740 I C II T II ' 
of 30 or 35 fathoms ; but then the fea mutt be very calm ; 
and what are 30 fathoms 'in companion to the immenfe 
deDth of home parts of the ocean, of that vaft abyfs’ which 
fifties travel through, where fcarcely any folar ray can 
pierce,anil ftill lefs when the waves are agitated violently 
by tempefts ? If the fenfe of fmelling therefore were not 
very perfeCt, how could they, in many /ituatioivs, feek 
their food, and avoid danger. 
Yet the fight, though fecond to the fmell, is by no 
mean3 imperfect in fifties. Lefs perfeCt than that of many 
other animals it mult be from the denfity of the fluid it 
lives in compared with atmofpherical air; yet let it be 
obferved, that the cryit'alline humour in fifties is much 
more convex than in birds, quadrupeds, and man ; it is 
nearly fplierical; the rays therefore from any object tnuft 
form a more acute angle on its furface ; they are more 
collected in an image,, and their refraftion is the greater 
as the angle of incidence is fmaller ; befides, the cryftal- 
line in fillies is denferthan in more perfeCt animals, which 
ftill increafes refradlion ; and further, it is now afcertain- 
ed, that the more inflammable any thanfparent f’ubftance 
is, the more ftrongly it refrafts the rays of light; and the 
c’ryftalline humour of fifties, being impregnated with oily 
matter, is more combuftible than that of molt other ani¬ 
mals, and thus refraction mult be ftill farther increafed. 
The fibres of the retina, that is, the final left branches of 
the optic nerve, are in many fifties 1,666,400 times-fmaller 
than a hair. Though fifties have no eyelids to defend 
them from the conftant aCtion of the fun’s rays, yet many 
fpecies have the faculty of drawing the eye to the bottom 
of the orbit, and fo conceal it in part under the rim of 
the aperture, which thus forms a kind of immoveable eye¬ 
lid ; and it muft not be forgotten, that fifties can rapidly 
fink to fuch a depth, even in rivers, as may prevent in¬ 
convenience from the brightnefs of the f'olar ray ; and in 
the bofom of the ocean they can lie, where no rays of light 
whatever can reach them. It muftftbe acknowledged, 
that fome fpecies, efpecially tliofe which relemble ferpents 
in ftiape, have their eyes conftantly veiled with an im¬ 
moveable membrane ; fo that in tliefe the fenfe of fight 
muft be weaker than that of hearing, and even of touch ; 
but in general the order of the fenfes will rank as we have 
fet tbetp down. Forfome farther particulars relating to the 
conformation of fifties, and efpecially to the abforbent fyf- 
tem, fee Comparative Anatomy, vol. i. p. 667-670. 
Upon the whole, the fenfitive powers of fifties appear to 
be fuch as will place them almoft at an equal diftance 
between the extremes of man and the loweft of animals. 
But in beauty and brightnefs of colour, fifties yield to no 
animals whatever. We fhall endeavour to explain how 
thefe ftriking tints are produced, which are fo admirably 
contrafted, often diftributed with fo much fymmetry, and 
fometimes fo fugitive. Thefe lively colours muft either 
refide in the teguments more or lefs foft, and in the body 
itfelf; or they are produced by the modifications of light 
pading through the tranfparent fcales; or they muft de¬ 
pend'entirely upon the fcales, whether tranfparent or 
opaqwe. 1 ' 
The foft parts of fifties may of themfelves exhibit all 
the colours. Accordingas the arterial ramifications, which 
run amidft the mufcles and approach the external furface, 
are more or lefs numerous, ftronger, or weaker, the foft 
parts of the animal will he white or red. The various 
nutritive juices which circulate in the abforbent veflels, 
or pervade the cellular texture, may impart the yellow or 
green colour with which thefe juices commonly abound. 
The veins difi'eminated in thefe very parts may add all 
the Andes of blue, purple, and violet; and thefe /hades 
of blue and violet, when mixed with yellow, will produce 
all the various tints of green; And thus thefe /even co¬ 
lours may decorate the bodies of fifties, and be di/femi- 
nated in fipots, bands, ftripes, or dots, according to the 
place occupied by the various matters from which they 
Mvife; and all this without'taking fcales at all into the 
«Queftion. 
if O L O G Y. 
