DAVENPORT, — Urnatella gracilis. 
PLATE IV. 
ABBREVIATIONS. 
an. Anus. mu. Muscle fibre. 
atr. Atrium. mu. ret. ta. Retractor muscle of tentacle. 
clc. Cloaca. neph. or per 
cl. cls. Closing cell. nph. | — re 
cl. fim. Flame cell. e. CEsophagus. 
cl. tb. Tubular cell. pa'chy.  Parenchyme. 
cta. Cuticula. rt. Rectum. 
di. sep. Dissepiment. spht. atr. Atrial sphincter. 
ec'drm. Ectoderm. sp'z. Spermatozoa. 
gn. Ganglion. te. Testis. 
int. Intestine. va. def. Vas deferens. 
Section through calyx at level indicated by line “ Fig. 22” in Fig. 18 
x 405. 
Section through 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. 
