94 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



tically regenerate all the rest of the body. Specimens showing 

 this process are sometimes found on the beaches. Fig. 

 33 shows such specimens found on the reefs in Samoa. 



During its development from the egg to the adult the 

 starfish passes through a remarkable metamorphosis. The 

 young when it issues from the egg is more or less ellipsoidal, and 

 is active and free-swimming, being provided with numerous 

 cilia. This larva soon changes to another curious form with 



FIG. 34. A sea-urchin, Strongylocentrotus franciscaniis, showing movable 



spines. (Reduced.) 



many prominent projections. This is so unlike a starfish 

 that the earlier naturalists did not realize that the larvae were 

 in any way related to the starfish and gave them the name 

 Bipinnaria, thinking they were fully developed adult animals. 

 The name is still used in referring to starfish larvae, but we now 

 know that the bipinnaria become, by later development, 

 adult starfish. 



Other Echinoderms. All the various starfish belong to the 

 class Aster oidea (Gr. aster, star; eidos, likeness) and although 

 they may differ much in general appearance they are all readily 



