XVI 



ECHINODEEMATA 



555 



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

 the aboral coelom breaks down into strands. 



or. v 







FIG. 410. Fixed larva of Antedon 

 rosacea viewed from the side in 

 order to show the origin of the 

 arms. (After Carpenter. ) 



AN, anal plate supporting the anus ; 

 R!-R :i , the three radials in a ray Other 

 letters as before. 



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

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



