96 On a new Genus of OUgochceta. 



IV. Affinities of the Genus Gordiodbilus. 



The relationships of this genus are not very plain, I was 

 at first disposed to place it near Acanthodrilus, on account of 

 the double atrial pores and the independence of the opening 

 of the vasa deferentia. It does not, however, in other 

 respects show any likeness to that genus ; and the points of 

 resemblance cited are not perhaps so important as they at 

 first appear. 



With the Eudrilidse there is not very much that this genus 

 has in common. Indeed the only structure which at all 

 recalls that family is the ventral calciferous pouch of segment 

 ix., unless, that is to say, the large ventral set^ of Oordio- 

 drilus tenuis be regarded as a further resemblance. 



The description which has been given above of these 

 ventral pouches shows that there is no great agreement in 

 detail with any Eudrilid ; but it might be considered to 

 represent a somewhat degenerate " Chylustasche," differing 

 principally in the reduction of the folding of the lining 

 membrane. The question is, whether the existence of the 

 unpaired median calciferous gland is an important resem- 

 blance or not. It is true that the Eudrilida? alone agree with 

 Gordiodrilus in possessing median ventral pouches. Among 

 the Enchytreidge a median dorsal pouch is met with. 



The reduction of the atria to a single pair in Gordiodrilus 

 ditheca is a fact of some importance : it is paralleled by the 

 similar reduction met with in the earthworm named by 

 myself Neodrilus monocystis ; in all other respects G. ditheca 

 agrees as closely with the other s])ecies of the genus in which 

 I have placed it as does Neodrilus with Acanthodrilus. 

 These facts seem to indicate that it is not necessary to lay too 

 much stress upon the duplication of an organ. Plenty of 

 other similar instances will at once occur to any one con- 

 versant with this group. 



The atria of Gordiodrilus in their minute structure most 

 resemble those of Ocnerodrilus ; these two genera, together 

 with Moniligaster, are the only terricolous forms wliich agree 

 with the aquatic genera in having but a single row of cells 

 forming the lining of the atrium. I am inclined to believe, 

 however, that the simplification of the structure of the atrium 

 thus produced is not necessarily a proof of afhnity with the 

 only other genus in which this has taken place in an exactly 

 similar way ; but as in other respects the genera Gordio- 

 drilus and Ocnerodrilus are not far apart, and as they must 

 both be undoubtedly referred to the large family Crypto- 



