Animal Luminescence 547 



Gueneau de Montbeillard pondered the question as to why wing- 

 less females of other insects are not also luminous and why the eggs 

 of the glowworm should be luminous, without giving too logical an 

 answer. He decided that luminescence of the eggs explains why the 

 female is most brilliant before the eggs are laid and loses its bril- 

 liancy afterwards, " as if the principle of the light in them was the 

 same as the principle of life." 



Another memoir on the glowworm came from Lausanne; Switzer- 

 land, written in 1786, by the mineralogist, Count Gregor de Razou- 

 mowsky (died 1837) . It added practically nothing new to knowl- 

 edge of the animal. Count Razoumowsky merely described the " ver 

 luisant " as " an insect of ways extremely gentle and peaceful, which 

 lives alone and occurs in numbers only by accident. ..." 



RELATION TO OXYGEN 



Boyle's discovery that the light of the glowworm disappears in a 

 vacuum and returns in air has already been mentioned. Apparently 

 the second person to try the vacuum experiment was C. P. D. 

 Beckerhinn, pharmacist of Strassburg, who obtained similar results 

 in 1789. 



One of the earliest studies on respiration of the glowworm was 

 that of Professor G. Forster of the University of Gottingen, who was 

 impressed with " the unbelievable power of dephlogisticated air 

 (oxygen) to ignite bodies and to facilitate respiration." He was 

 the first to submit a theory of the control of luminescence by admis- 

 sion of air to the light organ. Forster determined in 1782 that the 

 male glowworm (Lampyris splendidula) ceased to flash and its light 

 became steady and very bright in oxygen. The flashing began again 

 when the insects were removed to ordinary air. This behavior, 

 together with the fact that spiracles were present in the rear seg- 

 ments of the insect where the light was produced led him to believe 

 that respiration was concerned. He considered the flash to be con- 

 trolled by a sudden inspiration, and " that the light decreased as the 

 air in the tracheae became saturated with phlogiston, after they are 

 shut off by the will [of the insect]." The luminous material was 

 regarded as an animal humor comparable to phosphorus dissolved 

 in oil, which lights but does not burn in free air. Although Forster 

 could not imagine how the luminous substance was formed, he 

 considered it no more unusual than the production of an electric 

 fluid by electric fish, such as the torpedo. 



Like many others he clung to the phlogiston theory, but his ideas 

 were perfectly clear and his observations accurate. Forster also noted 



