CHAPTER I 
THE COLOURS OF ORGANISMS 
Colour Phenomena in General — Distinctions between Pig¬ 
mental and Structural Colours—Characters of Structural 
Colours and their Classification—Production of Light by 
Organisms (Phosphorescence). 
It is not necessary here to consider in detail the 
physical aspect of colour. Every one is more or less 
familiar with the fact that, in general terms, objects 
appear to us to be coloured because they absorb 
certain of the elements of white light and reflect 
the remainder. Thus the substance vermilion 
appears to us to be red because it absorbs all the 
components of the incident light except the red, 
and this it reflects ; it is a fundamental property of 
vermilion that it possesses this power of selective 
absorption. Practically all bodies do exercise 
selective absorption to a greater or less extent, 
but it is only when the absorption is marked in 
the visible part of the spectrum that we definitely 
recognise the bodies as coloured. When such 
coloured bodies can be employed to impart their 
own colour to animal or vegetable substances they 
