252 
SCANDINAVIAN FISHES. 
tiuct interval, without fin -membrane, the length of 
which corresponds to the width of two or three trans- 
verse rows of scales, between the two dorsal tins. In this 
species, as in the following one, we often find that the 
distance between the beginning of the first dorsal fin 
and that of the second is equal to the length of the base 
of the latter fin, or to the distance between this fin and 
the first upper, supporting ray of the caudal fin; or 
also exactly twice the least depth of tl\e tail. The base 
of the anal fin is generally somewhat shorter, though 
often only very slightly", than that of the second dorsal 
fin. The length of the caudal fin, which may be 
rounded, truncate with rounded corners, or even some- 
what forked, is generally equal to the base of the anal 
fin, varying between 14 and 16 of the length of the 
body. The distance between the beginning of the anal 
fin and the tip of the snout is 46 or 47 % of the length 
of the body. The tip of the ventral fins, which are 
generally longer in the male than in the female, usu- 
ally extends to the vent or even beyond it. The length 
of the rounded pectoral fins is between 1 / 6 and Vs of 
that of the body. The longitudinal diameter of the eye 
varies between 6 and 7 % of the length of the body, being 
comparatively greater, as usual, in young specimens. 
The interorbital space, which is somewhat depressed in 
the middle, is externally fairly broad in adult speci- 
mens, its breadth being equal to the horizontal diameter 
of the eye or somewhat greater. It is chiefly formed, 
however, by the upper dermal covering of the eyes, 
the breadth of the frontal bones between the eyes being 
at most equal to the diameter of the pupil. As a re- 
sult of this, in young specimens or in examples with 
thin or shrivelled skin, the eyes seem fairly close to- 
gether at the top. The gape is turned slightly up- 
wards, and the length of the lower jaw, the point of 
which projects somewhat beyond the tip of the snout, 
is about 9 % of the length of the body, or from 40 
to 44 % of that of the head. 
The Doubly-Spotted Goby is one of the most hand- 
some Scandinavian fishes; and as we are here able to 
refer to the figures of v. Wright and Thornam, the 
latter coloured under the supervision of the late Professor 
Malm, we leave to Heincke'' the further description of 
the beauty and the sudden variations of its colouring. 
° According to Kr0Yer, it is sometimes longer than the latter. 
b According to Kr0Yer, as much as 17 %. 
c Schr. Schl. Holst., 1. c. 
He begins with a description of the male in its spawn- 
ing-dress. 
“At the first glance we observe a deep velvet-black 
spot at the base of the caudal fin surrounded by a 
pretty golden, marginal ring. This spot is character- 
istic of the species, and appears in both sexes, but even 
during the spawning-season is less handsome in the 
female than in the male. Another black spot, without 
the golden margin, lies on each side of the body, be- 
hind the base of the pectoral fin; but this spot appears 
only in the male, and is one of the most important 
external sexual characters. In the female it is gen- 
erally entirely wanting, though there are sometimes 
faint traces of it. In the male during the spawning- 
season the upper part of the body is of a dark brown- 
ish-black ground-colour, often shading into green, on 
the head lighter, with a dash of red and a dull coppery 
lustre, on the back marked with five selliform, light 
spots with a dull metallic lustre, which are always set 
at fixed points, and which give the fish a singular 
appearance. The several spots are united at the middle 
of the back, at the base of the two dorsal fins, by 
narrow, irregular streaks of the same tint. The dark 
colour of the back extends somewhat below the middle 
of the sides, but from this point the belly is of an 
unvaried, light colour with a coppery lustre, as well as 
the tail, the lower part of which is, however, stained 
with a black pigment, while the under surface of the 
head is of a deep copper colour with a golden lustre. 
The transparent branchial lamella? render the branchial 
region blood-red. At the boundary between the light 
colour of the belly and the dark tint of the back, a 
little below the middle of the sides, is a row of spots 
with a shifting, gemmeous lustre of blue and green. 
A similar spot appears at the upper corner of the 
operculum. 
“The fins of the male, with the exception of the 
ventral and pectoral fins, which display only a dull 
lustre here and there, are by no means less brilliant 
in colour. The anal fin, the remainder of which is 
almost colourless, is marked with a dark, black streak 
along the base, a peculiarity which, however, appears 
with varying distinctness in the males of all our Go- 
bies. The caudal fin, behind the black, gold-edged 
