THE ANATOMY OP THE MADREPOBARIA. 413 



The Anatomy of the Madreporaria : IV. 



By 



G. Herbert Fowler, B.A., Ph.D., 



Assistant to the Jodrell Professor of Zoology in University College, London. 



With Plates XXXII and XXXIII. 



As was pointed out in a former paper ("Anat. Madrep.," 

 iii), the relations between the external body wall and the 

 corallum of Madreporaria appear to yield a distinctive mor- 

 phological character, aud to depend upon the presence or 

 absence of ccenenchyme. In all the genera yet examined in 

 which the individual polyps are more or less free and indepen- 

 dent of each other, the body wall is supported upon laminae of 

 mesogloea and endoderm (generally termed the " peripheral 

 lamella? "), which are continuous over the lip of the calyx with 

 the mesenteries, and bear a constant relation to them. But in 

 all the genera which form coeuenchyme, whether belonging to 

 the Perforata or to the Imperforata, the body wall rests upon 

 the little spikes or echinulations which stud the surface of the 

 corallum. From this it would appear that a distinction, between 

 forms with and without ccenenchyme, is justified by anatomical 

 differences at least as great as those which differentiate Per- 

 forata from Imperforata ; but our knowledge of the group is so 

 slight that any generalisation such as the above is to be 

 accepted with great caution. Of the 378 genera recognised by 

 Professor P. Martin Duncan, in his recent " Kevision of the 

 Madreporaria" (' Journ. Linn. Soc. Zool./ xvii), we have now 

 a more or less complete account of the anatomy of only sixteen 

 genera and a few more species, and the very foundations of a 

 true morphology of the group have yet to be laid. Indeed, 



