TURBINAEIA. 19 



Tlie interrelationship between the characters of the ccenencliyma antl of the calicles is a 

 difficult subject, Mliicli, however, will some day have to be worked out. A change in the 

 environment, leading to sliglit changes in the secretion and deposition of the skeletal 

 substance, will not only affect the ccenenchyma but alter tlie aspect of the calicles. 



ON THE ATTEMPT TO ARRANGE THESE VARIATIONS UNDER SO MANY 



SPECIFIC HEADINGS. 



In dividing the Turbinarian coralla into groups, according to their methods of growth, 

 tlie present writer places this feature in the foremost rank of importance. This is done 

 purely from practical considerations. In view of the enormous amount of variations 

 in the calicles, often on one and the same stock, and of our complete ignorance as to 

 the laws governing these variations, it seemed at present hopeless to find any satisfactory 

 leading character among them. Hence, in this Catalogue, they take a second place in the 

 systematic arrangement. 



The objections to grouping primarily according to the methods of growth are, how- 

 ever, very serious. In the first place, the methods of growth pass into one another, and 

 it is not always easy to decide whether a specimen shows one or the other type of growth ; 

 in the second place, a long series of specimens which, from their calicles, and from their 

 many transition forms, are clearly related, may show almost every type of growth. Still more 

 serious, again, is the fact that in the Torres Straits we find Turbinarians widely differing in the 

 characters of their calicles, yet revealing exactly the same methods of growth, which shows 

 that the form of the corallum is, in these cases at least, due to the en%-ironment. The same 

 seems also to be learnt from the fact that there are what appear to be local forms of growth, 

 very striking, but confined entirely to limited areas. For instance, the very striking form 

 assumed by T. i)cltata, described and figured by Ortmann * as " T. maxima " from Singapore, 

 closely resembles a specimen in the National Collection from the same locality. It looks 

 as if this were a local form of growth. Two specimens of T. pcltata, from Mauritius, differ in 

 form from all other specimens of T. •pcltata in the Collection. Are these local forms of growth 

 of any value ? If we classify strictly according to growth-forms, we should have to answer in 

 the affirmative. But this would lead to a needless splitting of specimens, closely united by 

 other characters. 



If, then, in the face of these facts, the types of growth are still chosen as the leading 

 principle in classification, it is because there really appeared no choice. No other characters 

 presented themselves with sufficient certainty or constancy to be made use of 



Theoretically, perhaps, the leading feature should have some connection with the forms 

 of the calicles— perhaps should even be supplied by them— inasmuch as they have the best 

 claim to represent the individual polyps which build the colony. This, indeed, as we have 



• Zool. Jabrb. Abt. Syst., ill. (1SS8) p. IGO, pi. vi. fig. 4. 



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