of some Corals from Fiji. 215 



generally covered with green weed with a varying quantity 

 of bivalve molluscs in great lumps ; Polytrema and Litho- 

 thamnion are not found. The absence of corals here is pro- 

 bably due largely to the greater movement of the part near the 

 surface of the water, destroying the colonies as well as causing 

 difficulty of fixation to the larvae. Another cause is found in 

 the lesser amount of light below the buoy, reef-building corals 

 feeding mainly by means of their commensal algae. Other con- 

 ditions being the same, the more intense the light the more 

 vigorous is the growth of these corals, but this is not the case with 

 the other organisms, which affix themselves to the buoys and 

 chains. The green algae are of extremely rapid and vigorous 

 growth as compared with corals, and in the waters of the tropics 

 undoubtedly do better in partial shade, than where freely exposed 

 to the sun's rays. Lamellibranch larvae affix themselves much 

 more readily than coral larvae 1 and with apparent ease in places, 

 where corals cannot grow. The increase in size of the shell 

 depends mainly on the food supply, but a high temperature is 

 likely to be at any stage of their existence fatal. The position 

 under the buoy should be — and indeed is, to judge from the size of 

 the shells and masses — extremely favourable, the surface move- 

 ments bringing an ample supply of food, and the buoy itself giving 

 shade from the vertical rays of the sun. Considering the com- 

 petitors, it would hence appear probable that any corals, which 

 might commence to grow under the buoy, would for a limited 

 depth ultimately be killed and overgrown. 



It is necessary to consider the physical conditions of the 

 harbour, since the rapidity of growth of the corals, as in the case 

 of the bivalves, depends very largely on the nature of these. 

 The so-called harbour of Levuka is a stretch of the lagoon, 

 opposite the town of the same name, within the great barrier 

 reef of Ovalau, which joins on to that of Viti Levu, the largest 

 island of the Fijies. There is here a small passage, caused 

 mainly in all probability by the necessity for an outlet for the 

 tidal waters; a small stream it is true comes down from the 

 mountains of Ovalau about half a mile up the coast, but the size 

 of this is due absolutely to the rains, and it can scarcely make 

 any appreciable difference to the salinity of the water, even if this 

 be an important factor. The town consists of a long straggling 

 street by the sea, and has not probably more than 600 inhabitants, 

 the shipping is inconsiderable, the shore is rocky, and the stream 

 drains a very small, uncultivated, rocky area, so that the water 

 is singularly clear even as compared with the lagoons of other 



1 This is well exemplified by the largest specimen of Stylophora, the base of 

 which has almost completely enclosed a shell of some species of Ostrea (?), the larva 

 of the coral probably in the first place affixing itself to the shell. 



