341 



The Structure and Development of the Nephridia 

 of Arenicola distata Stimpson. 



Ralph S. Lillie. 



With Plates 22—25 and one Textfisrure. 



1. Introdiictory. 



The ne})hriclia of Arenìcola weve first suggested to me as a sub- 

 jeet of anatomical aud embryological iuvestigation by Dr. C. 0. 

 WiiiTMAX, duriug the season of 1896 at the Marine Biological Labo- 

 ratory of Wood's Hole. The work then begun was subsequently 

 interrupted for a time; aud the greater part of the work described 

 in the following paper was completed during the 3'ears 1898 — 1901, 

 at the Marine Biological Laboratory and in the HuU Zoölogical 

 Laboratory of the University of Chicago. 



I take pleasure in expressiug my best thanks to Dr. Whitman 

 for bis continued interest and criticism. My thanks are also due to 

 Dr. C. M. Child of the University of Chicago, for much helpful 

 Information, especially with reference to the early developmeut; and 

 to my brother. Professor F. R. Lillie of the same University for 

 Constant aud valuable assistance. 



The nephridia of several species of the genus Arenicola bave 

 Iteeu at various times figured and briefly described in systematic or 

 Huatomical treatises; iiud in several instances bave been made the 

 subject of special iuvestigation. Claparède 1868) and Fauyel (1S99) 

 have given brief descriptious of the nephridia of A. Gruhii and 

 A. ecaudata respectirely. The greater number of such studies bave 

 beeu made on A. marina^ investigations on the nephridia of tliis 

 form have been made by Cosmovici (1880), Cunnixgham (18S7), 

 Benham (1891, 1893), Kyle (189Ö); and more recently by Gamble & 



