6 Mr. II. M. Bcriuin] on the 



again the same writer recognized the wall of Zaphrentis as 

 ''euthecate," which means that the persistent prototheca in 

 these early corals is the entheca or true primitive wall of 

 Heider and Ortmann, as compared with which all other thecae 

 are secondary. To this last opinion we shall return. 



Mention should also surely be made of Ludwig *, who, so 

 long ago as 1866, attempted to found a classification upon 

 his recognition of the prototheca as the primitive shell 

 (" Gehiiuse ") of the coral polyp. But beyond the interest 

 attaching to the fact that he thus emphasized the importance 

 of the prototheca in Madreporarian morphology his work has 

 no value, for he was led astray in his further analysis by a 

 fancied analogy with the shell of the mollusk. 



In the present paper, then, we start again from the recog- 

 nition of the prototheca, but this time, avoiding Ludwig's 

 mistake, we shall try to analyze some of the actual modifica- 

 tions which this primitive coral skeleton has undergone in the 

 progress of its evolution. So far from being as simple as 

 Ludvvig appears to have assumed it to be, it is a task of 

 considerable complexity to follow and of no small ditficulty to 

 describe. This paper, indeed, was begun five years ago, and 

 has been frequently rewritten. 



As I have shown, those parts of the coral skeleton called 

 epitheca must for the future be referred to the rim of the 

 prototheca. This seems simple and clear now, but in the past 

 the epitheca has been the stumbling-block of coral morphology. 

 It has been this for the very reason that it waited for the 

 discovery of the prototheca before there was any possibility of 

 its elucidation. The fact of tiie confusion in the prevailing 

 views as to what the epitheca is is familiar to every coral 

 student. For instance. Prof. Gregory, of Melbourne, after 

 all his years of work at corals, characteristically summed up 

 his despair of ever making anything out of it by declaring 

 that " there was no part of the coral skeleton over which 

 more time had been wasted " '\. This attitude and that 

 which is taken in this paper are poles asunder. Between 

 these two, authors and text-books hover. None are so bold 

 as Prof. Gregory, yet none have succeeded in formulating an 

 intelligible doctrine. 



We may here state that there is ample excuse for this 

 confusion, for even now that we know that the epitheca, as it 

 occurs in the majority of specimens, is only an extension of 

 the rim of the original cup, still in each case the problem as 



* ' Palfeontographica,' vol. xiv. 



t Pal£eontol. Indica, ser. ix. vol. ii. p. 11 (IDOO). 



