RANGE IN DEPTH OF CORALS. 89 



The facts presented are sufficient to show that temperature 

 has much to do with the distribution of reef-corals in latitude^ 

 while proving also that regional peculiarities exist that are not 

 thus accounted for. 



II. Distribution in Depth. 



Quoy and Gaymard were the first authors who ascertained 

 that reef-forming corals were confined to small depths, contrary 

 to the account of Foster and the early navigators. The mis- 

 take of previous voyagers was a natural one, for coral reefs 

 were proved to stand in an unfathomable ocean ; yet it was 

 from the first a mere opinion, as the fact of corals growing at 

 such depths had never been ascertained. The few species 

 which are met with in deep waters appear to be sparsely scat- 

 tered, and nowhere form accumulations or beds. 



The above-mentioned authors, who explored the Pacific in 

 the Uranie under D'Urville (and afterward also in the As- 

 trolabe), concluded from their observations that five or six 

 fathoms (30 or 36 feet) limited their downward distribution. 

 P^hrenberg, by his observations on the reefs of the Red Sea, 

 confirmed the observations of Quo}' and Gaymard ; he con- 

 cluded that living corals do not occur beyond six fathoms. 

 Mr. Stutchbury, after a visit to some of the Paumotus and 

 Tahiti, remarks, in Volume I. of the West of England Journal, 

 that the living clumps do not rise from a greater depth than 

 sixteen or seventeen fathoms. 



Mr. Darwin, who traversed the Pacific with Captain Fitzroy, 

 R.N., gives twenty fathoms as not too great a range. 



In his soundings ofT the fringing reefs of Mauritius, in 

 the Indian Ocean, on the leeward side of the island, he ob- 

 served especially two large species of Madrepores, and two 

 of Astraea ; and a Millepora down to fifteen fathoms, with 

 pIso, in the deeper parts, Seriatopora ; between fifteen and 

 twenty fathoms a bottom mostly of sand, but partly covered 

 with the Seriatopora, with 'a fragment of one of the Madre- 

 pores at twenty fathoms. He states that Capt. Moresby, in 



