MYSTERIOUS MIGRATION 233 



their skins and change to a new form. 



In the new form, retaining none of their original character- 

 istics, they would be known as megalops, which is to say, 

 they would still be outlandish looking creatures. But in this 

 new shape they would bear some faint resemblance to a crab, 

 although a horrible misshapen sort of crab with a wriggly tail 

 and a pair of claws in proportion to nothing except its appetite. 

 In this megalops stage the crab-to-be turns cannibal and greed- 

 ily devours its younger brothers and sisters which, not so 

 fortunate as itself, have not yet attained full megalops-hood. 

 Nor does it satisfy itself with young zoea, but munches its 

 grotesque way through Hfe devouring everything in sight, 

 shedding its skin, and growing the while until it moults for 

 the last time and emerges, wet and ever so tiny, on the beach 

 as a perfect crab. 



But not yet is this midget a land crab, for that is a matter 

 of training. Its ancestors, back in the remote centuries, took a 

 few hundreds of thousands of years to accomplish the transi- 

 tion from sea to land, at first clambering on the rocks of some 

 ancient sea, poking their heads into the air and then dashing 

 back again. So this baby crab recapitulates the history of its 

 ancient relatives. In the dark of the evening, for it becomes 

 nocturnal and no longer seeks the light, it creeps up on the 

 pure sand of the beach. But not very far. The sea is still its 

 mother and like a chick with a hen it dashes back to her for 

 protection. And it needs protection, for death stalks the beach 

 in a thousand forms. 



The greatest danger is that of drying up. Tucked away 

 under its eighth-inch body is a set of diminutive gills, tiny 

 little fringed tissues hidden ingeniously away where the gritty 

 sand may not reach and injure them. In the deeps of the water 

 these gills had served it well, gathering the oxygen from the 

 brine, distributing it through the tissues, and in all its baby- 



