ANATOMY OF THE MADREPORARIAN CORAL FUNGIA. 303 



The remaining orders are of constantly decreasing lengthy the 

 septenaries being very minute. All the mesenteries are firmly 

 attached by their upper border to the peristome. 



In the upper portions of the interseptal loculi there are no 

 synapticula; here the mesenteries are free to radiate across 

 the whole space between the mouth and the periphery of the 

 disc, and show in this part the ordinary structure, viz. a central 

 structureless supporting lamina, the Mesogloea,^ bearing a 

 layer of endoderm on each face. On one face are borne the 

 longitudinal, or retractor muscles, bundles of stout muscular 

 fibres developed from the endoderm, supported by and appear- 

 ing as if intimately connected with, supporting offsets of the 

 mesogloea. On the opposite side to the longitudinal muscles 

 are the transverse muscle-fibres, much more feebly developed 

 than the former, and having a general arrangement at right 

 angles to them ; they are not easy to see in Fungia. 



In the lower portions of the interseptal loculi the continuity 

 of the mesenteries is broken by the synapticula, and they 

 present special modifications of structure which can only be 

 understood by a careful comparison of figs. 10, 13, and 15. 

 Fig. 10 represents a mesentery of the third order dissected out 

 from a decalcified specimen, and viewed from the side. The 

 upper portion is seen to be complete, and exhibits the charac- 

 teristic arrangement of muscle-fibres, but it will be noticed 

 the longitudinal muscles are gathered into more distinct bundles 

 than is usually the case in Actinaria. Each face is covered 

 with a layer of endoderm, as may be seen by reference to figs. 

 13 and 15. The lower portion of the mesentery is necessarily 

 discontinuous owing to the intervention of the synapticula. 

 Here the mesogloea is seen to be continued into a number of 

 strong bands or ligaments to which the separate bundles of 

 longitudinal muscles are attached, these ligaments passing 

 down through the intersynapticular spaces to be fastened, 



1 I have coined this term as a substitute for the term " mesoderm " in the 

 Ccelenterata, and use it as the equivalent of the " Sliitzlamelle " or " Gallertr 

 substanz " of German authors, for reasons which are stated at the end of the 

 paper. 



