CLASSIFICATOET POSITION OF SOME MADREPORAEIA. 123 



exceedingly slov/ growth, and the evident influence of abundance and 

 lack of food upon the yearly growth, of recent corals of such genera 

 as CaryopliyUia and BalanopJiijlUa^ species of which may be kept in 

 aquaria. The idea of a dense mural tissue of carbonate of lime 

 covered with and containing soft structures, contracting suddenly 

 and expanding again, does not commend itself to the common sense 

 or the experience of the students of recent forms. What changes 

 occur during upward growth are slow and are not at the discre- 

 tion of the animal, as the wording of the translation given above 

 seems to indicate ; and in the method of growth of recent forms, 

 which is summarized by naturalists under the head of " growth- 

 ringing," and which is the old name for the " Yerjiingungs-process," 

 there is no development of a new form. 



Many years since Milne-Edwards and Jules Haime called the 

 phenomena described by Milaschewitsch " bourrelets d'accroisse- 

 ment," and, following them, zoophytologists have called the results 

 of alternations of growth, "growth-rings.'" It happens, both in 

 the recent and fossil forms, that wearing removes the projecting 

 part of the ring and exposes the outer part of the visceral cavity 

 and the ends of the septa ; and sometimes the older part of the wall 

 goes on growing and slightly overlaps the starved part. In fact, 

 the Prench naturalists carried the importance of this growth too far, 

 and some species were determined from its occurrence. It is a 

 passive process of nutrition ; it has been well observed ; and there is 

 no rejuvenescence about the phenomenon. Unfortunately both the de- 

 scriber of the Nattheim corals and Mr. Tomes sometimes confuse the 

 process with calicular budding, and do not discriminate the one from 

 the other. Calicular gemmation is very common in mdJiy recent 

 forms ; and, whilst it is sometimes accidental, at other times it is 

 apparently invariable. With regard to the genus Montlivaltia^ it 

 was known to the authors of the Hist. Nat. des Corall. that the 

 species were singularly subject to " bourrelets d'accroissement," but 

 it is not correct to state with Mr. Tomes that " under its agency 

 forms appear which at first sight may seem to be quite distinct 

 from Montlivaltia!^ The occurrence of calicular gemmation in a 

 Montlivaltia was not recorded by the founder of the genus, neither 

 do we find that the phenomenon enters into the generic attributes as 

 given by Milne-Edwards and Jules Haime. 



The genus Oppelismilia was founded by me in order to receive Mont- 

 livaltioi which increased by calicular gemmation ; and in the type the 

 epithecate bud within the calice, and on one side, has been mistaken 

 by my critics for an instance of rejuvenescence. Of the value of 

 the calicular gemmation in difi'erentiating genera there may be 

 diverse opinions, and yet it must be admitted that it is of sub- 

 generic value. In the " Revision of the Genera," Oppelismilia is 

 placed as a subgenus of Montlivaltia, and Montlivaltia turhata, 

 Milasch., and any forms which Mr. Tomes may have noticed with 

 calicular budding, will come within it. 



On the strength of the interesting form of growth which develops 

 growth-rings being of primary classificatory importance, which it 



