Madreporan'an Snhfamihj Montlporinoe. 129 



from Montipora^ we may assume that tlie protuberant calicles, 

 •which may, in some cases, be even tall and conical, suggest 

 that this branching off took ])lace at a very early stage in the 

 development ot" that genus. That these ]n-otuberances are 

 primitive, and not secondary returns to primitive conditions, 

 may, perhaps, be gathered from the very important fact that 

 the primary septa in the more protuberant calicles are 

 laminate, and, further, that these laminate radial structures 

 may even project down the outer wall of the protuberance as 

 costal ridges (Pi. II. fig. 5). It is specially worthy of note that 

 the less protuberant calicles, or those which open flush with the 

 surface, have the degenerated septal apparatus characteristic 

 of Montipora, while those which grow taller and slightly 

 larger develop radial skeletal laminas, septa and costa3. 

 A'V hile it is of course quite possible that this is a secondary 

 return to primitive conditions, there is no reason why we 

 should not assume it to be the persistence of such conditions. 

 The burden of proof, I think, rests with those who prefer the 

 former suggestion. 



I have been much struck by noting that many of the pro- 

 tuberant calicles with costal ridges running down their sides 

 show the tendency to a spiral twisting of the whole calicle 

 which 1 have already referred to in Turbinaria and Madre- 

 pora. This fact, again, seems to me to suggest that the 

 protuberance of the calicles is primitive and not atavistic. 



Hence, then, we conclude that Anacropora branched off 

 from Montipova before the degeneration of the calicles and of 

 their laminate radial skeleton had gone as far as it now has 

 in the latter genus. 



In this connexion it is worth noting that the axial streaming 

 layer is typically laminate or band-like, and that, in those 

 cases in which it appears most filamentous, examination 

 shows that this is a secondary condition due to the formation 

 of large perforations in the primitive longitudinal bands. 

 This band-reticulum, as we have seen above, can be best 

 traced to the outward streaming of the primitive laminate 

 radial structures composing the chief portion of the thick 

 walls of the parent and daughter polyps in the earlier stages 

 of colony formation. 



In addition to this important laminate structure of the 

 walls of the more protuberant calicles, the method of branching 

 is quite peculiar. All the known types are composed of 

 rather thin cylindrical stems more or less knotted (by the 

 protuberant calicles) like a thorn-stick. While the stems 

 are generally slightly curved, tlie branches come off suddenly 

 9X rather wide angles, the stem at the same time bending 



