THE ANATOMY OF THE MADEEPORARIA. 427 



Conclusions. 



The most important morphological points elucidated by a 

 stud}' of the species above described are as follows : 



1 . The apparent law that the body wall, when present, is 

 supported in acoeuenchymatous forms upon " peripheral 

 lamellae" of the mesenteries, and in ccenenchyrnatous species 

 upon the echinulations of the coenenchyme, is seen to require 

 modification. The two methods of support may coexist in a 

 coenenchymatous form (Madracis), and to a certain extent 

 in an accenenchymatous species (Amphihelia); further, the 

 body wall in accenenchymatous species may rest upon pseudo- 

 costse (? homologous with echinulations), either mainly (Am- 

 phihelia) or entirely (Stephanophyllia) ; or upon both pseudo- 

 costae and true costee (Sphenotrochus). At the same time it is 

 doubtful whether such exceptions to the law, formulated above, 

 will not eventually prove to be modifications due to exceptional 

 conditions, of which we are at present ignorant. 



2. The modifications of the mesenteries exhibited by pre- 

 viously described species of Seriatopora and Pocillopora are 

 seen to extend to other species of the same genus. 



3. The ultimate attachment of polyp to corallum consists, in 

 many genera, in a series of laminated offsets of mesoglcea in 

 the neighbourhood of the mesentery, such structures having 

 been previously described as calicoblastic in function. 



4. A sphincter muscle, comparable to the " Rotteken's 

 muscle" of Hexactinise, may occur among Madreporaria (Sphe- 

 notrochus). 



5. Follicle cells, which are perhaps immigrants from the 

 endoderm, may surround the ripening ovum as it lies in its 

 mesoglceal capsule (Sphenotrochus). 



6. A case of degradation, tending to obscure the individuality 

 of the polyps, is presented by Stephanaria. 



