212 A HISTORY OF FISHES 



Among the littoral fishes almost every conceivable type of 

 coloration is found, ranging from a simple and uniform grey 

 or brown to the most vivid and bizarre combinations of colours 

 and markings. As a rule, the spots and mottlings, when present, 

 tend to give the fishes a general resemblance to the ground or 

 to the rocks and weeds among which they swim. This pro- 

 tective resemblance is often remarkably exact, and among 

 granite rocks we find fishes with an elaborate series of granite 

 markings; similarly, black species are found among lumps of 

 lava, green ones among the lighter varieties of seaweeds, 

 olive-coloured fishes among the fucus-like weeds, and red ones 

 among the corals of similar shades. Seen apart from their 

 surroundings some of these fishes are difficult to explain in 

 terms of concealing colours, but studied in their natural haunts 

 many of the puzzling cases immediately become clear. For 

 example, many of the Sea Perches or Groupers [Epinephelus) have 

 the head and body covered all over with more or less hexagonal 

 spots of reddish brown, separated from one another by a pale 

 white or blue network — a reticulated pattern recalling that of 

 the Giraffes. Lieut.-Col. Alcock in his book A Naturalist 

 in Indian Seas records how he was in a boat with a native 

 fisherman who speared one of these fishes, which, when wounded, 

 took shelter in an adjacent clump of coral and lay concealed 

 therein. The red spots bore a most exact resemblance to the 

 coral polyps and the fish refused to leave its shelter and was 

 eventually captured. 



Judged from this standpoint, the vivid colours of the fishes 

 of tropical reefs are more easily understood. Seen as museum 

 specimens they appear as highly conspicuous objects, but 

 observed against a background of corals and associated forms 

 of animal life, themselves presenting a perfect riot of colour, 

 they attract comparatively little attention. Many of these 

 reef-dwelling forms exhibit an extraordinary variety of darker 

 markings of every description, the pattern, however, being 

 fairly constant in any particular species (Fig. 83). The purpose 

 of such markings is to break up the outline of the fish and to 

 conceal the shape. Some of the Butterfly-fishes [Chaetodon) have 

 the head crossed by a dark band, often bordered with white or 

 blue, while at the hinder end of the body is an eye-like spot 

 or ocellus, sometimes ringed with white or yellow (Fig. 830). 

 They are said to be in the habit of swimming for a short distance 

 very slowly tail first, but, if disturbed, they will dart off with 

 great rapidity head first in the opposite direction. It has been 



