102 THE HAUNTS OF LIFE 



ming larvae, called zoeae, marked by a spine 

 rising vertically above the back, and by a tail 

 sticking out at an angle to the rest of the body. 

 These larvae are swept out into the safety of 

 the open water, and they swim about near the 

 surface. They feed, they grow, they moult, 

 and another form of larva results. This does 

 the same, and a Megalops larva results, which 

 is beginning to be like a crab. It has lost the 

 spine; it has stalked eyes; it has got its full 

 complement of legs. Now this Megalops 

 bends its tail forwards and upwards under- 

 neath the anterior part of the body (the 

 cephalothorax] ; it ceases to be a free-swim- 

 mer; it sinks to the floor of the sea, and creeps 

 up the slope to its birthplace on the shore a 

 little crab about half the size of the nail of 

 our little finger. 



There is an interesting illustration of " The 

 Balance of Nature" in this connection. It 

 seems that the shore-waters are, on the aver- 

 age, richer in Plankton than any other waters, 

 the reason being that they are always receiving 

 abundant supplies of valuable salts brought 

 down from inland by rivers and streams. So 

 the shore-waters serve as a sort of nursery of 

 minute creatures that get swept out to sea to 



