Volume XIII. May, iSgy. Number 3. 



JOURNAL 



ON THE STRUCTURE OF THE DISCODRILID 

 NEPHRIDIUM.i 



By J. PERCY MOORE. 



I. Number and Position of the Nephridia. 



Although no less than six^ accounts of the discodrilid neph- 

 ridium are already extant, these fail to furnish us with the 

 information necessary to a careful comparison of the organ with 

 its homologue in other annelids. Five papers dealing with the 

 general anatomy of Branchiobdella parasita and its varieties 

 contain accounts of the excretory organs, but of these only one, 

 that of Lemoine (25), was based upon investigations conducted 

 with a knowledge of modern methods of research. Though in 

 some respects more complete than its predecessors, Lemoine's 

 description adds little of importance to the earlier accounts, 



^ Contributions from the Zoological Laboratory of the University of Pennsyl- 

 vania. No. 5. 



2 Voinov has recently contributed, after the present paper v/as in the hands of 

 the publishers, a more complete and accurate account of the nephridium of 

 Branchiobdella parasita. I have seen only the preliminary account (Comptes 

 Rendus Acad. Sci., Paris, CXXII (1896), 1069-1071) with which in the main my 

 results agree. This author is to be credited with the first correct description of 

 the relations of the several regions of the nephridium. The " red gland " is identi- 

 fied as a folded canal ; and excretion by fragmentation of the peritoneal corpuscles 

 described. 



