Ohio or Schuylkill; those of the reddish-coloured waters of the bayous of the Louisiana swamps look as if covered with a coppery tarnish; and, lastly, those met with in streams that glide beneath cedars or other firs have a pale and sallow complexion."[1] A no less authority than Dr. Günther states: "Trout with intense ocellated spots are generally found in clear rapid rivers, and in small open alpine pools; in the large lakes with pebbly bottom the fish are bright silvery, and the ocellated spots are mixed with or replaced by X-shaped black spots; in pools or parts of lakes with muddy or peaty bottom the Trout are of a darker colour generally, and when enclosed in caves or holes they may assume an almost uniform blackish colouration."[2] "Minnows have the power common to most fishes of rapidly assimilating to the varying colour of the stream. They change from brown to gold, from gold to brown."[3] The Paradise-fish (Polyacanthus sp.), a pet kept in confinement throughout China, has a colour in dark or muddy waters of a "dull uniform brown; and it is only when living in clear water, exposed to the sunlight, that the golden hue and red transverse bands make their appearance." "Cod from the British seas and German Ocean are usually greenish or brownish olive in colour, with a number of yellowish or brown spots; but more to the north darker, and often uniformly coloured specimens are more common; while in the race from Greenland, Scandinavia, and northern Norway, there is frequently a large irregular black patch on each side of the body."[4] In the South Atlantic Mr. Cunningham secured by the aid of the towing-net a bright blue Isopodous crustacean (Idotea annulata), and states that, according to Spence Bate, "the blue colour appears to be a peculiarity of pelagic species."[5]
Entomologists have long noticed the effects of assimilative colouration, even in our own country. Mr. Dale, of Glanvilles Wootton, has truly remarked: "Where do we find whitish or brilliant-coloured species of Lepidoptera, such as Melanargia galatea, Lyccena corydon, L. adonis, Eubolia bipunctaria,
