262 CONCLUSION. 



dent. I therefore managed to saw away the rock 

 in such a manner, as to leave a narrow slit along 

 the entire length of the tunnel, so as to expose the 

 slightest movement of the animal within. Having 

 natural support for its siphons, I expected that these 

 organs would be constantly retracted and extended ; 

 but such was not the case ; at least for so long a 

 period as I had anticipated. 



After repeated experiments, I have now discovered 

 that whether the siphons be protected as above 

 described or not, they will always be vigorously 

 exercised if the animal be placed in shallow water, 

 so that its tubes when fully extended will reach the 

 surface of the fluid. 



The conclusion, from what has been stated, is, that 

 the Pholas can no longer be considered a weak and 

 helpless animal. Possessed of a rasp-like shell, a 

 horny ligament, retractile tubes, a strong muscular 

 foot, and a powerful spring or stylet, it is not by 

 any means difficult to conceive that these agents 

 when they are all brought into play, are fully equal 

 to the task of excavating the rocky chamber in 

 which the animal lives. 



