EMBRYOLOGY OF ECHINODEKMS. 



127 



o 



FIG. 74. 



FIG. 74. Pluteus, with young sea-urchin, seen from the ventral sur- 

 face. (Drawn from nature by Mr. H. Garman.) 



a. Anterior end of body. a'. Pre-oral arms, a'', a'". Secondary oral 

 arms. a b. Ambulacral feet of sea-urchin. a u. Ventral auricular 

 process. 6. Posterior end of body. c. Post-oral aims, c, e, b. Ab-oral 

 surface of sea-urchin, n. Ventral lateral arms, o I. Oral lobe. q. Dorsal 

 lateral arms. s. Stomach. 



