72 THE WONDER OF LIFE 



tomy ' or self -mutilation, losing a member or part, but 

 saving the whole life, and able at leisure to regrow what 

 they have lost. Protective colour-resemblance is frequent, 

 as we may see in young shore-crabs (Carcinus mcenas) 

 which show many different colours and patterns, and 

 are often most effectively like the substratum of the rock- 

 pool on which they rest. We shall discuss later on the 

 extraordinary power of protective colour-change in some 

 prawns (Hippolyte varians), and that of young flat-fishes, 

 as they assimilate themselves to the sand or gravel, is not 

 less perfect, though within a narrower radius. The sand- 

 crab (Hyas araneus) and others mask their carapace with 

 seaweed, so that they move about under an innocent 

 disguise, anticipating on their own line such human tricks 

 as ' the walking wood of Birnam'. And this is only the 

 beginning of a list of life-saving adaptations in the shore- 

 area. 



We cannot pass from this brief study of the littoral 

 fauna without recalling the probability that it was on 

 the sea-shore that many of the most valuable of vital 

 acquisitions were made. Many of the great types of 

 animal life have been to school on the shore, and who 

 shall say what lessons they did not learn amid that rough- 

 and-tumble life, where changes come often, where competi- 

 tion is keen, where the discipline of dislodgment is ever 

 recurrent, where a premium is put on alertness and per- 

 sistence and adaptability ? The shore has been a great 

 school of life. Yet in saying this we do not wish to imply 

 that the wisdom of any animal race whatsoever has been 

 due to the premiums which individuals have paid to 

 experience. For this theory of entailment does not seem 

 to us to describe Nature's method. 



