BY K. M. JOHNSTON, F.L.S. 31 



1888. The ova of Salmo solar thus transported, amounted to 

 about eight hundred and fifty thousand. 



The ova were obtained under the direction of Toul, 

 Buckland, Francis Francis, Brady and others eminently 

 qualified to jutljjje — aided in each district by the most skilled 

 local experts. The pairs of parent fish, as might be expected, 

 represent many distinct individuals taken from many -widely 

 separated salmon rivers in England, Wales, Scotland, and 

 Ireland, including the Kivers Ribble, Hodder, and Tyne in 

 England ; the Dovey in Wales ; and the rivers Shannon, 

 LifEey, and Erne in Ireland. 



Now, assuming that one or two mistakes migbt have been 

 made by these various experts, this would not in any way 

 affect the greater number of ova collected and fertilised at 

 other times and places ; and surely it would be too prepos- 

 terous to assume that all the separate selections made by so 

 many experts failed owing to a similar mistake in each 

 separate case, in different districts, and at different periods. 

 The idea of hybridism under all such circumstances is 

 certainly extremely improbable. 



The names already mentioned as being concerned in the 

 selection are quite sufiicient to dismiss the hybrid theory a3 

 untenable as an explanation of the apparent absence iu 

 Tasmanian waters of the pronounced types of the Europeaa 

 Salmo solar. 



THE EXTINCTION THEORY. 



The second guess is not so easily disposed of, viz., that the 

 conditions of the new environment in Tasmania, whether of 

 temperature, food or enemies, were so adverse to the yoimg of 

 Salmo solar that they speedily died out. The non-ai^pearance 

 of unmistakable examples of Salmo salar after so many 

 years certainly adds great force to this concei:»tion, and would 

 of itself be conclusive if there were no alternative presented 

 to us accounting for the absence of typical forms of S. salar. 



As, however, altei'uative theories hereinafter discussed may 

 also account for the absence of the normal European type it 

 is necessary to examine the present theory most carefully. 

 First, let me confess that the extinction theory is sufticiently 

 reasonable to demand serious consideration. 



It is conceivable that the extremes of temperature in our 

 rivers and seas, or the numerous powerful enemies, such as 

 the barracouta, are such as may have accomplished the des- 

 truction of the progeny of Salmo salar. 



There are strong reasons, however, for the belief that the 

 theory of extinction on sucli grounds is unsatisfactory if not 

 untenable. In the first place the assumption that the local 

 temperature of our waters would cause the extinction of 

 Salvio salar, although apparently confirmed by the somewhat 



