CHAPTER II 
THE PIGMENTS OF ORGANISMS 
Natural and Artificial Pigments—Classification of Pigments— 
Pigments of Direct Physiological Importance—Derived 
Pigments—Waste Products—Reserve Products—Intro¬ 
duced Pigments—Distribution of Pigmental Colours— 
Spectroscopic Characters of Pigments. 
Although, as we have seen, some of the most 
beautiful colours of organisms are optical effects, or 
are produced by a combination of a pigment and a 
certain structure, yet the vast majority of the colours 
of plants, and the colours of many animals, owe their 
origin to pigments only. Before proceeding to con¬ 
sider the colours of the separate groups of animals 
and plants, we shall look for a little at pigments in 
general. 
The pigments or colouring-matters which are 
most familiar to artists and those engaged in the 
industries, are very frequently either artificial organic 
substances, such as the now familiar aniline dyes, 
or are inorganic compounds of the metals, such as 
ultramarine and Scheele’s green. Some, however, 
of the natural organic pigments are used in the arts. 
As is well known, the ancients obtained their Tyrian 
