Prototheca of the Madreporarla. 5 



platte," sole) and of a peripheral portion [epitheca). This 

 appears, however, now to have been a too literal rendering of 

 the facts of his observations, for no one who had seen several 

 of these epithecal saucers of different sizes and with edges 

 turned up to different heights at different curves, and the 

 skeletal bars springing indifferently from the sides and the 

 base, could possibly divide it into a basal and a peripheral 

 portion. 



Besides, in a young saucer-shaped colony it is obvious that 

 the turned-down side (the " epitheca ") of the parent becomes 

 the "basal plate" of the daughter, and in this successive 

 flattening down of the rim we can see the explanation of the 

 characteristic wrinkled appearance of the supporting epitheca 

 of so many horizontally expanding corals, whether single or 

 compound. Each furrow represents a pause in the outward 

 growth long enough to allow the rim of tl)e widening saucer- 

 shaped epitheca to grow upwards a short distance. The 

 next period of growth carries it downwards and outwards 

 again. This process has been actually seen by Lacaze- 

 Duthiers * in the development of BalanophijUia regia. This 

 writer observed three attempts of the basal secretion of the 

 larva to turn up to form a cup or " envelope calicinale," but 

 they were always futile ; the septa overran them and the edge 

 was flattened down again and continued as a basal secretion 

 {cf. PI. I. fig. 10). 



Before continuing with the history of this prototheca — that 

 is, with our account of some of its earliest modifications — it 

 will strengthen our argument to mention a few instances in 

 which earlier writers have come near to recognizing this 

 identity of the prototheca with the epitheca. As we might 

 expect, such an identification would be more probable in 

 relation to Palaeozoic forms, in whicli the primitive cup 

 remained longest in evidence and had not become so distorted 

 and masked as it is in the majority of the modern forms. 

 Milne-Edwards f, in describing the Palaeozoic genus Za- 

 jihreyitisj which, from its appearance in time, might have 

 been expected to have retained the prototheca^ says that it is 

 completely surrounded by an epitheca. Nicholson could not 

 distinguish the epitheca of these same corals from the wall. 

 Miss Ogilvie \ declared that in Zaphrentis the epitheca 

 " supplied the primitive base and periphery in one," and 

 again that the primitive wall of corals was epithecate ; and 



* Arch. Zool. exp^rimentale, (3) vol. v. 1897, pp. 179-183 & 230, pi. x. 

 figs. 19-24. 



t ' Les Coralliaires,' iii. p. 335 (1860). 

 X rhil. Trany. 1896, p. o2Q &c. 



