AND WHY THEY ARE WORN. 71 



tions of naturalists all over the world, we now 

 know that brilliant colouration is as often a form 

 of protective colouration as is the sober style 

 wherein the colours harmonise with rocks, or 

 mud, or reeds, and so forth, as the case may be. 

 Tnus birds often appear to be very conspicuously 

 coloured, because they are seen a2Xirt from their 

 surroundings. The hoopoe and the parrots are 

 admirable examples of this. The zebra, amongst 

 the mammals, is another wonderful illustration. 



When we turn to the fishes we discover that 

 the same rules appear to obtain. This is con- 

 spicuously the case with fishes which inhabit the 

 neighbourhood of coral reefs. Here we meet 

 with the gaudily striped and barred scaly-finned 

 fishes, the Choetodontidce, and the brilliant wrasses 

 or lip-fishes. These live in a world of colour, 

 for the coral animals themselves are also bril- 

 liantly coloured. The gurnards and mullets of 

 our own coasts are other instances of brightly 

 hued fi'shes. 



It is significant in this connection to note that 

 those fish which pass most of their time in mid- 

 water, like the herring, for instance, have the 

 under parts silvery or white and the upper parts 

 darker. This, again, appears to be a form of 

 protective colouration, for the dark upper surface 

 tends to screen them from the view of enemies 

 above, whilst the light under part performs a 

 like service against enemies below, which look 

 upwards towards the light. Many young fishes, 

 as we shall see, are perfectly transparent, and 

 therefore invisible. 



But the interpretation of colour is by no 



