i'i,(irM)i;K-risiii;s. 



;',r,7 



I'xitli PiirciiKr ;iii(l Acassiz (1. c) succeeded l)est in 

 rlicir e\i)eriineiits on s|)eciiiieii.s of liotliits wliidi \v(!i'e 

 sliit't(ul from \cssels .iiid liottoins oi' different colours 

 ;ind into dilfei'<'nt liiiiils, ;il\\;i\s with llie I'csull lh;it on 

 .■I dark l)ot1oni and in dark en\ ironinents llic lisli lurns 

 dark, while it assumes a liiihtcr liiil when the circum- 

 stiiiicc'S arc re\'ersed. In this mannei- it conceals itself 

 in its free state, either to lie in andmsh for some \ictini 



l>(!sidestiie iridocytes of Pouchet — pigmental bodies 

 or cells contiUiiinjLi' ))o\verf"ully refractive, microscopical 

 disks arranged in i)arallel lines or heaped like the coins 

 in a roll, to the presence (jf uiiicli bodies the gray 

 coloui- of ihe skin of the Flounders is due — we here 

 fnid chromatophon;s" ol black, scllow and rcil. '1 he 

 black clironiatopliores, whicii are always more or less 

 ramifii'd \\ hen tlie\' exiiand. but nia\ contrait into a 



or to escape the notice of some foe. IJut PoL'ciiET, I tiny ilot, lie nearot tiie surface; and the position ot 

 whose sid)jecls were Turbots of different sizes, \arving the \cllow and reil varies considei'ably in the ditiereiit 

 in length lu'twccn l! and 2") cm., i'ound that the\ lost si)ecies. The varying expansion oi- contraction of these 

 this power of changing colour when he blinded them, cells, is adapted to the colours of liie surroundings ot 

 and also forgot to cover ihemseho with sand when the tisii, and produces that arrangement of colours on 

 ])laeed on a sandy bottom, an end which thev other- the eye side of the Flounders which sometimes renders 

 wise attain (piite >kilfnll\' b\' a few sharp strokes with 

 the hind part of the bod\'. It was thus e\ident that 

 sight was a uecessai'\' adjunct of the changes of colour. 

 The \isual sensations pass from the eves to the brain. 



them so dilHcidt to di.scover. 



'I"liu>. the ner\-ous system and. in p.-irticular. the 

 sense of si"ht ai-e the determinant factors in the chan«res 



)f c(dour: and Poicriirf h; 



Iso siiowii that habit exei"- 



whei'e the\- are e\changeil for nervous \ibrations that i cises no sniaii influence on this faculty. ( hit of a inim- 

 start the expansion or contraction of the chromato- ber of 'rurl)ots that wi^re kept alive in ;i \\i-\\, he se- 

 phores: and these nerxous \ibratious. according to 



Piirniiri'. are con\c\-ed partl\- along the Trifacial nerve 

 (the tifth pair of nerves in the head), ])artly by the 

 great sympathetic ciiaiu of ganglia, to the spinal nerves. 

 The sjiinal cord itself, accordii:g to PofCiii-yf's iiivesti- 

 i^'atioiis, does not pla\" the least part in the transmission 

 of these \ibrations: but the s\-m|);ithetic ner\ous chain 

 which lies bi-neath the \i'rtebra' on each side, and is 

 connected with the cranial nerves, especially with the 

 Trifacial nerxc, sends out branches to each i)air of the 

 spinal nerves. If these nerves are destroyed in that 

 part of their course that contains elements of the sym- 



lecied the palest. He then put it in a \essel with a 

 brown bottom, and five days elapsed Ijefore the fish 

 c()idd adapt its colour to that ot tlie bottom. He now 

 moved it to a liglit sand\- bottom, and in two da\'s 

 the fish had regained its foi-mer liglit colour. Again 

 he nitncd it to a l)i'own bottom, and now onh' tw(j 

 hours pro(Iuced the same effect as it had taken five 

 da\s to gain before. "The facult\- of changing cohnir," 

 .says Pot ciiF.r. "is thus intiuencc<l by habit, and this 

 too, soon enough, for the riirl)ot in (piestion had lived 

 at nio.st only three months on the light bottom wiiere 

 we found it. From an anatomical point of \ iew it is 

 pathetic nervous system, they also lose the power of very ditticnit to explain this Italiit. Perhaps the nerves 

 transmitting an\- intluence to the clnomatophores. This that start the contraction or expansion of the chromatic 

 comiexion between tlie action of the brain and that of cells, are in some way paralysed by want of exercise, 

 the sympathetic nervous system on the chromatophores ' and recpiire s(jnie time to recover from this paralysis, 

 in the skin, may well serve as an explanation of the < >r ha\c the chromatic cells lost too umch t)f their con- 

 blending — in many ca.ses quite incom|)reliensible — of tractile mattery Or must we look for the reason of 

 voluntary and involuntary changes in the colour of the their immobility outside them: perhaps in the surround- 

 -kin under the intluence of phenomena of light or sen- ing tissues, the resistance of which prevents the ex- 

 snal impressions, a circumstance which may often be | pun.sion of the cells? All these are i|uestions to which 

 ol)served even in the higher animals. The development no answer can be given at present. lUit we can easily 

 of the spawning-dress .seems also to be due chiefly to realise that the fact that habit thus gains influence sn 

 the intluence exerci.sed by the sMupathetic nervous sy- </i(irklf/, is of some zoological importance. As it can 

 stem at the time for the higher development of the be .shown that the faculty of changing colour may l)e 

 irenerative orjrans and their maturation. restricted in so >hort a time, we nuist also acknowledge 



" PoucilKT, who proposes to reserve llie name of cliroiiintopliurcs for Uie more developed cliromatic eells — in the ( 'tplialopoiln for 

 e.xiimple — calls these more protoplasiiiatie tells ehromoblasts. 



