908 
SCANDINAVIAN FISHES. 
The clearest expression of the evolutional course 
of the form-series we here find in the relation between 
the depth of the snout at the rostral protuberances 
and the length of the maxillaries: the former increases 
and the latter decreases, so that the averages rise with 
great regularity from left to right in the last line but 
one of the table. Yet these averages, as we have men- 
tioned, must be considered with reference to the size 
of the specimen: among small specimens both of Nils- 
sonii and lavaretus for example the manocentrous show 
a smaller average than the pycnocentrous; but the law 
of evolution tells us, according to the preceding table, 
that if the former had been permitted to attain a 
sufficient size, their percentages for this relation would 
undoubtedly have risen enough to fill their place in 
the series. 
Bearing this result in mind, we can easily deter- 
mine the systematic value of the peculiarities which 
seem to characterize the Gwyniad where it lives under 
exceptional conditions. In Enare Traesk for example 
(Finnish Lapland) it sometimes develops the beaked 
form" at a length of 14 or 15 cm. and with a depth 
of snout persistently answering to the shallow snout 
of the typical blasikar, though it is quite manocentrous, 
with no more gill-rakers than a polcur. But to coin 
a special name for such a form, is of questionable 
utility, for a similar prolongation of the snout, though 
not quite so great, may be observed in young blasikar , 
for example from Qvickjock, where they attain matu- 
rity at about the same size'. 
The relation between the two groups, the one c 
collected round the bldsik type, the other** round the 
fetsik type, is evidently the same as that between 
trutta and salar among the Salmons. They come so 
near each other that constant characters to distinguish 
them cannot be adduced; the one is a more advanced 
development of the other, and they intermingle in their 
spawning operations *. However unlike the differentia- 
tion of form may be in localities at a distance from 
each other, variations as great may be observed in the 
same water, the extremes of the form-series appearing 
side by side. No wonder then that ichthyologists have 
failed sharply to define local varieties, though a more 
than adequate number of names have been proposed 
to this end. 
The coloration of the Gwyniad is essentially the 
same as that of the Vendace, and is subject to the 
same variations of light or dark tone. The back is of 
a, lustrous steel-blue, whence the name of bldsik , or 
black, in which case the latter colour also extends to 
the upper part of the head and forward over the snout, 
or, like the top of the head, of a more greenish gray 
tint and more or less transparent, the transparency being 
most noticeable in the occiput and the snout, though 
the tip of the latter is commonly brownish black. The 
sides of the body have a silvery lustre, but often pass 
into a dirty gray, which colour has given rise to the 
name of grdsik , and is sometimes uniformly distributed 
over the middle of the sides, but generally more pro- 
minent at the limits between the longitudinal rows of 
scales below the lateral line. The ventral side is of a 
purer white, at the middle milky white. The sides of 
the head partake in the silvery lustre of the sides of 
the body; but on the gill-cover this hue frequently 
passes into a brassy lustre; and the articular process 
of the operculum is of a brownish black colour, which 
is continued back in a longitudinal stripe. The yel- 
loAvish colour often extends to the cheeks and jaws. 
The lower part of the head is of the same colour as 
the belly. No less variable is the coloration of the 
fins. Sometimes all of them are entirely black; but in 
the lighter varieties they may all be light, greenish 
gray or transparent. As a rule, however, they are 
light (gray or dashed with red) at the base, but the 
outer part of the fin-membrane is dark, grayish or 
brownish black, this being due to a rarer or denser 
agglomeration of brownish black pigment, which is 
sometimes merely besprinkled on the tips of the pec- 
toral and ventral fins. The same pigment is frequently 
scattered in fine dots over the skin of the whole body 7 , 
and usually collects on the middle or bottom of the 
dorsal fin, on the upper part of the head, on the inner 
(hind) surface of the pectoral and ventral fins, and 
sometimes here and there on the sides of the body, 
“ Smitt, 1. c., tafl. V, fig. 89. 
6 Smitt, 1. c., tab. metr. X, No. 169. 
c Fatio’s Coregonus dispersus. 
d Fatio’s Coregonus balleus. 
e Fatio has recognised a biending of characters in his “species composita”, Coregonus Suidteri ( Fne Vert. Suisse, vol. V, p. 270). 
f They are sometimes entirely wanting in the light varieties. 
