206 OLIGOCHAETA 



SUPERPAMILY LUMBRICULIDES. 



This group includes the families Naididae, Tubificidae, and Lumbriculidae. 



Vaillant (6) united the two first of these families into one ; the chief distinction 

 drawn between them by d'UdeKEM was the fact, that in the first asexual propagation 

 by budding takes place — a phenomenon quite unknown in the Tubificidae. Vaillant 

 is disinclined to allow that this is a distinction of first-rate importance, and I agree 

 with him. In the first place, among the parallel group of the Polychaeta, the forms 

 which multiply by budding are not in every case very widely separated from those 

 which do not exhibit this mode of development ; in the second place, it is not 

 easy to draw a hard and fast line between this budding and the breaking up of 

 a Lumbriculus into pieces which are severally capable of independent growth. 



As to structure, it is difficult to fix upon characters which absolutely divide the 

 two families. Ilyodrilus is a Tubificid in, perhaps, most of its characters ; the 

 position, for instance, of the generative apertures is as in other Tubificidae ; the 

 vascular system has the complications that are found in other members of that 

 family, but are not found in the Naids. The spermiducal glands, however, are 

 Naidiform. JJncinais is another annectent form ; it certainly shows the cephaiization 

 so characteristic of, but not universal in, the Naids ; on the other hand, the sexual 

 organs ^ are situated further back than in any other Naid in which their position 

 is known; finally, the setae are entirely uncinate — a state of affairs not found in 

 any other Naid, but often met with among the Tubificidae, e.g. in Limnodrilus. 



The Lumbriculidae are, at first sight, rather far removed from the Naids and the 

 Tubificids ; but, at best, the separation cannot be a wide one ; compared, for 

 example, to the characters which separate two such well-marked families as the 

 Geoscolicidae and the Eudrilidae, the differences between the Lumbriculidae and 

 the Tubificidae are by no means great. The main difference is the fact that in the 

 Lumbriculidae there are two pairs of sperm-ducts ; this character is quite universal 

 if we except certain dubious forms, to be dealt with immediately. Li Sutroa, 

 however, which Eisen (2) has justly referred to the Lumbriculidae, one of the 

 two pairs of sperm- ducts is decidedly smaller than the other, and seems to show 



' It is possible, however, that, as Eenham has pointed out, the 'testes and ovaries' of Uncinais are 

 in reality sperm-sacs and egg-sacs ; in this ease the position of the generative organs may not be so nnlike 

 that of other Kaids. 



