STRUCTURE OF EARTHWORM ALLIED TO NEMEBTODRILUS. 547 



described in the Oligochseta. As will be seen from fig. 19, 

 the muscle connecting the two pairs of setse lies within the 

 chamber. The membrane which forms the walls of the 

 chamber is nearly homogeneous in appearance^ with a covering 

 and lining of epithelium only recognisable by the nuclei. 



§ Alimentary Canal. 



The alimentary canal of Libyodrilus presents certain im- 

 portant differences from that of other Eudrilidse. There is in 

 the first place no trace that I could discover of oesophageal 

 glands, or of those impaired ventral pouches termed " chylus- 

 taschen " by Michaelsen, which occur in so many Eudrilids. 



The position of the three gizzards is another point of interest. 

 In Heliodrilus and Hyperiodrilus there are a larger 

 number of gizzards, which are situated as in Lumbricus at 

 the junction of the oesophagus and intestine ; the three gizzards 

 of Libyodrilus occupy a similar position. 



In his memoir upon the classification of earthworms Perrier 

 remarked upon the occurrence in all the Anticlitellians of the 

 gizzard behind the organs of generation and the contractile 

 hearts of the vascular system ; from this group he distinguished 

 both the Post- and Intra-clitellian worms by the fact that the 

 gizzard was placed in front of the essential organs of repro- 

 duction. 



This distinction held good until my own discovery of 

 the position of the gizzards in the two Eudrilids above 

 referred to. In some forms — for instance, a Teleudrilu s — the 

 gizzard has the forward position which characterises the 

 majority of worms belonging to Perrier's two groups of Intra- 

 clitellians and Postclitellians ; but I am disposed to think 

 that the arrangement of these organs found in Heliodrilus, 

 Hyperiodrilus, and Libyodrilus will prove to be more 

 characteristic of the group. There are no particular reasons 

 that I can see for placing the Eudrilidse in the neighbourhood 

 of the Lumbricidse, and thus one of the characters of the latter 

 group can no longer be regarded as distinctive. Dr. Horst 



