LUMINOUS ORGANS 737 



is summarized in his three classical books — The Nature of Animal Light (1920), Living 

 Light (1940), and Dioluminescence (1952). Rarely has a biologist made a subject so 

 peculiarly his own. 



The Occurrence of Bioluminescence 



BiOLUMiNESCEXCE, the production of light b}^ Hving organisms, is a very 

 widespread phenomenon, for it is seen among fungi, ^ in many types of bacteria 

 and in scattered representatives of all the animal phyla from Protozoa to 

 Fishes. Several fungi '^ have this property, some of them j^arasitic on living 

 vegetation, such as Agaricus olearius which grows at the foot of the olive 



Figs. 884 and 885. — Luminous Organs associated with the Eyes in Fish. 



In both fishes the himinous organ is a compact mass of white tissue lying 

 underneath the eye, the back of which is covered with black pigment to keep the light 

 from the eye of the fish. The organ is composed of a large lunnber of glatidular tubes 

 containing luminous bacteria in great abundance which seem to be the source of the 

 light. The organ is constantly luminous but the two fish have developed different 

 mechanisms to extinguish the luminescence periodically (after Hein). 



(a) 



Fig. 885. 



Fig. 884. — Photoblepharon palpebnitus, showing the luminous organ (cross- 

 hatched) exposed (a). On the ventral border of the organ is a fold of opaque black 

 tissue which can be drawn up over the surface of the organ like an eyelid, thus 

 extinguishing the light (b). On its retraction the luminescence again becomes 

 evident (c). 



Fig. 885. — Anomalops katoptron. The luminous organ (cross-hatched) is 

 inverted into a pocket of pigmented tissue so that the light is periodically obscured. 



trees of Southern Europe and served as the foiuidation of modern experi- 

 mental work on this subject by Fabre (1855), while to others is due the 

 luminescence of decaying wood in the forests, a phenomenon known to 

 Aristotle. Bacteria of many types — cocci, bacilli, pseudomonas, vibrios — 

 similarly luminesce. ^ Micro-organisms are also the source of the luminescence 

 of many molluscs and fishes, sometimes saprophytic on the surface of the 

 animal, sometimes parasitic within it. In the squid. Loligo, for example, 

 luminous bacteria are retained within open organs and in some shallow-water 

 fishes similar symbiotic bacteria flourish in a palisade of tubules in special 

 organs in the cheeks or lower jaw. In contradistinction to the luminescence 



1 Some green plants, mosses, for example, which live in dark caves, appetir to luminesce, 

 but the light is due to total internal reflection from spherical cells. 



2 For review, see Wassink (1948) who listed 65 species of luminous fimgi. 

 ^ For reviews, see Molisch (1912), Johnson (1947). 



S.O. — vol,. T. ^"^ 



