POLYZOA. 



63 



forms a delicate silvery lace-work, encrusting shells and seaweeds 

 (especially red alg&e) on almost every shore. The long horny spine 

 at the base of the membranous area of each cell gives the crust a 



Fig. 11. 



Flustra cribriformis. 



Fig. 12. 



Electra pilosa. A, iucrusting a seaweed, natural size ; B, cells 

 maguified ; a, lid or operculum. 



pilose appearance. In Electra verticillata from West Africa, the cells 

 form an elegant branched colony, the branches being composed of 

 regular verticils of cells. 



Memhranipora membranacea occurs in the form of horny incrusta- Case A 1. 



