328 CONTROL OF BIOLUMINESCENCE 



Renilla luminescence, as seen in Dr. Nicol's records, directly reflects 

 the underlying chemical kinetics. There is indeed one possible deduc- 

 tion which can be made about Renilla, though not from Dr. Nicol's 

 present records (which integrate the light from the animal as a 

 whole), which is that the time-intensity curve for the individual 

 siphonozooid cluster must be skewed. This is shown by the fact, noted 

 by Parker (1920), that the leading edge of the wave (first rank of 

 clusters ) is the brightest. 



The firefly flash is even more difficult to analyze because its bril- 

 liance and short duration prevent visual study of the course of excita- 

 tion through the luminous tissue, and no recordings have been made 

 of the time relations between light emission from different regions 

 of the organ in the same flash. Since the organ itself occupies two 

 abdominal segments in the males of most common American fireflies, 

 asynchrony between the two segments is a distinct possibility, 

 although the early firefly experiments of Briicke (1881), leniently 

 considered, indicate that the innervation could conceivably be so 

 arranged that the two segments are stimulated simultaneously some- 

 what as in the unified response of the squid mantle (Young, 1938). 

 Even so, one would be dealing with from 6000 to 15,000 effectors, 

 depending on whether one considers the "cylinder" or the photocyte 

 to be the smallest individually controlled unit (Buck, 1948), so that 

 it is likely a fortiori that the time-intensity curve for the whole organ 

 represents an integration of many separate asynchronous events rather 

 than the simultaneous firing of all the photocytes in the organ. The 

 strong resemblance of the time-intensity curves of some firefly flashes 

 to the normal distribution curve may be significant in this connection, 

 although I understand from Dr. Hastings that a symmetrical flash is 

 the exception, rather than the rule. However, a gaussian type of 

 curve might reflect the distribution of any one of several factors 

 affecting the control of luminescence, for example the distribution of 

 responsiveness among the individual effectors to a linear change in 

 stimulation frequency (action potentials in nerve). Similarly, plateau- 

 shaped, bimodal or skewed time-intensity curves might result rather 

 simply from the mere architectonics of innervation in the light organ 

 when the recording is made from the animal as a whole (Figs. 1-4), 



