186 CARNEGIE INSTITUTION OF WASHINGTON. 



tensive study of the coral reefs of American Samoa which was com- 

 menced in 1917. 



The following investigators studied under the auspices of the 

 Department of Marine Biology during the year: 



L. R. Gary, Princeton University, Samoa, July 5 to 28. Alcyonaria, and study of mate- 

 rial from borings through reefs. 



R. T. Chamberlin, Chicago University, Samoa, July 5 to 28. Geologic relation of Tutuila 

 Island to its surrounding reefs. 



U. Dahlgren, Princeton University. Electric organs in fishes. 



E. N. Harvey, Princeton University. Chemistry of animal luminescence. 



C. B. Lipman, California University. Samoa, May 31 to June 22. Bacteria of the Pacific 



in relation to precipitation of calcium carbonate. 

 W. H. Longley, Goucher College. Samoa, July 5 to August 27. Colors and patterns of 



reef-fishes in their relation to natural selection. 

 A. G. Mayor, Carnegie Institution of Washington. Samoa, Tonga, and Fiji, March 28 to 



July 28. Biology and growth-rate of coral reefs. 



F. A. Potts, Trinity Hall, Cambridge University, England. Samoa, Tonga, and Fiji, March 



28 to July 28. Growth-rate of invertebrates in tropical Pacific. 

 W. A. Setchell, California University. Samoa, May 31 to July 28. Marine and land plants 



of Samoa. 

 A. L. Treadwell, Vassar College. Puget Sound, Fiji, and Samoa, February 13 to June 22. 



Marine anneUds. 



Mr. John W. Mills, chief engineer of the laboratory, accompanied 

 us to Samoa and Fiji and devised an ingenious improvement in the 

 core barrel by means of which a core may be brought up, even when 

 the material being bored through is loose sand. Using this apparatus, 

 he made two borings, one of 120 feet through the Utelei reef on the 

 west side of Pago Pago Harbor, 925 feet from shore, and another of 

 156 feet through the Aua reef on the east side of Pago Pago Harbor, 

 512 feet from shore. Hard basalt was found at the bottom of the reef 

 in each case, showing that the modern fringing reefs in Pago Pago 

 Harbor have grown outward over basalt and not over ancient sub- 

 merged reefs. On the Utelei side of the harbor our borings show that 

 the reef has pushed outward from the shore over a basaltic slope or 

 submarine platform, the maxinium depth of which is 120 feet; but on 

 the Aua side of the harbor the boring was made in the submerged 

 trough of a valley, the hard basaltic bottom of which, 512 feet from 

 shore, was found at a depth of 156 feet below present sea-level. Thus 

 the modern reefs of Tutuila appear not to be superimposed upon the 

 ancient reefs now submerged to a depth of about 180 feet, but to be 

 independent structures which have grown out over the submerged 

 basaltic slopes of the island after the sea had assumed its present level. 



The nearly completed U. S. hydrographic chart of Tutuila shows 

 that the island was once largely surrounded by a barrier reef which, 

 in some places, especially along the north shore, had fused with a 

 fringing reef that had grown outward from the shores. The top of 

 these reefs is now dead and submerged about 180 feet. In later times 

 the sea stood about 10 feet higher than at present, while the prominent 



