132 



HANDBOOK OF INVERTEBRATE ZOOLOGY. 



a. The structure of the larva. 



At first sight there seems to be little likeness between 

 the starfish larva (Figs. 78 and 79), and the pluteus of 

 a sea-urchin, but more careful examination shows that 



2 



LUInXtl 



am 



Fig. 78. 



Fig. 78. — Bipinnarian larva of starfish, as seen in ventral view. 

 (Drawn from nature by E. B. Wilson. ) 



a. Anterior end. a. Pre-oral arms. 6. Posterior end. 1. Pre-oral 

 iciliated ridge. 2. Post-oral ciliated ridge. S. Anterior median ventral 

 lobe. J^. Anterior median dorsal lobe. c. Post-oral arms. i. Intestine, 

 m. Mouth, n. Lateral arm. o. Anus. oe. CEsophagus. q, q.' Dorsal 

 lateral arms. s. Stomach, ww'. Water tubes, am. Flattened poste- 

 jior end of left water tube. 



