358 OLIGOCHAETA 



various types will be found treated of in the introduction to the description of the 

 genera and species of the subfamily Cryptodrilidae. On the other hand, the Peri- 

 chaetidae are obviously nearly connected, through the remarkable forms with eight 

 setae in anterior segments, with Cryptodrilus and its immediate allies. 



Certain peculiarities of structure are found only in the family Megascolicidae, and 

 some of these occur in all of the three subfamilies into which it is divided. The principal 

 of these is the peculiar form of the spermiducal gland, which I term ' lobate ' ; this kind of 

 spermiducal gland is found in all the Perichaetidae with a very few exceptions, and in 

 a great many of the Cryptodrilidae ; at first sight it may appear not to exist in any 

 Acanthodrilid ; but the genus Diplocardia has spermiducal glands, which are, at 

 any rate, a step in this direction. In no other family of the Oligochaeta do glands 

 of this particular description exist. In this family only are there nephridia which 

 ramify within the coelom and open on to the exterior by numerous pores ; the 

 integumental network of certain Eudrilids, which is derived from a series of paired 

 nephridia being a different thing. 



Among the higher Oligochaeta the Megascolicidae are the only genera which have 

 spermathecae furnished with diverticula of a different structure to the pouch ; and, 

 furthermore, there are only a few exceptions to the universality of these spermathecal 

 appendages in the group. 



The very general position of the male pore upon the eighteenth segment of the 

 body is a characteristic of the Megascolicidae ; in no genus are the male pores far 

 from this segment, if they are not upon it. 



These are the principal facts which lead me to associate together the three families 

 Perichaetidae, Cryptodrilidae, and Acanthodrilidae, within what I may term a super- 

 family, Megascolicidae. 



It is noteworthy too that certain peculiarities of structure which occur in the 

 group are confined to it, and are found in more than one of its three families. 



The continuous circle of setae, so universal in the Perichaetidae, occurs nowhere 

 else among the Oligochaeta except in the Acanthodrilidae. Even in so rare a point 

 of structure as the enclosure of the dorsal blood-vessel in a coelomic space we find 

 that the only two examples, Deinodrilus benhami and Megascolides australis, are 

 in this group. The peculiar intestinal glands of Megascolex coeruleun are repeated in 

 Ty[>liMeu$. The peculiar condition of the gizzard in Perichaeta, occupying, as it 

 does, two segments, with a suppression of the intervening mesentery, is repeated in 

 the genus Typhueus. 



As to negative characters, these are numerous. The most striking, perhaps, though 

 by it the family does not contrast with the Eudrilidae, is the absence of specially 



