SEGMENTAL ORGAN OF PODARKE OBSCURA. 25 1 



June were fixed as well as males obtained throughout the sea- 

 son. Flemming's fluid and sublimate-acetic were found to be 

 the best fixatives. The material was then sectioned and stained 

 in iron hematoxylin. 



I wish to thank Professor Wilson who suggested the work and 

 under whose direction it has been completed. Thanks are also 

 due Professor Treadwell and Dr. McGregor for their aid in col- 

 lecting material. 



The nephridia of Podarke are present in pairs in every segment 

 of the body except the first few. A general cross-section of the 

 body (as is seen in Fig. i) shows a fairly typical annelid struc- 



FlG. I. X II S- A partly diagrammatic transverse section of body. A', ectoderm ; 

 D.L.M, dorsal longitudinal muscle; CM, circular muscle; /, intestine; O.M, 

 oblique muscle; V.L.M, ventral longitudinal muscle; Nrv, nerve; N, nephridium. 

 (The inner end corresponds to the cavity seen in Figs. 2 and 3. ) 



ture, i. e., the outer layer of epithelial cells, a thin layer of circu- 

 lar muscles, and two pairs only of longitudinal muscles, a ventral 

 and a dorsal pair. In such a section the nephridium is found 

 following the dorsal surface of the ventral longitudinal muscle 

 band. It is a simple tube with practically no convolutions, open- 

 ing to the exterior laterally on the ventral surface, at outer limit 

 of the ventral longitudinal muscles. (This opening is definitely 

 shown in Fig. 4, the transverse section did not pass through the 

 opening.) The nephridium extends along the upper surface of 

 the muscle, then bends diagonally inward in the segment toward 

 the median plane and forward toward the anterior dissepiment 



