I 



THE SEASHORE 171 



mammal. The broad fact is, that the shore fauna is very 

 representative. 



We must not, of course, include among the shore forms those 

 pelagic animals, such as jelly-fishes, which are often stranded in 

 enormous numbers. On the other hand, we have to remember 

 that many of the truly littoral animals spend their youthful life 

 in the open sea ; they are delicate larvae, quite unsuited for the 

 rush and tumble of the shore, but safe as swimmers or drifters in 

 open water. Many seashore Worms, Echinoderms, Crustaceans, 

 and Molluscs have pelagic larvae. 



The characteristic of the shore area as distinguished from other 

 haunts of life is its variety and changefulness. ' The conditions 

 of life on the shore are in some ways the most stimulating in the 

 world. It is the meeting-place of air, water, and land. Vicissi- 

 tudes are not exceptional, but normal. Ebb and flow of tides, 

 freshwater floods and desiccation under a hot sun, the alternation 

 of day and night felt much more markedly than on the open 

 sea, the endless variations between gently lapping waves and 

 blasting breakers, the slow changes of subsidence or elevation, 

 these are some of the vicissitudes to which shore animals are 

 exposed." l 



Partly because the conditions of life on the shore are very 

 changeful, partly because of the dense population, and partly 

 because of the self-assertiveness natural to vigorous, lusty 

 creatures, there is much struggle and competition on the shore. 

 The heron standing alert by the water's edge is on the outlook 

 for fishes, which are on the outlook for shrimps, which are on 

 the outlook for still smaller fry, and so on it goes. The oyster- 

 catcher seeks with a neat stroke of its strong bill to knock the 

 limpet off the rock ; the limpet does its best not to be taken 

 by surprise. There are combats between rival shore-crabs, 

 such as Carcinus mcenas, and between hermit-crabs (Eupagurus 

 bernhardus). There is the quieter kind of non-competitive 

 struggle of the living organism against the vicissitudes of 

 its environment, when shore animals adjust themselves, or 

 re-act in the direction of adjusting themselves, to unfavourable 

 conditions. 



1 See (Thomson) p. 222. 



