EMBRYOLOGY OF ECHINODEIiMS. 



125 



FIG. 73. 



FIG. 73. Ventral view of the spicular skeleton of the fully developed 

 pluteus of Arbacia punctulata. (Drawn from nature by Mr. H. Garman. ) 



Letters of reference for Figs. 71, 1'2, and 73. 



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

 anus, a b. Amhulacral feet of young sea-urchin, b. Posterior end of 

 body. c. Post-oral arms. d. Lateral spicules of body. e. Transverse 

 ventral spicules. /. Spicules of pre-oral arms. g. Spicules of post-oral 

 arms. i. Stomach. //*. Mouth, n. Ventral lateral anns. o. Anus. 

 o I. Oral lobe. q. Dorsal lateral arms. ?. Spicules of ventral lateral 

 arms. s. Stomach. t. Spicules of dorsal lateral arms. u. Median 

 dorsal spicule. v. Posterior transverse bar. w. Spine from spicule r. 

 .c. Spine from spicule t. 



