POLYZOA. 



59 



or mandible hinged on below. In life, the avicularium sways to and 

 fro on its stalk, with the lower " jaw " continually snapping up and 

 down in the most ludicrous fashion. The beak is capable of seizing 

 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 muscles 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 Buffula Ucornis* (Fig. 7), from 1950 fathoms in the Southern Case A. 



Upriglit 

 Fig. 7. part. 



Bugula hicorms. Cells magnified. (After Busk.) 



Indian Ocean, each cell is provided with two avicularia with remark- 

 ably long stalks. The graceful vase-shaped KinefosMas cyatlms * 



