﻿14 MADEEPOKAEIA. 



There is no record of any Montipora occurring in the Atlantic or West Indies. The 

 3fanopora, comprcssa " from the Mediterranean " * is due to a wrong identification by Esper 

 of a true Montiporan with the Millepora compressa of Linnfeus. 



VII. A GENERAL REVIEW OF THE VARIATIONS PRESENTED BY THE 

 REPRESENTATIVES OF THE GENUS. 



Variations in growth-form. — Every possible form of stock occurs in this genus, — foliate, 

 massive, ramose, &c. 



That some systematic value must be attributed to growth-form, no one who has handled 

 many specimens of one and the same type can doubt. Certain definite specialisations of the 

 ccenenchyma are apparently more consistent witli one particular growtli-form than with any 

 other, e.g. M. verrucosa tends to form flat solid masses ; but at the same time, irregularly 

 branched forms may occur. Other coenenchymatous specialisations seem to be consistent with 

 almost any shape of corallum, and in these cases growth-form fails as a character of 

 importance. 



In spite, however, of these difficulties, certain lines of distinction exist, e.g. the thin 

 foliaceous method of growth is sufficiently marked to be useful. 



Although, therefore, the fact that the great plasticity of the ccenenchyma undoubtedly 

 depreciates the taxonomic value of growth-form, yet it has a real value which, though it 

 cannot yet be defined, cannot be ignored. 



One modification of gxowth-form illustrated by the Collection deserves to be mentioned, 

 viz. that of the detached and rolled fragment. The profusion with which different types 

 throw up knobs and branches inevitably results in some of these being broken off. Of these 

 detached fragments, some at least do not reattach themselves to the substratum, but yet 

 may go on growing. Such free fragments of three different types occur in the Collection, 

 and show remarkable similarity in their methods of adaptation. Two of them {M. multiformis 

 and M. indentata) tend to form globular masses of short branches with rounded tops radiating 

 outwards in all directions from a common centre ; on the tips of these branches the specimens 

 appear to have rested (see M. multiformis, PI. VI.). In the third (if. caliculata) the mass 

 was heavy, but the tendency of the upper surface to cover itself with short upgrowths is quite 

 distinct. While in this last case the affinity is clear, in the former cases, but for the presence 

 of transitional forms, both would have been classed as new species. 



Variations in the calielcs. — Owing to the feeble development of the polyps, the variations 

 in size of the calicles are confined to very narrow limits. The number of septa is also very 

 uniform, though the different degrees of development of the two cycles are important. One 

 septum, or two opposite primary septa, are frequently greatly developed as directives. These, 



* Dana's Zoophytes, p. 494. 



