XVI 



ECHINODEEMATA 



555 



The " axial organ " becomes a tube, and the vertical mesentery of 

 the afebral coelom breaks down into strands. 



Fig. 410. — Fixed larva of Aniedon 

 rosacea viewed from the side in 

 order to show the origin of the 

 arms. (After Carpenter.) 

 AN, anal plate supporting the amis ; 



Ri-K', the three radials in a ray Other 



letters as before. 



Beyond this stage Seeliger could not rear his larvae, and here 

 Perrier's observations may be said to commence; some splendid 



