12 Pub. Puget Sound Biol. Sta. Vol. 2, No. 32 



PLATE 4 

 a.. Anus. 



a. t., Azygos tentacle. 



h. p. 6, Sixth hydrocoele pouch. 



m., Mouth. 



m. p.. Madrepore. 



t. k., Ternimal knob. 



t. s.. Terminal spines. 



Fig. 13. Larva showing the retrogressively developing preoral lobe, 

 distinct mouth, ring and radial canals, 3 jjairs of tube-feet in the first 

 5 rays, the 6th ray lagging behind with only 2 pair. X ^^• 



Fig. 14. Aboral view of a stage in which the 3 arms of the preoral 

 lobe have been resorbed and the preoral lobe much diminished in size. 

 The fixing disk, now the sole larval organ of attachment, is nearly sepa- 

 rated as the terminal knob. The position of the madrepore and anus, the 

 appearance of the first spines, and the still interiorly developed 6th ray 

 also is shown. X '14. 



Fig, 15. Oral view of the same specimen as in figure 14, showing 

 the open mouth, the functional tube-feet, prominent ring and radial canals, 

 and azygos tentacle, the 6th ray still inferior with 1 pair of tube-feet less 

 than the other rays. X 44. 



