MARINE BIOLOGICAL STATION ON PUFFIN ISLAND. 13 



head always facing the one way in order that they may fit 

 into the depressions. 



It is not yet known by what sense the hmpets are able 

 to find their way back to their roosts when they leave them 

 in search of food. It is certainly not by sight, as the eyes 

 are very simple and imperfect. It has been proved by 

 experiment that it is not by smell ; w^hile taste, and feel 

 can scarcely help. There may be a sense of direction 

 different from anything we know of in our own experience ; 

 but what the exact method is by which the limpet finds its 

 way about, can go back the way it has come, and can 

 recognise its own roost amongst a number of similar 

 neighbouring depressions, has still to be discovered. 



Now^ for the interest of the present specimen. It is so 

 closely moulded to the iron bar that I am of opinion that 

 it could not have been in the habit of leaving its home and 

 prowling about. In the first place, the bar was short, and 

 was loose, and free to roll about, and it would be very 

 difficult for a crawling snail-like animal such as the limpet 

 to cross from the bar to the rocks even if its support was 

 stationary, but if, as seems likely, the bar was being rolled 

 about by the waves, one does not see that it would be 

 possible for the limpet to re-find its roost, if it ever left it. 

 Possibly, how^ever, as some think, the limpet never loosens 

 its hold when covered by the tide. This would remove 

 the difficulty partly but not wholly. Then, in the second 

 place, the shape of the shell in this specimen is such that 

 I do not see that the animal could crawl over the rocks, or 

 could occupy any position other than that on the bar in 

 which we found it. 



After examining this specimen, I looked carefully at 

 the limpets scattered over the rocks, and found several 

 in w^hich the animal was situated at the bottom of a 

 deep pit, from which it would be very difficult, if possible 



