20 CONTROLLED NATURAL SELECTION 
knowledge of the subject is meagre, and prob- 
ably untrustworthy. It may be that there 
are pleasing scents, the purpose of which is to 
attract enemies. 
One other method, by means of which 
animals render themselves conspicuous, re- 
mains to be considered, namely colour. This 
has been left to the last, because it is the 
most important and because a previous con- 
sideration of the other methods may render 
its consideration more comprehensible. This 
is dealt with in the next chapter. 
