PHOLAS MUSSEL COCKLE. 7 9 



against a possibility of either being accidentally 

 shifted, I at the same time sketched on the latter 

 the true position of the Pholas in the hole. By this 

 check, I could tell at a glance if there had been the 

 slightest deviation. 



For two whole months, not a day passed that I 

 did not look several times at the Pholas; and I can 

 positively declare, that during that entire period the 

 creature never moved, nor even oscillated its body, 

 more than the eighth part of an inch, either right or 

 left. At the end of eight weeks, however, upon 

 peering into the tank, I saw that a change had 

 occurred. The crosses exactly corresponded, but the 

 position of the animal had varied ! nay more, the 

 valves, which in general were clean, now exhibited a 

 furry or dusty appearance, shewing that they had 

 been at work for several hours. Even while I stood, to 

 my great delight, the boring operation was resumed. 



Now, to see a Pholas loose in the tank, or quietly 

 seated in the rock, extending and retracting his 

 syphons, would fail to give one the slightest idea of 

 his extraordinary appearance when enlarging his 

 dwelling. He is quite a different animal, appearing 

 to have suddenly acquired a most marvellous degree 

 of energy and perseverance, forming so striking a 

 contrast to his usual quiet, passive habits. 



In the first place, he retracts his tube to, and even 

 under the level of his shell just as a man about to 

 urge onward some heavy mass with his shoulders, 

 would depress his head to increase and concentrate 



