I\ 



PHYLUM ECHINODKRMATA 



431 



opens. A smaller adoral band ((tor) in the interior of the 

 mouth has the function of attracting nutrient particles. The 



cuvr 

 fjur 

 rru> 



Fro. 343.— Diagrams of the development of the larvae of Echinoderms. 1, Primitive form of 

 Ecl)inoderm larva ; 2 and 3, Development of an auricularia (Holothuroidea) ; 4, 5, and 6, 

 Development of a I'ipinnaria (Asteroidea) ; 7, 8, and 9, Development of a pluteiis (Echinoidea 

 and Ophiuroidea). aor. adoral band of cilia ; all. alimentary canal ; an. anus ; 6, b. processes 

 or arms ; mc. mouth ; por. peri-oral ciliated band and processes. (From Leuckart and 

 N'itsche's Diagrams.) 



peri-oral band undergoes characteristic changes in the different 

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



