EMBRYOLOGY OF ECHENODERMS. 



131 



the tow-net or dip-net, and since their greater size renders 

 them much more fit than the pluteus for studying the 

 mode in which the young echinoderm is formed inside the 

 larva, the student should if possible rear some of them in 

 small aquaria, and study the development of the young 

 starfish. The full-grown larva is about one-twelfth of an 



FIG. 77. 



FIG. 77. Oral surface of the young sea-urchin, 

 by Mr. H. Garman. ) 



(Drawn from nature 





inch long, transparent, and of the shape shown in Fig. 

 78. This figure shows the bipinnarian larva of a southern 

 starfish, but the brachiolaria of our common species is 

 almost exactly like it, and the student should have no 

 difficulty in recognizing it when captured. 



