322 THE WORLD OF THE SEA. 
with a viscous secretion, and their tissue is penetrated by.an oily 
fat, upon which the salt water has no action. 
Some of these creatures are painted with brilliant colours, and 
are robed in elegant costumes. They need not fear comparison 
with the butterflies or birds of the gaudiest plumage. The mullet 
and perch are clothed in scarlet; the mackerel and dolphin wear 
coats shot with emerald; the pike has his breast mailed with 
silver plates; while the salmon glides through the waters with a 
metallic lustre. In fact, the finny tribes can find representatives 
to furnish all the colours of the rainbow. However, for the most 
part, the tints, vivid and bright though they seem, are evanescent, 
THE MONOCENTRIS OF JAPAN. 
(Monocentris Faponicus.) 
and the least cause changes them from brilliancy to dulness; the 
time of the year, the health of the fish, taking it from its native 
element, all having their effect upon its colour. It was one of the 
pleasures of the Romans to watch the rapidly changing hues of the 
red mullet as it struggled in the agonies of death. 
The property of phosphorescence seems to be enjoyed by some 
of them; and, according to Borda, fish of this kind can be seen at 
three fathoms depth in a calm sea. 
Bennet describes a shark which emits a green, phosphorescent 
light from the whole of the under surface of its body. He found 
one individual whose light came as it were from one chamber. The 
appearance of this monster was hideous enough in the daylight; but 
in the dark, when luminous with an unearthly glow, it can be better 
imagined than described. When the shark dies, which happens 
