PHYLUM ECHINODERMATA 



223 



color. There is some remnant of the pentamerous condition in that 

 there are five double rows of tube feet extending lengthwise on 

 five sides of the body of some forms, others have less or none. The 

 expanded body of a holothurian is soft like a bladder partly filled 

 with liquid and the body wall is very muscular. The madreporite 

 is located internally. The row^s of tube feet serve as structures of 



■Oral fen-f-ac/es 



R/n0 cai/7a/ 



Po//<frtf 

 ves/c/es 





Afnpa//ae 





/nusc/es 



/nusc/e ba/7cf 



Coviencrr7 



Soncrcf 



cr— -\V^/r?^esf/'^e 



!_'- b/ooc/ yessef 



bfood vessel 



t ^ ^^fBi fiespira-^ory 



/?a(;f/'a/ n7U5c/es 



Fig. 120. — Diagram showing the internal anatomy of a sea cucumber. (From 

 Wolcott, Animal Biology, published by McGraw-Hill Book Company.) 



locomotion and for clinging. Some of them, next to the mouth, 

 assist the tentacles in procuring food. Within the cloaca are the 

 openings of two long tubular respiratory trees which receive water 

 to assist in respiration. The tube feet, tentacles, cloaca, and other 

 organs serve in respiration. These respiratory trees function also 

 as excretory organs. The madreporite draws water from the inside 

 of the body cavity. 



