Interrelationships of the Madrepori'].T?. 1*53 



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 

 tjje former case is, for the sake of simplicity, alone illustrated. 



In Mondpora we have almorst 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, i. 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 pi'imitive ^[ontipore, i. 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 ccEnenchyma, in Anacropora laminate septa and costae 

 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 tiie 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 Madreporidae can be deduced from a common 

 parent. The two last mentioned are associated by the pecu- 

 liar structure of the ccenenchyma, 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- 

 porinje. 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 Afadrepora, 

 Turbinaria, and Astrceopora into a second subfamily — the 



Ann. dc Mag. X. Hist. Ser. 6. Vol. xx. 10 



