40 RESULTS OF THE ATTEMPTS TO ACCLIMATISE SALMO SALAR. 



calls tliem races, but, as be himself remarks, it would " be 

 difficult " to discriminate between a race aud a species. 



When we consider all such matters, what assurance remains 

 to us " that the remaining and only trustworthy specific 

 character differentiating S'ahno salar from Salmo trtdta"* 

 — viz., " eleven rows of scales in an oblique row from the 

 adipose fin to the lateral line, all forms of S. irutta having 

 fourteen or more such scales," — does not break down or 

 become modified in the totally different environinont of the 

 antipodean waters of Tasmania to which S. salar h;is been 

 so largely introduced ? 



Are English ichthyologists prepared to declare a priori that 

 the scales of the variable genus Salmo are alone fixed, and 

 cannot be modified by the changed conditions of a totally 

 different environment? Surely not. 



If this possible modification be admitted by them, Avhat 

 becomes of the classification which depends upon this last 

 critical test for the separate specific recognition of the large, 

 matui-e silvery forms of Salmo salar and Salmo trutta. The 

 answer is simple enough : the classifier's final tost breaks down 

 entirely as a guide to the proper classification of the two 

 supposed distinct species. The experience of acclimatisation 

 of S. salar, and its results in the waters of Tasmania, 

 formerly devoid of any form of the genus Salmo, affords 

 better evidence to naturalists bearing upon variability than 

 can possibly be obtained in regions, as in Europe, where the 

 varialiility due to influence of any one locality or river is 

 being disturbed, and inferences obscured, and made hazardous 

 by the constant influx of stragglers originally bred in other 

 localities where other characteristics have been developed, and 

 which may be perpetuated for a considerable time with more 

 or less persistency in foreign waters among the prevailing 

 local types. 



No such interfusion from foreign sources can affect the 

 progeny of undoubted S. salar, largely introduced at different 

 times, and S. trutta only once introduced in small number, 

 in Tasmanian waters ; and consequently in such a region 

 there is less uncertainty as to what may or may not l)e the 

 extent of the modifying effect of environment j>fj- se than in 

 European waters where each region's locally-bred forms are 

 continually being interfused with immigrants bred in distant 

 regions. 



The conclusions to be drawn from these differing conditions 

 have not yet received that amount jf attention from classifiers 

 which they deserve, for it is too evident that a priori and not 

 a posteriori argument still largely colours the opinions of 

 many, and this ari.ses, no doubt, from the treacherous tendency 



• Sec ymurc, Janunrj- 12, 1888 



