XVI 



ECHINODERMATA 



559 



adult life, when it can swim freely from place to place, and can also 

 attach itself by its cirri. 



When we review the life-history which has just been described, 



Fig. 413. — The stalked larva and 

 adult form of Antedon muUi- 

 spina. (After P. H. Carpenter.) 



A, larva. B, adult, i, basal plate ; dr, 

 cirrus ; pin, pinnule ; ri, first radial plate ; 

 r2, second radial plate ; r^, third radial 

 plate. 



we may note, first of all, that some of the stages through which the 

 young Crinoid passes in its growth, till it loses its stalk, correspond 

 to the permanent condition in other genera of Crinoidea, both living 



