PORITES. 21 
prs 
the pali(palic trabecule). Its presence at all depends upon these last named synapticule, 
and its size depends upon the size of the fossa in the first instance, and further upon the 
number of the synapticule joining the septal granules. We have seen cases above in which the 
completed synapticul of the septal granules thicken the wall; but other cases occur in which 
they increase the size of the columellar tangle (see P. Timor Laut. 1). It is easily seen to which 
part of the ealicle such septal synapticule belong, because the larger portions of the interseptal 
loculi run down either inside of them or outside. In the former case they belong to the wall, 
in the latter to the columellar tangle. 
Other elements of the columellar tangle are (1) the horizontal bars which join the central 
trabecula with the palic trabecule, or to the palic synapticule—these may be arranged nearly 
symmetrically like the spokes of a wheel—and (2) the central trabecula itself, the tip of which 
appears as the columellar tubercle. When this appears flattened in the directive plane, its 
appearance is probably only partially due to real flattening, but partly, also, to the presence 
of directive junctions between it and the septa in the same plane. In G, fig. 3, it is seen 
continuous with the ventral directive septum, forming together with two palic synapticule 
a trident. 
The Fossa.—This, excepting in the deep calicles, is almost filled up with the columellar 
tangle and with the central tubercle, which rises to about the height of the septa. Cases of 
dimorphism, however, occur, in which in certain calicles the fossee remain very deep and open. 
Whether these open fosse are persistent, or only remain so temporarily while their polyps are 
ripening their sexual products, is not known. In a few cases, in which the fosse are filled up 
by the columellar tangle and tubercle, one or more interseptal loculi may be greatly enlarged 
as if to take the place of the open fossa. 
Tabule,—These are usually, if not invariably, discoverable in Porites, as we should expect 
them to be. Compare what was said under this heading in Vol. IV. p. 22. They are ex- 
tremely delicate, and might easily escape notice. 
Growth-forms.—All the forms produced by the stocks of this genus may again be 
assumed, as in Goniopora, to start from small astreiform colonies. (On the use of this term 
astreiform, and its applicability to the Poritide, see Vol. IV. p. 23.) The later specialisations 
of this colony, so as to form larger solid and branching masses, do not differ in any important 
point from those regulating the growth-forms of Goniopora. The chief difference to be pointed 
out is that in Porites the plasticity seems to be much greater. This may perhaps be accounted 
for by the much smaller size of the calicles. 
One remarkable variation in the texture of branching forms has to be specially noted. In 
the one set the trabecular elements are greatly developed, and their tips cover the surface with a 
mosaic of granules. But there is another and very different set, in which the horizontal 
elements are most strongly developed, and the surface is thus flaky, though without this 
difference appearing in the growth-forms produced—at least, I have not noticed any way of 
discovering from the shape alone the nature of the texture. It is quite reasonable to suppose 
that in these branching forms the strengthening of the horizontal elements would be highly 