But, if laminre very tranfparent, and as it were colour- 
lefs, ftiould be fpread over thefe tints, it will not change 
their nature; it will only, like a light varnifti, increaVc 
their brightnefs ; it gives them the brilliancy of poliftied 
metals when fiivered or gilt. And, if, thefe laminre, or 
fcales, have other tints .peculiar to themfelves, fuch tints 
neceffarily mix with thole which ftiine through thofe dia¬ 
phanous laminae, and either produce new colours, or in- 
creafe the efteft of the former ones. From the union of 
thefe caufes arife thofe beautiful colours which are ob¬ 
ferved'on a vaft number of rHh. No clafs of animals has 
been fo favoured in this refpeCt ; none has received a 
clothing more elegant, more varied, or more rich. Let 
thofe, for example, who have feen the dorados, the cliet- 
odonsy or the gilt-heads, fwimming near the furface of a 
ftill water, and reflecting the bright rays of the fun, fay 
if the ftiining plumes of the peacock or humming-bird, 
the brilliancy of the diamond, the fplendour of goid, or 
the -reflection of precious ftones, can exceed the fpeCtacle 
they prefent. But the /bales are not always colourlefs or 
tranfparent; nor are they confined to one colour upon each 
fcale ; for every kind of fcale may have fpots,'ftripes,'or 
bands, upon a diftinCt ground.' Farther, when the fcaleS 
lie flat upon the /kin, it will be readily conceived'that 
they may refleCt the .colours through the (kin, or exhibit 
them as mixed with their own ; but, when the fcale is 
faftened to the /kin only by a fmall part of its circum¬ 
ference, and goes /helving upwards, as often happens, it 
can then exhibit its own colours only. And this brings 
us to fpeak of the aCtion of light in brightening the co¬ 
lours of fi/h. 
We knowq that, in organifed bodies, particular colours 
varying from white are not produced without the pre- 
fence of light in combination with the principles of fuch 
bodies. We fee this in plants, which become white when 
deprived of light; we obferve it in quadrupeds, birds, 
and reptiles, in which the lower parts of the body, as le/s 
expofcd to the rays of the fun, are always diftinguiftied 
by paler tints. We fee it in fifties, of which the under 
furface, leaft expoled to the rays of light, is never painted 
with fuch rich colours a3 the upper parts ; and we may 
obferve the fame thing, for the molt part, in every parti¬ 
cular fcale. When the fcales (helve oyer each other 
like tiles upon a houfe, that part of the fcale which is 
concealed is never adorned with the fame tints exhibited 
by the part expofed to the light. To produce beautiful 
colours, it is necefiary that a certain quantity of luminous 
fluid fliould unite and give life to the colouring matters 
originating from within. 
But, in whatever manner, or in whatever part of the 
body, the matter is elaborated which forms and maintains 
the fcales, we cannot doubt but its principles are modi¬ 
fied by the nature of the aliment which the fi/h feeds upon. 
It is particularly, obferved, that almoft all thofe fpecies 
which feed upon fhell-fi/h exhibit very vivid colours ; 
and thus thefe crultaceous animals, whofe juices tinge 
their fc»d covering with fuch bright tints, feem to pre- 
ferve enough of their properties after death to impart 
thofe tints to the rudiments of the fcales they are deftined 
to give birth to. 
The reader will readily conclude, from what we have 
urged, that;, in thole countries where a great quantity of 
light pervades the bofom of the waters, the fifties will be 
moft richly coloured. And in fa ft thofe which rival in 
brilliancy the moft highly poliftied metals, or the moft 
precious gems, are generally found between the tropics, 
where the furface of the fea is fo frequently pervaded by 
the rays of an unc-louded fun. With almoit equal beauty 
are thofe fpecies decorated which live amid the polar leas, 
where mountains of ice and eternal (nows folidified by 
cold, infinitely reflect from multiplied furfaces the daz¬ 
zling light of the /'un during the long days, and of the 
moon and aurora borealis during the long nights, of thefe 
hyperborean regions. 
Thefe- beautiful colours,, however, can only be fup- 
pofed 
