GENERAL REMARKS. 11 
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—whick 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 ceenenchyma ; 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 ccenenchyma 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 hmits, 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 in M. 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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