358 MR. GEOEGE BROOK ON THE 



fined to the genus. One frequently finds that in radial corallites 

 the outer directive septum is broad and the other five primaries 

 equal. In other species the primary septa of both axial and 

 radial corallites are of equal breadth, in which case the bilateral 

 arrangement of parts in the polyp is not indicated by the relative 

 importance of the directive septa. Unfortunately we yet know 

 little of the structure of the polyps in the genera Anacropora 

 and Montipora, but the relative importance of their septa is 

 subject to the same variations as in JKadrepora. In Anacropora 

 the corallites are prominent, and the branches resemble those of 

 Madrepora so closely that it is not until the absence of an axial 

 corallite is observed that the generic distinction is realized. In 

 this genus the directive septa are usually broader than the others. 

 In Montipora the septa are sometimes all rudimentary, but in 

 other cases the directives are very broad and may even meet in 

 the middle line to form a false columella such as occurs in certain 

 species of Madrepora. A bilateral arrangement of parts is thus 

 as well marked by the septa of Anacropora and Montipora as in 

 Madrepora, and one may infer a somewhat similar structure in 

 the polyps. The polyps of Forites have not been studied, but 

 they bear no external resemblance to those of Madrepora. 

 Eowler also has shown that the polyps of Turhinaria do not 

 conform to the Madrepora type. 



Eidley, in 1884, discussed the mode of budding in Madrepora 

 and Montipora, and considered that there is a fundamental dif- 

 ference between the two types, dependent on the terminality or 

 non-terminality of the distal corallite. He pointed out that 

 Isopora, Studer (a subgenus of Madrepora), is not without 

 apical corallites as had been supposed, but that each lobe is 

 provided with several instead of one. In both Madrepora and 

 Montipora there is a more or less abundant trabeculate ccenen- 

 chyma. In Madrepora the budding is centrifugal, i. e. new buds 

 arise below the apical corallite. In Montipora the apex consists 

 of undiff'erentiated coenenchyma and new buds are added above 

 those existing, i. e. centripetally. He compared the condition to 

 determinate and indeterminate inflorescence. The mode of bud- 

 ding va. Anacropora is the same as in the genus Montipora. Ridley 

 therefore suggests the establishment of two subfamilies, Madre- 

 poringe and Montiporinse, with characters based on this dis- 

 tinction. 



The terms " centrifugal " and " centripetal " do not appear^to 



