PHOLADIDyE. 
381 
Hey are born to dig their grave, and there they die in the groove of a 
r ock. What a profound mystery does the organization of animal life 
present ! What, thoughts does not the life of these little beings suggest! 
Submerged at the bottom of the waters, penned up eternally in a 
gallery of stone not an inch in depth ! For what were they created ? 
Human intelligence recoils before such unfathomable mysteries ! 
How the Pholadm contrive, with their inefficient tools, to bore into 
the heart of the stone which shelters them, is a point by no means 
settled. The organization of the 
mollusc is not even perfectly known. 
Hr its structure the shell differs 
notably from other Acephalous Mol- 
luscs, which led Linnaeus to place it 
Hth the multivalve shells. Between 
He two ordinary valves, in short, 
His shell presents certain accessary 
Pieces, smaller than the true valves, 
a nd placed near the hinge, as re- 
presented in Pholas dadylus (Fig. 
174), pieces which would not be 
Here without a purpose. 
The shell is equivalve, gaping 
°n each side, swelling below, very 
Hin, transparent, and white. The 
a nimal is a thick, white, elongated, fleshy body ; its mouth opening 
a nteriorly, throws out a long tube traversed by two canals or syphons, 
Hrough ono of which the water necessary for the respiration of the 
a uiiual is absorbed, and ejected through the other. Through another 
°pening in the mantle a very thick and short foot is protruded. 
“We lift one from its cavity,” says Gosse, “all helpless and unre- 
sisting, yet manifesting its indignation at the untimely disturbance by 
successive spasmodic contractions of these rough yellow syphons, each 
a ccompaniecl with a forcible jet d’eau, a polite squirt of sea-water into 
°Ur face ; while at each contraction in length the base swells out, till 
He compressed valves of the sharp shell threaten to pierce through its 
substance.” 
By what means do the Pholades contrive to hollow out their cell ? 
H T hat implement do they employ in their very limited space ? This 
