GENEEAL EEMAEK8. H 



with specimens in which a colony of a younger generation forms an incrustation over the 

 branches of a dead colony of the same species. In such cases new corallites are added from 

 a marginal mass of undifferentiated tissue until the apex of the dead branch is reached and 

 only later, when independent growth begins, is the mode of budding changed. It also seems 

 probable that the 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. 

 A further point remains to be noticed, which appears to me important. As a result of the 

 peculiar mode of budding in the genus Madrepora — which leads to the formation of a type of 

 colony termed " patrio-ramose " by Dana — there is no coenenchyma in the true sense of the 

 word, excepting at points where the colony is incrusting. The radial corallites are arranged 

 on the branches at variable intervals, and the space between them is usually considered to 

 consist of coenenchyma ; but these intervals really form part of the thickened wall of the axial 

 corallite around which the radial corallites are developed, and the trabecular network of which 

 they are composed is not precisely comparable with the interzooidal coenenchyma of Turbi- 

 naria, for example, which is a true secretion of interzooidal tissue, and not of the walls of the 

 zooids themselves. 



The Septa and their Relation to Tentacles. — The number of septa present in the corallites 

 of the various species is, within certain limits, subject to considerable variation. The typical 

 number may be regarded as 12, viz., 6 primary ones and 6 of a second cycle, which is usually 

 less developed. Quelch recorded that mM. mirabilis, Quelch, certain of the corallites possess 

 a third cycle of septa, making 24 in all. This has hitherto been the only instance on- record 

 of the occurrence of a third cycle of septa in the genus Madrepora. I am now enabled to 

 add 2 or 3 other species to the list, and it is of interest to note that the third cycle is present 

 usually, but not invariably, only in certain of the corallites which are nearly or completely 

 immersed. It appears reasonable to expect the polyps in such cases to be provided with 24 

 instead of 12 mesenteries, and it would be interesting to ascertain the precise manner in 

 which the additional mesenteries are formed. 



The septa are generally most fully developed in the axial corallites, but even there the 

 number in many species never exceeds 6. In other cases 2 or 4 of the second cycle may 

 be present, but by far the greater number of species have the second as well as the primary 

 cycle complete in the axial corallites. The members of the primary series may be equal 

 or subequal, or more rarely the directive septa may be more prominent than any of the 

 others. In the radial corallites there is almost every variation from the apparent absence of 

 septa to a development as complete as that of the axial corallites or in certain cases even 

 more complete. The usual order of development is that the directive septa appear first, then 

 the remaining members of the primary series are added, usually but not always simultaneously. 

 Of the second cycle one may frequently note the presence of two septa — one on each side of 

 the outer directive — before the others appear ; and in other cases there may be three or four 

 before the final stage is reached. A third cycle of septa, in the rare instances in which it 

 occurs, is usually confined to radial corallites, but in one species occurs in the axial corallites. 

 Whilst in axial corallites the most usual arrangement is for the primary septa to be subequal, 



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