MYSTERIOUS MIGRATION 235 



ing beach crabs desert the shore and step back into the dark 

 mystery of the island. It is the crossing of their Rubicon. For 

 a full year they will not see the ocean again, and when they 

 return their life's purpose will have been accomplished. Many 

 will never see it again. But dauntless they move ahead. Go in- 

 land, their instinct says, go inland to the very center of the 

 island. 



Hundreds fall by the way. Some are killed by birds, some 

 perish by accident, falling into deep holes from which there 

 is no escape. The latter die of starvation and thirst, for the 

 islands are places of httle water. Only by nibbling on little 

 twigs and on green vegetation can they secure the water they 

 need so badly. The gills still must be kept moist. Should they 

 dry, even slightly, death will quickly follow. 



Above all they avoid the sun. Ten minutes' full exposure 

 in the sun means certain disaster. Crabs have no sweat glands 

 to keep them cool and, when the tropical rays beat down on 

 their purplish backs, their shells become so hot they can 

 scarcely be touched. But the crabs do not live that long. With 

 the first sudden rise in temperature they become drowsy, their 

 legs fold wearily under them, and they fall to the ground, 

 Once fallen they never rise again. 



I discovered this quite by accident one day when I cornered 

 a crab in an open glade. Frantically it tried to reach the shade. 

 It even lost all fear of me and tried to scramble between my 

 legs. But I did not know the reason for its panic and kept it 

 in the open. Hardly three minutes had passed before its claws 

 fell weakly to the ground and it toppled on its face. A mo- 

 ment later it was dead. 



Out of the thousands that die by the way a certain number 

 reach the appointed place and distribute themselves over the 

 land. In the shade of the bushes and around the roots of the 

 trees they excavate deep holes, long curving cavities in the soil. 



