GUDGEON. 
745 
in old specimens a little less than half that of the 
longest outer rays. 
The paired fins are similar to each other in general 
form, when the ventrals are not fully expanded. Both 
pairs are of an oblique oval shape; but the pectoral 
fins are more pointed arid longer. The length of the 
latter varies between about 20 and 15 %, that of the 
ventral fins between about 15 and 13 % of the length 
of the body. In their position too, these paired fins 
resemble each other, the pectoral fins when expanded 
being drawn down to the flat ventral margin, where 
they project horizontally outwards like the ventral fins. 
The position of the latter is such that the distance from 
the tip of the snout to the foremost (outermost) point 
of their insertion is about 43 % of the length of the 
body, and from the said point in the insertion of these 
fins to the corresponding point in that of the pectorals 
about 23 % of the same. 
The scales are of moderate size, but rather thin, 
and their form varies considerably, being rounded and 
quadrangular, semi-elliptical (rounded behind), or round- 
ed and triangular. In the anterior (covered) part, which 
is the shorter, but deeper, we find only concentric, fine 
strife; the posterior part, on the other hand, is marked 
with a number (as many as 24) of radiating strife, the ends 
of which at the hind margin of the scale form fine and 
fairly regular notches in this margin. The lateral line is 
fairly straight, in front slightly curved in a downward di- 
rection, and keeps to the middle of the sides of the body. 
In coloration the Gudgeon is one of the most sin- 
gular of our Cyprinoids, not indeed for any remarkable 
beauty of coloui though in this respect it is but 
little inferior to our most handsome species, the Min- 
now — but for its possession of more varied hues than 
most of the Scandinavian forms of this family. The 
back is grayish green, darker (shading into brown) or 
lighter according to the colour and light of the envi- 
ronments of the fish, and transparent when the light 
falls directly upon it. The belly is milky white. The 
colour of the back extends forward on the top of the 
head, the snout, and the outside of the barbels. On the 
upper part of the sides of the snout, just below the 
nostrils, appears a dark, fairly broad, longitudinal band, 
which is continued across the upper part of the eye 
more or less distinctly on the temple. Below the eye 
too, lies a more or less distinct band, formed by more 
or less densely agglomerated collections of dark pig- 
ment. Similar irregular spots also occur on the oper- 
culum and preoperculum; but the sides of the head are 
otherwise coated with a brassy and silvery lustre finely 
punctated with brown. The lower jaw and the branch- 
iostegal membrane are of the same colour as the belly. 
The iris is below of a silvery lustre, but finely punc- 
tated with brown. The silvery lustre of the sides of 
the body shades more or less distinctly into violet, and 
this bluish colour collects at certain points into a more 
or less regular row of undefined spots above and along 
the lateral line, now of a lighter blue, now shading 
even into blackish brown. The scales of the lateral 
line are marked, at least in the anterior part there- 
of, by a dense agglomeration of dark brown pigment 
on each side of the canal itself; and more scattered 
dots of similar pigment at the margins of the scales 
form a network of brown over the whole body. All 
the fins are light and transparent, of a more or less 
pronounced yellowish green. This last colour is most 
prominent on the rays, which are also marked — -in the 
dorsal and caudal fin always, in the other fins some- 
times, but with far less density — with brownish, elon- 
gated spots, together forming more or less regular trans- 
verse bands and most distinct on the caudal fin. 
The most trustworthy external distinction between 
the sexes during the spawning-season is the dermal 
eruption, consisting of small, fine, verrucose tubercles 
on the head and the forepart of the back, which is 
general among the male Cyprinoids. A dark blue spot 
on the gill-cover, more prominent than in the females, 
is also a usual characteristic of this sex during the said 
period. Furthermore, according to Fatio, the longest 
rays in the pectoral fins of the male are thickened during 
the spawning-season; but we have failed to find any e A i- 
de ns e of this. The most general difference between the 
sexes lies, however, in the longer and higher fins of the 
males; but the changes of growth — young specimens 
of both sexes being similar in this respect — impair the 
validity of the sexual characters drawn from this rela- 
tion. We have, however, found one of these characters 
to hold good in all our specimens: in all the males 
the length of the lower jaw is less, in the females 
more, than 55 % of the length of the ventral fins". 
“ The position of the vent, which in other cases gives the most easily expressed sexual character, and which has been stated in the 
Gudgeon to lie in the females behind, in the males in front of, the middle of the body, varies so considerably that in a male 107 mm. long 
for example we found the distance from the vent to the tip of the snout to be 58 mm. 
