308 



THE OCEAN WORLD. 



The Flustra are marine Bryozoa, whose skin in hardening forms a 

 thin shell of horny or cellular appearance ; their little cells, more or 

 less horny, are grouped symmetrically, somewhat like the cells in a 

 hee-hive. Sometimes they form a crust which covers the algae and 

 other submarine bodies ; sometimes they form ribbon-like stems. In 



Fig. 123. Flustra foliacea (Linnrcus). 



some species the cells are only found on one side ; in others they occupy 

 both. Their orifices are extremely small, and defended by spines 

 quite microscopic (Fig. 123). 



Their tentacles are covered with cilia, always vibratile, disposed in a 

 straight line, which in their movements produce the effect which a 

 row of animated pearls might be supposed to produce if rolled 

 upwards from the base to the summit of the organ. 



The Eschara form leaf-like expansions, the entrance to their cells 

 having also their protecting spines. 



The expansions still represent microscopic bee-hives, the inhabitants 

 of which enjoy at once a common and an independent existence. As 



