564 History of Luminescence 



ology of Noctiluca was studied in great detail. Some of tlie smaller 

 flagellates are reproduced in figure 40. 



The fine structure of Noctiluca was first described by P. Van 

 Beneden (1846) , using observations of Verhaege, who published in 

 1848, and by L. Doyere (1846) . As early as 1850, J. L. A. de Quatre- 

 fages (1810-1892) made a classic study of both morphology and 

 physiology of Noctiluca, and was followed by a host of workers on 

 structure and relationships, including T. H. Huxley in 1855. Quatre- 

 fages' famous figure of Noctiluca shows very clearly that the light 

 comes from minute granules scattered in the protoplasm (see fig. 

 45) . He distinguished between " the flash " resulting from stimula- 

 tion, and the " steady glow " which appeared under unfavorable 

 conditions. Quatrefages paid particular attention to the steady glow, 

 observing that it might occur locally in one region and then shift 

 its position, and could be observed even in fragments of the animal 

 as many bright spots of light, each spot made up of a " cluster of 

 minute instantaneous scintillations, dense at the center and more 

 scattered toward the circumference of the spot." 



It is the response of a luminous form to stimulation, which 

 intrigued the earlier workers. This response is characteristic of the 

 animal kingdom, since bacteria and fungi emit a steady light. Many 

 remarked how sea water seemed on fire when struck by oars, but 

 the modern concept of stimulation of a cell by mechanical, elec- 

 trical, chemical, or thermal stimuli developed during the first part 

 of the nineteenth century, largely as a result of the Galvani experi- 

 ments with frog's legs (1791). As indicated in the next section, 

 Spallanzani studied the relation between contraction and lumines- 

 cence in medusae in 1793, and von Humboldt stimulated a medusa 

 electrically in 1799. 



James Macartney (1810) had called special attention to the flash 

 of Noctiluca on mechanical agitation (as well as to the stimulation 

 of medusae mechanically, electrically, on heating, or when plunged 

 into " spirits ") but the first electrical stimulation of minute marine 

 forms, probably dinoflagellates, was made by C. H. Pfaff (1823) at 

 Kiel. The first electrical stimulation of Noctiluca was attempted by 

 J. H. Pring (1849) , who, curiously enough, observed no effect from 

 two " Smee batteries " imtil the current had been passed for some 

 time, when the Noctiluca gave a constant glow, an effect possibly 

 due to electrolysis products. Pring studied the luminescence of 

 Noctiluca in some detail, speculating on the nature of the phospho- 

 rescent matter and demonstrating that luminescence was indepen- 

 dent of previous exposure to sunlight. He spoke of animal light as 

 " vital phosphorescence " and found that the light of Noctilucae 



