8 o 
COLOUR IN NATURE 
CHAP. 
translucent colours of the Coelentera. That some part 
at least of the charm is due to childish reminiscences 
of tales of coral islands and tropical seas, few would 
deny, but apart from this, many of the polypes and 
sea-anemones of our own shores are adorned with 
tints which afford intensest pleasure to a colour- 
loving eye. 
The Coelentera include a large number of forms, 
which are almost all marine, and are found in greatest 
abundance in warm seas. Many of them are of 
sedentary habit, and frequently of peculiarly plant¬ 
like appearance ; many in their method of growth 
or in their peculiar shape present a strong superficial 
resemblance to seaweed. All are characterised by 
relatively great simplicity of structure, and therefore, 
in accordance with the principles which we have 
already considered, their colours are due to the 
presence of pigment in the coloured tissues, and not 
to effects of structure. As a group, therefore, the 
Coelentera are plant-like not only in general habit, 
but also in the development of a large series of 
brilliant pigments. Owing to their simplicity of 
structure and the absence of true internal skeleton, all 
are during life more or less transparent or translucent, 
and this translucency adds an extraordinary delicacy 
to their colouring. Unfortunately this colouring 
cannot be seen in preserved specimens, both on 
account of the fugitive nature of the pigments, and 
on account of the loss of the transparency during the 
process of preservation. During life the transparent 
appearance is largely increased by the habit which 
most possess of distending the tentacles and the 
body by means of sea-water, while death is usually 
