ANATOMY OF MUSSA AND EUPHYLLIA. 47 



(vide fig. 6), and that the two structures are homologous. 

 Where a ccenosarc is present it develops a secondary connec- 

 tion with the echinulations of the ccenenchyme and is sup- 

 ported on them, the extrathecal part of the mesenteries being 

 at the same time aborted. This is equally the case in the 

 aporose forms Seiiatopora and Pocillopora, and the perforate 

 Turbinaria and others. No distinction then can be drawn 

 between aporosa and perforate on account of the presence of 

 a well-developed " Randplatte " containing extrathecal coelen- 

 teron divided up by mesenteries into exocoeles and entocceles. 

 The difference between the two groups depends upon the 

 nature of the connection established between the peripheral 

 ends of adjacent septa. It is solid and continuous, an aporose 

 theca is the result ; it is loose and trabecular, a perforate theca 

 is formed. The manner in which the mesenteries may be 

 pierced, as it were, by outgrowths from the walls of adjacent 

 septa, is well shown by the formation of synapticula in Fungia. 

 In this form processes arise from the walls of the septa which 

 grow towards similar processes from the contiguous septa, and 

 meeting them fuse with them to form synapticula. This may 

 easily be understood by a study of a carefully macerated 

 corallum. I have shown that the mesenteries are actually 

 perforated by these synapticula, and that a simple canal 

 system exists connecting the extrathecal with the intrathecal 

 ccelenteron. This process is carried out further and in a more 

 complicated manner in the perforate. My researches on 

 Fungia have shown that the elevation of the Fungidae into a 

 group Fungida is altogether groundless. Their anatomy does 

 not differ from that of other Madreporaria either in the 

 arrangement of tentacles, as Dana erroneously described, or in 

 the internal structure as Professor Duncan inferred from Pro- 

 fessor Moseley's perfectly correct description of the soft parts 

 of a Bathyactis after decalcification. I have not yet had the 

 opportunity of investigating Bathyactis, but Professor Mose- 

 ley's description of the appearance of its soft parts after 

 decalcification exactly tallies with the appearance of Fungia 

 under the same circumstances. 



