188 THE HARMONIES OF NATURE. 



thousands that originally left the damp forest-grounds, com- 

 paratively but a small number return, emaciated and exhausted, 

 to their mountain-burrows, and a few weeks after, millions of 

 the little crabs which have been hatched on the shore may be 

 seen making their way up to the hills. Who can explain to us 

 the mysterious voice which prompts them to seek an unknown 

 home, so different from the scene where they first drew breath ; 

 who tells them that far from the torrid shore they are sure to 

 find a more congenial retreat in the cool shades of the forest ; 

 and who, throughout countless years, directs these constant mi- 

 grations from the sea to the uplands, and then again from the 

 mountains to the brink of the ocean ? 



