MR. SHAW'S EXPERIMENTS 33 



two lots of eggs of a salmon, weighing eighteen 

 pounds, were impregnated with the milt of two 

 male parrs, and there ensued precisely the same 

 result as before. Again, in December, 1838, four 

 lots of ova from an adult salmon were impregnated 

 with the milt of four parrs with similar success ; 

 and the same parrs, being afterwards placed in a 

 private pond, assumed the migratory dress in the 

 following May, not in the most minute degree 

 differing from what in the Tweed are universally 

 called smolts, and are acknowledged by all to be 

 the young of the salmon." 



All these experiments appear to me to be quite 

 conclusive, and of a nature to satisfy any one who 

 has not pledged himself to an opposite theory. 

 But if any thing were still wanting, it has been 

 completely supplied by an additional experiment, 

 which clenches the proof. 



On the 4th of January, 1837, a male parr, itself 

 the produce of a male parr and female adult salmon, 

 was made by expression of the milt to impregnate 

 the eggs of a salmon weighing twelve pounds ; and 

 for the better security of the lot the whole was 

 placed in a wooden trough, over which a sheet of 

 fine copper wire-gauze was fixed. The trough was 

 then placed in a stream of water previously pre- 

 pared for its reception, and the results were 

 precisely of a corresponding nature to those already 

 detailed. 



Now, if the parr and the salmon were distinct 

 species, their produce would be hybrids, and would 

 not, therefore, breed again, according to the rules 

 of nature established to prevent the confusion of 



D 



