82 
COLOUR IN NATURE 
CHAP. 
polypes, but owing to the way in which these are 
spread over it, they have a superficial appearance of 
enclosing the coral within their own soft parts. 
Distribution of Colours 
The coral-reefs of warm seas are largely formed 
of such colonial sea-anemones, the simpler colonial 
forms which do not produce a limy skeleton being 
notably absent from these regions. In their living 
condition on the reefs the polypes themselves, as 
well as the skeleton with its organic covering, are all 
coloured, often with the brightest of tints. Further, 
it seems to be relatively rare for the whole colony to 
be of one tint. Sometimes the polypes are sharply 
contrasted in colour with the coral, sometimes the 
youngest portions of the colony differ entirely in 
colour from the older; while in those forms in which 
the individual polypes attain a considerable size, the 
tentacles may be banded or tipped with a colour 
quite different from the ordinary ground - colour. 
According to Dr. Hickson (A Naturalist in N. 
Celebes, London, 1889) the commonest tint is a deep 
greenish-brown, and next to that, and especially in 
the younger parts, a bright green. Again, a study 
of the descriptions and plates in Mr. Saville 
Kent’s great book on the Barrier Reef of Australia 
shows that after these come shades of red, pink, and 
yellow, and more rarely electric blue. According to 
Saville Kent there is great and striking variation 
in tint both within the limits of a species and even 
during the course of the life-history of a single 
colony. 
