IX 
THE MARKINGS OF ORGANISMS 
205 
Though there is no successional repetition in a 
Vertebrate, the rule that parts occupying similar 
positions tend to be similarly coloured holds good 
here as in Invertebrates. The similarity seems, 
however, here to have relation to position with refer¬ 
ence to the median axis of the body only. A brief 
study of birds’ feathers affords very convincing proof 
of this. Thus, though the secondary quills of one 
wing in a bird showing complicated feather-markings 
resemble those of the other wing, it will be found 
that the quills are not all absolutely the same, but 
form a graduated series, of which the first and last 
members may differ very considerably. The usual 
difference between the markings of the two sides 
of the vane may be explained in wing-quills as due 
to the unequal development of the two sides, but, 
except in the case of the central rectrices, it is quite 
as common in the tail-quills, in which the two sides 
are equally developed. In short, it is a general fact 
that in Vertebrates, where the coloration depends 
upon the colours of the epidermal outgrowths, the 
pattern has reference to the body as a whole, the 
colours of the individual structures being completely 
subordinated to that whole. 
As to the nature and meaning of patterns, there 
can be little doubt that in simple organisms they are 
closely related to segmentation, are expressions of 
the same process. It has been dimly suggested by 
various authors, but nowhere with such force and 
eloquence as by Mr. Bateson, that both patterns and 
segmentation may be purely mechanical phenomena, 
and that “ the perfection and symmetry of the pro¬ 
cess, whether in type or in variety, may be an ex- 
