2 SURVEY OF LUMINOUS ORGANISMS 



family Anomalopidae, from the Banda Islands. These fish are charac- 

 terized by a white spot under the eye, made up of a large group of 

 elongated cells, richly supplied with blood vessels, forming a distinct 

 oval organ in which the symbiotic luminous bacteria grow. The light 

 is continuous but can be cut off — in Photoblepharon by a black fold 

 of skin which is drawn over the organ like an eyelid, in Anomalops 

 by rotating the organ so that the light shines against the body, rather 

 than out toward the surroundings. Nothing is known of the embry- 

 ology of these fish, but all individuals are luminous and the bacteria 

 could have entered the light organ from the sea water. There are open- 

 ings between the region of luminous cells and the environment. Usu- 

 ally fish or squid with symbiotic luminous bacteria possess such open 

 luminous organs, often with a long duct through which the bacteria 

 can be squeezed, as in the fish Malacocephalus. Symbiotic luminous 

 bacteria often require a special culture medium for luminescence, 

 whereas saprophytic forms will live on any dead animal. 



Table I (column 2, type of light) presents the distribution of all 

 groups (arranged phylogenetically ) in which species have been re- 

 ported as luminous while living. The luminous forms in which bacterial 

 symbiosis (Bs) or bacterial parasitism (Bp) have been observed, are 

 contrasted with self-luminous forms, marked E or I. In the first column 

 of the table, the habitat of the luminous groups is indicated, whether 

 marine, M, fresh water, F, or terrestrial, T. It will be observed that 

 bacterial symbiosis is most common among the fish. Sometimes it is 

 difficult to distinguish between harmless parasitic luminous bacteria 

 and the symbiotic variety. Certain squid usually contain luminous 

 bacteria in a special gland, but in some individuals no light is visible 

 on dissecting and opening the gland. In such cases how can one 

 decide between symbiosis and harmless penetration by luminous 

 bacteria? It was once supposed that all bioluminescences were of 

 bacterial origin, but it is now quite certain that symbiosis among 

 luminous animals is not nearly as widespread as had been supposed. 

 The reader is referred to the work of Pierantoni ( 1936, 1939 ) ' and 

 of Buchner ( 1953 ) for a discussion of this field. 



" Literature prior to 1951 will be found in the bibliography of Harvey 

 in Biohwnnescence, Academic Press, New York, 1952. Only later references 

 are given in this paper. 



