904 
SCANDINAVIAN FISHES. 
Vendace, varying on an average about 7 % (in polcur 
about 8 %, in tschir nearly 9 %) of the length of the 
body, between 33 and 40 % (in polcur 41 — 45 %, in 
tschir 52 %) of the length of the head, or between 44 
and 52 % (in polcur 56 — 61 %, in tschir 73 %) of the 
length of the head reduced. Some Gwyniad forms 
may indeed be said to lie characterized by a shallow 
tail (an elongated body); but it should be observed 
that this character is also a character of age. Conse- 
quently it happens that, in certain lakes, especially in 
Lake Bolmen in Smaland, where it has longest been 
known, but also in many other lakes from Lapland to 
Smaland, we meet with a Gwyniad form (Nilsson’s 
Coregonus lavaretus, Malm’s forma holmensis) which 
differs, so far as we know, constantly from the allied 
forms in the shallow peduncle of its tail. But in other 
waters, for example in the system of small lakes in 
Smaland which falls into the Baltic through the River 
Morrum, this very form is developed into the form 
with deeper tail, which else has its most typical repre- 
sentative in the Lake Ring Gwyniad (V alenciennes’ 
Coregonus Nilssonii). The hlasikar in the uppermost 
of the said lakes — Helga and Bergunda" — in most 
respects afford an instructive example of the changes 
of growth through which the Gwyniad passes in the 
less advanced stages of its form-series. In particular 
they show how the least depth of the body, the most 
distinctive character of holmensis, increases with age so 
as to approach the typical Coregonus Nilssonii. In 
o 
Asnen, a lake of greater size and situated nearer the 
outlet of the system, the Nilssonii type 6 is developed 
at an earlier age (a smaller length) than in the two 
said lakes. In this locality it therefore seems that 
Cor. holmensis should really be regarded as a young 
stage of Cor. Nilssonii , which in other places, for ex- 
ample in Lake Bolin, may persist as a separate form. 
The deeper form of the body is most often accom- 
panied by a special arrangement of the scales that 
gives the fish a singular appearance. When the skin 
is distended, the rows of scales part from each other 0 , 
and the exposed portion of each scale becomes hexagonal 
instead of semicircular. The Gwyniad then displays a 
striking resemblance to the Grayling. In the hlasikar 
— but especially in the typical Lake Ring Gwyniad — 
we also find a special form of scale, at least in the 
rows nearest to the lateral line, the free (hind) margin 
of the scale becoming more or less elongated at the 
middle (forming a rounded obtuse angle instead of a 
circular arc). But in all the Gwyniads examined by 
us this difference also appears between the scales on 
the sides of the tail and those on the forepart of the 
body. The character assigned by Lilljeborg to Core- 
gonus Nilssonii, that the exposed part of the scale in 
the rows nearest to the lateral line is more than half 
as long as high, may be found in most Gwyniads, at 
least in solitary scales. 
While it often happens, especially among the hld- 
sikar , that the comparatively great size of the eyes is 
persistent longer than usual — a relation which Wide- 
gren expressed by establishing a separate species, Core- 
gonus megalops — the fetsikar run to the opposite ex- 
treme, the reduction in the relative size of the eyes 
during growth proceeding more rapidly and advancing 
further than usual. The form produced in this man- 
ner we have called microps, less in order to indicate 
the importance of the difference as such, than because 
it is usually accompanied by an increased fatness which 
has rendered the form economically important. It 
occurs, according to the collections of the Royal Mu- 
seum, in the Gulf of Bothnia, the rivers of Norrland, 
Lake Wener, and Bohuslan. Malmgren sent home 
specimens of a similar form from Lake Ladoga. The 
same importance is shared by another form, from the 
o 
Angerman and Torne Elfs, which is characterized by 
a comparatively small head, and which we have there- 
fore named microcephalus. 
None of these forms seems quite to deserve the 
rank of an independent variety. They sometimes appear 
to occur alone, but as a rule at least two are found 
in the same lake or river — Lake Wener possesses at 
least 7 of these forms — and that they intermingle 
during the spawning, is more than probable. But as 
a rule a distinction may be drawn between them in 
the following manner: 
a Smitt, ]. c., tab. metr. XI, Nos. 210 — -215. 
b 1. c., Nos. 216 and 217. 
c A striking example of this is Siebold’s figure of Coregonus acronius {Susswasserf. Mitteleur., taf. II), monstrously swollen owiDg 
to the expansion of the air-bladder when the fish was drawn up from deep water; but the same appearance is almost as marked in gravid 
females. We have above seen a similar difference in the appearance of the scales among the Perches for example: — cf. the Carass Perch 
(fig. 3, p. 29) with the common Perch. 
