and 533 will serve for the discrimination of the 

 species. I include the species of Octochaetus and Diplocardia. 



Two out of the three species described by PERKIER appear to me to be hardly recognizable ; this 

 is hardly the fault of the descriher, for he characterized them sufficiently to enable them to 

 be separated from each other ; there are not, however, enough points dealt with to fix their 

 position with anything like certainty in the present state of our knowledge of the genus ; it is 

 certain, though, that they are all members of the family Acanthodrilidae. One of these species 

 is, I believe, as was first pointed out by HORST, identical with that named provisionally A. layardi 

 by myself (0). I now give some notes about the two remaining forms. 



(l) A. dbtusus. This is a large worm, measuring about 700 mm. The male pores are said to be 

 on the nineteenth and twenty-first segments. Penial setae ornamented with spinelets. Dorsal pores 

 are present. Nephridia paired. A single gizzard in segments vii-ix. A pair of organs which 

 seem to be most probably the sperm-sacs are present in the twelfth segment (the thirteenth is 

 mentioned, but this seems most likely to be an error). It is suggested that they are the ovaries, 

 but, although the segment which contains them bears out this suggestion, the sketch given is 

 more like a pair of sperm-sacs. The spermathecae have no diverticula. The worm is from New 

 Caledonia. The difficulty which prevents me from placing this species in the genus Acanthodrilus 

 as here defined is, of course, the position of the male pores. Had it not been for the existence 

 of the American Diplocardia, I should have been tempted, in spite of PERRIER'S accuracy in description, 



1 Not, as in A. novae-zelandiae, single whore it traverses the septa. 



