158 History of Luminescence 



Beccari's (1747) interest in bioluminescences ^ is shown by the 

 study (with Monti and Galeati) in 1724 of Pholas dactylus, the 

 boring mollusc, brought to Bologna by Marsigli. Their goal was 

 the same as that of Reaumur, preservation of the luminescence. 

 However, they attained greater success. The luminous material 

 could be kept for over a year by mixing it with flour or adding 

 honey, thereby forming a paste that would luminesce when added 

 to water.^° 



Bioluminescence Discoveries 



Throughout the eighteenth century knowledge of animal light 

 increased by the slow process of accretion; facts were added from 

 time to time. Biological textbooks in the modern sense were un- 

 known, and no general monograph on the subject appeared. Natural 

 histories merely mentioned that an animal was luminous. 



Some progress was made in proving that most phosphorescence of 

 the sea is due to living organisms, but the light of wood and flesh 

 was generally regarded merely as a natural phosphor to be contrasted 

 with the artificial variety, made by man. There was no certain 

 knowledge of luminous bacteria or fungal mycelium, although 

 " animalcules " were occasionally suspected as the cause of the light. 



The work of Reaumer and of Beccari and associates on the lumi- 

 nescence of Pholas, mentioned previously, that of Spallanzani on 

 luminous jellyfish (1794) , and the various studies of the effect of 

 gases on the firefly and on luminous wood and flesh, made toward 

 the end of the century, represent the experimental approach to the 

 bioluminescence problem. The belief was gaining that the light of 

 organisms was due to phosphorus or something like phosphorus, and 

 resulted from a slow combustion. 



Descriptions of new luminous animals continued, but the number 

 reported was small, compared with the new species to be described 

 in the nineteenth century. The published list begins with Meriam's 

 (1705) observation of light from the lantern fly, Fulgora. Swim- 

 ming worms (" Insects ") in the canals of Venice were seen by 



as electric bodies. This opinion was expressed by an anonymous writer, actually 

 Antoine-Joseph Dezallier d'Argenville, a member of the Royal Society of Sciences of 

 Montpellier. He sometiifles wrote under the pseudonym, Alexandre le Blond. His 

 book, L'Histoire naturelles eclaircie dans deux de ses parties principales, la Uthologie 

 et la conchylologie dont I'une traite des pierres et I'autre des coquillages, appeared at 

 Paris in 1742. The section on " Phosphores " contains nothing new, except the author's 

 identification of phosphors with electricity, but a rather complete list of the known 

 luminescences is presented. 



^ For details, see Chapter XVI of this book. 



^^ When the author started work on luminescence in 1916, Professor Raphael Dubois 

 kindly shipped him a jar of the siphons of Pholas, preserved in sugar, from Tamaris- 

 sur-Mer, France. 



