COLORATION 173 



thus resembling both in shape and colour the fronds of the sur- 

 rounding fucoids and other marine algae amongst which the Fish 

 lives. 



Many of the Fishes frequenting the coral reefs of the East 

 Indian and Pacific areas, especially those belonging to the Teleo- 

 stean families Chaetodontidae and Pornacentridae, have a most 

 brilliant and vivid coloration, frequently marked by bands or 

 stripes of different tint. So far from rendering these Fishes 

 unduly conspicuous, there can be little doubt that, by harmonising 

 with the striking and varied colours of the anemone-like coral 

 polypes, their coloration is distinctly protective ; and it is inter- 

 esting to note that similar colour-patterns have been indepen- 

 dently reproduced in both families. 1 Even the reef-frequenting 

 Fiat-Fishes (Pleuronectidae) have the usually sombre upper surface 

 ornamented by vivid colours and striking patterns. 



Pelagic Fishes, like the Herring, Mackerel, Flying-Fish (Exo- 

 coetus), and many others, often have the belly and sides silvery or 

 white, and the back dark green, black, or steely blue. Seen from 

 below against the light sky, or viewed from above against the 

 background of the dark water, these Fishes would seem to be 

 practically invisible to their predatory foes, whether Fishes or 

 Birds, or at all events not easily detected. 



Coloration may not only be protective, but also aggressive, by 

 helping to conceal the proximity of an animal from its prey ; add 

 to this some device for deceiving and attracting the prey, and we 

 have an example of " alluring " coloration. 2 



As an example of coloration which is both aggressive and 

 alluring, the Angler-Fish or Fishing-Frog (Lophius piscatorius) of 

 our own coasts may be quoted. Naturally sluggish and inactive 

 in its habits, and often using its muscular pectoral fins for crawl- 

 ing about the sea-bottom, the Angler- Fish usually hides itself in 

 the sand or amongst sea-weeds, which it closely resembles in 

 general colour. Curious branched tag-like processes of soft skin 

 fringe the sides of the head and body, and in appearance and 

 colour resemble the smaller fronds of the surrounding sea-weed. 

 So far the coloration is simply aggressive, and helps to conceal 

 the Fish from its prey, but in addition the animal is provided 

 with a special device for luring its prey within the reach of 

 its capacious and Frog-like mouth. The first three spines 



1 Giinther, Study of Fishes, London, 1880, p. 52-1. 2 Poulton, op. tit. p. 72. 



