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OLIGOCHAETA 



the segments which these organs always occupy in the genus Acanthodrilus, diflFer 

 from those of other species in not possessing any diverticula ; ' esse sono assolutamente 

 prive di diverticoli, fatto che ho verificato anche coUe sezionij sapendo che il Beddaed 

 considera la presenza dei diverticoli nelle spermateche degli Acantodrili come costante,' 

 says Dr. Rosa (6, p- 518). The second point in which this species diflfers from the 

 genus with which it was associated by Rosa is in the position of the calciferous 

 glands ; these are present to the number of a single pair only. In other Acantho- 

 drilidae there may be only a single pair of these organs ; but where there is one pair 

 only (as in 0. multiporus) that pair is placed far back in the seventeenth or in the 

 eighteenth segment. More characteristic of the family is the existence of three pairs ; 

 all the members of the genus Benhaynia have three pairs. 



More recently I have examined an Acanthodriloid worm which is not far distant 

 from ' Acanthodrilus ' spegazzinii in structure. This species was referred by myself 

 (25) to a separate genus on account of the four following characters (two of which 

 were described by Rosa in his species) : — 



(i) Spermathecae without diverticula. 

 (3) Calciferous glands one pair in ix. 



(3) Spermiducal glands tubular, lined by a single layer of cells. 



(4) Setae of segments xvii-xix, unmodified. 



The other characters of the genus given in the above diagnosis are not alone 

 sufiicient to distinguish it from other Acanthodrilidae, but taken collectively serve 

 to strengthen the arguments for its separation. Since my paper was published 

 EiSEN has met with two other species (4), which he assigns to the same genus ; 

 the characters of these species necessitate but a slight revision of the generic 

 characters. Both of them have spermathecae with diverticula. There is no doubt, 

 however, in my mind that they are rightly assigned to this genus. In the following 

 table the characters of the species are given: — 



