THE ANATOMY. NEPHRIDIA 



35 



which passes to the exterior and opens on to it through a small contractile bladder ; 

 there appears to be no distinction here between the more or less glandular part of 

 the organ in other Oligochaeta. Bolsius has lately discovered that the lumen is 

 really a complex network. Among the Naidomorpha, the Lumbriculidae, and a few 

 Tubificids, the funnel (totally absent in Aniphichaeta and Chaetogaster) is followed by 

 an oval swelling coloured brown, and within which the nephridial tube appears to 

 be branched and to form a small network; Vejdovsky describes a network along the 



Fig. 6. 



NEPHEIDIUM OF LUMBEICUS. 

 (From Benham.) 



a-A the narrow part of tlie tube partly ciliated, h-j ciliated wider tube expanding at C into ampulla. 

 k-n. Wide tube. E. Muscular duct. I. Funnel. O. External orifice, t. Peritoneal layer, s. Muscular 

 fibres, r. Nucleus of cell. F. G. 2nd and 3rd loops of nephridium. 



course of the nephridial tubes of Chaetogaster; this matter will be referred to again 

 in considering the more complex nephridia of the earthworms. 



The nephridium, of Lumbricus. The most elaborate description of this organ 

 is due to Benham (9), whom we shall here follow. The nephridium is divisible 

 fii'st of all into two regions — one lying in the segment in front of that which bears 



F 3 



