EMBRYOLOGY OF ECHINODERMS. 



139 



side of the larva ; the body of the larva is absorbed or cast 

 oft', and the young starfish escapes, in the form shown 

 from above in Fig. 82. In this figure 1 is the anterior 

 ray, and 4 and 5 the two rays which were at the ends 

 of the spiral band in the larva. The calcareous skeleton 

 develops rapidly, and the sucking feet grow out from the 

 water-tubes, as shown from below in Fig. 83. Notice that 



FIG. 83. 



FIG. 83. Oral surface of the same starfish, a few days older. (Drawn 

 from nature by E. B. Wilson.) 



the radiating water-tubes are, at this stage, internal, and 

 covered by the skeleton, as in the adult sea-urchin, and 

 that there are no ambulacra! furrows. 



