Davenport, — Urnatella gracilis. 



PLATE IV. 



ABBREVIATIONS. 



an. 

 atr. 

 clc. 

 cl. els. 

 cl. Jim . 

 cl. tb. 

 eta. 

 di. Sep. 



Anus. 

 Atrium. 

 Cloaca. 

 Closing cell. 

 Flame cell. 

 Tubular cell. 

 Cuticula. 

 Dissepiment. 



ec'drm. Ectoderm. 



gn. 

 int. 



Ganglion. 

 Intestine. 



Fig. 22. 



" -is. 



" 24. 

 " 26. 



26. 

 27. 

 28. 



29. 



Section through calyx at level indicated by line " Fig. 22" in Fig. 18 



X 405. 

 Section tlirough calyx above the last at level indicated by line " Fig 23 " 



in Fig. 18. X 405. 

 Longitudinal section through young stalk showing development of septum. 



X 405. 

 Transverse section through closing cells at base of calyx. Section passes 



through a flame cell at the left. The lower part of the section lies 



below the dissepiment, the position of which is indicated by the line 



di. Sep. X 670. 

 Longitudinal section through tentacle and atrial sphincter. X 405. 

 Two adjacent tentacles cut transversely near their bases. X 405. 

 Part of nearly median section of calyx, passing through cloaca and vas 



deferens. X 405. 

 Median section through nephridium aud adjacent organs of young calyx 



to show the development of the nephridium. X 1000. 



