Interrelationships of the Madreporide. 133 
of the daughters seems, as a rule, to be limited to their free 
or outer sides; the fresh buds turn upwards if the growing 
edge is accompanied by an epitheca, but may turn up or down 
indifferently if the growing edge is free. In the diagrams 
the former case is, for the sake of simplicity, alone illustrated. 
In Montipora we have almost all possible growth-formations 
resulting from this aggregation of small thick-walled polyps, 
aided by the secondary additions of tissue, above described as 
the “thickening layers.” These begin to form at varying 
distances from the growing edges or apices, ¢. e. after the 
budding of the polyps has ceased. May not this fresh 
growth be correlated with the very early budding of the 
Montiporan polyps and their subsequent continued but limited 
growth—limited, that is, by the abundant secretion of skeletal 
matter—which is the characteristic feature of the genus ? 
In Anacropora the growth-form is highly specialized. We 
may thus look upon Anacropora as a survival of a special 
growth-form of some more primitive Montipore, 7. e. of some 
Montipore in which the degeneration of the protuberant 
conical wall had not gone so far as it has in the modern 
representatives of the genus. While in Montipora the lami- 
nate radial elements of the calyx have almost entirely disap- 
peared, being only occasionally found in a few large primaries, 
directives and others, and, again, in the streaming layer of 
the coenenchyma, in Anacropora laminate septa and coste 
appear in ‘the more protuberant calicles in addition to the 
lamination of the streaming axial layer. It is further worth 
noting that not only does the occasional presence of laminate 
directives support the deduction of Montipora from an ances- 
tral polyp with laminate radial skeleton, but the mere presence 
of directives points also that way, that is, if the explanation 
of the rise of directives above given is correct. The primi- 
tive epitheca, which is lost in Anacropora, persists and plays 
a great part in the formation of many Montiporan coralla. 
In these different ways all the genera which are at present 
included in the Madreporide can be deduced from a common 
parent. ‘he two last mentioned are associated by the pecu- 
liar structure of the coenenchyma, which, as we have seen, is 
traceable to the great thickness of the porous walls of the 
individual polyps. ‘These, then, form the subfamily Monti- 
porine. ‘The remaining three genera are also united by one 
character in common, viz. the typical upgrowth of the polyp- 
walls into freely protuberant calicles, their basal portions 
alone being fused together to form a ccenenchyma. I can 
see no reason why this character should not unite Madrepora, 
Turbinaria, and Astraopora into a second subfamily—the 
Ann, & Mag. N. Hist. Ser. 6. Vol. xx. 10 
