The Black-and- Yellow Grosbeak 



These cases, further, throw light on the 

 origin of protective mimicry where it does 

 exist. 



Protective mimicry is usually said to have 

 been brought about by the action of natural 

 selection. This is not strictly accurate. Natural 

 selection cannot cause two showy, dissimilar 

 species to resemble one another ; all it can do 

 is to seize upon and perfect a resemblance that 

 has been caused by the numerous factors that 

 have co-operated to bring about all the diversity 

 of organic life upon this earth. 



173 



