252 



SCANDINAVIAN FISHES. 



tinct interval, without fin-merabraiie, the length of 

 which corresponds to the width of two or three trans- 

 verse rows of scales, between the two dorsal fins. In this 

 species, as in the folloAving 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 tlie 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 the tail. The base 

 of the anal fin is generally some\vhat shorter, though 

 often only very slightly", than that of the second doi'sal 

 fin. The length of the caudal fin, which may be 

 rounded, truncate with rounded corners, or even some- 

 what forked, is generally eipial 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 Ijetween Ve ''"^ ^U 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 bi'eadth 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 

 tliin 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. 



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 mai'gin, 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 ^vith a dull metallic lustre, Avhich 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 tlie 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 l)lack 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 

 coloui- 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 



" According to Kroyku, it is sometimes longer tlian tlie laUer. 

 ' According to KiioYKU, as mnth as 17 %. 

 ' Sclir. Sclil. Hoist., 1. c. 



I 



