360 ON THE AFFINITIES OF THE GENUS MADEEPOEA. 



immersed corallites which frequently occupy the lines of fusion 

 between adjoining branches are formed by the primitive and not 

 by the specialized mode of budding. 



The classification of Actiniaria and Antipatharia is largely 

 based on the structure of the polyps, and it seems extremely 

 probable that before a natural classification of the Madreporaria 

 is possible, much more information on this point must be avail- 

 able. In many cases difference of structure in the polyps is no 

 doubt associated with a distinctive type of skeleton, but at present 

 we are unable to use these characters to the best advantage. 

 Still the marked bilateral arrangement of the septa in Anacro- 

 pora and many Montiporce appears to indicate an affinity with the 

 genus Madrepora which, so far as we know at present, is not 

 shared by any other genus. It therefore seems desirable to 

 inquire whether Dana's views should be accepted as modified by 

 Hidley, or whether we should regard Madrepora and Montipora 

 as members of distinct, though closely allied, families. 



Madrepora^ with its axial corallites and radial bud-corallites, 

 stands alone, and, so far as I am aware, there is no approach to 

 this mode of colony formation in any other genus, taking into 

 consideration the indirect means by which it is attained and the 

 consequent absence of true coenenchyma. It is also evident that 

 both Madrepora and Montipora, as at present understood, will 

 sooner or later be considerably subdivided, so that for purposes 

 of convenience the course adopted by Ortmann has its advan- 

 tages. The point, however, remains that the characteristic mode 

 of colony formation in Madrepora is confined to the formation of 

 independent branches and that at first in all colonies, and always 

 so long as incrustation continues, the mode of budding is not 

 characteristic. On this account it appears reasonable to suppose 

 that the species of Madrepora form a specialized group which 

 indicate their affinities in the incrusting stage. A final de- 

 cision can only be arrived at when we know much more about the 

 structure of the polyps and their relation to the skeleton which 

 they produce ; but in the meantime I prefer to adopt the course 

 suggested by Ridley and divide the Madreporidae into two sub- 

 families : — 



Madreporinse — gen. Madrepora. 



Montiporinse — gen. Anacropora. 

 gen. Montipora. 



