Animal Luminescence 579 



One of the earliest attempts to preserve the light of Pholas was 

 made by Balthasar de Monconnys, the physician of Lyons, who 

 traveled widely through southern Europe. In his Journal des Voy- 

 ages (Part IL 434) , published at Lyon in 1665, he described how a 

 transparent liquid from the " ballari " or " dattes de mer," which he 

 obtained near Ancona in May 1664, would remain luminous the 

 next day, having been prepared the night before, but when the 

 liquid was distilled, the light disappeared. No doubt the experi- 

 ment reflected the goal of many philosophers— a persistent luminous 

 material. This goal seemed to have been realized by the discovery 

 in 1669 of the element phosphorus, the " phosphorus mirabilis " of 

 Krafft. 



With the new interest in experimental science in the early 

 eighteenth century, it is not surprising that attention should again 

 be directed to methods of preserving the luminous secretion of 

 Pholas. The mollusc was the subject of a monograph in the 

 Me'mo?re5 of the French Academy by Reaumur (1683-1757) in 1723, 

 " Des Merveilles des Dails ou de la Lumiere qui ils Repandent," and 

 several communications appeared as a result of work in 1724 from 

 an Italian group of investigators, Beccari, Monti, and Galeati (1747) 

 working at the Bologna Academy of Science. 



Reaumur's title is a translation of Pliny's De Dactylis, Eorumque 

 Miraculis. He noticed that the fresher the Pholas, the more light it 

 produced, whereas other " fish " became more luminous the longer 

 they were kept, a reflection of the growth of luminous bacteria on 

 the dead animal. He was the first to observe that by drying the 

 luminous parts of an animal, in this case Pholas, and then moisten- 

 ing with fresh water or sea water, the light would be restored. If 

 dried six days, light still appeared on moistening but was much 

 weaker. Brandy {eau de vie) immediately extinguished the light 

 of Pholas. Salt preserved it for some time, but his attempts to pre- 

 pare a permanent lighting liquid, a durable phosphor, failed. 



Nevertheless, Reaumur called Pholas a true natural phosphor. 

 He reasoned that the light was connected with a kind of fermenta- 

 tion, which might vary from time to time since even fresh caught 

 specimens of Pholas did not always luminesce, and he compared 

 the light of Pholas to that of the glowworm. When this animal 

 mates it is characterized by a particular kind of fermentation and 

 " it is probable that the light which spreads from the vers luisant 

 owes part of its vivacity to this fermentation." Reaumur's (1712) 

 plate of Pholas (dail) is reproduced as figure 49. 



The work of Beccari, Monti, and Galeati started when Count 

 Marsigli brought some specimens of living Pholas in the rock where 



