860 



MR. E. S. UUSSELL — ENVIRONMENTAL 



[Nov. 26, 



several fixed from 10-12 mm. long. Davis (4) found a limpet 

 ■g-^ inch long homing, and also smaller ones. 



From all these observations, then, the following conclusions 

 can be drawn; — (1) that every limpet of 15 mm. and upwards 

 occupies, for long periods at a time, a definitely fixed position, to 

 which it returns after any wanderings that it may make for 

 food ; (2) that limpets under 15 mm., if not yet settled in a 

 definite position, at least never wander far away, and so generally 

 keep to the same stone ; (3) that limpets wander chiefly when 

 covered by the tide. 



In many cases, of course, the limpet settles down at a much 

 smaller size than 15 mm. — for example, « at 10 mm., d at 7 mm., 

 and e at 5*5 mm. The factors delaying fixation would seem to be 

 three : 1st, a short exposure to air; 2nd, the moisture and shelter 

 afibrded by weed ; 3rd, want of a sviitable place for settling down. 

 The late fixation of low- water limpets is undoubtedly due to the 

 first two caizses, which usually act in conjunction with one another. 

 The third factor comes into play in the case where a small limpet 

 establishes itself on a stone which is completely covered with 

 barnacles, and can find no uncovered patch of rock on which to 

 settle down. 



II. High-xoater and Loiv-ivater Lwipets. 



Table III. gives the average ratios for 300 limpets collected at 

 two different stations near high-water mark, 200 at Station 1 , and 

 100 at Station 2. 



Table III. 



High-water Limpets. 



