200 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1917. 



RELATION OF CORALS TO TEMPERATURE. 



In the foregoing pages the relations of corals to violently agitated 

 or relatively quiet water and to depth of water have been particularly 

 discussed. The relations of corals to the temperature of the water 

 will now be considered, and it will be introduced by a table showing 

 the distribution of the genera of Hawaiian corals according to tem- 

 perature. The surface temperatures in this table are for the period 

 between March 27 and August 29, 1902, and, therefore, do not rej)re- 

 sent the minimum temperature for the year. The temperature rela- 

 tions of reef-corals will be considered later. If this table is com- 

 pared with the table showing the bathymetric distribution of coral 

 genera in the Hawaiian Islands, it will be evident that the names in 

 the first column of each table are the same. A further examination 

 of the table showing the distribution of genera according to tem- 

 perature will reveal that a temperature of about 22.8° C. is the bound- 

 ary between the shoal-water and the deep-water faunas. The names 

 of the genera that were obtained at temperatures above 15.6° C, but 

 not so high as 22.8° C. and above 4.5° C, are those that appear in the 

 columns 183 to 732 meters in depth ; the genera dredged between tem- 

 peratures of 4.5° and —1.12° C. were those collected between 1,464 

 and 2,105 meters in depth. The temperature of the deep-sea fauna 

 ranges between somewhat less than 22.8° C. (about 15.6° C.) and 

 — 1.12° C, with the maximum development between 10° C. and 4.5° C. 



Bisirihution of genera of corals according to temperature in the Hawaiian Islands. 



1 Not obtained at a temperature so high as 21° C.= 70° F. 



2 Not obtained at a temperature so low as 21° C.=70° F. 

 • Temperature range doubtful. 



