80 THE PHYSIOLOGY OF EARTHWORMS 



Cordier (1934) that resorption of particles occurs in the nephri- 

 dium of oHgochaetes. Particulate matter injected into the coelom of 

 the worm is found to accumulate in the wall of the middle tube, 

 the finer particles being taken up at the proximal end, the larger 

 particles at the middle, of the middle tube. Cordier postulated that 

 the process of water resorption may occur in the wide tube of the 

 nephridium by analogy with the distal convoluted tubule of the 

 vertebrate kidney which has a similar cytological make-up. 

 Ramsay (1949b) finds that none of his experiments refute this 

 idea, but neither do they make it any more likely. Similarly he 

 throws little light upon the likelihood of salt-resorption taking 

 place in the same region. And there for the moment the matter 

 rests. 



Nephridial Activity under Changing Conditions 



More information about the activity of the nephridia under 

 changing external conditions has been presented by Roots (1955, 

 1956). She isolated nephridia completely from the body into saline 

 solution, either frog Ringer diluted with an equal volume of 

 M/400 NaHCOs or 66% frog Ringer alone. Though survival in 

 these solutions was often prolonged, up to 22 hours, it is perhaps 

 unfortunate that no one has yet undertaken the plea by Ramsay 

 (1949b) that further knowledge of the ionic composition of the 

 coelomic fluid of the earthworm is necessary in order that isolated 

 tissue experiments may be more realistic. However, Roots obtained 

 nephridia from L. terrestris and A. chlorotica and subjected them to 

 media of various strengths. When the saline is suddenly diluted the 

 nephridiostome cilia become more active, wdth an increased 

 amplitude of beat, returning after a variable period to the original 

 state. Long-term treatment with hypotonic solutions leads to arrest 

 of the cilia, more quickly in L. terrestris than in ^. chlorotica. Vesicles 

 form in the cells of the nephridiostome under these conditions. 



Hypertonic solutions, on the other hand, decrease the activity of 

 nephridial cilia. The cilia again become active within 30 seconds 

 after replacement in isotonic saline. These temporary changes in 

 activity should be compared with those described by Ramsay and 

 mentioned above. 



The concentrations of media used by Roots varied from 30- 

 300% frog Ringer (diluted with MHOO NaHCOs) and bear little 



