162 CARNEGIE INSTITUTION OF WASHINGTON. 



reef. Physiological studies showed that corals can usually adjust 

 their metabolism to meet a wide range in the variation of the oxygen 

 supply in the sea-water, and that the oxygen is always much more than 

 sufficient for the corals, and death due to heat occurs at practically 

 the same temperature for the same species of coral, whether the oxygen 

 in the sea-water is normal, three times as great, or only one-third the 

 normal. It seems, then, that Winterstein's hypothesis that death 

 from heat is due to asphyxiation is not supported. Other studies 

 made at Tortugas suggest that carbonic acid accumulates in tissues 

 under the influence of high temperature more rapidly than it can be 

 eliminated, and being toxic causes death. 



Many Samoan corals were measured, weighed, and replaced on the 

 reef, and it is hoped that we may return to Samoa in 1918 to drill 

 through the coral reef, determine the growth-rate of Pacific corals, and 

 evaluate the factors which may change fringing reefs into barriers, 

 such factors being of value to navigation in the Pacific. 



Professor L. R. Gary carried out ecological studies of Alcyonaria in 

 Samoa, determined their temperature reactions, gathered data for 

 estimating their growth-rate, and discovered their part in building up 

 reef limestones. In order to complete these studies, it will be necessary 

 for him to return to Samoa in 1918. 



Upon our return, a day was spent upon Oahu, Hawaiian Islands, 

 where Dr. C. Montague Cooke jr. kindly transported us to all the 

 important streams and springs in the vicinity of Honolulu. We found 

 these to be decidedly more alkaline than are the streams of Tutuila, 

 due doubtless to the solution of the elevated limestones found upon 

 Oahu, these being absent from Tutuila. 



Daily tests were made of the surface-waters of the Pacific between 

 San Francisco, CaUfornia, and Pago Pago, Samoa. These showed 

 that the surface-water under the equator is a fraction of a degree 

 cooler than that in latitude 5° north or south of the equator, this being 

 due to convection, the cold deep water coming to the surface. Also, 

 the warm tropical water is more alkaline than is the cold current ofif 

 the coast of California, and the easterly counter-currents met with 

 occasionally upon the surface of the tropical Pacific are apparently 

 apt to be less alkaline than is the water of the prevailing westerly 

 drift. This suggests that these counter-currents may be in regions 

 where deep-sea water is coming to the surface. In these studies use 

 was made of a standardized set of thymolsulphonephthalein tubes 

 made and presented by Professor J. F. McClendon. Later, at Tor- 

 tugas, Professor McClendon found that the surface-waters of the ocean 

 show a diurnal range in alkalinity, due to the photosynthesis of plant- 

 cells. Thus he found that the water becomes relatively acid during 

 the night, due to accumulation of CO2, whereas in sunlight the plants 

 consume the CO2, thus augmenting the alkalinity of the water. 



