Supplemental data on this subject from French bathy- 

 scaph operations are also lacking. This is probably be- 

 cause the French have had unusual success with their 

 underwater illumination system. In lieu of measuring 

 light penetration, they have concentrated on obtaining 

 information about plankton distribution and the quantity 

 of suspended particles in the water. 



Preparation for the daylight penetration observations 

 by the author in the Mediterranean"''^ (1957) included a 

 reduction of ambient light within the sphere and a short 

 dark adaptation period. Only a minimum amount of light 

 was used within the sphere for operating the craft. This 

 precaution was supplemented by the use of a tight-fitting 

 rubber face mask with glass removed, which excluded 

 all ambient sphere light when the front edge of the mask 

 was held firmly against the hull of the sphere around the 

 window. External illumination was not employed during 

 the descent until after the extinction of daylight was ob- 

 served. 



Dark- adaptation time on this dive was limited to that 

 required to reach depth after the start of the dive (about 

 30 minutes). To extend capability for visual detection of 

 daylight penetration, an investigator should have a one- 

 hour dark- adaptation period. 



Marine Biology 



During the 1958-1960 bathyscaph diving program, a 

 variety of habitats were encountered. Within the Loma 

 Sea Valley, a fauna of fishes and invertebrates was 

 encountered that varied with time and space both on the 

 sea floor and in midwater. Temporal changes were 

 striking. Invertebrate populations in particular were 

 noted to vary tremendously in species, quantity, and 

 distribution. The extreme variability in this area appears 

 to be caused by variations in water mass movement. 



There are significant differences in species occupy- 

 ing the region of the Loma Sea Valley (about 800 to 1000 

 feet) as compared to the San Diego Trough (about 3600 to 

 42 00 feet). The San Diego Trough fauna is dominated by 

 brittle starfish, tube worms, holothurians, and sablefish. 



The sea floor fauna in the Guam area was depauper- 

 ated. Living organisms were found to be abundant down 



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