EMBRYOLOGY OF ECHINODEEMS. 121 



ules (d) are also separated from each other, and nearly 

 resorbed. The pre-oral and post-oral arms are somewhat 

 longer than before, and more pigmented. The process (n) 

 of Fig. 68, in the lateral angle of the ciliated ridge, is 

 now a short, club-shaped arm (Fig. 69, n), thickly covered 

 with small pigment spots, and containing a small, needle- 



1) 



FIG. 70. 



FIG. 70. Dorsal view of an older larva. (Drawn from nature by 

 W. K. Brooks. ) 



t. Spicule of dorsal lateral arms. Other letters as in Fig. (39. 



like spicule. The process (q) is a little longer than before, 

 but it is not yet a distinct arm, although traces of a small, 



