INTRODUCTION. 85 



study these seeming distinctions, and decide if they are 

 constant. 



Specific characters are, I believe, sufficiently tangible 

 and constant in nature, and never need be mistaken ; this 

 will hereafter be illustrated. I would, however, first speak 

 strongly in disfavor of the growing belief in the hybridism 

 of birds. I do not believe that, generally speaking, hybrids 

 occur ; there are a few cases, but they are exceptions. In 

 many instances the so-called hybrids are but abnormal con- 

 ditions of plumage, that can be accounted for on entirely 

 natural grounds. But sometimes the ornithologist, in his 

 haste to make new species, has divided the two opposite 

 stages of color in one species, calling each by a different 

 specific name, and has afterwards found specimens that 

 in their peculiar plumage, size, etc. naturally form con- 

 necting links between the two; in his perplexity as to 

 which of these to refer it, he has hit upon the fortunate (?) 

 expedient of calling it a "hybrid. 1 ' Would it not have 

 been much better, if, at first, he had taken a large num- 

 ber of specimens, and, studying them, seen what the sup- 

 posed hybrids really were 1 



A species consists in a bird's being so organized that it 

 always reproduces young which are like itself; or, if they 

 differ, the variation never exceeds fixed points. More- 

 over, I believe that a true species will seldom mate with 

 others having different characteristics; or, if such a union 

 occurs, the offspring are always infertile ; thus, by 

 these never-varying laws, species are kept from amalga- 

 mating. Take, for an illustration, the Robin, a bird that 

 since its discovery has never had a single variety or local 

 race called a "new species" (at which I marvel greatly, how- 

 ever). The typical specimen has a clear red breast, black 

 head, and immaculate slate-colored back and wings, which 

 at once distinguish it from all others of the Turdinae. 

 We also have a Robin that is very light-colored, with the 



