THE ANATOMY. NEPHRIDIA 



i.-, 



Fig. 10. 



network of Perichaeta, etc., but to be a branching of the epiblastio duct of the 

 nephridium. The duct of the nephridium of Allolotophora 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 Libyo- 

 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 Libyodrilus 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 Libyo- 

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

 the first part of it to appear is a continuous 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 

 MEYER 1 and CUNNINGHAM 2 ) 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 Liln/odrilus. The fabulous (?) connecting duct of Polygordius is 

 perhaps of the same nature. 



The genera Merjascolex and Megascolides probably others will be discovered when 



LIBYODRILUS INTEGUMENTAL NEPHRIDIAL 

 NETWORK. 



i. Dorsal blood-vessel, i. Supra-oesophagoal blood-vnnL 

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

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

 mental network. 7. Vine canals of network. 



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

 3 On some points in the Anatomy of Polychacta. Q. J. Micr. Sci. vol. xxviii. 



