16 MADREPORAEIA. 



glomerate forms arise from cups. Yet the fact that their method of budding is typically 

 that of the Turbinarians,* and that that method of budding can be traced to the cup- 

 formation, would justify us in assuming that, if there are no early cups in these cases, they 

 liave been secondarily lost. This stage may either have been lost by the suppression of larval 

 dispersion, owing to the great stability of massive stocks and the secondary budding of their 

 lengthening polyps, or have been merely obliterated by the first ring of buds branching off 

 from their parent polyp so close to the basal epitheca that no stalk is formed, and the 

 epitheca expands with the expanding edge of the cup. 



These glomerate forms have been thought to connect Turhinaria with Astrccopora, but 

 the resemblance can clearly be only one of convergence, when the great difference between 

 their respective methods of budding is taken into account (Plate XX.). 



8. Bifrontal Type. — In this group the folds of the margin of the primitive cup regularly 

 fuse back to back, so that, after the first cup stage, calicles appear on both faces of the fronds 

 (Plates XXI.-XXIII.). 



These eight types of growth do not at all exhaust the possible developments of the early 

 cup form. A few single specimens occur which cannot be brought under any definite rule, 

 although perhaps, when the Turbinarians are stiU better known, some of these may prove to 

 be normal types of growth. 



Variations in the Polyp-Cavities. 



The calicles vary so greatly in size,t and in other respects, even in one and the same 

 coraUum, that one is discouraged from seeking any absolutely reliable systematic characters 

 in them. A corallum which, for instance, forms either fronds or cylinders, may produce 

 calicles on the fronds which bear but very little resemblance to those on the cylinders. A 

 stock consisting only of cylinders would never be classed as specifically related with one 

 consisting only of fronds. It is only when other stocks occur which show both forms of 

 growth that the specific identity can be established. Here, again, it is apparent that no 

 definitive classification of the Turbinarians can be arrived at until our collections are very 

 much more complete. Certain distinctions nevertheless exist in the characters of the calicles, 

 but they are often very difficult to appreciate. 



Size — diameter of the Aperture. — In spite of a great variability in this respect, an average 

 size can be ascertained, care being taken only to include calicles which appear to be quite 

 normal — developing, that is, neither at the tips of prominences nor in the bottoms of valleys. 



ilaryin of the A2)erturc. — By this I mean the fringe of the coenenchyma immediately 

 surrounding the calicle. The latter, in opening at the surface of the ccenenchyma, affects it in 

 various ways. (1) The calicles project above, or are immersed in the ccenenchyma ; and 

 (2) in projecting they carry up the ccenenchyma in various ways. 



* See Ann. and Mag. Nat. Hist., (6) xv. (1895) pi. xix. fig. 7. 



t This remarkable variability has been emphasised by Professor Jeffrey Bell, in a note ' On the 

 Variations observed in large masses of Turhinaria,' Journ. E. Micro. Soc, 1895, p. 148 ; cf. also PI. XIX. 



