120 THE EVOLUTIONIST AT LARGE. 



of swarming bees around their queen. In 

 like manner the Jamaican land-crabs, which 

 themselves live on the mountain-tops, come 

 down every year to lay their eggs in the 

 Caribbean ; because, like -all other crabs, 

 they pass their first larval stage as swimming 

 tadpoles, and afterwards take instinctively to 

 the mountains, as the salmon takes to the sea. 

 Such a habit could only have arisen by one 

 generation after another venturing further 

 and further inland, while always returning at 

 the proper season to the native element for 

 the deposition of the eggs. 



These trout here, however, differ from the 

 salmon in one important particular beside 

 their relative size, and that is that they are 

 beautifully speckled in their mature form, in- 

 stead of being merely silvery like the larger 

 species. The origin of the pretty speckles is 

 probably to be found in the constant selection 

 by the fish of the most beautiful among their 

 number as mates. Just as singing birds are 

 in their fullest and clearest song at the nest- 



