^4 THE BIOLOGY OF THE SEA-SHORE 



Retrospect. — ^We have now discussed the different prob- 

 lems confronting shore animals and given brief illustrations 

 of the way in which they are met. Some of these problems 

 are of such importance as to have had a profound effect on 

 both structure and behaviour. 



In particular, the feature of the shore as a region of 

 intense dynamic action — the biological importance of the 

 wave, in fact — is reflected in the numerous devices to secure 

 adhesion and especially in the small size and squat shape of 

 the animals inhabiting there. Where shells are present (as 

 in numerous shore Gasteropods) these are typically stout, 

 flattened, with reduced spires, coarsely sculptured and 

 severely inornate. The limpet shape is the most typical. 



The other great feature of the shore, viz. as a region of 

 extraordinarily fluctuating conditions, is reflected in the 

 possession by shore animals of a greatly increased adapt- 

 ability and a marked capacity for weathering sudden changes ; 

 in short, a greater tenacity of life. On the other hand, it 

 is safe to say that in the majority of cases, a place has been 

 obtained on the shore only at the cost of surrendering 

 considerable periods of potential activity. 



