172 FISHES CHAP. 
stream near Ivy Bridge have become much lighter since the pollu- 
tion of the water by white china clay.’ As an illustration of the 
necessity of vision to such colour-changes, it may be mentioned 
that blind Fishes cannot vary their tint in this protective fashion. 
A blind Turbot living upon a light sandy bottom differed from 
its fellows in being much darker and more conspicuous. Dark 
Trout have been observed among their light-coloured brethren in 
a chalk stream in Hampshire, but the former were invariably 
blind, probably, as their larger size indicated, through age.” 
Of other forms of protective resemblance, reference may be 
made to the bottom-feeding Flat-Fishes (Pleuronectidae), many of 
which have the upper surface of the body coloured with various 
shades of brown, speckled with black or light specks or blotches, 
in harmony with the prevailing tints of the sandy banks which 
usually form their feeding-ground. When disturbed these Fishes 
court concealment, and render themselves still less conspicuous by 
partially burying themselves in the sand. Many of the Skates 
and Rays, which have a white ventral surface, have the back 
mottled and coloured in accordance with the colour of the sea- 
bottom, but in this case it is possible that the advantage lies 
in enabling the Fish to secure passing prey by concealing its own 
whereabouts. 
Striking examples of protective coloration occur among the 
Pipe-Fishes and Sea-Horses (Syngnathidae),which usually frequent 
groves of Zostera, Fucoids, and other sea-weeds. A British 
species of Pipe-Fish (Siphonostoma typhle), which lives among the 
blades of the sea-grass, Zostera, is olive-green in colour, and is a 
typical example of protective resemblance both in colour and in 
the slender elongated shape of the body. Similar protective re- 
semblances are noticeable among the Sea-Horses, the coloration 
varying with the general hue of their environment of sea-weed; but 
the climax is certainly reached by the singular Australian species, 
Phyllopteryx eques (Fig. 388)4 In this Fish the skin is produced 
into numerous long, flattened, branched filaments, which are pro- 
longed from the extremities of spine-like outgrowths of the dermal 
skeleton, and marked by alternate bands of brown and orange,” 
Poulton, op. cit. p. 82. 2 Ibid. p. 86. 
Cunningham and MacMunn, op. cit. p. 773. 
C. Stewart, quoted by Poulton, op. cit. p. 67. 
Saville Kent, op. cit. p. 186, describes the colours of the living Fish as ‘‘ various 
shades of light crimson and lilac.” 
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3 
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