VoL. 2] Robertson.—Non-Incrusting Bryozoa. 239 
sheath (par. mus.). Likewise, extending from the base of the 
tentacles to the basal wall of the zocecium another band of re- 
tractor muscles is visible whose contraction draws the polypide 
within the zoccium (re. mus.). Fig. 2 represents a zocecium of 
Fig. 2—Bowerbankia imbricata. A zoccium and inclosed polypide. a. 
anus; giz. gizzard; int. intestine; m. mouth; ws. esophagus; py. 
val. pyloric valve; st. stomach; tent. tentacle. 
Bowerbankia imbricata, in which the polypide is expanded. 
Here the cesophagus (@s.) is stretched out to its fullest extent, 
the mouth (m.) being at the upper margin, and the tentacles 
outside the zoecium. This polypide possesses a region between 
the wsophagus and stomach known as the gizzard lined with 
large cells (giz.). The intestine (int.) is much elongated, the 
anus (a.) reaching almost to the summit of the body wall. The 
tentacles are commonly arranged in the form of a bell, but have 
