CHARACTERISTICS AND HABITS OF FISHES 41 



highly developed phosphorescent organs known as 

 photophores, consisting essentially of a group of gland 

 cells that secrete the phosphorescent fluid. These 

 organs are generally distributed in rows along the sides 

 and ventral surface of the fish. Some fishes possess 

 more complex and highly developed organs containing, 

 in addition to the gland cells, a system of blood vessels 

 and nerves, a transparent, protecting membrane and 

 reflector, an iris-like diaphragm and a lens. These more 

 complex organs are generally larger and less numerous 

 than the simpler ones. Possibly they are used to 

 search for, or to attract, prey. 



The phosphorescence of decaying fish and meat is 

 due to the presence on the fish or meat of certain bac- 

 teria of putrefaction, which are themselves phosphores- 

 cent. When seen under the microscope, the individual 

 bacteria appear as shining points of light. 



4 (1457H) 



