MIGRATION OF SALMON FRY. 307 



again with the old salmon, and therefore that 

 such produce are not mules, but of the same 

 species with their parents." Mr. Shaw also proves 

 that the milt of the common river trout will 

 impregnate the ova of the female salmon. It 

 remains hereafter to be seen whether the bull 

 trout, or salmo eriox, is or is not the produce of 

 that impregnation. It appears that the sea trout 

 is not, but is a distinct species. 



Generally in May, the parr having become 

 smolts, or salmon fry, being about two years old, 

 and seven inches in length, migrate for the first 

 time to the sea. If they return in about a month 

 they weigh from a pound to two pounds each, are 

 long and thin, and much forked in the tail. 

 " They keep on," says Mr. Scrope, " ascending 

 the river during the summer months, the new- 

 comers increasing afterwards about a pound and a 

 half a month on an average, but much less in 

 their very young state. The most plentiful sea- 

 son in the Tweed, if there is a flood, is about the 

 18th of July, at which period they weigh from 

 four to six pounds; and those which leave the 

 salt for the fresh water at the end of September, 

 and during the month of October, sometimes 

 come up the river of the weight of ten and eleven 

 pounds, and even more. All these fish are known 

 in the north by the name of gilses, but by the 

 London fishmongers are generally, I believe, 

 x 2 



