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CORRESPONDING SOCIETIES. 331 
structure, of similar, but not identical, material. The fate of the zebra-pattern 
in hybrids shows that structure, and not utility, is at the root of the matter. 
When a zebra is crossed with a donkey the hybrid has a smaller number of 
stripes, but these are very vividly marked, one along the dorsal middle line, 
one or two on the shoulder, and many on the legs. When it is crossed with a 
horse the hybrid is much more fully striped than the zebra parent, but the stripes 
are faint, almost invisible. Nor can it be supposed that the patterns charac- 
teristic of the different races or species of giraffe have separate utilities, although 
each of them may serve equally for protective concealment. 
Although colour and pattern may combine to produce a result, the colour 
differences accentuating the structural differences, it frequently happens that 
the outlines of colour and pattern do not conform. In such cases the separate 
factors produce a result that is in a sense accidental, and that, although it may 
be useful, cannot have been produced because it was useful. Ruskin, who was an 
acute observer of natural objects, called attention to this in his chapter ‘The 
Lamp of Beauty’ in ‘The Seven Lamps of Architecture.’ ‘I am quite sure,’ he 
wrote, ‘that any person familiar with natural objects will never be surprised at 
any appearance of care or finish in them. That is the condition of the universe. 
But there is cause both for surprise and inquiry whenever we see anything like 
carelessness or incompletion; that is not a common condition; it must be one 
appointed for some singular purpose. I believe that such surprise will be forcibly 
felt by anyone who, after carefully studying the lines of some variegated organic 
form, will set himself to copy with similar diligence those of its colours. The 
boundaries of the forms he will assuredly, whatever the object, have found 
drawn with a delicacy and precision which’ no human hand can follow. Those 
of its colours he will find in many cases, though governed by a certain rude 
symmetry, yet irregular, blotched, imperfect, liable to all kinds of accidents, and 
awkwardnesses. Look at the tracery of the lines on a camp shell, and see how 
oddly and awkwardly its tents are pitched. It is not, indeed, always so; there 
is occasionally, as in the eye of a peacock’s plume, an apparent precision, but 
still a precision far inferior to that of the drawing of the filaments which bear 
that lovely stain’; and in the plurality of cases a degree of looseness and varia- 
tion, and still more singularly, of harshness and violence in arrangement, is 
admitted in colour which would be monstrous in form. Observe the difference 
in the precision of a fish’s scales and of the spots on them.’ 
Analysis of the differences noted by Ruskin would probably show that when 
there was a coincidence of colour-outline with pattern-outline, the colour was 
fundamentally structural in character, that is to say either the result of 
interference and reflections, or of chemical differences in the different parts. 
In so far, the colouration would be in a sense accidental, a secondary result of 
the pattern. When the colour does not conform with structural lines, it is 
most often pigmentary, an exudation of the products of excretion staining the 
surface according to the osmotic conditions, or the relation of the internal 
organs to the external covering. Here again the total result of pattern and 
colour is still more accidental, due to uncorrelated factors. The work of the 
most modern school of painting, with its display of startling primary colours, 
and its insistence on masses rather than on outlines, is training us (in a fashion 
that doubtless would have been most repugnant to Ruskin, and that he would 
have denounced in language as vivid as a canvas of Matisse) to see beauty in com- 
bimations that we have been accustomed to regard as incongruous, and to 
comprehend harmony and design without the aid of the familiar scaffolding of 
outline and perspective. I admit in the fullest way that Nature may be a 
better guide than our acquired prepossessions, and that colour may show its 
highest value when it is divorced from form. I wish only to remind you that 
pattern is an inevitable outcrop of structure; that there must be colour, and 
that there must be combinations of colour and pattern. The living world, even 
if selection had played no part in moulding it, would still be a shining wonder, 
infinitely diversified. 
In the two groups of the animal kingdom with which I am most familiar, 
there seems to be a general process, rather different in the two cases, according 
to which the evolution of colouration has taken place. In each case there has 
been a transition from patterns that are the plain consequence of growth- 
