PROGRESS IN BIOLOGICAL INQUIRIES, 19 31 493 



underwent physiological changes, one of which, perhaps, was the 

 lost power of the young to undergo the transformation from parr to 

 smolt. which immunizes the young of the sea salmon against any 

 harmful effects in the transition from fresh to salt water. 



In addition to all the other evidence, and there is considerable, that 

 the lake salmon (the preferred designation) should be regarded as a 

 distinct species, tables of percentages of proportional measurements 

 were prepared and analyzed, and comparison made with like pro- 

 portions of sea salmon. Some of the proportions show no differences 

 whatever, excepting those due to sex, age, or size of the fish. In fact, 

 it is only by averages that any of the proportions show differences, 

 for they all overlap as they do with other species of Salmonidse. 

 There seems to be no possible way to describe an individual salmonid 

 in terms of proportions by which a species can always be positively 

 identified, but the enseiiibJe of proportions, after elimination of vari- 

 ations due to sex, size, and age, when expressed in averages, tells the 

 story. One authority on the sea trout of Europe {Salmo trutta) 

 states, in effect, that it can not invariably be distinguished from 

 Salmo salar, but there can be no doubt about their being distinct 

 species. 



In one set of proportions the landlocked salmon differs from the 

 sea salmon (by averages) in exactly the same way that Salmo trutta 

 does. This is in the proportion of the part of the body known as 

 the caudal peduncle, which in the landlocked salmon averages much 

 stouter than that of the sea salmon. The difference is most clearly 

 shown by averages of the percental proportions of the least depth of 

 the caudal peduncle to the distances from adipose and anal fins to 

 caudal, as above mentioned. These proportions are greater in the 

 male of both species than in the females, but the differences between 

 the two species are maintained in both sexes. 



Chars. — As in the case of other Salmonidae, there has been no uni- 

 formity and stability of classification of the chars (Salvelinus and 

 others). One reason for this is that no one has had an adequate view 

 of the whole field, and, therefore, individual opinions have been based 

 upon glimpses only of the situation outside of immediate surround- 

 ings. 



In ichthyology generally, both European and American systema- 

 tists have iDeen more or less at variance in their interpretations and 

 manner of expressing what they saw. In both countries, but more 

 particularly in Europe, there have been two schools of systematic 

 ichthyology. The tendency of one, which was the larger school, was 

 to reduce the number of nominal species to its lowest terms. That of 

 the other was to multiply them particularly as pertained to local 

 faunas. 



Thus there have been those who have regarded all the chars of 

 Europe as constituting a single species, with local variations. Others, 

 especially in Great Britain, have discerned in those variations char- 

 acters regarded as of specific significance. 



The single species advocates have extended their conception of 

 that species to include chars of the Arctic regions of both Europe 

 and North America whenever they have had the occasion to consider 

 them. In America the same tendencies have obtained, but not always 

 consistently. 



