196 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



crown, inside of shell golden yellow or flesh-tint, fine ribs 

 towards edges. 



Habitat. — Patella inhabits the- intertidal zone, affixing 

 itself to rocks with snch force that it is dislodged only 

 with some difficulty. The method of this adhesion is not 

 known with absolute certainty. Limpets will hold on 

 very tenaciously to a surface smaller than the foot, so it 

 seems improbable that the latter acts like a sucker as has 

 been suggested. Another Anew is that the animal is 

 fixed to the rock by means of a glutinous snbstance 

 secreted by its foot, but, from examination of specimens 

 allowed, to fix themselves to plate glass, it seems that this 

 idea is also ill-founded. The most plausible explanation, 

 and the one supported by our evidence, is that it is a 

 case of adhesion of two very closely apposed surfaces, the 

 foot being, so to speak, rolled out on the rock. 



When the young limpet finds a suitable spot, it makes a 

 home of it, returning thither even after wandering some 

 distance in search of food. This " homing " faculty, noted 

 by observers since the days of Aristotle, is one of the most 

 remarkable endowments of the limpet, and it will be 

 referred to further on, when the sense organs are described. 

 One of us has studied this matter by observing animals, 

 specially marked with enamel paint, which were moved 

 and watched at suitable intervals. 



As a result of continued residence on one spot an oval 

 depression is formed in the rock-surface, at any rate on 

 the softer and smoother rocks. This is called the limpet's 

 scar. It has been suggested that; the scar is made by the 

 chemical action of an acid secretion of the foot, but there 

 is no proof that any sue!) secretion is produced, and well- 

 marked scars are formed upon siliceous rocks. The 

 distinctness of the soar appears to vary inversely as the 

 hardness of the rocks, and its peripheral portion is 



