412 



GENERAL ZOOLOGY 



Examples : Plumatella princeps, common in American ponds 

 and streams; Bugula flabellata, Vineyard Sound; Cristatella 

 mucedo, in ponds; colony, an elongated jellylike mass, 3 to 

 25 cm. in length. 



Fig. 239. — Flustra membranacea (after Nitsche), a single animal, a, anus; ek 

 ectocyst; en, entocyst; /, funiculus; g, ganglion; k, collar, which permits retrac- 

 tion; m, stomach, also dermomuscular sac; o, esophagus. (From Hertwig's 

 Manual of Zoology by Kingsley. Henry Holt & Company. After Claparede.) 



PHYLUM 10— BRACHIOPODA 



Brachiopods are characterized by a bivalve shell, which suggests 

 a relationship to a mollusc, such as a clam or oyster; but the valves 

 of the brachiopod are dorsal and ventral instead of right and left 

 as in molluscs. As a rule, the animal is attached by a muscular 

 stalk, the peduncle, which is a prolongation of the body, passing 

 out between the valves or through an opening in the ventral 

 valve (Fig. 240) . The animal is attached to the valves by means 

 of thin sheets of tissue called mantles. Within the space between 

 the dorsal and ventral mantles are the lophophores, a pair of hol- 

 low coiled tentacles attached at either side of the mouth. Each 

 lophophore has a ciliated groove, along one side of which are 

 small ciliated tentacles. The lophophore gives the name to the 

 group (Brachiopoda — arm-footed) and serves as a sensory-respira- 

 tory organ and also to direct food to the mouth. The mouth is a 

 simple opening into a digestive tube, differentiated into esophagus, 



