X 
THE COLOURS OF FISHES 
209 
and colouring there is a remarkable uniformity of 
pigments. With a few exceptions, turacin being per¬ 
haps the most important, the pigments seem to be all 
either lipochromes or melanins, the lipochromes pre¬ 
dominating in fishes, amphibians, lizards, and birds, 
the melanins in snakes and mammals (Krukenberg). 
As the melanins are often regarded as derivatives 
of haemoglobin, and the lipochromes of fats, some 
would say that there are two kinds of pigments in 
Vertebrates—effete blood pigments and modified fats 
(see Kiikenthal). Secondly, in many cases the 
general coloration is due either to structural effects 
or to the patterns and markings rather than simply 
to the pigments themselves. The development of 
structural colours is associated with the degree of 
development of the cuticular outgrowths, and reaches 
perhaps its greatest height in birds. In mammals 
bright structural colours are rare, and the frequent 
beauty of colour is due solely to the unequal 
distribution of the melanin pigments which gives 
rise to bands or spots. Eimer has endeavoured to 
prove that in all Vertebrates longitudinal markings 
are the most primitive form of coloration, and that 
spots, transverse stripes, or uniform coloration are 
secondary derivatives. His work on the Markings 
of Animals shows, at least, that there is an 
extraordinary constancy in the markings which run 
through orders, as is, for example, well seen in the 
Carnivora among mammals. 
Sexual dimorphism of colour is another char¬ 
acter which is exceedingly common among Verte¬ 
brates. This may manifest itself simply in the 
greater brightness or purity of tint in the male as 
p 
