OF SOUTHERN INDIA. 
3 
surrounded by tbe soft or partially hardened parts of the animal. This kind of pro- 
gress has been called by Dana foot-secretion, and forms the so-called of the 
Gorgokid^ or AxtipatuidjI!. In the so-called Madreporaria the sclerification takes 
place in the whole derma, either externally as exotJieca or internally as endotheca, 
or in the central column, forming the so-called columella ; all these secretions begin 
at the base of the individuums and spread gradually ux)wards, forming a more or 
less complete eup or calyx. The endothecal system is strengthened by a sclcrifica- 
tion of the mesenterial membranes or laminae, which extend towards the centre of 
the animal and form the so-called se-pla, wdiile externally these often correspond to 
or pass into similar elevations, called the costa. The septa are either conneeted by 
vertical cross bars at certain regular distances, as in the Fuxgidm, called synapticula, 
or they are connected by more horizontally distributed curved laminae in irregular 
manner; these arc called dissepiments. These, again, arc distinguished as endo- 
tliecal or exotliecal dissepiments, according to whether they become developed 
between the septa or between the costae. The columella is either a true one, 
solid, columnar, fibrose, spongiose, or laminar, or it is a pseudo-columella, merely 
formed by a twisted prolongation of some septa. 
Between the inner terminations of the septa and the columella there are in 
some forms of corals lamellar or styliform processes developed, which are called pali. 
Both the septa and pali generally follow certain rules in the course of theh 
development. As already observed, the original number of septa is either six* or 
eight ; these are called the primaries, the subsequent the secondaries, and so on. 
Taking six primaries as the most usual number, each of the six original compart- 
ments, including all the septa of subsequent orders, is called a system, and the row 
of septa itself a cycle. The six primaries are followed by six secondaries, each 
system being divided by one septum, this being the second cycle. This is followed 
again by a division of each compartment into two by a septum, there being twelve 
of them in all, forming the third cycle. Up to this the septa of each cycle are in 
a regularly formed corallum equal in length and strength. The fourth cycle is 
formed by twenty-four septa, but they are not equal, because after the third cycle 
each subsequent order consists merely of twelve septa. Thus we have in the fourth 
cycle twelve septa of the fourth and the same number of the fifth order. The rule 
is, that the twelve younger septa appear first next to the oldest septa, and then to 
the next older, and so on, and that according to theh appearance they increase in 
length and strength. In the same way we get forty-eight septa in the fifth cycle, 
belonging to the 6th, 7tb, 8th, and 9 th orders, and soon; the coi'al would then 
possess ninety-six septa, of nine different orders, in five cycles and six systems. 
The jiali always appear after the full development of the septa, and, therefore, 
they are never present opposite the septa of the last, but always the preceding 
* According to Ludwig, the Kugosa also have originally six in-imary septa, hut two of them become obsolete, the 
further development becoming, therefore, asymmetrical. 
( 135 ) 
