ME. H. il. BERNARD ON" EECE^'X PORITID^E. 141 



on tlie corroded bases of large stocks. The septa of sucli young 

 forms are seen, to be irregular and granular, and, as a rule, to rise 

 but little above the columella-tangle. The fossa is consequently 

 shallow. Further, the skeleton has always naturally to pass 

 through a stage when it is small and incomplete, as compar.^d 

 with its secreting polyp, which rises in a column above it. 

 Arrest at such a stage would account for the polyp in Porites 

 rising high above its shallow calicle. 



Lastly, this argument is quite in keeping with the tendency 

 to bud very early, which I have already noted as characteristic 

 of recent Madreporidse *. The conditions in Forites are simply 

 explained if we assume them to have acquired the habit of 

 budding still earlier, i. e. when the skeleton is quite immature. 



So far, then, as the genus Porites, with its minute polyps and 

 feebly-developed skeletons, is concerned, the above arguments 

 appear to me to be fairly conclusive as to their relationship with 

 some primitive Madreporidae as fixed young forms. 



The chief qualification of this conclusion would tend towards 

 suggesting a polyphyletic origin to Porites. There is no reason 

 to suppose that this arrest of development happened only ouce. 

 If it is possible at all, it is likely to have taken place more than 

 once and at different stages in the phylogenetic development of 

 the Madreporidae. Indeed, we might ask whether it is absolutely 

 necessary to assume an exclusively Madreporid origin. These 

 points must be left for future discussion. They require a much 

 wider survey of forms than we now possess, and a more profound 

 insight into the essential morphology of the Madreporarian 

 groups. 



The genus Q-oniopora, Q. & G. — The first known forms of this 

 genus led to their being placed near, and even among, the 

 Astraeidse (Milne-Edwards & Haime). These last-named authors 

 kept the name Goniopora for forms with thick-walled, rather 

 shallow calicles, but gave the name Porastrcea to those with thin 

 walls. This latter name explains itstlf. Dana first placed the 

 genus with Porites, with which it agrees in almost every respect 

 except in size of calicles. The only difference I have myself 

 been able to discover can be referred simply to increased growth. 

 A third cycle of septa appears, which may be merely rudimentary, 



* Brit. Mus. Madrep. vol. iii. p. 12. 



11* 



