PDF - Wallace Online
PDF - Wallace Online PDF - Wallace Online
410 TROPICAL NATUREON THE ORIGINOF THE COLOUR-SENSEThroughout the preceding discussion we have acceptedthe subjective phenomena of colour that is, our perceptionof varied hues and the mental emotions excited by them asultimate facts needing no explanation. Yet they presentcertain features well worthy of attention, a brief considerationof which will form a fitting sequel to the present essay.The perception of colour seems, to the present writer, themost wonderful and the most mysterious of our sensations.Its extreme diversities and exquisite beauties seem out ofproportion to the causes that are supposed to have producedthem, or the physical needs to which they minister. If welook at pure tints of red, green, blue, and yellow, they appearso absolutely contrasted and unlike each other, that it isalmost impossible to believe (what we nevertheless know tobe the fact) that the rays of light producing these very distinctsensations differ only in wave-length and rate of vibration,and that there is from one to the other a continuousseries and gradation of such vibrating waves. The positivediversity we see in them must then depend upon specialadaptations in ourselves ;and the question arises, For whatpurpose have our visual organs and mental perceptions becomeso highly specialised in this respect?When the sense of sight was first developed in the animalkingdom, we can hardly doubt that what was perceived waslight only, and its more or less complete withdrawal. As thesense became perfected, more delicate gradations of light andshade would be perceived, and thereseems no reason why avisual capacity might not have been developed as perfect asour own, or even more so in respect of light and shade, butentirely insensible to differences of colour, except in so faras these implied a difference in the quantity of light.Theworld would in that case appear somewhat as we see it ingood stereoscopic photographs ;and we all know how exquisitelybeautiful such pictures are, and how completelythey give us all requisite information as to form, surfacetexture.,solidity, and distance, and even to some extent as tocolour, for almost all colours are distinguishable in a photographby some differences of tint, and it is quite conceivable
vi ORIGIN OF THE COLOUR-SENSE 411that visual organs might exist which would differentiate whatwe term colour by delicate gradations of some one characteristicneutral tint. Now such a capacity of vision wouldbe simple as compared with that which we actually possess,which, besides distinguishing infinite gradations of the quantityof light, distinguishes also, by a totally distinct set ofsensations, gradations of quality, as determined by differencesof wave-lengths or rate of vibration. At what grade inanimal development this new and more complex sense firstbegan to appear we have no means of determining. Thefact that the higher vertebrates, and even some insects, distinguishwhat are to us diversities of colour by no meansproves that their sensations of colour bear any resemblancewhatever to ours. An insect's capacity to distinguish redfrom blue or yellow may be (and probably due is) to perceptionsof a totally distinct nature, and quite unaccompanied byany of that sense of enjoyment or even of radical distinctnesswhich pure colours excite in us. Mammalia and birds, whosestructure and emotions are so similar to our own, do probablyreceive somewhat similar impressions of colour ;but we haveno evidence to show that they experience pleasurable emotionsfrom colour itself when not associated with the satisfaction oftheir wants or the gratification of their passions.The primary necessity which led to the development ofthe sense of colour was probably the need of distinguishingobjects much alike in form and size, but differing in importantproperties, such as ripe and unripe, or eatable and poisonousfruits, flowers with honey or without, the sexes of the sameor of closely allied species. In most cases the strongest contrastwould be the most useful, especiallyas the colours ofthe objects to be distinguished would form but minute spotsor points when compared with the broad masses of tint ofsky, earth, or foliage against which they would be set.Throughout the long epochs in which the sense of sightwas being gradually developed in the higher animals, theirvisual organs would be mainly subjected to two groups ofra ys the green from vegetation, and the blue from the sky.The immense preponderance of these over all other groups ofrays would naturally lead the eye to become specially adaptedfor their perception and it is quite ; possible that at first
- Page 376 and 377: TROPICAL NATUREment are much more n
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vi ORIGIN OF THE COLOUR-SENSE 411that visual organs might exist which would differentiate whatwe term colour by delicate gradations of some one characteristicneutral tint. Now such a capacity of vision wouldbe simple as compared with that which we actually possess,which, besides distinguishing infinite gradations of the quantityof light, distinguishes also, by a totally distinct set ofsensations, gradations of quality, as determined by differencesof wave-lengths or rate of vibration. At what grade inanimal development this new and more complex sense firstbegan to appear we have no means of determining. Thefact that the higher vertebrates, and even some insects, distinguishwhat are to us diversities of colour by no meansproves that their sensations of colour bear any resemblancewhatever to ours. An insect's capacity to distinguish redfrom blue or yellow may be (and probably due is) to perceptionsof a totally distinct nature, and quite unaccompanied byany of that sense of enjoyment or even of radical distinctnesswhich pure colours excite in us. Mammalia and birds, whosestructure and emotions are so similar to our own, do probablyreceive somewhat similar impressions of colour ;but we haveno evidence to show that they experience pleasurable emotionsfrom colour itself when not associated with the satisfaction oftheir wants or the gratification of their passions.The primary necessity which led to the development ofthe sense of colour was probably the need of distinguishingobjects much alike in form and size, but differing in importantproperties, such as ripe and unripe, or eatable and poisonousfruits, flowers with honey or without, the sexes of the sameor of closely allied species. In most cases the strongest contrastwould be the most useful, especiallyas the colours ofthe objects to be distinguished would form but minute spotsor points when compared with the broad masses of tint ofsky, earth, or foliage against which they would be set.Throughout the long epochs in which the sense of sightwas being gradually developed in the higher animals, theirvisual organs would be mainly subjected to two groups ofra ys the green from vegetation, and the blue from the sky.The immense preponderance of these over all other groups ofrays would naturally lead the eye to become specially adaptedfor their perception and it is quite ; possible that at first
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