Spring on a Hill-stream 27 



in the watery cracks between the up-tilted strata 

 of the rocks. The increase of toads is checked both 

 by flood and drought. Strong floods wash the 

 strings of spawn out of the shallow pools ; and it is 

 probably often devoured by trout when it is washed 

 into the main channel, like the chub's spawn in the 

 lower reaches of the stream. In a droughty May 

 the pools dry up, and the tadpoles perish, as some- 

 times also happens to the frog's tadpoles in the 

 muddier pools and channels in the meadows. Both 

 toads and frogs must lay their eggs in water ; but 

 while frogs haunt pools and wet meadows all through 

 the summer, toads often travel far from their birth- 

 place to damp and shady spots. In spring they 

 often fail to hit upon a pool which provides safe 

 shelter for their spawn and tadpoles ; and this 

 is apparently one reason why the frog is the much 

 commoner species. 



The alternations of sunshine and cold storms 

 have an immediate effect both on trout and on 

 their insect food. On the rockier streams there is 

 seldom any abundant hatch of fly in spring, such as 

 is common on many rivers which flow over broad 

 stretches of gravel. March browns drift above the 

 rougher hill-streams in a thin sprinkling, rather 

 than in the dense swarms which will suddenly 

 appear on the surface of level and gravelly northern 

 streams in a few minutes of warm sunshine on even 

 the bitterest days. The hill-trout pick up their 

 strength and substance little by little on a mixed 

 diet ; and their steady recovery after the scarcity 

 of winter is as noticeable as that of a human con- 



