EMBRYOLOGY OF ECHINODEEMS. 



125 



Fig. 73. 

 Fig. 73. — Ventral view of the spicular skeleton of the fully develoi)ed 

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

 Letters of reference for Figs. 71, 72, and 73. 



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

 [arms, a h. Ambulacral feet of yovmg sea-urchin, h. Posterior end of 

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

 [ventral spicules. /. Spicules of pre-oral arms. y. Spicules of post-oral 

 larms. i. Stomach, m. Mouth, n. Ventral lateral arms. o. Anus. 

 10 I. Oral lobe, q. Dorsal lateral arms. r. Spicules of ventral lateral 

 farms. s. Stomach. t. Spicules of dorsal lateral arms. «. Median 

 dorsal spicule, c. Posterior transverse bar. w. Spine from spicule r. 

 X. Spine from spicule t. 



