II. 



REPRESENTATIVE SPECIES. 



The almost universal existence of representative 

 species is one of the most remarkable facts elicited 

 by the scientific study of ornithology. The im- 

 j)ortant bearing of this curious phenomenon on the 

 evolution and origin of species is palpable to every 

 student of birds. These representative species may 

 be roughly divided into two very distinct classes. 

 In the first place, they consist of distinct species, 

 obviously very closely allied to each other, and to a 

 })arent species ; and in the second place, of mere 

 forms or races of variable degrees of distinctness, 

 yet only imperfectly segregated from a parent form. 

 As a general rule, the wider and more extensive the 

 geographical breeding area of a species is, the more 

 that species has become divided into representative 

 races or species, which owe their segregation to the 

 different aspects of climate and the varying con- 

 ditions of life inevitably correlated with an extensive 

 area of dispersal. It is also a very remarkable fact, 



