169 



Table III.— A SURVEY OF THE DISTRIBUTION OF THE GROWTH-FORMS. 



[N.B. — On Table I. will be found references to all tbc published figures 

 illustrative of these forms.] 



In previous volumes of the Coral Catalogue, the usual practice of assuming that the 

 growth-form must be the leading taxonomic character has been more or less closely followed. 

 I have given reasons, in the Introduction, p. 32, for doubting the correctness of this assump- 

 tion. We do not know, for instance, whether the variations in the form of the calicles go 

 first and cause the variations in the form of the colony, or vice versa. The necessity of 

 choosing between these alternatives is avoided in this volume, and the specimens are arranged 

 in an order based upon the one certain fact we know about them, viz. where they occur on the 

 earth's surface. A complete justification for this departure from the usual plan is afforded by 

 the following survey. However excellent the growth-form as a tentative taxonomic character 

 may ultimately prove to be, this table shows how completely it would fail us in the present 

 state of our knowledge. We cannot apply it for the simple reason that in a very large pro- 

 portion of cases the necessary data are not forthcoming. Only in the case of the recent forms, 

 when the specimens are whole, can the method of growth be discovered, and even then it is 

 often possible for the same result to have been reached along different lines. In fact, only 

 series of specimens can give us accurate information. When, therefore, we have to deal with 

 a collection of recent and fossil forms, many of the former and most of the latter being mere 

 fragments, the growth-form as a taxonomic character of any but the very roughest kind is 

 clearly impracticable. We are even at times at a loss to decide as to which of the three rough 

 divisions used by earlier authors, massive, encrusting, or ramose, individual specimens belong.* 

 After many vain attempts to make the best of the material contained in the descriptive 

 part of this Catalogue, I have decided to give as exact a classification according to growth- 

 form as I can of all those representatives of the genus in which this character can be approxi- 

 mately defined, and then at the end of each division to give a list of others which may possibly 

 belong to it, but which cannot for certain be brought under any of the headings. These 

 latter are nearly 50 per cent, of the whole number. It is, I take it, more instructive and 

 more useful for future work on the genus, to make a start with an ideal table, however 

 incomplete and fragmentary, than to pitch the scheme at a lower le\-el simply in order to make 



* Prof. Bell wrote in 189.5 (Journ. R. Micro. Soc, p. 149) : " It becomes at once obvious that it 

 is impossible to frame anytliing like a satisfactory diagnosis of :iny coral of encrusting habit, unless 

 a piece of some size is at the disposal of the doscriber, while it is no less cle:ir that it would be no 

 difficult task to give different specific names to pieces which might bo shown by a larger example to 

 be but parts of one 'stupendous whole.' " 



