30 RESULTS OF THE ATTEMPTS TO ACCLIMATISE SALMO SALAR. 



To this question several rough £;uesses have been made by 

 various authorities, but all of which are most uusatisfactorj, 

 as in my opinion none of them were arrived at either by a 

 scientific method or in a scientific spirit. They were purely 

 rough guesses, as already described. 



It is not necessary to discuss the whole of the opinions 

 advanced at different times. It will be sufticient to bring 

 under review the three which have found more or less favour 

 with some. These are — 



1 (the Hybrid Theory). — That the ova introduced were 



not derived from parents that were true types of 

 !>ah))o solar, but owing to mistake either the ova of 

 hybrid forms were introtlucetl, or that the ova of 

 S. salar by mistake were fertilised (artificially) by 

 the semen of S. frntta or vice versa. 



2 (the Extinction Theory). — That the conditions of the 



new environment in Tasmania, whether of tempei*a- 

 ture, food, or enemies, were so adverse to the young 

 of the S. salar that they speedily died out. 



3 (the Exodus Theory). — That the temperature of our 



waters range so high that in consequence the fish 



do not return to their native rivers, but wander 



away from our shores to more congenial waters. 



Thus we have to examine three distinct conceptions, which. 



for convenience may respectively be classed as (1) the hybrid 



theory, (2) the extinction theory, and (3) the exodus theory. 



THE HYBRID THEORY. 



That hybrid breeds between the various species of salmon 

 exist in large numbers in European and American waters is 

 too well confirmed by Johnson, Gunthor, Day, Brady, Francis, 

 Buckland, and other authorities, whose observations hafve 

 been extensive and accurate. That these hybrids interbreed 

 and perpetuate their several overlapping varieties has also 

 received the most ample confirmation. 



To assume, however, as Dr. Gunthor seems to have done in, 

 his " Study of Fishes " (p. 642), that only hybrid forms havo 

 been introduced to Tasmania, is quite a different matter, and 

 is, moreover, without justification, when all the facts of the 

 case arc judicially examined. 



In the first place, let it bo clearly understood that the ova 

 stated to have been obtained from hoiia Jhlr examples of 

 tSahno salar have neither been collected at one time, at ono 

 place, nor from one ]>articular pair ; neither havo they been 

 selected and fertilised by one j)articular person. 



On the contrary, there were five distinct shipments of ova 

 successfully transported and finally hatched and liberated in 

 Tasmanian waters in the years 18G4, 18GG, 1884, 1885, and 



