Growth^ and Habits of Coral Zoophytes, 57 



Mr Darwin, who traversed the Pacific with Captain Fitzroy, 

 R.N., gives 20 fathoms as not too great a range, and men- 

 tions reported instances of growing reefs in 25 or even 30 

 fathoms. He states that in the Red Sea, according to Captain 

 Morehead, living corals occur at 25 fathoms. At Keeling 

 Atoll growing corals are described by him as wholly disap- 

 pearing beyond 20 fathoms ; and at the Maldives and Chagos 

 at a less depth. Other facts brought forward by Mr Darwin 

 relate to Caryophylliae, and those species which have a wide 

 range beyond reef-forming zoophytes. 



It thus appears that all recent investigators since Quoy 

 and Gaymard have agreed in assigning a comparatively 

 small depth to growing corals. The observations on this 

 point, made during the cruise of the expedition, tend to 

 confirm this opinion. The conclusion is borne out by the 

 fact, that soundings in the course of the various and exten- 

 sive surveys affbrd no evidence of growing coral beyond 20 

 fathoms. Where the depth was 15 fathoms, coral sand and 

 fragments were almost uniformly reported. Among the 

 Feejee Islands the extent of coral reef grounds surveyed 

 was many hundreds of square miles, besides the more careful 

 examination of harbours. The reefs of the Navigator Islands 

 were also sounded out, with others at the Society group, 

 besides numerous coral islands ; and through all these re- 

 gions no evidence was obtained of corals living at a greater 

 depth than 15 or 20 fathoms. Within the reefs west of Viti 

 Lebu, and Vanua Lebu, the anchor of the Peacock was 

 dropped sixty times in water from 12 to 24 fathoms deep, 

 and in no case struck among growing corals ; it usually 

 sunk into a muddy or sandy bottom. Patches of reef were 

 encountered at times, but they were at a less depth than 12 

 fathoms. By means of a drag, occasionally dropped in the 

 same channels, some fleshy Alcyonia, and a few Hydroidea 

 were brought up, but no reef-forming species. 



Outside of the reef of Upolu corals were seen by the writer 

 growing in 12 fathoms. Lieutenant Emmons brought up 

 with a boat anchor a large Dendrophyllia from a depth of 

 14 J fathoms at the Feejees ; and this species was after- 

 wards found near the surface. Dendrophyllia, it may be 

 remembered, is one of the deep water genera. 



