60 The Production of Light by Certain Fishes. 



2. If dried, the organ will give only a faint light when again moistened with water. 

 This is characteristic of luminous bacteria. The luminous organs of most other forms 

 can be dried without much loss of photogenic power. 



3. Luciferin and lucif erase can not be demonstrated; this is also true of himmous 



bflct'Grift. 



4. The light is extinguished without a preliminary flash by fresh water and other 

 cytolytic (bacterioljiic) agents. The significance of this is discussed in the text. 



' 5. Sodium fluoride of 1 to 0.5 per cent concentration extinguishes readily the light 

 of an emulsion of the gland. 



6. Potassium cyanide has an inhibiting effect on light production in about the same 

 concentration as with luminous bacteria. 



To these observations must be added the very suggestive fact that 

 the Hght of PhotoUepharon and Anomalops continues night and day 

 without ceasing and quite independently of stimulation. This is a 

 characteristic of luminous bacteria and fungi alone among organisms, 

 and very strongly suggests that the light is actually due to symbiotic 

 luminous bacteria. 



Actual proof that the bacteria found in the organ are lummous 

 can come only when these are grown artificially. My attempts in 

 this direction have failed. Good growths of bacteria were obtained 

 on pepton-agar, but they produced no hght. One might expect that a 

 symbiotic form would require rather definite food materials to produce 

 Ught, and it is, perhaps, not surprising that culture experiments have 

 failed. Certainly, the ocular and chemical evidence, if not the 

 cultural evidence, supports the view that the light of these hving fish 

 is bacterial in origin. 



LITERATURE. 



VoRDERMANN, A. G., 1900, Twee Lichtgevende Visschen van Banda,: I kanleweri Batoe 

 (Heterophthalmus palpebratus Lac^pede) en Ikan lewen Ajar {Heterophthal- 

 mus Blkv.?). Naturk. Tijdschrift voor Nederlandisch.-Indie, lix, p. 72. 



Weber, Max, 1902. Siboga Expeditie. Introduction et description de l'exp6dition, p. 108. 



Steche, Otto, 1909, Die Leuchtorgane von Anomalops katoptron \mA PhotoUepharon 

 palpebratus, zwei Oberflachenfischen aus dem Malauschen Archipel. Zeitsch. 

 Wiss. zool., xciii, p. 349. , , , . j r • r 



PiERANTONi, Umberto, 1918, I microrganismi fisiologica e la lunmescenza degli animali. 

 Scientia, xxiii, pp. 102-110. 



