PHOLAS MUSSEL COCKLE. 77 



" Now it may seem presumption on my part, after 

 so many learned opinions have been cited, and the 

 question left still undecided in the latest and most 

 careful treatises, to venture anything like a judgment 

 of my own. ' Who shall decide when doctors dis- 

 agree 1 ?' but I must confess that it does not seem 

 difficult to imagine the Pholas making its way into 

 its stony bed, by the simple process of licking a hole. 

 Reaumur observed, that when he removed the living 

 animal from its place, and put it in soft clay, it 

 quickly before his very eyes buried itself in that 

 substance. Although the stones in which some of 

 the species burrow are certainly harder than the clay, 

 yet it must be remembered that the clays in cabinet 

 specimens are much harder than when under water ; 

 and that this sucking and licking, and rubbing with 

 the foot, which is certainly of stouter material than 

 the rest of the animal, would be powerfully aided by 

 the action of the salt water. We see in the caves 

 below cliffs, how water can excavate hard rocks when 

 acting in circular currents, and we can easily imagine 

 how it would act in enlarging a cavity already begun. 

 In fact, we see, in the case of deserted holes of boring 

 bivalves, instances of the enlarging power of small 

 currents. If Reaumur's specimens could so easily 

 perforate the soft clay during the progress of a mere 

 experiment, how shall it be difficult to understand 

 perforation, by the same simple means, of a harder 

 substance during the gradual growth of the animal ? 

 While thinking on this matter, it occurred to me to 



