MR. SHAW'S EXPERIMENTS. 53 



In a letter to Mr. Shaw, written in the spring (1840), 

 I suggested to him to impregnate the ova of the Salmon 

 with the milt of the common river Trout, imagining 

 that the produce, if any, might be what is called in 

 the Tweed the Bull Trout, which exactly resembles in 

 outward appearance and general size what one would 

 conceive such a process would create. 



I learn from Mr. Shaw's last paper that he has suc- 

 ceeded in breeding the Sea Trout by artificial impreg- 

 nation with their own species ; so that the produce 

 of this cross, that is, of the River Trout and Salmon, 

 cannot be the Sea Trout of the Spey and other rivers, 

 but may possibly prove what I suggested. It is at 

 least a very curious coincidence, that the Tweed, which 

 abounds in common Trout, abounds also in Bull Trout ; 

 whereas in the Annan and the Tay, where Trout are 

 very scarce, the Grey or Bull Trout is very scarce also. 

 But though crosses may be produced by mechanical 

 impregnation, it is a matter of grave consideration 

 whether such take place naturally. Trout, however, 

 are always seen near the spawning beds of the other 

 Salmonidoe. 



"The young of these Sea Trout," says Mr. Shaw, 

 " at the age of six months bear no very marked re- 

 semblance to the young of the real Salmon, either in 

 the parr or fry state ; and as they advance in age and 

 size the resemblance becomes still slighter. But upon 

 comparing them with the common Trout, the resem- 

 blance is very striking, the general outline of the fish 

 being much less elegant than that of the young Salmon 

 or Parr ; the external markings being also more pecu- 

 4 



