s;^,(; 



SCANDINAVIAN I'ISIIES. 



and lliat oi' tliu bodv. The irt'iieral t'onn series in this 

 relation is the foUowini:: 



Here tiie series is irre.u'ular: idphiits occupies an \ Tiie ciianges uf growth liere follow a regular 



intermediate place in the averages, stfif/tiaUs having a course with increasing averages, at least in the females 

 lower average, and salrcJiiiKS the highest of all. We i of scdvdintts and alpinus and in the males of stag- 

 arrive at the same result, if we examine the several ' nnJis. Nearly all the males have greater averages than 

 stages of growth; e. g. the third (III): females of the same form and age. The form series, 



expressed in averages for all our specimens, is as 



follows: 



Ranged in this manner the form series ascends 

 with fair regularity, at least in the females, towards 

 salvdiiiKs: and the changes ot growth are also in di- 

 rect proportion to age. Thus, for example, we find 



In this relation, as in many others — we will 

 not give more examples here ~ the influence of a 

 marked sexual difference on the development of form 

 has ranged siar/nalis, with the female characters, on 

 one side of alpinus, and salrcli/ius, Avitli the male cha- 

 racters, on tiie other. If al]iiiius were omitted from 

 the comparison, or if we were ignorant of its existence, 

 the relation between salreliints and stai/nalis would 

 seem almost exactly similar to that between frufta 

 and salar. 



The character, derived from the situation of the 

 ventral flns, which as a rule — not entirely fi-ee from 

 exceptions — separates alpinus from salrcliniis, is mere- 

 ly an expression of the extremes in an evolution of 

 form still proceeding. Its signification appears without 

 difficulty from the following table of averages: 



Not only the form f>f the Salmonrs, but also their 

 manner of life indicates their common descent. It 

 seems most probable that the Salmons Avere originally 

 marine fishes of an arctic or subarctic (boreal) region, 

 that for procreative purposes they made their Avay 

 into arms of the sea and the mouths of rivers, and 

 that by a stronger and stronger development of this 

 rovins: disposition they were transformed to fresh-water 

 fislies for a great part of their life, or finally changed 

 their abodes for all time. Among the Scandinavian 

 Salmons the Blaukla.r (Sabno .'<ctlar) represents the most 

 migratory type, the Sa?lbling (iS'. salrclinu.'<) is most 

 completely a fresh-water fish. As there is nothing in 

 the form characters to indicate an evolution of true 

 Salmon from ('h;u-r, but everything seems to favour 

 the converse opinion, it is most natural to assume that 

 the primitive forms were marine fishes. 



During their life in fresh Avater the Salmons ac- 

 quire a coloration quite different from their sea dress: 

 the epidermis becomes tumid, conceals the scales in a 

 greater or less degree, and assumes a darker colour, 

 gray, grayish or greenish brown, partly black and red 

 or yellowish, developing at the same time spots of black 

 and red. But this coloration appears, in general cases, 

 only as the generative organs approach maturity; and 

 at times the Salmons remain long enough in fresh 

 water before these organs are fully ripe for spawning. 



