EMBRYOLOGY OF ECHINODERMS. 



Ill 



In a side view (Fig. G2), the outline of the body 

 is much as it was at the last stage, but the ecto- 

 derm is pushed inwards between 

 the ciliated ridge (c) , and the 

 anterior lobe (a), so as to nearly 

 meet the digestive tract, thus indi- 

 cating the point (m), where the 

 mouth is soon to be formed by the C.y 

 union of the ectoderm of the ante- 

 rior end of the body to the endo- 

 demi of the iriner end of the prima- 

 tive digestive cavity. 



t. 



Fig. 63. 



Fig. 62. 



Fig. 62. —Side view 

 of the same larva. 



Fig. as. —Ventral 

 view of an older larva. 

 (Drawn from nature by 

 W. K. Brooks.) 



a. Oral or anterior 

 end. b. Posterior end, 

 c. Post-oral arms, d, e, 

 f, g. Spicular skeleton. 

 /. Intestine, in. Mouth. 

 0. Armfl. oe. CEsopha- 

 gus. s. Stomach. 



b. At the end of the next thirty-six hours, the larva 

 which is shown in ventral view in Fig. 63, and in side 



