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almost always be found several examples of tlie soles. The 

 side-swimmers or flat fishes (Pleuronectidae) to which the 

 soles belong , are a very singular group. Their bodies are 

 twisted sideways from right to left, and the head so turned 

 that both eyes are on the same side. Then the two sides are 

 entirely different in colour and skin, for the one turned down- 

 wards is white, like the bellies of many other animals, while 

 the upper side , on which are the eyes, is always of a dark 

 colour, and has, besides, the power of changing its colour to 

 that of the ground. Many of these fish can imitate the white 

 pebbles strewn in the grey sand, by causing similar light spots 

 to appear on their dark skins. This power of imitation greatly 

 protects the fish, and it is not always easy to see them in the 

 tanks. They are first betrayed by their protruding opalescent 

 eyes, which they can move singly in all directions and thus 

 command the whole neighbourhood. The sole catches its prey, 

 consisting of the smaller fish that also live on muddy bottoms, 

 by impelling its body forward with lightning-like rapidity. 

 The sole swims very actively , gracefully undulating its flat 

 body, and always turning the side on which are the eyes upper- 

 most. When it wishes to bury itself a few strong strokes with 

 its dorsal fins are sufficient to throw up a quantity of sand 

 which falls back upon its body; when it again lies on the watch, 

 immoveable for hours together. 



Flat fish increase in an extraordinary manner, which fact is 

 partly explained by the natural protection afforded them by 

 their power of imitating the colour of surrounding objects. They 

 also form a large part of human economy, for all kinds have 

 excellent flesh not easily spoiled, and can therefore be imported 

 far into the interior. Many kinds attain an enormous size. In 

 consequence, they are an important article of commerce in the 

 North. Germany, England, France, Holland and Denmark con- 

 sume immense quantities. Imports to the value of 80,000 pounds 

 sterling are annually brought to London alone from Holland, 

 and this is at most the fourth part of what that city consu- 

 mes. In Italian markets flat fish are among the commonest 

 and most highly prized. They are fished in different ways, 

 sometimes with the harpoon and drags , sometimes with the 

 angle and ground-lines. 



The principal flat-fish are the turbot, sole, flounder, plaice 

 and dab. Only the smaller kinds can be accommodated in the 

 Aquarium; the Sole (Solea vulgaris), the Turbot (Rhombus 

 maximus), and similar kinds are usually to be found. 



