The Natural History of the Salmon. 59 



the Salmonidae. Dr. Gunther says: "We have 

 mentioned that many points in the life history 

 of the Salmonoids still remain very obscure. 



" i. Johnson, a correspondent of Willoughby 

 (' Hist. Pise.' p. 194), had already expressed his belief 

 that the different Salmonoids interbreed, and this 

 view has since been shared by many who have 

 observed these fishes in nature. Hybrids between 

 the Sewin (S. Cambricus) and the River Trout 

 (S. fario} were numerous in the Rhymney and 

 other rivers in South Wales, before Salmonoids were 

 almost exterminated by the pollutions allowed to 

 pass into those streams, and so variable in their 

 characters that the passage from one species to the 

 other could be demonstrated in an almost unbroken 

 series, which might induce some naturalists to 

 regard both species as identical. Abundant evi- 

 dence of a similar character has accumulated, 

 showing the frequent occurrence of hybrids between 

 S. fario and 5. trutta. Hybrids between the 6". 

 fario and species of Char have been abundantly 

 bred by continental pisciculturists. In some rivers 

 the conditions appear to be more favourable to 

 hybridism than in others, in which hybrids are of 

 comparatively rare occurrence. Hybrids between 

 the salmon and some other species are very scarce 

 everywhere. The hybrids are sexually as much 

 developed as the pure breed, and nothing what- 



