DEPARTMENT OF MARINE BIOLOGY. 



223 



tion of their "coral sand" and "coral mud" and some analyses Quin has made 

 of the calcareous sand on the shores of St. Croix Island, Danish West Indies. 



Analyses of sea-sand from Cane Bay, St. Croix Island} 



Origin. 



Number of grains. 



No. 1. No. 2, 



No. 3, 



Total 



Vegetable : 



Fragments of NuUipore (mostly red) 



Fragments of Calc. Weed (Halimeda) 



Fragments of Corallines 



Animal : 



Foraminiferous shells (whole and fragments) 



Shells, molluscous (mostly fragmentary) . . . . 



Fragments of Echinus spines 



Fragments of small crustaceous shells 



Minute Serpula tubes 



Fragments of Echinus shell 



Agglutinated grains (sam.e substances) 



Not determined 



Totals 



14 



7 

 3 



19 

 6 

 3 

 1 

 

 

 1 



34 

 24 

 23 



47 

 21 

 2 

 

 3 

 1 

 6 

 14 



27 

 13 

 10 



34 

 15 

 4 

 1 

 1 

 

 9 

 11 



75 

 44 

 36 j 



100] 



42 

 9( 



2 



41 



11 



62 



175 125 



155 



1.58 



16 

 33 



362 



iQuin, John T., The Building of an Island, p. 15, 1907. 



These statements show that Murray and Renard should not have applied 

 the terms " coral sand" and " coral mud" to the material so designated by them ; 

 while Quin did not fall into their error. 



From the tables on pages 227 and 228 it will be seen that there is no single 

 formula for the growth-rate of corals, as the rate of growth is different for differ- 

 ent species and in each species it varies in accord with differences in local eco- 

 logic conditions. In order to understand the factors controlling growth-rate, 

 the ecologic factors common to the entire reef tract should be ascertained, and 

 each species should be studied to discover the subordinate ecologic conditions 

 of its more restricted habitat. Investigations of the Florida reef tract along 

 both these lines have been made, and the data are largely assembled preparatory 

 to publishing them. Some of the results have been presented in my previous 

 papers, and if space permitted they would be summarized here. 



Observations and experiments were conducted on the growth-rate of Tor- 

 tugas corals as follows : 



(1) Colonies obtained from planulae whose history is known. They were 

 planted (a) off the northwest face of Fort Jefferson moat-wall ; (6) on the reef 

 off the northwest side of Loggerhead Key. 



(2) Colonies cemented to tiles. Of these: (a) were planted off the north- 

 west face of Fort Jefferson moat-wall ; (b) on the reef off Loggerhead Key. 



(3) Colonies naturally attached: (a) in Fort Jefferson moat; (b) on piers of 

 the Fort Jefferson wharf; (c) on the outside of the northwest face of the Fort 

 Jefferson moat-wall ; (d) on the reef off the northwest face of Loggerhead Key. 



The observations and experiments in the Bahamas were made on the 

 leeward side of the north end of a small island, known as Golding Cay, which is 

 on the east side of Andros Island at the mouth of South Bight. The speci- 

 mens included: (a) those cemented to tiles and planted; (6) those living 

 naturally attached. 



The size of the colonies of all species of corals seems limited, but some 

 attain large dimensions, 2 to 3 meters or even more in diameter, and nearly as 



