REGENERATION 



687 



Some Holothurians (sea cucumbers) eviscerate themselves when 

 roughly handled or kept in an unfavorable environment. Such in- 

 dividuals may regenerate a complete new viscera. 



1 Madreporite 

 Reqeneratincj ray 



\^3 



Fig. 367. — Regeneration in tlie starfish. Above, starfish regenerating part of 

 the central disc and three arms ; below, arm of starfish regenerating the remainder 

 of the body. 



Cliordata 



Regenerative capacity varies widely in this phylum. Increased 

 complexity is generally accompanied by reduced regenerative ca- 

 pacity within the phylum, but the Pisces form a notable exception. 

 This order is relatively primitive in many respects, but many fishes 

 have a relatively limited capacity to regenerate lost parts. 



