308 DIMYARIA.—PHOLADIDA. 
be the means by which the larvee effect their first 
lodgment; but, considermg the arrangement of 
the parts of the body in the adult animal, it seems 
to us that Mr. Garner’s view of their being the 
primary cause of the perforation, whilst the rasping 
of the valves is secondary, should be reversed. 
Such currents must be most effective in clearing 
away loosened and loosening particles. If there 
be any chemical action aiding, it must be due to 
the carbonic acid set free during the respiratory 
process. Evidence of a secreted solvent there is 
none. 
To the same authority I am indebted for another 
interesting fact in the history of this genus. 
“A remarkable property of the animals of this 
genus, and one which has long attracted notice, is 
their phosphorescence when placed in the dark. 
This phenomenon is exhibited by some other 
acephalous mollusks, and by the compound tuni- 
eated genus Pyrosoma. The light is of a bluish- 
white hue, and is regarded by Mayer to proceed 
from a luminous mucus, like that given off by the 
Meduse. ‘This mucus is thrown off into the sur- 
rounding water, so that the currents proceeding 
from the animal are luminous. Dr. Coldstream 
states, that the light is given out most strongly by 
the internal surfaces of the respiratory tubes, and 
that it is strongest in summer. Professor John 
Miiller 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.” * 
* Brit. Moll. i. 104, e¢ seq. 
