836 
SCANDINAVIAN FISHES. 
and that of the body. The general form series in this 
relation is the following: 
Average 
alpinus. 
stagnalis. 
salvelinus. 
Length of the maxillaries in % of that of 
the body 
7.9 
7.6 
9.8 
Average distance of the ventral fins from 
the tip of the snout in % of the 
length of the body. 
I. 
11. 
111. 
IV. 
V. 
(cf 
Salmo salvelinus < 
51.7 
51.4 
52.6 
54.3 
— 
1.9 
51.4 
51.5 
51.9 
52.2 
— 
I d* 
Salmo stagnalis < 
— 
48.7 
49.i 
50.3 
— 
1 9 
— 
46.i 
47.9 
49.4 
47.o 
I’c? 
Salmo alpinus < 
19 
47.5 
48.2 
48.i 
— 
— 
40.4 
47.2 
47.7 
— 
— 
Here the series is irregular: alpinus occupies an 
intermediate place in the averages, stagnalis having a 
lower average, and salvelinus the highest of all. We 
arrive at the same result, if we examine the several 
stages of growth; e. g. the third (III): 
Average 
stagnalis. 
alpinus. 
salvelinus. 
Length of the maxillaries in % of that 
C? 
7.8 
9.9 
9.9 
of the body < 
1 9 
7.3 
8.1 
9.6 
Ranged in this manner the form series ascends 
with fair regularity, at least in the females, towards 
salvelinus; and the changes of 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 stagnalis, with the female characters, on 
one side of alpinus, and salvelinus , with the male cha- 
racters, on the other. If alpinus were omitted from 
the comparison, or if we were ignorant of its existence, 
the relation between salvelinus and stagnalis would 
seem almost exactly similar to that between trutta 
and salar. 
The character, derived from the situation of the 
ventral fins, which as a rule — not. entirely free from 
exceptions — separates alpinus from salvelinus, 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: 
The changes of growth here follow a regular 
course with increasing averages, at least in the females 
of salvelinus and alpinus and in the males of stag- 
nalis. Nearly all the males have greater averages than 
females of the same form and age. The form series, 
expressed in averages for all our specimens, is as 
follows: 
Average 
alpinus. 
stagnalis. 
salvelinus. 
Distance of 
the snout 
the ventral fins from the tip of 
in % of the length of the body 
47.4 
48.5 
52.o 
Not only the form of the Salmones, but also their 
manner of life indicates their common descent. It 
seems most probable that the Salmons were originally 
marine fishes of an arctic or subarctic (boreal) region, 
that for procreative purposes they made their way 
into arms of the sea and the mouths of rivers, and 
that by a stronger and stronger development of this 
roving disposition they were transformed to fresh-water 
fishes for a great part of their life, or finally changed 
their abodes for all time. Among the Scandinavian 
Salmons the Blanklax ( Salmo salar ) represents the most 
migratory type, the Saddling ( S . salvelinus ) is most 
completely a fresh-water fish. As there is nothing in 
the form characters to indicate an evolution of true 
Salmon from Charr, 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 water 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. 
