132 ME. H. M. BEENAED ON EECENT POEITIDai. 



with a layer of ectoderm- cells. The whole skeleton is thus 

 outside the polyp, and could never have been built up by afusiou 

 of spicules developed inside the body. 



With regard to the general bearing of Dr. von Koch's dis- 

 covery on the origin and classification of the Madreporaria, I 

 venture to believe that the phylogenetic scheme which was pre- 

 sented in my last paper to this Society supplies us with a solid 

 foundation on which to build up a natural system. That this 

 scheme was only partially seen by Dr. von Koch himself is not 

 to be woudered at ; the clue to it lay hid entirely in the epi- 

 theca, the great importance of which seems everywhere to have 

 escaped attention. Dr. v. Koch's conclusion was that the " basal 

 plate " with the " epitheca" (that term being commonly limited 

 to the continuation of the basal plate a short way up the sides 

 of the polyp) together formed the primitive skeletal cup of the 

 Madreporaria *. 



This description, though correct in fact, fails to recognize the 

 fundamental morphological importance of the epitheca. My own 

 systematic studies had, on the other hand, led me, along quite 

 independent lines, to the conclusion that the epitheca, from which 

 it is impossible to separate the basal plate as a distinct morpho- 

 logical unit, had been at one time the most important element in 

 the skeleton, and that, though it is now very generally vestigial, 

 it was the original cup-like exoskeleton of the Stony Corals from 

 which all the later internal (septal) skeletons had been developed 

 by infoldings. This view is fully supported by the facts : — 

 (1) That the epitheca forms such cup-like exoskeletons in the 

 earliest stages of many (? all) Stony Corals ; (2) that transitional 

 forms such as Alveopora occur, in which the primitive importance 

 of the epitheca is much longer retained ; (3) that many 

 Palaeozoic corals are almost purely epithecate; and (4) that 

 published drawings of sections of Flabellum show the septa as if 

 they were still formed as simple infoldings of an external 

 wall t. 



This was summed up in my previous paper (I. c. p. 514) in the 

 following words : — " The Madreporarian skeleton may be de- 

 scribed as the rigid secretion of the basal portion of the columni- 

 form body of a polyp into which the flexible upper portion may 



Gegenbaur's Festschrift, ii. 1896, p. 272. 

 Cf. p. 134. 



t t7/. p. 134. 



