pear later. Compai^e Figs. 23 and 25. 



In the next stage we find, two oral funnels, or oscula, 

 and a small vesicle developed at the tip of ea-h oral ann. 

 The other portions of the arm are still open and fringed with 

 digitella as before, but the outline is no longer a regular 

 curve, for at intervals there are folds in the margin. The 

 deepest folas are the most distal and they beccxne progressive- 

 ly more shallow towards the base of the arm. The central 

 mouth is itill widely open. The subgenital cavities are 

 well developed at this stage. Figs. 52, 53, and 54. Figs. 53 

 and 54 show how they are produced by the great increase in the 

 thickness of the jelly of the pillars of the proboscis ard of 

 the oral arms. By the growth of these structures these cav- 

 ities are necessarily produced. The only special adaptations 

 are the subsequent growth and folding of the dorsal wall and 

 the narrowing of the orifice. The marginal lobes of the um- 

 brella now begin to broaden and thus approach the adult condi- 

 tion, but there is only a single "velar lobe" between two rho- 

 palial ones. 



At a little later stage when there are three oral funnels 

 at the tips of the anus (Fig. 25 ) the re-entrant angles be- 

 tween the pillars of the proboscis have grown inward, met at. 



- 56 



