8o 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 



