Animal Luminescence 565 



went out when acids, ether, chloroform or hydrogen sulphide were 

 added to the sea water, but that nitrogen, hydrogen, and nitrous 

 oxid had no effect. In carbon dioxide, the Noctilucae gave a steady 

 glow which disappeared after a short time. 



Quatrefages (1850) also studied the effects of electricity. Became 

 to the conclusion that the light was not a secretion, as in Pholas and 

 Medusae, but was connected with contraction, since all agents which 

 cause contraction of the sarcode would cause luminescence. This 

 view was no doubt influenced by his previous study (1843) of lumi- 

 nous marine worms. More specifically Quatrefages thought the scin- 

 tillations of Noctiluca came from rupture of protoplasmic filaments 

 and the permanent glow from contraction of filaments adhering to 

 the surface envelope of the Noctiluca. Light emission was considered 

 a vital act connected with muscle action, a concept which has per- 

 sisted in bioluminescence literature for over fifty years. 



Later workers of the nineteenth century were mostly concerned 

 with morphology, but some physiological experiments were under- 

 taken. C. Robin and C. Legros (1866) were astonished at the slight 

 mechanical disturbance necessary to produce light. Observing Nocti- 

 lucae under a microscope, they noted that a local touch of the sur- 

 face with a needle would result in luminescence only in the touched 

 spot; it did not spread to the rest of the animal. In this way all 

 regions of Noctiluca were found to be capable of luminescence. 

 Later Robin (1878) took exception to Quatrefages' statement that 

 light production was always connected with contractility, since he 

 had observed that slight vibrations which did not cause tentacle 

 movement or shortening of protoplasmic strands would, neverthe- 

 less, excite luminescence. 



W. Vignal (1878) and J. Massart (1893) carried out the most 

 comprehensive and extensive studies. Vignal distinguished between 

 the effect of the current in causing retraction of the protoplasmic 

 strands, in stimulating the tentacle and in causing luminescence, 

 while Massart (1893) emphasized that the light emission was a re- 

 sponse to stimulation, comparable to muscle contraction or gland 

 secretion, rather than a result of muscle contraction, as Quatrefages 

 had implied. He found that not only would chemical and electrical 

 stimuli cause light emission but also changes in the salt content of 

 the medium, as when fresh water or concentrated salt came in con- 

 tact with the animals. The fatiguing effect of continued stimulation 

 was particularly noted and the physiology of Noctiluca given a 

 modern interpretation. The reversible narcotic action on lumines- 

 cence of various compounds was clearly established by Massart. 



