212 W. B. BENHAM. 



of Cryptodrilus;^ but see above as to whether large nephridia 

 are really present in this genus unaccompanied by a network. 



Brachydrilus possesses four nephridia per somite_, all 

 alike. 



In a large number of genera the anterior nephridia — 

 both in those retaining a network and those with lai*ge 

 nej)hridia — are more or less modified. For instance, Beddard 

 was the first to show for Ac. dissimilis that a group of 

 tubules on each side of the pharynx is connected, by 

 means of a strong duct, with the buccal cavity ; the same is the 

 case withDichog aster andDigaster — all genera in which the 

 nephridia are in the form of a network elsewhere in the body. 



In Megascolides, Baldwin Spencer has described and 

 figured the presence of numerous nephridial tubules around 

 the pharynx, which open separately into the cavity of the 

 alimentary tract. 



In other cases, e. g. Typhseus and Deinodrilus, the tubules 

 of the network are much more abundant in the first two or 

 three somites, but do not communicate with the cavity of the 

 pharynx. 



We are, therefore, entitled to consider that these anterior 

 nephridia are used by the worm for some other purpose in addi- 

 tion to excretion: they are probably used for softening or other- 

 wise acting on the food, either when the everted buccal region 

 has seized the food, or previously to this. How the external 

 aperture of a group of tubules has shifted from its position on 

 the body-wall to the pharyngeal wall, and how at the same 

 time, in some cases, the numerous apertures have united into 

 a duct, we do not know. We can only form conjectures on the 

 subject. The epiblast is known to grow in at the blastopore, 

 so as to form the lining of the pharynx ; and the shifting of 

 the nephridiopores may perhaps be connected with this 

 invagination. 



I have used in my diagnoses of the genera the term 

 "pepto-nephridium"" to indicate this modification of the 



1 Beddard describes a similar alternation in Ac. rosce and Ac. dissimilis. 

 '^ n£7rrw = I soften. 



