The percentages of total observations for the three types of displays 

 in this region are as follows: 



Sheet 'type 57^ 



Spark type 7fo 



Glowing-ball type 36fo 



Fewer displays have been reported to the south of the Tropic of Capri- 

 corn. The percentages of total observations for this region for three- 

 month periods are as follows: 



January through March 13^ 



April through June 3^^ 



Jvily through September 11^ 



October through December k'2Jo 



Data are inconclusive as to the types of displays most frequently ob- 

 served, although both sheet type and glowing-ball type bioluminescence 

 appear to be more frequent than the spark type. 



Pyrosoma (the fire cylinder) is responsible for the more spectacular 

 glowing-ball displays throughout the year in this area. When luminescing, 

 as observers aboard the USS VANCE noted in September I96I in the South- 

 west Pacific, they were visible at a distance of 75 to 100 yards. 



Large shoals of medusae also create brilliant displays of light in 

 this area. In November 1950 observers on board the SS WAIHEMO noted a 

 brilliant "phosphorescent" region as they steamed along in the western 

 South Pacific. "Where the wash broke, the sea was brilliant blue, nearly 

 as bright and the same color as the arc from a welding torch." Intense 

 patches of light about the size of dinner plates also were observed. 

 This reference to an arc light indicates the brilliance of some bio- 

 luminescence, sufficient to outline a ship in light. 



Of special interest are the very brilliant snow white sheet-type 

 displays which occur in the Banda Sea and have been observed most fre- 

 quently dioring June through September. Because of these unusual 

 displays the Banda Sea often is referred to as the "white sea." A 

 characteristic of the displays is the suddenness with which they occur. 

 The sea, normal in appearance, suddenly becomes "milky" as if a light 

 switch had been thrown. The light is so strong that the sky may appear 

 to be lighted, and the ocean may give the appearance of a snow covered 

 land scene to observers. These exceptional sheet-type displays prob- 

 ably are due to large concentrations of dinoflagellates such as 

 Noctiluca . 



An article in the Washington "Sunday Star" of 9 February 1958 con- 

 cerned recollections of an observer in the 1920'e in Sandakan Harbor, 

 British Worth Borneo. He stated: 



33 



