56 BRITISH FRESHWATER FISHES 



larger. Although the silvery Sea-trout and non- 

 migratory Brown Trout differ so much in habits 

 and appearance, there are no structural differences, 

 and the young are indistinguishable ; other reasons 

 for referring them to the same species may be here 

 given. 



It has been shown experimentally that Sea- 



FiG. 9. — Head of a large male Trout. 



trout, if prevented from going to the sea, will live 

 and breed in fresh water ; conversely Brook Trout 

 exported to New Zealand have found their way to 

 the sea and have given rise to an anadromous race. 

 Estuarine Trout are often intermediate in appear- 

 ance and habits between the migratory and non- 

 migratory fish, and there is good reason to believe 

 that in nature the ranks of the Sea-trout are rein- 

 forced by the offspring of the River-trout and 



