SOME RECENT MEMOIRS UPON OLIGOCHJETA. 195 



the two latter (which are allied to Tubifex) are contractile 

 branchiae, not branched however, on some of the posterior 

 segments of the body. More numerous are indications of 

 affinity with the leeches. I may, in the first place, refer 

 to that group of parasitic Oligochaeta, once placed among 

 the leeches but now usually allowed to be true Oligochaeta, 

 for which Vejdovsky has proposed the name of Disco- 

 drilidae on account of their posterior sucker. An American 

 genus Bdellodrilus has lately been studied with care by 

 Moore whose results entirely confirm the placing of the 

 worms amono- the Oligochaeta and their removal from the 

 leeches. Their chief points of likeness to the Hirudinea are 

 (1) absence of setae ; (2) existence of jaws ; (3) presence of a 

 sucker ; (4) median unpaired character of reproductive pores. 

 The first and last of these characters are, however, 

 found in a few undoubted Oligochaeta, for instance, Anachczta, 

 as its name denotes, has no setae, and besides Mr. Moore 

 describes large gland cells in Bdellodrilus which may re- 

 present setigerous cells of Oligochaeta. As to the median 

 generative pores they are very frequent among Oligochaeta. 

 The reproductive organs themselves are decidedly upon the 

 Oligochaetous pattern. The gonads are entirely free from 

 their ducts, and there is a single spermatheca, a structure 

 entirely wanting among the true leeches. The male ducts 

 are two pairs, opening freely by ciliated mouths into the 

 coelom and uniting into a common terminal atrium. Their 

 arrangement recalls that of the Lumbriculidae. The ovaries 

 are proliferations of the coelomic walls and their contents 

 escape to the exterior by a slit in the body walls lined by 

 epithelium, a kind of rudimentary oviduct paralleled in the 

 Enchytraeidae, and in the Eudrilid Nentertodrilus. There 

 is nothing leech-like about the reproductive organs, except- 

 ing the terminal penis — a structure, however, which is 

 also found in many Eudrilids and in some other Oligo- 

 chaeta. The conclusions of the author that the Disco- 

 drilidae are Oligochaeta slightly modified for a parasitic 

 life is quite borne out by their structure. We may admit 

 at the same time that this modification is in the direction 

 of the leeches. 



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