﻿10 MADEEPOEAEIA. 



The Calicles. — In the formation of the colony, the budding and an-angement of the 

 calicles are quite overshadowed by the profuse development of the ccenenchyma. While 

 this ordinarily subordinate tissue runs riot, the calicles remain minute and insignificant like 

 the living polyps which inhabit them (see above, p. 7). The genus presents us with a 

 striking example of the subordination and degradation of the individuals for the sake of 

 certain advantages to be gained for the colony. They, the individuals, remain at a peculiarly 

 low level of development among the Madreporarian polyps, while, on the other hand, the stony 

 colonies to which they give rise, stand liigh in' their class for variety and beauty of form, and 

 perhaps excel all others for plasticity in accommodating themselves to almost any method of 

 growth. 



The calicles are then peculiar on account of their small size and the characteristically 

 stunted condition of theii' sejptal apparatus. They are seldom more than one millimetre in 

 diameter, and may be so small as to be invisible to the naked eye (e.g. M. 2^orosa, PL I. fig. 4) 



The septal apparatus very rarely consists of more than two cycles, of which the secon- 

 daries are, as a rule, rudimentary. More than two cycles may be found in double calicles, an 

 abnormality which is rare in Montqwra but common in Tarhinaria. 



The septa themselves are typically vertical rows of septal spines. Occasionally, however, 

 a few rather more conspicuous primaries (often only the directives) may be either con- 

 tinuously or interruptedly laminate. 



The tips of the septal spines occasionally unite some distance down in the fossa to form 

 a columella-like body (e.g. M. Ellisi), but tliis is certainly not typically the case, as Martin 

 Duncan supposed. There are no known species with pali. 



As we have already seen, the calicle wall, meaning thereby the ring of ccenenchyma 

 immediately enclosing the polyp cavity, does not typically protrude above the surface of the 

 ccenenchyma as is the case in Madrcjjora, Turbinaria, and Astrceopora. On the contrary, the 

 cavity opens either level with the surface of the ccenenchyma, or else is immersed by the 

 regular or irregular swellings of the latter or by its crowds of tubercles. 



There are, however, certain partial exceptions to this rule. For instance, whenever 

 the special layer of the ccenenchyma in which the calicles are imbedded is thin, then the 

 calicle may open in the centre of a mound. This is. most commonly seen on the under 

 surface, but also, in very thin explanate corals, on the upper surface also. This primitive 

 condition is retained in the allied genus Anacropora, see p. 168. 



There are, however, two kinds of false-cahcle formation, which may at times assume 

 striking superficial resemblance to the typical protuberant calicles of Madrepora and 

 Turhinaria. The first is a specialisation of the foveolate rampart formation ; groups of such 

 ramparts rise higher than the rest, and fresh calicles open on the highest points and often 

 n.ppear like true protuberant calicles (see M. caliculafa, p. 57). 



The second occurs in the tuberculate group. The ring of tubercles immediately sur 

 rounding a calicle may be arranged so close to one another as to appear like a protuberant 

 calicle wall. The actual aperture of the calicle is, however, generally in the base of the pit 



