THE SEA SHORE 41 



rubens. A variety of prawns and also sticklebacks pene- 

 trate far up rivers, being apparently indifferent to the 

 change from salt to fresh water — a barrier which effectively 

 prevents the great majority of shore beasts from passing 

 up estuaries. 



We have dealt with the plants and animals of the 

 sea shore, very briefly, it is true, but in sufficient detail 

 we hope, to give some idea of their variety and of the 

 different types found under different conditions, and it is 

 now time to consider the many peculiarities of the shore 

 beasts and the particular devices they possess to enable 

 them to live and propagate their kind in the strange section 

 of the earth's surface which they have chosen for their 

 home. 



Methods of Attack and Defence 



Of the first importance are means of attack and defence. 

 Purely mechanical weapons are not particularly common 

 and are best exemplified by the powerful pincer-like claws 

 of the larger crustaceans, especially lobsters and crabs. 

 In the former the two pincers are never quite alike and 

 if a lobster be examined it will be found that one of the 

 claws is larger with rounded, irregular teeth — clearly 

 adapted for crushing — and the other slenderer with 

 numerous sharp teeth and is used for cutting. There is no 

 regular arrangement of these claws which may occur on 

 either side ; they are immensely strong and, in the case of 

 the shore crab, have been found capable of supporting a 

 weight equal to about thirty times that of the body, whereas 

 a man's right hand when clenched is unable to support a 

 weight equivalent to that of his own body ! Poison is 

 largely used, especially by the anemones and hydroids and 

 all their allies, which possess batteries of stinging cells, the 

 action of which is described on page 203. All over tne 



