DEPARTMENT OF MARINE BIOLOGY. 153 



life. Thus the Atlantic corals receive nearly all of their food from the 

 rising tide which flows inward over the flats from deep water, while 

 on the ebb-tide but little food is brought to them. 



In the Pacific, on the other hand, the limestone platforms are usually- 

 covered with water 15 to 20 fathoms deep instead of 3 to 6 fathoms 

 as in the Atlantic. Moreover, the Pacific submerged platforms are 

 usually less extensive than those of the Bahamas and West Indies 

 and there is less precipitated limestone mud over their bottoms than 

 in the Atlantic. Thus food conditions for corals are apparently better 

 in the Pacific than in the Atlantic, and, as is well known, the growth- 

 rate of such lowly organized forms as coelenterates is chiefly a factor 

 of their food supply. 



Using Winkler's method, it was found that among Samoan corals 

 Pocillopora consumes about twice as much oxygen in a given time as 

 does Acropora, and the latter has a higher rate of oxygen consumption 

 than has Pontes. Acropora and Pocillopora live best in the cool, 

 pure, and relatively agitated waters of the seaward parts of the reef- 

 flat, while Porites heads are characteristic of hot inner flats or silted 

 regions off the mouths of streams. 



For a number of years Professor WilUam H. Longley, of Goucher 

 College, has made a study of the colors and patterns of fishes in rela- 

 tion to their habits and has shown that these colors and color patterns 

 serve in large measure to render the fishes inconspicuous and thus 

 possibly to facilitate their escape from enemies. It seemed advisable 

 that he should extend these studies into the Pacific, and accordingly he 

 spent two months in the Hawaiian Islands, provided with a diving- 

 hood, submarine cameras, and apparatus for color photography. Dur- 

 ing this visit he was most kindly entertained and aided by Dr. C. 

 Montague Cooke, jr., and by George A. Cooke, esq., the latter taking 

 Professor Longley to his place on Molokai Island, in a coral-reef region 

 favorably situated for these studies. Professor Longley was thus 

 enabled to achieve a decided success in this difficult work, wherein he 

 had often to remain for 4 or 5 hours at a time under water of con- 

 siderable depth. The details appear in his report pubhshed herewith. 



The following investigators studied under the Department of 

 Marine Biology during the year 1917-18: 



L. R. Gary, June 18 to September 24, studied the Alcyonaria of the reefs of Samoa and 



Fiji. 

 IILric Dahlgren, April to Jime, visited the southern United States for study of luminous 



organs in insects. 

 E. Newton Harvey, September 1917 to January 1918, visited Japan to study the chemistry 



of the light-producing substances in marine animals. 

 WilUam H. Longley, June to September 1918, visited the Hawaiian Islands to study the 



relation of color and color-pattern of reef fishes to their environment. 

 Alfred G. Mayor visited Tobago, British West Indies, Samoa, and Fiji Islands, in the 



study of the siphonophores of the West Indies, the coral reefs of the Pacific, and 



the alkaUnity of the Atlantic and Pacific Oceans. 

 A. L. Treadwell, March 8 to May 8, 1918, visited Tobago to study the Eunicidse of the 



coral reefs. 



