ANATOMY OF A STARFISH — PEDICELLARIAE 



433 



The 



fixin 



and 



pose 



into 



last-n.imed ossicle increases the certainty of the grip by 

 g tlie lower parts of each blade in the same vertical plane, 

 preventing lateral slipping, so tliat it serves the same pur^ 

 as the pivot in a pair of scissors 

 a groove on the side of this piece. 



Each blade, in fact, fits 

 The muscles which close 



mad. 



^^^r.^^^^-^?^^^..},,^ .^ 



s;-^ - ^--^^ 



S^ 



'^Si^ 



fOr 



kjH-*''2> 



-j^j, anus 



w 



Fio. 185. — Asterias rnbens, seer 



, - i, dorsal spines. 





m 



m 



from the aboral surface, x 1. mad, Madreporite. 



the blades arise from the lower ends (handles) of the blades, 

 and are united below to form a common muscular string which 

 attaches the whole organ to one of the plates of the skeleton. 

 An attempt of the victim to tear the pedicellaria out is resisted 

 by the contraction of this string, which thus brings about a 

 closer grip of tlie blades. In order that the blades may open 

 they must first be lifted out of the grooves on the basal piece — 

 this is effected by special lifting muscles. The opening is 

 VOL. I 2 F 



