PHOSPHORESCENCE OF PHOLADES. 491 



wax so that the notion of a menstruum that would 

 act indifferently upon all these substances, is, at pre- 

 sent at least, purely hypothetical. 



Some of these bivalves are gifted with a phospho- 

 rescent faculty, and amongst these the Pholas holds 

 a conspicuous place. Pliny says, " The phospho- 

 rescent fluid is so abundant in them, that it shines 

 about the mouths of those who eat Dactyli, shines 

 on their hands, and even on their clothes, from drops 

 falling thereon;" and according to Reaumur, the 

 Pholas secretes the fluid in sufficient abundance to 

 answer this account. He removed the animal from 

 the shell, and on placing it in the dark, the light 

 appeared to emanate from every part of the surface, 

 and on tearing it to pieces the internal parts seemed 

 to be equally luminous : 



" Take him, and cut him out in little stars, 

 And lie will make the face of heaven so fine, 

 That all the world will be in love with night." 



After having handled this Pholas, Reaumur, at 

 first by accident and then on purpose, washed his 

 fingers in a glass of water, which then appeared in 

 the dark " as a vessel of milk would do in the full 

 light of noon." The light thus emitted is of a bluish 

 white colour, and is stronger in proportion as the 

 animal is fresh and lively, more especially during the 

 summer season. 



What can be the use of this remarkable brilliancy 

 to animals lying concealed in deep holes, which they 

 have bored in clay or rocks, and for what purpose 

 they illuminate their gloomy cells, it is difficult to 



