XVI 



ECHINODEEMATA 



555 



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

 the aboral coeloui breaks down into strands. 



or.ir 







Fit;. 410. Fixed larva of Aitl< i <l<'i< 

 rosacea viewed from the side in 

 order to show the origin of the 

 arms. (After Carpenter. ) 



AN, anal pink- support in;; flic anus: 

 R1-R :! , the thii-c railials in a ray Otlirr 

 liM I IMS as I it-fore. 



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

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



