Interrelationships of the Madreporide. 131 
and Astrwopora—can be usefully united in a second sub- 
family ; so that, for the future, the Madreporide will consist, 
so far as we at present know, of two subfamilies—the Madre- 
porine, comprising three genera, and the Montiporine, 
comprising two genera. 
The strongest argument in favour of this classification lies 
in the fact that the five genera can be deduced from a 
common ancestral form. In describing this form we are, for 
obvious reasons, confined to a consideration of its parent polyp, 
and not of its colony. Every colony starts from a parent 
polyp, and, indeed, receives its chief characteristic from the 
structure, growth, and method of budding of this individual, 
directly developed from the attached larva. Hence it is enough 
if we can trace any group of colony formations back to a 
common ancestral parent polyp. 
Reference to the analyses already given in this and in the 
earlier papers on Turbinaria and Astreopora shows that this 
common parent polyp possessed the following leading charac- 
teristics: —(1) a porous wall, with laminate radial structures ; 
(2) a well-developed saucer-shaped epitheca; (3) the habit 
of very early budding while the parent polyp was still very 
small; (4) the production of true buds, starting from the 
smallest beginnings out of the sides of the polyp, and forming 
their skeletons, at least in the first stages, upon and with 
some slight modification of the radial symmetry of the porous 
wall of the parent polyp*. 
From such a form we may deduce the genera under dis- 
cussion along the following lines of specialization :— 
Madrepora.—The skeleton of the parent polyp grew in 
height, and consequently somewhat in size, shooting upwards 
in a tall cone with thickening base (fig.4a). The buds grew out 
in tiers from its sides, remaining comparatively small. The 
radial structures persist as lamine, and those septa of the 
buds would be largest which could start at once upon, and in 
the same plane with, one of the radial laminate structures 
(cost) of the parent; hence the “ directive” septa of the 
buds are typically radially symmetrical with those of the 
arent. ‘The epitheca is left behind. 
Turbinaria.—A ring of buds shoots up round and from 
the sides of the parent polyp, together forming a cup, the wall 
of each bud rising up as a distinct cone above the level of the 
fusion of their walls to form the common ccenenchyma (fig. 4d), 
* For Miss Ogilvie’s alternative derivation of the Madreporidx see 
Phil. Trans. vol, clxxxvii., 1696. This has been criticized by me in the 
Geological Mag. vol. iv. 1897, p. 170. 
