456 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1960 



moonless night. Particularly noteworthy were their observations on 

 the schooling of luminous fishes, and the colors and mode of action of 

 different kinds of light organs. Many deeper dives have been made 

 since then in Bathyscaphes, and the biological results have been con- 

 cerned especially with the vertical distribution of oceanic species. 

 Another line of attack has been to send down protected photomul- 

 tiplier tubes and cameras, that are triggered by luminous flashes, into 

 the depths. Photomultipliers sent down to 3,750 m. (about 21/^ miles) 

 by Clarke have provided information about the density and vertical 

 distribution of luminescent animals. In a region of maximal lumines- 

 cence at 900 m., flashing occurred at rates of 160 per minute, provid- 

 ing an almost continuous backgromid light having a radiant flux 

 greater than 1 X 10"^ microwatt per cm. square receptor surface. Such 

 observations serve to emphasize the ubiquitous and constant occur- 

 rence of luminescence in the ocean depths, below levels reached by 

 daylight, and the important part it must play in the lives of marine 

 animals inliabiting those regions. 



