304 W. ELAXLAND BENHAM. 



ment is absolutely wrong — at least for the nephridium of 

 Lumbricus herculeus, Savigny (= L. agricola, HoJ0F- 

 meister, = L. terrestris, Linnaeus) — a careful examina- 

 tion of a living nephridium will readily show. How far the 

 description of the excretory organ holds for all species of 

 Lumbricus I am not yet in a position to say; but from 

 examination of those of Allolobophora, sp., Criodrilus, 

 and other genera^ I can confidently state that the cilia are 

 confined to certain limited tracts of the "narrow tube " 

 (and to the whole of the " middle tube ''). 



There are three such ciliated tracts in the narrow tube : 

 the first extends from the funnel to just beyond the point 

 labelled " b ^' (in fig. 2) — it reaches, that is to say, just round 

 the bend of the tube where the latter enters the second loop ; 

 this tract was quite correctly described by Gegenbaur. The 

 second ciliated tract is at the apex of the middle loop (F), 

 between the letters c, c' (fig. 2). I have observed that the 

 extent of this tract varies to a very slight degree ; but the 

 cilia are always here, in the outer bend of the tube. The 

 third tract of cilia lies in loop G ; it commences (at e) where 

 the narrow tube bends sharply upon itself, and extends about 

 halfway along this loop, ceasing at e' (fig. 2). 



Gegenbaur thought that the cilia recommenced at this point 

 e, and extended right along to the end of the narrow tube. 



It is comparatively easy to satisfy oneself as to the existence 

 of these isolated tracts of cilia, either by observation on 

 the living nephridium, or in series of sections ; for if the whole 

 tube were ciliated we should expect the cilia to be visible in 

 every section of every tube if they were visible in any one 

 section, but such is not the case; not only in Lumbricus, 

 but in other genera of earthworms, I have sections in con- 

 secutive series which show cilia only in certain parts 

 (fig. 15). 1 

 Wherever these cilia occur they are arranged in a spiral 



1 Howes (' Biological Atlas '). in liis figure of a portion of the third loop, 

 shows correctly the structure of the different tubes, and represents one part 

 of the "narrow tube" ciliated, and the parallel portion nou -ciliated. 



