FLOLNDKli-FISHES. 



yG9 



Almost the .s;mie rcinnrks jippU- to the system of | 

 the Intei-Jil line. As a rule it is well-developed, though j 

 sometimes externally indistinct, in all the Scandinavian 

 species its extent is normal, tii()ii,i;ii ;i portion of it on 

 the head is sometimes reduced h\- tlie remo\ ;d of the 

 e\c. Tims, in the Turljot all tliose branches of the 

 .system tiiat ;ippenr in ;i. Codfish for exami)le, ;irc vv- 

 peated, ;is appears from a comparison between fig. 104 

 and fig. 105. Fi'om the temporal region on each side 

 of the body an occipital (supratemporal, sj)f) branch 

 runs up towards the dorsal edge. In the Flounders 

 this branch runs to each side of the dorsal fin and 

 coasts it in a forwai'd direction to the beginning of the 

 tin, or ramifies, in which case it may follow the base 



eye passes straight through the liead to the remainder 

 of the frontorostral branch of the blind side. In several 

 exotic genera the lateral line of the body is doubled 

 or even trebled, partly, as we have mentioned above, 

 by a dorsal branch coasting the base of the dorsal fin, 

 and partly by a ventral brancli along the base (if the 

 anal iin. in these cases it may happen either that both 

 sides of the lindy are alike in this respect, or that the 

 eye side is furnished with two or three lateral lines 

 and the blind side with one or none. 



All tlie fin-rays are soft (articulated), sometimes 

 simple and sometimes branched. Sometimes they are 

 simple in all the fins, sometimes branched in the caudal 

 fin alone, sometimes in the paired fins as well, and 



Fig. 100. Ceplialic system of the lateral line on tlie eye side of a | Fig. 107. Corresponding figure of the blind side of the liead in the 

 Plaice. After Traquair. spti; dorsal branch of the lateral line. For ' same fish. After Traquair. For the signification of the letters see 

 the signification of the rest of the letters see the preceding figure. the preceding figure. 



of the dorsal fin both forward and back (fig. 106). 

 Down from the temporal region runs the mandibular 

 branch {m), along the hind margin of the preoperculum 

 and on the under surface of tiie lower jaw. In a for- 

 ward direction the frontorosti'al branch (fr) crosses the 

 frontal and ethmoid bones to the turbinate bones, with 

 a connecting liranch (c) between or behind the eyes, 

 from the branch on one side of the lx)dy to that on 

 the other. Each frontorostral branch sends out a sub- 

 orbital branch {so) behind the e\e. In the Plaice (figs. 

 106 and 107) the frontorostral branch of the blind side 

 disappears behind the orbital region; l)ut the connecting 

 branch is persistent, being externallv visible on the eye 

 side, and at the hind margin of the upper (transferred) 



See n tVtit a via n Fish e.< . 



sometimes branched in all the fins. The pectoral fins 

 are usually set fairlj' high, and the ventral fins in front 

 of, or sometimes exactly in, the perpendicular dropped 

 from tlie insertion of the former fins. These paired 

 fins, however, are very often reduced, as we have men- 

 tioned above; and the ventral fins may be sometimes 

 united by the fin-membrane to the anal fin. In this 

 case, when only one of the ventral fins (that of the 

 eye side) is developed, it presents the external appear- 

 ance of an anterior lobe of the anal fin. 



At the beginning of the latter fin, just behind the 

 vent, there sometimes projects a strong spine. This is 

 the lower end of the first interhannal spine of the anal 

 fin, which spine is also called the ]JOstabdominaI bone, 



47 



