548 THE WONDER OF LIFE 



or in some way safe. ' They require ', as Wallace said, 

 ' some signal or danger flag, which shall serve as a warning 

 to would-be enemies not to attack them, and they have 

 usually obtained this in the form of conspicuous or brilliant 

 coloration, very distinct from the protective tints of the 

 defenceless animals allied to them '. It is satisfactory that 

 this interpretation has been justified by a number of 

 experiments, which go to show that hungry animals, once or 

 twice duped by having conspicuous unpalatable caterpillars 

 and the like given to them to eat, soon learn by experience 

 and are aided in this by the impressiveness of the colouring. 

 Even in fishes, whose cerebrum remains at a very low level, 

 an association between colour and a gustatory experience 

 may be established and retained. It has to be admitted, 

 however, that in many cases the experiment of offering 

 conspicuous unpalatable caterpillars and the like to hungry 

 animals has failed to confirm the theory of warning color- 

 ation, so that each case has to be judged on its own merits. 

 In some cases there appears to be truth in the interesting 

 suggestion of Eisig, that very abundant deposition of a 

 waste-matter pigment may render an animal at once 

 unpalatable and conspicuous. 



This much seems certain, that numerous noxious or 

 aggressive types, such as wasps, coral snakes, and skunks, 

 are conspicuously coloured. A familiar and plausible 

 illustration may be found in the common salamander 

 (Salamandra maculosa), which is conspicuous in its black 

 and yellow livery and has a very glandular skin the 

 secretion of which is perhaps noxious. 



Recognition -Marks and Guide -Marks. A fourth 

 use of coloration is to aid animals in the rapid recog- 

 nition of their kith and kin, and in the rapid execution of 



