POLYZOA. 
59 
or mandible hinged on below. In life, the avicularium sways to and 
' continually snapping up and 
The beak is capable of seizing 
fro on its stalk, with the lower "jaw 
down in the most ludicrous fashion, 
and holding quite large objects. 
The function of these curious appendages is partly to warn off 
trespassers and partly to capture and retain small animals till de- 
composition has set in ; in the latter case, the currents set up by 
the tentacles draw in the particles to the mouths of the poly- 
pides. The avicularia have arisen by modification of the ordinary 
cells, in which the muscules have developed at the expense of the 
degenerated polypides, the cells have become much smaller, of 
different shape, and separated out from the rest ; the mandible 
represents the lid or operculum of the ordinary cell. The avicu- 
laria vary greatly in size and shape in the different genera ; in 
Flustra, for instance, these organs closely resemble the ordinary cells. 
In Bugula Ucomis* (Fig. 7), from 1950 fathoms in the Southern 
Figr. 
Bugula Ucomis. Cells magnified. (After Busk.) 
Indian Ocean, each cell is provided with two avicularia with remark- 
ably long stalks. The graceful vase-shaped Kinetoskias cyathus * 
Case A. 
Upright 
part. 
