GOBIES. 



248 



The Scandinavian Gobii may most easily he dis- 

 tinguished tVom the two t'oUowing genevn hy the num- 

 lier (if ra\s in the Hrst dors.al fin, which in the former, 

 as a rule, is not nntlei' 6; l)ut (he most universal char- 

 acter lies in the arrangement of the jaw-teeth in several 

 I'ows, tlie front row containing the largest teeth. The 

 size of the gape and the form of the body, wliich shows 

 strong lateral compression onh' in (he caudal ])art and 

 sometimes only at the extreme end tiicrcof, are with 

 these exceptions the most striking characlci's of the 

 true Gobies. The branchiostegal rays are o in luimber, 

 the three middle ones being closer to each other at 

 the base than to the other two, and the second (the 

 next to the lowest) generally marking with its point 

 the angle at \vhich the branchiostegal membrane turns 

 inwards to its union \vith tlic isthmus, on about a level 

 with the l(jwer end of tlie base of the pectoral tin. 



The difterences between the sexes have been re- 

 marked in [larticular by Malm" and Heincke''. In the 

 males, wliich may also be recognised externally I)y 

 their longer and more pointed genital papilla, one or 

 more of the anterior rays in the first dorsal fin, and 

 the posterior rays in both the second dorsal and 

 the anal fins, are, as a rule, elongated. In colour they 

 are distinguished by the greater abundance of black 

 pigment, especially in tlie anal and ventral fins, by 

 ocellate spots and by stripes of a particular colour on 

 the dorsal fins and the sides of the body. But these 

 sexual differences vary according to age and size, the 

 older and larger females very often resembling the 

 males in colour. The coloration is also far from con- 

 stant, being deepest, as usual, during the spawning- 

 season, and being further subject to sudden changes 

 in accordance with, the mood of the fish and the colour 

 and light of its surroundings. 



Heincke was the first to point out, among the 

 changes of growth, the increase in the number of rays 

 in the first doi'sal fin — in one species {Gobi us fla- 

 vesceits) he found that young specimens had 5 rays in 

 this fin, old specimens 6 or (in most cases) 7 or (ex- 



also points out the individual variations. Out of 208 

 specimens of this species which he examined, eight had 

 8 rays in tlie first dorsal fin, three 6, and the rest 7\ 



The cxtcMit of tiie scaly covering on the ariterioi- 

 jjart of the body also varies with age, as far as this 

 can be fixed l)y tiie size of the specimen. Winthek'' 

 and after iiim Collett' and Lii.ljebokg-', believed that 

 the most im]jortant specific characters within this genus 

 were to be found in the ditt'erences which the species 

 often show in tiie extent of the naked (scaleless) part 

 of the body. In the small species the scales ai'e want- 

 ing on the belly, on the body in front of the ventral 

 and pectoral fins, aiid also on a strip of the back along 

 the whole base of the first dorsal fin or the anterior 

 part thereof. In the large species of the genus which 

 belong to the Scandinavian fauna, on the otiiei- liand, 

 it is a standing rule that the whole body, with the 

 exception of tlie head, is covered with scales, and some- 

 times the occiput and the forehead behind the eyes, 

 are also scaly. Heixcke has shown that the largest 

 Scandinavian species, Gohius nu/er, during the growth 

 of individual specimens passes through stages of de- 

 velo])raent which, with regard to the extent of the 

 scales, correspond to the adult state of the smaller 

 species. In a specimen 21 mm. in length, he found 

 the head, with the occiput and a narrow strip along 

 the base of the first dorsal fin, as well as the belly 

 between the ventral fins and the vent, entirely liare of 

 scales. Of the fry of the same species Lilljeborg" 

 also remarks that "no scales appear on the top of the 

 head or on the occiput." In a male Gohiits niger from 

 KansS, in the island-belt of Gothenburg, 67 ram. long, 

 the scales are also wanting both on the throat in front 

 of the ventral fins and on the part of the dorsal edge 

 already referred to. In the same way there are no 

 scales in front of the ventral fins in a Gohius minutus 

 50 mm. long, from the island-belt of Stockholm. 



These observations clearly show that neither the 

 variable colour of the body, nor the number of rays 

 in the first dorsal fin, nor even the extent of the scales 

 ceptionally) 8. In connexion with this circumstance he | on the front part of the body may be used as a trust- 



" Skand. Naturf. Mode Kbhvn 1873, Beretn., p. 382. 



' Arch. f. Naturg., 46:ter Jalirg. (1880) Bd. I, pp. 304 etc. 



' According to Canestrisi (Arcli. Zoo!. Anat. Fis., Geneva 1861, vol. I, fasc, II, p. 125), the number of rays in the first dorsal (in 

 of Gobius gnttatiis also varies between 6 and 7. 



■' Naturh. Tidskr., Kblivn, ser. 3, vol. IX (1874), pp. 197 etc. 



' Christ. Vid. Selsk. Forh. 1874, pp. 153 etc. 



•'' Sv., ^t'org. Fisk., I, pp. 563 etc. 



» L. c, p. .o70. 



