INTRODUCTION. 23 
tween suborders, and 3 & 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 
yellow) ; 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 
type 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 subspecific, title, e. g., Turdus (Hylocichia) 
Swainsoni, Var. Alicice, or simply Turdus Alicie.” Family- 
names end in ida, those of subfamilies in ine. 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 
17 Turdus Alicie is often ranked as a species. 
