HOW CRABS GROW 59 



"shells," in order that the soft bodies under- 

 neath may increase in size. 



So once in every year, until it reaches its full 

 size, every crab has to cast off its shelly cover- 

 ing and get a new one in its place. A few days 

 before the change takes place it always goes 

 and hides away in some dark crevice among the 

 rocks, or behind an overhanging mass of sea- 

 weed, where none of its many enemies are likely 

 to find it. It knows perfectly well, you see, that 

 while it is without its coat of mail it will be 

 quite helpless; for its claws will be so soft that 

 it will not be able to use them, while its body 

 will be quite unprotected. Then a very strange 

 thing indeed takes place. Something like a 

 third part of its flesh turns into water ! If you 

 were to catch the animal at this time and to 

 shake it, you would be able to hear the water 

 swishing about inside its shell ! Then it gets 

 very restless indeed, and begins to wriggle about 

 a good deal, turning and twisting from side to 

 side, and rubbing its legs against one another, 

 till it is quite tired out. It then rests for a little 

 while, and begins to wriggle and twist about 

 again. The fact is that it is trying to get loose, 

 as it were, inside its "shell." After a time it 

 succeeds in doing this, so that the "shell" is 

 no longer fastened to its body at all. Then, 

 quite suddenly, a rent opens right across its 

 back, and the crab gathers itself together and 



