DESCRIPTIONS OF GENERA AND SPECIES 593 



respects interesting; as in all the Eudrilidae the main interest naturally centres in 

 the reproductive organs. 



There are the usual two pairs of testes present in segments x and xi. Sperm- 

 sacs of a racemose form lie in the two segments xi and xii. Nothing is said as to 

 the mode of connexion between the sperm-ducts and the terminal glands ; the latter 

 open into a common muscular sac, which communicates with the single external 

 orifice upon segment xvii. Corresponding to each gland is a longish muscular tube, 

 to the proximal end of which are attached retractile muscles ; each of these tubes is 

 filled with a granular mass— evidently the secretion of the gland. At the proximal 

 end of the retractor muscles, where they become continuous with the musculature of 

 the body-wall, is 'a slight outgrowth of finely-granular structure, and in this lie 

 two small irregularly shaped horny bodies.' These are regarded by Michaelsen as 

 rudimentary penial setae ; and the muscular tubes with their retractors as penes ; 

 that this interpretation is probably correct is shown by the fact that in one 

 individual they were protruded. 



The female organs of generation are no less remarkable ; the median opening of 

 the spermathecal sac lies on the boundary line between segments xiv and xv ; this 

 orifice leads into a small sac from which arises on each side a short muscular canal; 

 these are considered to be the spermathecae. 



These tubes open into the interior of two large thin-walled sacs, which com- 

 municate with each other above the gut in the thirteenth segment. The large sacs 

 are completely filled with developing ova, and are to be looked upon as particularly 

 large ovarian sacs. These large pear-shaped ovarian sacs join the receptacula ovorum 

 by means of a short tube, near to the opening of which into the ovarian sac opens 

 also (into the ovarian sac) the oviduct. Michaelsen figures a slight swelling upon 

 the ' ovarian sac ' just in front of the receptaculum ovorum ; I myself should be 

 inclined to look upon this as the true ovarian sac, which has become, as in 

 Lihyodrilus, almost indistinguishable from the spermathecal sac owing to the 

 disappearance of the narrow connecting canal, which is present, for instance, in 

 Poly tor eutus. The muscular tubes communicating with the external pore may 

 possibly be true spermathecae (i. e. of epidermic origin). 



In regard to other structures Metadrilus shows no important differences from 

 other Eudrilidae ; the absence of nephridiopores may perhaps be accounted for by 

 the existence of an integumental plexus as in Lihyodrilus. The strong gizzard is in 

 V ; the oesophagus has no caeca of any description ; the intestine begins in xvi, and 

 has no typhlosole, 



4G 



