PHYLUM ECHINODERMATA 



201 



FIG. 139. Aboral view of a basket-fish, Astrophyton linckii. 

 (From the Cambridge Natural History, after Thompson.) 



Regeneration. - - The term brittle-star is derived from the fact 

 that these animals break 

 off their arms if they be- 

 come injured. This auto- 

 tomy often allows the in- 

 dividual to escape from 

 its enemies, and is of no 

 serious consequence, since 

 new arms are speedily 

 regenerated. In a num- 

 ber of species the aboral 

 covering of the disc is 

 normally cast off, prob- 

 ably for reproductive pur- 



poses. 



FIG. 140. Oral view of Ophioglypha 

 bitllatii, n brittle-star. (From the Cam- 

 bridge Natural History, after Thompson.) 



