MORPHOLOGY OF THE MADREPORARIA. 49 



gather unworthy of the importance attached to it, though on 

 grounds which I do not consider the most fundamental. My 

 demonstration that the protoseptal stage of rugose corals is hex- 

 ameral, like the corresponding stage in modern corals, proves that 

 the Tetracoralla and Hexacoralla are more closely related than 

 has been supposed, even though from this stage they diverge to 

 the same degree as do modern zoanthids and hexactinians. 

 Bernard's assertion is in harmony with others published by 

 Bourne and Ogilvie. In making such these authors have wholly 

 neglected or minimized the significance of the difference in septal 

 sequence between fossil and modern corals, and hitherto it is only 

 such a character which has rendered possible a natural classifica- 

 tion of the Anthozoa. Morphologists and systematists know of 

 no character among the Anthozoa of greater value for taxonomic 

 purposes than the mesenterial (and septal) plan. The hexameral 

 protoseptal stage indicates that the tetracorallids and hexacoral- 

 lids have a common ancestry, but beyond this stage we have no 

 evidence as to their relationships ; we have no forms which indi- 

 cate how the divergence took place, any more than we have for 

 the soft-bodied hexactinians and zoanthids. We cannot think of 

 them as one group derived from the other, but as divergences 

 from a common ancestry. 



When this account was practically completed I received three 

 papers from Prof. N. Yakovleff, all devoted to studies of the 

 Rugosa. 1 One, " Ueber die Morphologic und Morphogenie der 

 Rugosa," contains special reference to the subject of the present 

 contribution, and calls for notice. Yakovleff has found that in 

 Russian specimens of Lophophyllum proliferum the concave and 

 convex sides of the corallite are the reverse of those in American 

 specimens. In Russian examples the main or ventral-directive 

 septum occurs on the convex side, while in the American it is on 

 the concave side of the coral, the ventral axial fossula varying in 



1 I. "Die Fauna der oberen Abtheilung der palaeozoischen Ablagerungen irn 

 Donez-Bassin. II., Die Korallen," Mem. du Comite Geolagique, Nouv. Serie, Livr. 

 12. 1903. 



2. "A Contribution to the Characteristic of Corals of the Group Rugosa." Ann. 

 Mag. Nat. Hist., Ser. 7, Vol. XIII., Feb., 1904. 



3. " Ueber die Morphologic und Morphogenie der Rugosa," Ver. der Russisch- 

 Kaiserlichen Mineralogischen Gesellschaft zu St. Petersburg, Bd. XLI., Lief. 2, 1904, 



