236 
COLOUR IN NATURE 
CHAP. 
Colours of Reptiles, especially Lizards 
and Snakes 
Among Reptiles the colours are most conspicuous, 
and have been most studied among snakes and 
lizards. In lizards black, gray, brown, and green 
are common colours, while most display very distinct 
and constant markings. According to Eimer the 
typical ground plan of the dark markings consists of 
seven longitudinal bands. The pigments seem to 
consist of the dark “ melanins ” and lipochromes, the 
green colour of, eg ., the green lizard being not due 
to a green pigment but to the structure of the skin, 
and to the contained yellow and black pigments. 
According to Krukenberg lipochromes are rare or 
perhaps absent in snakes, while melanins largely 
predominate. Yellow pigments do occur freely in 
snakes but their nature is undetermined, probably 
they are merely altered lipochromes ; for the peculi¬ 
arities which Krukenberg enumerates may be due to 
impurities or to decomposition. Lizards frequently 
exhibit the type of coloration known as protective, 
and, as is well known, have often considerable power 
of colour-change, best exemplified in the chameleon. 
It is interesting to note that the aberrant poisonous 
lizard Helodevma diverges markedly in colour from 
other lizards, being vividly marked with black and 
yellow, instead of showing the sober greenish hues 
of most lizards with their beautiful but unobtrusive 
striping. In its histological characters the skin of 
lizards shows much similarity to that of the frog, the 
power of colour-change, when present, being again due 
