CORALS AND CORAL-ANIMALS. 159 



Chromo plate No. IV. The diameter of the coral-stock in its unbroken state was about 

 eighteen inches. 



A generic coral genus that is usually allotted a systematic position in the vicinity 

 of Euphyllia, is that of Galaxea. The compound coralla of the species of this genus 

 take the form of lobate or encrusting masses of considerable size, which may include 

 many hundred individual corallites. The corallum, divested of its organic tissues, presents a 

 remarkable appearance, that readil}' distinguishes it from any other coral type. Its compo- 

 nent corallites are subcylindrical, rarely thicker than an ordinary lead-pencil, and, projecting 

 for half-an-inch or so in close proximity to one another, they form a basal calcareous sub- 

 stratum, looking like bleached almonds thickly inserted in a frosted cake. The apparent 

 independence of the individual corallites, as thus viewed, is entirely superficial. On cutting 

 away the intervening basal calcareous matter, technically termed the "coenenchyma," these 

 corallites can be traced downwards until they are found to be united with their fellows. 

 The crowded mass has, in fact, been developed by a process of continued fission and gem- 

 mation, from a single original corallite ; and the entire structure may therefore be aptly 

 compared to the corallum of an Euphyllia, in which a secondary deposit of calcareous coenen- 

 chyma has filled up the interspaces between the component corallites, to such an extent that 

 their distal terminations are alone visible. 



The living polyps of the genus Galaxea correspond, to some extent, with those of Euphyllia. 

 The tops of the tentacles in their normally extended state are distinctly knobbed, while greens 

 and browns of various shades represent the dominating tints. The tentacles, however, are much 

 fewer, being usually twenty-four in number ; as in all corals, their number corresponds with 

 that of the internal subdivisions or septa of the coral cup. The six largest of these septa, 

 forming what is termed the primary cycle, project to a considerable extent beyond the rim 

 of the corallite, and their corresponding tentacles in the living organism stand up vertically 

 above their lellows of the second cycle, which, for the most part, assume a horizontal direction. 

 In many instances these six erect, primary, tentacles differ conspicuously in hue from the more 

 abundant horizontal series. In one corallum of Galaxea Esperi, collected on the Warrior reef, 

 the six erect tentacles were purplish-brown with white terminal knobs, and the horizontal ones 

 a bright grass-green with paler knobs of the same tint, as delineated in Fig. 9 ot Chromo plate 

 No. IV. In another instance, the erect tentacles were green and the horizontal ones light 

 brown ; while in other colony-stocks the polyps were uniformly tinted, and ranged in colour troni 

 lemon-yellow to bright grass-green. In the Galaxea, briefly referred to in the preceding 

 description of the species of Euphyllia, as exhibiting, through partial isolation from sunlight, 

 an abnormally bleached condition, the polyps on the upper or exposed surface were a pale 

 brown with lighter tips, the six erect tentacles having a yellower tinge. On the under, light-screened, 

 surface, of the same corallum, the more numerous horizontal tentacles were transparent white, 



