PHYLUM ECHINODERMATA 



431 



opens. A smaller adoral band {nor) in the interior of the 

 mouth has the function of attracting nutrient particles. The 



Fio. 343. — Diagrams of the development of the larvse of Xlctlinoderxns. 1, Pi-imitive form of 

 Echinoderm lai'va ; 2 and 3, Development of an auriculavia (Holothuroidoa) ; 4, Tj, and Q, 

 Development of a hrpinnai-ia (Asteroidea) ; 7, 8, and 9, Development of a pluteus (Echinoidea 

 and Ophiiiroidea), aor. adoral band of cilia ; ati. alimentary canal ; an. anus ; b, b. procespes 

 or arms; mo. mouth; por. peri-oral ciliated band and processes. (B'rum Leuckart and 

 Nitsche's Diagrams.) 



peri-oral band undergoes characteristic changes in the different 

 classes, and the form of the larva at the same time becomes 



