COMPARATIVE ANATOMY OF SOME lUUTISII ACTINLE, 



531 



are neither so deep nor so regularly arranged as those examined in 

 S. miniata and S. ornata. 



In the upper part of the column wall a very strong radial ectodermal 

 muscle is present ; an endodermal muscle is also present. There are 



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Fig. 6.—S. sphyrodeta. Vertical section through the body-wall, 

 showing the sphincter muscle. 



three distinct lobes to the mesenterial filaments (Fig. 8) ; they are 

 shaped differently from those figured for 8. milmani. 



The mesogloea in the tentacle is very weak and the endoderm forms a 

 very thin layer. 



