122 



THE COLOUKS OF ANIMALS 



In order to realise these results it must be remembered 

 that the appearance represented by (4) or (5) is very 

 rarely seen in nature, except when the pupa is dis- 

 eased. By far the commonest varieties met with are 

 those represented by (3), which are therefore called 

 normal forms. 



Special advantages of the Small Tortoiseshell for 

 purposes of experiment 



From the results expressed in the tabular form 

 given above, it was clear that this species was very 

 susceptible to surrounding colours, and that black 

 and gold produced the most opposite effects. Another 

 advantage in the use of this species is the fact that 

 the caterpillars live in companies, each of which 



