894 
Proceedings of the Royal Society 
The increased temperature during the bright sunlight of the sea- 
water covering the reef-flats probably assists in the solution of the 
dead coral. On two occasions, whilst wading at mid-day in water 
ankle-deep (3 to 4 inches), I found its temperature to be about 
15 degrees (Fahr.), above that of the surface of the sea. Where the 
water was a foot in depth, the increase in temperature was about 
8 degrees. 
Sea-water, 
. 84° 
Sea-water, 
. 83° 
Reef-flat — 
Reef-flat — 
(a) 3 to 4 in., 
p 
o 
o 
T— H 
(a) 3 to 4 in., 
. 98° 
(5) 12 in., 
. 92° 
(6) 12 in., . 
no observation. 
Still higher temperatures are to be found in the waters of the 
shallow pools that have been left on the reef-flats by the retreating 
tide, and are exposed to the rays of the noon-day sun. In a pool 
an inch in depth, and frequented by small fish and hermit-crabs, the 
water was heated up to 106° (Fahr.). In another pool, 4 inches 
deep, the temperature was 99°. The temperature of the sea at the 
time of these observations was 83°. After the sky had been 
clouded over for an hour, the shallower pool had lost 7 or 8 degrees 
of heat ; whilst the temperature of the deeper pool had only fallen 
about 3 degrees, and still remained about 13 degrees above that of 
the surface of the sea. 
The Organic Degradation of Coral Reefs . — It was a singular mis- 
conception respecting the habits of holothurians that led me to the 
consideration of the degradation of reefs by the numerous organisms 
living upon them. It was stated by Mr Darwin,* on the authority 
of Dr Allan, that these animals subsist on living coral. Professor 
Dana,f however, pointed out that this habit was not warranted by 
the evidence; and Professor A. Agassiz, J in his memoir on the 
Florida reefs, expressly states that holothurians do not feed on 
the living coral ; Professor Semper § evidently holds the same 
view. During my lengthened stay in the Solomon Group, 
I never observed a single instance of this habit, and I arrived 
somewhat reluctantly at a conclusion which compelled me to give 
* Coral Reefs (1842), p. 14. 
f Corals and Coral Islands (1872), p. 229 ; vide also his earlier works. 
J Mem. Amer. Acad. Arts and Sci., vol. xi. part ii. No. i. 1885, p. 127. 
§ Animal Life , vol. xxxi. Internat. Scient. Ser., p. 413. 
