DESCRIPTIONS OF GENERA AND SPECIES 523 



(except Microscolex modestus) they do; but it might be replied to this that in 

 Dichogaster damonis, there are three pairs of tubular glands having the structure 

 of the spermiducal glands of these and other earthworms. 



Eliminate two of these three pairs and the condition found in the undoubtedly 

 Acanthodrilid genus Neodrilus is arrived at. I think it must be admitted that the 

 Acanthodrilidae have near relations to the Cryptodrilidae. At present, however, 

 they differ by the situation of the spermiducal glands and the sperm-duct pores 

 upon two or three consecutive segments. 



The genus Kerria seems to tend in the direction of the small group Ocnero- 

 drilidae^; it has, as has the genus Ocnerodrilus and its near ally Gordiodrilus, 

 spermiducal glands composed of only a single layer of epithelium; the spermathecae 

 have no appendices, and there is a single pair of caleiferous glands in the ninth 

 segment. If the description by Peekiee of the position of the spermiducal glands 

 on consecutive segments in A. obtusus be confirmed, there is another point of 

 similarity between Acanthodrilus and Qordiodrilus. But this has, in my opinion, 

 yet to be put beyond legitimate doubt. 



The genera of Acanthodrilidae. 



The family Acanthodrilidae can be divided up into several genera ; there can be 

 no doubt of the distinctness of Beinodrilus and Plagiochaeta, the characters of 

 which are given below. Whether the absence of the second pair of spermiducal 

 glands and spermathecae is sufficient to distinguish my genus Neodrilus is not by 

 any means so certain; the original description of this worm has been confirmed 

 (and added to) by Benham; in A. schmardae one of the two pairs of glands, and 

 similarly one of the two pairs of spermathecae, is decidedly smaller than the other; 

 this leads, therefore, in the direction of Neodrilus; moreover, we have in the not 

 far distant genus Gordiodrilus one species in which the spermiducal glands are 

 reduced to a single pair ; considering the close resemblance which Neodrilus bears 

 in other characters to the genus Acanthodrilus, I am of opinion, that it should not 

 be separated generically from such a form as A. dissimilis. 



In a recent paper KosA. has described a remarkable species of 'Acanthodrilus,' 

 which he named 'Acanthodrilus spegazzinii.' This Acanthodrilid has only one pair 

 of testes, and the spermathecae have no diverticula. In a worm which I have more 

 recently (25) described from the Pilcomayo river the same characters are found; in 

 addition to this the spermiducal glands are lined by a single layer of cells only ; it 



' Including Ocnerodrilus, Nanrwdrilus, ' and Gordiodrilus. 



3xa 



