GLOW-WORMS, TERMITES, SHELLS 237 



intricate channels into innumerable smaller water- 

 courses. The land-shells that cover that area will be 

 moved onward by the advancing flow, and the water- 

 shells that occupy the mountain streams will be spread 

 over the now swampy land. 



I will mention one other observation in connection 

 with the dispersal of shells. Just below the summit of 

 one of the forest-clad hills that confine the valley, and 

 at an altitude of 8800 feet, I found a shallow muddy 

 pool not more than twenty yards in width. A few 

 other similar pools lay close by. The litde patches 

 of stagnant water were completely isolated on this 

 mountain top which was bounded by deep valleys 

 on either side. Now this pool was teeming with 

 bivalve molluscs. I never saw so many bivalves 

 together in any pool. But I could not find a single 

 univalve. 



The questions arise : How came this mountain pool 

 to be stocked with shells, and why are there no 

 univalves ? I see no other way by which shells could 

 have been carried to a pool at such a height except 

 in the way suggested by Darwin, namely by clinging 

 to the feet of water-birds and being thus transferred 

 from pool to pool. It might be thought that water- 

 birds would never visit a mountain summit, but 

 I was told by the Rev. Mr. Lawrence, who had 

 observed the birds on this hill for many years, that he 

 had records of a teal and a green sandpiper alighting 

 on these pools. 



How are we to explain the presence of bivalves 

 alone ? Is it not possible that bivalves with their 

 power of grasping objects between their shells would 

 be more likely to cling firmly to the toes or feathers 



