36(i 



SCANDINAVIAN FI8IIK.S. 



described. The foi'iiiev .•issiiined that the eye in its These radical nlteratioiis are accoui])aiiied l>v a coii- 



wanderiiigs penetrates ;i ])iirt of the still lueinbivin- ' sidera-ble difi'ei'ence in the shape of the body -witliin tlic 



ous frontal bones of the blind side, while the latter i various 2renera of this series: I mt the intermediate forms 



! 

 in his tiiiures shows the passage of the eye just j prevent us from shar])lv limiting the groups we should 



under the lower ends of the interspinal bones of 



the dorsal tin. 



like to deiim\ and most Avriters agree in referring all 

 these forms to one common family. 



1am. PLEURONECTIDiE. 



liodij hi (idiilf spec'niiiuis deep (did sfroiif/li/ comjircssed, iritli the cije side, in tlir iKitiind jidsifiim, tinned ii/nrards 

 and the hiiiid side dDinnnirds. Dorsal and anal fins Joni/, occapi/inf/ at least flie i/reater part af the leni/tli af 

 the fsh. Ih-anr]iii)strf/a] rails ('> — v. Pseiidohrai/eliid' present or irantiiifi. Air-liladder fienendlij irantini/. Pi/Jorie 



appe)ida(ies feir or iraidini/. 



This fimilv, whirh was established bv Cuvikh 

 under the nnme of I'aissaiis plats, I'ionoelht's'' Pisces 

 jdaiii. sjtiiKisi, bore the name of ^ii^TToi-iduQ \n as early 

 a writer as AiiisToTi.K; but its present svstematic name, 

 fieiiriineetiihe, is no olch'i' than in BoNAPAiiTKs' time. 



The shape of the bodv is no deeper here than in 

 inanv other tishes, in certain Chietodonts and Caraiigidcc 

 for example: and in the Rays flatness of body is conjoined 

 with tlie same hal)its and in great jjart the same co- 

 loration and maimer of loccnnotioii as tliose of the !• lat- 

 fishes. The asymmetry of the latter, however, as we 

 have rera;irked above, is always enougli to distinguish 

 them. Whether tliis characteristic is immediately con- 

 nected, as some have assumed, \vith the general ab- 

 sence of the air-bhidder in the Flatfishes, is a very 

 doubtful j)oint, for both in Paralirlitlii/s (Psciiddrliniu- 

 hi(s) dentatiis {melanoi/aster) and in liatJiiis (lilionihus) 

 macalatiis Ahassiz'' found the air-bladder "well-deve- 

 loped" in tlie frv e\en before the eve liad begini its 

 wanderings. Again, the air-bladder is not wanting in 

 all tlie rest of the members of this family. Costa' 

 found it [n'esent in several Mediterranean species, even 

 when full-grown, its size being greatest in Itlioinhnid- 

 ichthjis jxidas: it is iiardly a functional organ, ho'we\er, 

 and (luring the course of development it shrinks or 



clian"'es into a lilandular or;;an, accordiim' to Costa, a 

 lymphatic ganglion. The loss of the air-bladder, like 

 tlie asymmetry, is thus a change of development. This 

 is also true of the different coloiu'S of the two sides of 

 tiie body. So long as the frA" are symmetrical, the 

 pigment is ei|iially distriliuted on each side of the body: 

 and even . during the wanderings of the e^e, the dif- 

 ference is slight. During this period dark transverse 

 bands usually appear on the dorsal and anal tins and 

 the neiii'hbourinii' i)arts of the sides, as far inwards as 

 to the end of the interspinal bones; and these trans- 

 verse bands belong to the blind as ^vell as to the eye 

 side. During the advancing metamorphosis to asym- 

 metr\', howe\cr, the liliiid side loses more and more of 

 its pigment, until at last, in most cases, it is lileached 

 (|uite white, and the colour of the bod\- collects on the eve 

 side. In recent times, chiefly thrcnigh the researches of the 

 Frenchman Pouchet', science has been enabled positively 

 to refer these changes of colour to the nervous system. 

 The lively description HeinckI') has given us of 

 the changes of colour in (johias darescens (see al)o^■e, 

 p. 252) is a striking example of the power possessed 

 by fishes in general of adapting their own colour to 

 that of their surroundings: but the Flatfishes enjoy this 

 faculty to a still higher degree, esi)eciallv during youth. 



" lii'ijii. Anim., ctlit. I (1817), [>. 218. 



'' Ik Piscil)H.s- (1554), p. .H09. The Kays wore pisceD plaui, cartilugiael. 



'■ Hagij., 18:-?1; .S'//.?/. Irlit. Isis 1833. Rafinesque called (lie f.Tiiiily Plaironectia (1815), and Risso used the Fivnch name Fleiiro- 

 iiectides (182G). 



'' Dcvel. Flovnd., 1. e., p. 11, pi. VI and VII. 



*■ Fii, Ref/ii. Nap., Malacott., Sottohr., Pleuron., p. 64. 



•' On tlie connection of nerven and clirnmohlast.^, Moiithl. Mier. Jmini., Dec. 1871, p. 285: /'c* clidiKjeiiients dc coloration uVo».« I'ir,- 

 fliience des nerfs, Joiirn. de I'Atiat., Pliys. 1871!, pji. 1 and li:!. )d. I — IV. Cf. Smitt: I'r dc liOgrc djm'en.-: iiU-ccl:Iiiii/f=liistoriii. p. 271. 



