730 



MR. J. P. MCMUERICH ON THE SYSTEMATIC 



are also thin, the latter containing a few scattered and almost 

 spherical mucous glands, without distinct indication of muscle 

 fibres. The outer wall of the fosse joins the column proper at the 

 apparent margin, and at once a change of structure is observable. 

 The niesogloea becomes decidedly thicker and its outer surface 

 irregular; the ectoderm thickens and becomes richly supplied 

 with gland cells, which, with the greater thickness of the layer, 

 assume an oval or pyriform shape ; and a weak circular endo- 

 dermal musculature becomes evident. But there is no sign of a 

 sphincter, either endodermal or mesogloeal. One would expect 



Text-fisfure 1. 



Sections through the margin and outermost tentacles of an individual from 

 Woods Hole. ^=tentacle ; wj=margin. 



to find a mesogloeal sphincter just below the apparent margin, 

 but in the several individuals that were sectioned I looked in 

 vain for even traces of it. 



In two particulars, then, Sagartia h(xue differs notably from 

 the typical members of the genus to which it has been assigned, 

 namely, in the presence of a- deep fosse and in the absence of a 

 mesoglosal sphincter. In the one feature it shows some resem- 

 blance to Metridiimi, and in the absence of a sphincter it is 



