48 



OLIGOCHAETA 



Fisr. 



II. 



is in fact no room for doubt that these ' salivary glands' in Odochaetus multiporua 

 are nephridia, modified doubtless to perform some function other than that performed 

 by the nephridia in the other segments of the body — though physiological observations 

 are -wanting as to -what this function is. In Rhinodrilus ecuadoriensis Benham 

 has described the first pair of nephridia as somewhat different in appearance from 

 the remaining organs and as opening into the buccal cavity. Such glands also occur 

 in Acanthodrilus annectens and in its near ally Acanthodrilus palvdosus. In certain 

 earthworms there are a pair of large nephridia occupying the first two or three 

 segments of the body, which appear to resemble those of Odochaetus already described ; 

 such glands occur in Pontoscolex (see woodcut), where they were originally termed 



by Peekier 'glandes k mucosit^'; I showed that these 

 organs are undoubtedly nephridia ; they do not, however, 

 actually open into the gut, but so near to it that when 

 the anterior segments are, as is occasionally the case in 

 this worm, inverted, the orifice is actually sheltered by 

 the inversion. These glands cannot be really distinguished 

 from the ' peptonephridia ' of Odochaetus, etc. 



Spencer described in the Australian Megascolides 

 australis a number of fine tubes opening into the buccal 

 cavity, which are clearly nephridia ; in that worm the 

 nephi'idial system is of the diffuse kind ; and the tubes 

 lying in the anterior section of the body open into the 

 buccal cavity. The difference between the condition 

 which characterises this worm and that found in Odo- 

 chaetus is simply that there are numerous openings 

 instead of only a single one on each side. It seems 

 reasonable to suppose that the two organs are referable 

 to precisely the same category. Curiously enough the 

 same presence of numerous nephridial tubes opening 

 into the buccal cavity occurs in the Eudrilid Libyo- 

 drilus; in that worm there is a fine network of tubes in the walls of the buccal 

 cavity, opening here and there into the interior of that cavity. In all these cases 

 it will be observed that the nephridia which are connected with the anterior part 

 of the alimentary canal show precisely the same modifications as the nephridial 

 tubes whicli are not so connected, but which open directly on to the exterior. 

 There are in both cases paired and diffuse nephridial tubes. There can be no 

 doubt, it would seem, that the buccal cavity of these tropical earthworms, like 



PONTOSCOLEX CORETHHL'EUS. 



(After Perrier.) 



g. c. Cerebral ganglia. 6. Buccal cavity. 

 p. k. Pliaiynx, os. Oesophagus, g. a. First 

 nephridium Cglande & mucosit^'). o.g. 

 External orifice of same. 0.8. Second 

 nephridium. n. Nerve cord. /. Vacuities 

 in muscular layer for implantation of 

 setae. 



