190 CARNEGIE INSTITUTION OF WASHINGTON. 



In this connection Mayor determined the death temperature of 

 Tortugas corals in normal sea-water, and also in water heated to the 

 same temperature but made acid by adding HCl so as to be about 

 6 Ph, or in other experiments by adding CO2 so as to produce the same 

 degree of acidity. The corals died at the same temperature in this 

 acid sea-water as in normal sea-water, but the lowering of metabolism 

 due to CO2 tends to counteract the effect of heat to raise metabolism 

 and the animals produce less CO2 when CO2 is already present in 

 excess in the surrounding water, thus practically maintaining their 

 normal resistance to heat. Death from high temperature appears to 

 result from the accumulation of CO2 in the tissues and not to asphyxia- 

 tion or to hydrogen-ions in the surrounding water. 



In another series of experiments Mayor found that the rate of nerve- 

 conduction in Cassiopea tissue deprived of muscles may be the same as 

 in tissue possessing muscles. In other words, the rate of the pulsation- 

 wave in Cassiopea is determined by the nerve-net, not by the presence 

 or absence of subumbrella muscles. Another research by Mayor at 

 Tortugas was upon the rate of nerve-conduction in Cassiopea placed in 

 sea-water deprived of its absorbed air. Rings of Cassiopea were 

 placed under an air-pump, and it was found that the rate of nerve- 

 conduction remained normal when the oxygen-supply was reduced to 

 20 per cent of the amount found normally in sea-water. Further 

 reduction causes a progressive decline in rate, but nerve-conduction 

 continues until the oxygen is reduced to 5 per cent, its normal amount. 



In another set of experiments at Tortugas, Mayor found that holo- 

 thurians (Stichopus) of average size may dissolve at least 414 grams of 

 limestone sand per annum in their intestines ; but further observations 

 are required before a well-established figure for this loss of limestone 

 over reef-flats is ascertained. 



Professor Asa A. Schaeffer found 5 new and 5 imperfectly known 

 species of salt-water amoeba at Tortugas. He also carried out physio- 

 logical experiments and determined the ability of these forms to with- 

 stand fresh or brackish water, as will appear in his report published 

 herewith. 



Dr. R. C. Wells made a direct determination of the CO2 content of 

 Tortugas sea-water, confirming McClendon's observation that in 

 shallow water the CO2 content is greater at night than in the day, the 

 carbon being consumed by plants in photosynthesis. Details appear 

 in his report published herewith. 



Studies of the hydrogen-ion concentration of the surface-water of the 

 Atlantic and Pacific were continued by Mayor, and these support his 

 previously expressed conclusion that the counter-currents moving to 

 the eastward over the surface of the equatorial Pacific consist of water 

 which has come to the surface from a depth of at least 200 fathoms. 

 The water of these easterly currents is relatively acid and gives out 



