JOHN BUCK 325 



duration would not change with increasing total light (total luciferin) 

 as long as the enzyme-substrate ratio was unchanged. Actually, of 

 course, the shortening of the Pelogiu responses is an artifact of amplifi- 

 cation and would disappear if the intensities were equalized, but it 

 nevertheless justifies some discussion of the general relation between 

 the kinetics of light emission by the organism as a whole and the 

 kinetics of light production in the underlying photochemical system. 

 The discussion will perhaps be useful also in reference to the striking 

 similarity in form (though not in absolute rate), pointed out by Dr. 

 McElroy, between the "pseudoflash" given by anaerobic firefly ex- 

 tracts upon admission of oxygen and the normal flash of the intact 

 firefly. 



Although twenty years ago it was still possible to think of the actual 

 light-emitting reaction as involving primarily two reactants, luciferin 

 and luciferase, and although the decay portion of the duration- 

 intensity curve of some firefly flashes is logarithmic. Brown and King 

 ( 1931 ) and Snell ( 1932 ) clearly recognized the difficulty of relating 

 the control of luminescence directly to the underlying chemistry. At 

 our more sophisticated level of knowledge today, with many enzyme 

 cycles involved, there is much more difficulty in fixing upon the rate- 

 limiting reaction except in highly purified, in vitro systems. 



In extracellular luminescence, as in CJmetopterus, obvious kinetic 

 complications are caused by extraneous factors such as secretion 

 delay and mixing delay ( N icol, 1952 ) . However, even considering 

 intracellular photogeny and making the simplifying assumptions that 

 the response is triggered by a single nerve impulse and that the 

 photogenic cell is a unit ( with all quanta being emitted simultaneously 

 and with the accretion and decay phases clearly dependent on 

 defined reactions), a formidable degree of kinetic indeterminism may 

 enter purely at the biological level of organization as soon as the 

 response of intact animals is considered. This is well illustrated in 

 Renilla where the response is sufficiently leisurely for one to see 

 that several ranks of siphonozooid clusters (each cluster being itself 

 composed of several individual siphonozooids and each siphonozooid 

 of several cells) are involved at a given instant in each luminous 

 wave. One must sternly eschew, therefore, the temptation to guess that 

 the beautifully reproducible and quite possibly logarithmic decay of 



