BIOLOGY OF LIGHT PRODUCTION — MALUF 383 



should anaesthesia of the normal animal initially abolish luminescence? 

 We would expect, on the contrary, the "contractile mechanism" to 

 relax and thus admit oxygen. Also, why should stimulation of the 

 ventral nerve cord of the decerebrate creature produce glowing? 

 We would expect, on the contrary, the "contractile mechanism" to 

 contract and thus impede the oxygen supply. The tracheal end-cells 

 are not exclusive to the photogenic organs but are present at the 

 tracheoles of all insects (cf. Deegener, 1928) and Bongardt (1903) has 

 described tracheal end-cells in the light-organs of larvae of Phos- 

 phaenus hemipterus — an animal which displays no brisk flashing 

 rhythm. 



Now, von Wielowieski (1882), Emery (1884-86), Watase* (1895), 

 Bongardt (1903), and Townshend (1904) had believed that the 

 tracheoles entering the photogenic organs of Lampyridae terminate 

 intercellularly. Von Wielowieski (1889) later considered that they end 

 intracellularly. Williams' (1916-17) illustrations indicate intracellular 

 penetration. Lund's (1911) observations bear out the latter view- 

 point conclusively: "The fact that they do penetrate into the cyto 

 plasm is clearly shown by the fact that cross-sections of the tracheoles 

 appear close to the nuclei of the large photogenic cells in the same 

 focal plane ..." For other literature concerning the intra- 

 cellular penetration of tracheoles in the tissues of insects in general, 

 cf. Wigglesworth (1931). 



Wigglesworth's (1929, 1930, 1931, 1932) direct observations on the 

 motion of air and liquid into the tracheoles during activity and rest 

 of the corresponding tissues should be well known and will, in time, 

 become classical. His observations on translucent insects show that 

 the tracheoles do not collapse when the fluid leaves them. His con- 

 clusion with respect to the phenomenon is that, during activity, 

 due to elaboration of metabolites (e. g., lactic acid) of lower 

 molecular weight than the precursors, the osmotic pressure in the blood 

 and tissue fluids is raised, thus causing a withdrawal of liquid from the 

 semipermeable tracheoles into the tissues. The writer (1938) pre- 

 sented cogent evidence that light-production is the result of a rise 

 in the osmotic pressure of the photogenic cells consequent to a rise 

 in their metabolic activity as a result of nervous stimulation. The 

 rise in osmotic pressure must draw air into the tracheoles and thus 

 causes light production. With the immediate oxidation and recon- 

 version of the metabolites, the intracellular osmotic pressure must 

 fall rapidly and, as a consequence and due to capillarity, the tra- 

 cheoles will become filled with fluid once more and the photogenic 

 cells will cease to produce light (fig. 1). The oxygen that would 

 gradually diffuse into the photogenic cells through the column of 

 fluid in the tracheoles is probably only just adequate for maintenance 

 of the cells and would hence be consumed too rapidly to allow for 



