122 KENDALL: NEW ENGLAND SALMONS. 



distinction than the characters usually mentioned in diagnosis. To the acclimatist and 

 fish culturahst their recognition is of vital importance, for which reason, when such 

 differences exist they should be recognized taxonomically. 



Comparison of Percentile Proportions of Lake Salmon and Atlantic Salmon. 



Smitt (1895, p. 830) says that the variability of form within the genus Salmo has 

 hitherto rendered it impossible to define with certainty the numerous species that have 

 been adopted. But referring to this variability he again pertinently remarks: 'Still, 

 both from a scientific and economic point of view it is of importance to know the con- 

 ditions that involve the said inconstancy; and to this end it has been necessary to de- 

 note by special names the more or less constant forms that appear under different cir- 

 cumstances and different locaUties.' 



The question as to what constitutes a species has already been discussed at some 

 length. It was suggested that there are two sorts of species. These 'more or less constant 

 forms' which Smitt found desirable to designate by 'special names' constitute one of 

 these two sorts of species. They are the taxonomic species, i. e., forms which in structure 

 conform to certain accepted codes or rules of zoological nomenclature. Taxonomic 

 species are not always stable nor immutable, they depend upon the point of view of the 

 taxonomist as Smitt intimated. The other sort of species I designate as natural species. 

 They may or may not constantly differ in visible structure. They may or may not also 

 be recognized as taxonomic species. The greater number of individuals observed the 

 less likely are they to be regarded as distinct taxonomic species, especially if constant 

 or fixed characters are looked for. The variations of proportions complicate the problem 

 of finding in them any distinguishing specific or racial character of taxonomic value. 



Certain variations of structure and dimension are regular changes involved in growth. 

 Others are sexual or incident to reproductive development, etc. They are inherent in 

 each and every species. 



Some structures and dimensions vary more than others. Salmon of the same age and 

 sex may differ considerably in their proportions even in the same season. For example, 

 of two fish of the same age, caught in the same place and at the same time, one may have 

 spawned in the preceding season and thus have undergone modifications of proportions 

 incident to the breeding season; while the other may never have spawned. At the same 

 time, however, each fish possesses characters which either do not change or else show 

 very httle modification. Again the modified proportions exhibited in the breeding 

 season have been acquired by gradual change through the feeding season immediately 

 preceding it. Therefore, through the summer and early fall, salmon which are to spawn 

 that fall may show a wider range of variations than those which are not going to spawn 

 that season. The changes of proportions which accompany the development of the 

 breeding condition are most pronounced in the male, particularly as pertains to the 

 head. One of these is the lengthening of the muzzle, which involves the snout and lower 

 jaw, by actual proliferation of tissue. The proportion of the length of the head to the 



