272 THE SPONGES OF THE WEST-CENTRAL PACIFIC 



oceanic salinity is obviously important, and the lack of salinity in land drain- 

 age is merely an obstacle to be overcome. The helpful factors must have been 

 in solution or in suspension in the drainage. It is here suggested that there are 

 many such factors — some organic, some inorganic. Further study of this 

 situation needs to be correlated with the matter of sponge nutrition, a subject 

 about which all too little is known. 



Throughout the four groups of islands, temperatures were frequently 

 taken. That of the air, during June, July, August, and September, was con- 

 sistently near 30° C. Even the predawn temperature seldom fell to 28°. Only 

 at Guam did daylight temperatures often go above 32°, but on that island it 

 was frequently as high as 33°. I did not take open ocean readings. Lagoon 

 temperatures were almost always a little under the temperatures of air in 

 daylight, but varied in place to place from 28° to 29°. In water so shallow 

 that one could wade in it, however, the water temperature in daylight was 

 higher than the air temperature. For example, on June 25, 1949, at Ailing- 

 lap-lap Atoll, near Bikajela Islet, the noon air temperature was 30°, but the 

 noon water temperature where the depth was only one meter was 32°. 



The lagoons about Guam should be studied carefully as to temperature. 

 On September 20, 1949, I encountered a remarkably warm water region in 

 Merizo Bay at the south end of Guam. Unfortunately, I did not have a 

 thermometer in the canoe at this time. This was in a place where a gentle 

 current had been flowing over a table reef, with the water depth chiefly under 

 2 meters, often under 1 meter. A traverse of about a kilometer of such shal- 

 lows led to warmer and warmer water, and the two divers began to exclaim 

 that the water was hot. I tested it with arms and legs, and it was definitely 

 like what one would have for water in a bathtub. It was doubtless not quite 

 40°, but it certainly did not fall many degrees short of that temperature. 

 There were no sponges in this region of (at least intermittently) hot water. 



The coldest temperatures encountered during the summer were at the 

 furthest south point, at Ebon Atoll, latitude 4° 35' north. On two successive 

 nights I required a blanket covering for comfortable sleep, and it was note- 

 worthy that the natives had blankets ready to use for themselves, as well as to 

 lend. On July 5th, the dawn air temperature was only 26°, and I am sure it 

 had been at least a little cooler before dawn. On the same day the afternoon 

 air temperature reached 29.5°. 



Year around inhabitants of these four groups of islands state that there 

 is little diurnal variation in temperature of air and water and that also there 

 is remarkably little seasonal or annual variation. Therefore, it appears likely, 

 except for small, local, peculiar situations (such as at Merizo Bay, above 

 mentioned) that fluctuation of temperature plays no very great part in the 

 ecology of the Porifera of the Western Pacific. 



Sponges exhibit great effects of ecological nature in response to neighbor- 

 ing forms of life. Of course, the effects received from other living organisms 



