38a 
THE OCEAN WORLD. 
has long puzzled philosophers. The animal was supposed by some to 
secrete an acid which dissolved the stone and other substances. But 
how could this be done without dissolving the shell ? De Blainvill e 
thought that a simple movement of the shell, incessantly repeated, 
would suffice to pierce the stone macerated by the water inhaled 
through the breathing apparatus. Experiment proves that this e x ' 
planation is the correct one. Mr. Eobertson, of Brighton, exhibited 
living Pholades in the act of boring through masses of chalk : “ ^ 
living combination of three implements: a hydraulic apparatus, a 
rasp, and a syringe.” “If you examine these living shells,” says Gosse, 
“ you will see that the fore part, where the foot protrudes, is set with 
stony points arranged in transverse and longitudinal rows, the forme 1 
being the result of elevated ridges, radiating from the hinge, the latter 
that of the edges of successive growths of the shell. These points 
have the most accurate resemblance to those set on a steel rasp in a 
blacksmith’s shop. It is interesting to know that the shell is p re ' 
served from being itself prematurely worn away by the fact that it lS 
composed of aragonite, a substance much harder than those rocks m 
which the Pholas burrows. The animal,” Gosse adds, “ turns in d' 
burrow from side to side when at work, adhering to the interior by 
the foot, and therefore only partially rotating to and fro. The sub' 
stance is abraded in the form of a fine powder, which is gradually ejected 
from the mouth of the hole by contraction of the bronchial syphon- 
The Pholades are met with 
on every sea shore, and art! 
plentiful in the Channel ; 011 
the French coast they aie 
called Bails, and sought f° r 
their fine flavour. As example 
of the genus, we may quot ,e 
Pholas dadylm (Fig. 17^) ’ 
Pholas Candida, found in th e 
Channel, and in the Atlantic 
Ocean, which lives buried 111 
the mud or in decayed wood , 
Pholas crispata (Fig- 175)> 
also found in the Channel ; Pholas papyracea (Fig. 176); and Phol (lS 
melanoma (Fig. 177). 
Fig. 175. Pholas crispata (Linnajus). 
