THE ANATOMY. NEPHRIDIA 



45 



lO. 



network of Ferichaeta, etc., but to be a branching of the epiblastic duct of the 

 nephridium. The duct of the nephridium of Allolobophora is said by Vejdovsky (9) 

 to branch in the integument, and I have already referred to the way in which 

 that duct runs for a considerable distance between the two muscular coats before 

 opening on to the exterior. In some few of the genital segments it seemed to me 

 that the paired nephridia in Lihyo- 



drilus were absent, but that the net- ^" 



work was present. One cannot help 

 being reminded by these facts of the 

 excretory system in the Nematoda and 

 the Acanthocephala ; in both these 

 groups the excretory system seems to 

 occur in the shape of tubes running 

 in the integument ; the Lemnisci of 

 the Acanthocephala (and an homo- 

 logous structure has been described 

 in certain Nematodes) are processes of 

 the body-wall occupied by a quantity 

 of tubes which are doubtless of an ex- 

 cretory nature. Eliminate the paired 

 nephridia of Lihyodrilus and the re- 

 maining part of the excretory system 

 would be exceedingly like that of the 

 two groups of worms referred to. To 



a certain extent I have followed the development of the excretory organs in Lihyo- 

 drilus s the integumental network is, as one would suppose, a secondary development ; 

 the first part of it to appear is a contiauous longitudinal duct on each side connecting 

 the nephridia of following segments. I imagine that Vejdovsky is correct in regarding 

 the longitudinal duct connecting the nephridia of Lanice conchilega (described by 

 Meyeb^ and Cunningham^) as formed out of the terminal epiblastic part of the 

 nephridia — the ' bladder' of the nephridium of Lumbricus — which have become fused 

 together ; it is therefore of some interest to note that a similar single connexion is 

 first developed in Lihyodril-us. The fabulous (?) connecting duct of Polygordius is 

 perhaps of the same nature. 



The genera Megascolex and MegascoUdes — probably others will be discovered when 



LIBYODEILUS INTEGUMENTAL NEPHEIDIAL 



NETWOEK. 



I. Dorsal blood-vessel. 2. Supra^oesophageal blood-vessel. 

 3. Infra-oesophageal blood-vessel. 4. Ventral blood-vessel. 

 5. Nephridium. 6. One of longitudinal trunks of integu- 

 mental network. 7. Fine canals of network. 



' Quoted by Lang in his monograph on the Polyclada in Fauna u. Flora des Golfea von Neapel. 

 '■' On some points in the Anatomy of Polychaeta. Q. J. Mior. Sci. vol. xxviii. 



