COLOUR IN NATURE 
CHAP. 
186 
changing tints of the hapless cuttles which the storms 
of spring cast upon the beach. To those who have 
not, no learned talk of chromatophores will suggest 
the delicate rosy flush which comes and fades as one 
touches the sensitive skin. 
The cuttles of our own shores are chiefly remark¬ 
able for their changing tints rather than for their 
brilliancy, but some tropical forms display very 
bright colours. Thus Octopus pictus is of a yellowish 
colour with spots “ suffused with shades of the 
richest ultramarine blue, each spot having a light 
centre and a dark annular border ” (Saville Kent). 
According to Agassiz the deep-sea cuttles are usually 
brown or purplish-brown. 
2. Colours of Shells .—The fact that most shells 
are distinguished by their rich and beautiful colour¬ 
ing is familiar enough ; their variety and beauty of 
marking has endeared them alike to the savage, the 
child, and the artist. Brightness of colour is most 
common among the shallow-water forms, especially 
of the tropics ; deep-sea forms tend to be pale in 
colour, but often possess an iridescent sheen absent 
from those living in shallow water (Agassiz). Many 
shells are coloured on the inner surface as well as the 
outer, and the colouring-matter is rarely uniformly 
diffused, being most frequently arranged to form 
patterns and markings. According to Dr. Woodward, 
“ those which are habitually fixed or stationary (like 
Spondylus and Pecten pleuronectes') have the upper 
valve richly tinted whilst the lower one is colourless.” 
In some cases the mantle is coloured and marked in 
the same way as the shell. In Ianthvna the upturned 
base of the shell is coloured by the violet pigment 
