20 McMURRICH 



summit of the pouch. Here a small number of muscle proc- 

 esses may be seen projecting from the inner surface of the 

 mesoglosa, which is here slightly thickened. The ectoderm 

 over the summits of the verrucse is similar to that described for 

 the verrucae of Ccrciis pediiiiadatus by von Heider ('77) and 

 for those of PJiymantlius critcifer by myself ('89), the layer of 

 cells at the base of the epithelium in the latter form being also 

 present here. Indeed, the only difference between the structure 

 of the verrucoe of the present species and those of Phymanthus 

 is the existence of a special musculature on the endodermal 

 surface of the summits of the papillae in the former. 



The sphincter, which occurs below the fosse intervening be- 

 tween the margin and the bases of the outermost tentacles, is of 

 the circumscribed pedunculate bipinnate variety ^ (Fig. 10), and 

 is strong. The ectodermal musculature of the disc is well de- 

 veloped, the processes of mesogloea which support it anastomos- 

 ing somewhat to form a reticulum, a condition intermediate be- 

 tween the typical ectodermal and the mesogloeal arrangements 

 being thus produced (Fig. 11). Transverse sections of the 

 tentacles show that their ectodermal musculature is also well 

 developed, but no anastomoses of the mesogloeal processes 

 occur (Fig. 12). 



The walls of the stomatodaeum are thrown into well-marked 

 longitudinal ridges and are richly supplied with glands, except 



^ It seems advisable that certain terms should be agreed upon for the descrip- 

 tion of the principal varieties of endodermal and mesogloeal sphincters. So far as 

 the endodermal are concerned, the terms "diffuse " and " circumscribed," already 

 in general use, serve to divide them into tvs-o groups ; but a further subdivision of 

 the circumscribed forms would be useful. I would suggest as a first subdivision 

 that those which arise by a number of main branches from the column mesogloea, 

 as in Myonanthiis auibigims and Oulactis californica for example, be grouped as 

 "sessile," while those which have a distinct peduncle be termed "pedunculate." 

 The latter group may again be divided, according as the lamellae radiate from a 

 central mass or are inserted into an axial lamella, into " palmate " and " pinnate " 

 varieties. Such a classification may be represented in tabular form, thus : 



Endodermal sphincter ....-,. " .. , f sessile. , , 



^ ( cnxumscribed . . . . < , , ^ f palmate. 



1 pedunculate ....<• 

 ^ 1^ pmnate. 



Such a classification is of course merely tentative and presumably imperfect, but 

 it may serve to some extent to obviate the long description now necessary. 



