5 
To these, as well as to a multitude of other private and published 
sources I wish to express thanks for aid and assistance. 
CLASSIFICATION. 
The first step in any science is that of classification. The present 
system of generic grouping of species was first advanced by Linnzus in 
his epoch-making ‘“‘ Systema Nature ”’ and has since been followed con- 
sistently by zoologists. By this, species are grouped together in genera 
aecording to fundamental structural relationships and not accidental 
resemblances. The fact that upon the discovery of the laws of evolution 
these relationships were found to agree with lines of descent proved the 
logic of the system and gave it an added meaning. Thus the various 
specific members of a genus can be conceived as having descended from a 
common specific ancestor; the genera of a family from a common generic 
one, etc. 
Dealing only with existing North American birds, they may be divided 
into a number of Orders, which are the largest groups with which the 
Canadian ornithologist has direct concern. Orders are divided into 
Families, Families into Genera, and Genera into Species. ‘These divisions 
may be again subdivided into Suborders, Subfamilies, Subgenera, and 
Subspecies whose positions in the scheme are evident from their titles. 
Though the limitations of book construction necessitate the presenta- 
tion of the classification scheme as a linear succession of forms following 
one another in single file, it should be borne in mind that the system is 
not linear in conception. The component species instead of following a 
single line of relationship and sequence from the lowest to the highest 
present many parallel or divergent lines of equal or subordinate rank. 
The class Aves or Birds may be represented by a tree, the height of the 
tree representing time in geological ages from the earliest at the bottom 
to the present near the top. The trunk should be shown as double at the 
base; one stem would be a short dead stump and would represent the 
fossil toothed birds which became extinct before present geological time; 
the other, large and thrifty, would represent the modern untoothed forms. 
This in turn would divide into two main branches a short way from the 
base and would represent the two subclasses, the Raft-breasted and the 
Keel-breasted birds. The former would be represented by much the 
smaller branch, whereas the latter would divide and subdivide into 
branches representing first, orders; next, families; then, genera; and 
finally species. 
The value of these divisions, that is, the amount of differentiation 
sufficient to raise a group of genera to a family, or a collection of families 
to an order, is a matter for experienced individual decision as there is no 
authoritative ruling upon the subject. However, there has gradually 
grown up an approximate agreement on this subject, though the constant 
tendency among specialists has been to make finer and finer distinctions 
and to multiply the number of the various groups. 
The smallest division generally accepted is the Species. Though 
everyone has a more or less accurate conception as to what a species is, 
whether it be called by that name or another, no satisfactory definition 
has ever been constructed for it. It is what is commonly known as a 
