INTRODUCTION. 23 



tween suborders, and 3 X between orders. Forms in nature 

 are everywhere so delicately blended that theoretically it is 

 almost impossible to " draw any lines." A species (even 

 though exhibiting much individual variation) is constituted by 

 all those birds, who, since the present organization of birds 

 has existed, might be the descendants of a single pair. 



[The phenomena of albinism and melanism can here be only 

 briefly referred to. In the latter, which is very rare, birds are 

 abnormally dark or black. In albinism, which is not uncom- 

 mon, birds are partially or wholly abnormally white (or even 

 3'ellow) ; sometimes they are partly bleached. Such condi- 

 tions of plumage need cause confusion only among birds of 

 the same genus, and rarely then, being seldom complete.] 

 There are often varieties, geographical races, or forms rendered 

 appreciably distinct by the effects of climate, etc. By a strict 

 definition of the term, varieties must have different distribu- 

 tions (at least during the breeding-season), though accidental 

 stragglers may occur far from their usual habitat. A specific 

 tyjye is usually the variety first named. Hybrids, or " crosses," 

 are the joint offspring of two species, but they do not often 

 occur among birds in a natural state. 



A bird's scientific name consists of a generic (subgeneric) and 

 specific, or also subspeciSc, title, e. g., Turclus (Hylocichla) 

 Swainsoni, Var. Alicice, or simply Turclus Alicioi^'' Family- 

 names end in idm, those of subfamilies in ince. Scientific 

 names are usually begun with a capital, are italicized, and, 

 when following English names, put in parenthesis. Specific 

 names, however, are ordinarily spelt without a capital, unless 

 derived from proper names. It is best to form no Latin 



" Turdus Alicia is often ranked as a species. 



