Davenpobt. — Urnatella gracilis. 



PLATE III. 



ABBREVIATIONS. 



an. Anus. 



atr. Atrium. 



clc. Cloaca. 



cl. ds. Closing cell of septum. 



cl. hp. Hepatic cells. 



eta. Cuticula. 



di. sep. Dissepiment. 



ga. Stomach 



gn. Ganglion. 



in. Intestine. 



kmp'drm. Kamptoderm. 



loph. atr. Atrial ridge. 



Fig. 18. Median section of calyx of Urnatella. Camera drawing made from sev- 

 eral adjacent sections. X 405. 

 " 19. Section through plane of line " Fig. 19 " on Fig. 18. X 96. 

 Figs. 20, 20*. Longitudinal and cross sections through chief nephriaium of calyx. 

 X 610. 

 " 21", 2P, 21=. Tliree sections taken across nephridiura of one individual at 

 different places, to show nature of the lumen and wall. Fig. 21* nearer 

 the distal end of tubule. Fig. 21°, third section from mouth of tubule, 

 at point of union of two nephridia into one. X 700. 



