EMBRYOLOGY OF ECHINODEKMS. 



119 



iated ridge, and which at the stage shown in Fig. 65, lies 

 at the point where the oesophagus joins the stomach, is 







n. 



b. 



FIG. 68. 



FIG. 68. Ventral view of an older larva. (Drawn from nature by 

 W. K. Brooks.) 



a, a', b, c, d, e, f, y, i, m, oe, p, and s. As in Fig. 65. a". Lip. 

 n. Point where ventral lateral arm is to be developed. 



now pushed back so that it lies on the ventral surface of 

 the posterior half of the stomach. 



