215 
of some Corals from Fiji. 
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. 
