DEPARTMENT OF MARINE BIOLOGY. 



225 



apparently could live in water of considerably lower salinity than prevails 

 in coral-reef regions. As the lowest recorded salinity in Fort Jefferson moat 

 after a heavy rain was only 32.14, it is evident the corals, even in a lagoon, 

 are running no great risk of being killed by dilution of sea-water through 

 access of rain-water. 



Because of the difficulty of concentrating a sufficiently large quantity of 

 water for properly keeping the specimens of corals, experiments with concen- 

 trated sea-water were not tried. Furthermore, as the dilution experiments 

 accorded with the results obtained from similar experiments by students of 

 other organisms, it seems safe to infer that although corals will live in con- 

 siderably diluted sea-water they will not endure a concentration much greater 

 than the highest recorded for Tortugas water, which is 36.29. 



A series of experiments was made to ascertain how long the common species 

 of corals would endure the exclusion of light by placing specimens in a light- 

 proof live-car. They were put into the live-car on June 14 and examined on 

 June 28. On July 12 Dr. Mayer reexamined the specimens left in the car and 

 reported their condition as stated in the column headed "28 days," and he 

 again examined them and reported their condition on July 27, as given in the 

 column headed 43 days. 



Effect of exclusion of light on Tortugas corals. 



Species. 



Dichocoenia stokesi. 

 Eusmilia aspera . . . 



Oculina diffusa . 



Orbicella annularis. . 

 Orbicella cavernosa. . 



14 days. 



Pale 



..do 



..do 



28 days. 



Reddish brown, but alive. 

 Very pale, light brown; 



not quite dead; polyps 



retracted. 



Very pale 

 alive. 



brown , but 



43 days. 



Nearly killed ; some 



tissue left. 

 Pale 



Fa via f ragum do . 



Maeandra areolata . . |. . .do. 



Mseandra strigosa.. . i. . .do. 



Mseandra clivosa . 



..do. 



Manicina gyrosa. ..... .do. 



Siderastrea radians do. 



Siderastrea siderea do. 



Agaricia purpurea 



(from Loggerhead 



Reef). 

 Agaricia purpurea 



(from off Garden 



Key). 

 Acropora muricata 



(cervicornis). 



Po rites clavaria 



Porites furcata 



Porites astreoides 



Part of one colony 

 killed. 



Pale 



Killed ; tissue nearly 

 all macerated. 



Pale 



..do 



Nearly white; plant cells 

 dead, but alive; polyps 

 expanded. 



Dead, macerated. 



Pale, but alive 



Very pale, but alive. 

 ..do 



.do. 



.do. 



Somewhat pale, but ahve , 



..do 



Dead. 



Dead. 



Very pale, but alive 



2 or 3 specimens dead ; the 



one ahve very pale. 

 Pale, but alive 



Alive ; reddish brown. 



One of 2 specimens 

 dead ; live one very 

 pale; polyps re- 

 tracted. 

 Nearly all dead; a few 

 polj'ps alive but 

 retracted and com- 

 pletely bleached. 



Alive, but colorless. 



Both of 2 specimens 



alive. 

 Paler, but still alive. 

 Colorless, but still 



alive. 

 Almost colorless, but 



alive. 

 Very pale, but alive. 



Do. 



Colorless, but alive. 

 Not found. 



Bright olive green; 

 both of 2 colonies 

 ahve, but djang 

 around the bases. 



