162 
EDIBLE BRITISH MOLLUSKS. 
eaten, they give forth their light, and the same, too, 
when in the hands: the very drops, in fact, that fall 
from them on the ground, or on the clothes, are of the 
same luminous nature/^* * * § 
Dr. Coldstream states that ^Hhe phosphorescent light 
of this mollusk is given out most strongly by the in- 
ternal surfaces of the respiratory tubes, and that it is 
strongest in summer ; and Professor John Muller has 
observed, that when Pholades are placed in a vacuum, 
the light disappears, but reappears on the admission of 
air ; also, that when dried, they recover their luminous 
property on being rubbed or moistened. 
Many others have also made experiments with the 
Pholas, and have studied its phosphorescence, viz. Reau- 
mur, Beccaria, Marsilius, Galeatus, and Montius. The 
two first mentioned endeavoured to render this ^lumi- 
nosity permanent, and the best result was obtained by 
placing the dead mollusk in honey, by which its pro- 
perty of emitting light lasted more than a year. When- 
ever it was plunged into warm water, the body of the 
Pholas gave as much light as ever.^^J 
Beccaria also found that a single Pholas rendered 
seven ounces of milk so luminous that the faces of 
persons might be distinguished by it, and it looked as if 
transparent.^^ § 
Pholas dactyluSj or the long oyster, as it is called at 
Weymouth, is not often eaten in England, but is gene- 
rally used for bait. A Newhaven fisherman, however, 
told me they sometimes collect some for eating from 
* Pliny, Nat. Hist. vol. ii. bk. ix. c. 87. 
t Porbes and Hanley, vol. i. p. 107. 
+ ‘Phosphorescence,’ by T. L. Phipson, Ph.D., P.C.S., p. 105. 
§ Ibid. p. 104. 
