PHOLAS CRISPATA, LINN., AS A BORER. 39 
has furnished a subject for various observations and experiments 
to different learned men, especially to M. Reaumur and M. Bec- 
carius, who particularly devoted their attention to the subject of 
phosphoric light. The luminous quality of the Pholas is in pro- 
portion to its freshness, but even when in a dry state it may 
be revived by the application of fresh or salt water. Brandy 
immediately extinguishes the light. A solution of seawater 
(sic) increases it; and ammoniac diminishes it a little; oil of tartar 
nearly extinguishes it, and the acids entirely. The luminous 
water, when poured upon fresh calcined gypsum, rock crystal, or 
sugar, becomes more vivid. Milk, rendered luminous by the 
Pholas, loses its shining quality when mixed with sulphuric acid, 
but regains it on the addition of oil of tartar. Colour substances 
are differently and powerfully affected by it; white appears to 
imbibe and emit the greatest quantity ; yellow and green in less 
proportion ; red will emit hardly any light; violet least of all. 
A single Pholas will render seven ounces of milk so beautifully 
luminous that surrounding objects are clearly visible by its light. 
This luminous quality entirely disappears when the milk which 
contains it is excluded from the air, but again revives on exposure 
to the atmosphere. In the exhausted receiver of an air-pump, 
the Pholas loses his light. The reason for this remarkable pro- 
vision, as well as the purpose to which it is applied in the animal 
economy, are unknown.” 
