LIMPET. 



21 



spot, it forms a hollow in the place where it 

 rests, corresponding in size with the shape of the 

 shell. Into this depression the shell sinks, and 

 consequently there is no possibility of reaching 

 its edge, where alone it is vulnerable. When, 

 however, it is not warned, and prepared for resist- 

 ance, it can be easily detached by a shai-p move- 

 ment of the hand. 



In general, it is not a migratory creature, and, 

 consequently, is often seen to be so covered with 

 parasites of various kinds, that its form can 

 hardly be recognised. I have now in my aqua- 

 rium a limpet- shell, on which a specimen of the 

 common laver {TJlva latissima) and another of 

 Forphpra laciniata have affixed themselves, and 

 are growing luxuriantly. There was also in the 

 same tank another limpet-shell, on which was 

 growing a whole forest of sea-grass {Enteromorpha 

 compressa), expanding as widely as the crown of 

 a man's hat. The acorn barnacle, too, often takes 

 possession of the limpets, and it frequently 

 happens that, in some dark cavity of rock, a 

 colony of limpets may be found, each so covered 

 with these sessile barnacles, that not a particle 

 of the original shell is visible. Of this, however, 

 we will speak hereafter. 



The figure, plate B, fig. 3 a, represents the 



