GENERAL DISTRIBUTION. 
167 
the most barren islands at the Poles, aye, even on those 
which have never been scanned by human eye. In the 
green fields of cultivated districts we can scarce take a step 
without meeting with some of these citizens of the world, 
or without hearing the voices of these creatures of which 
we are so fond: north, south, east, and west; on all 
sides birds are to be found. Long before man appeared 
they were settled inhabitants of this earthly sphere. 
The extraordinarily extensive distribution of the 
feathered creation reveals to us an indescribable diversity 
in development, arising from a common form; each 
creature being exclusively constructed, so as to meet the 
requirements of the existence peculiar to it. Research 
teaches us to recognize, in this fact, an immutable law of 
Nature : uncertainty disappears, and certainty lies before 
us. Thus, it becomes possible for us to determine, 
through comparison with those animals with which we 
are already acquainted, the homes or abodes of species 
yet unknown to us, or by means of an exact knowledge of 
its locality to determine in prospective the form and 
colour of a species. Certain characteristics, which are to 
be found among all animals in one and the same district, 
may, after examination, be accepted as distinctive. 
The home of the bird is twofold, land and water. The 
slightest observation will at once show us the difference 
of form existing between birds occupying either. They 
always possess a certain stamp, which hears an evident 
relation to one or the other. Inasmuch as the charac¬ 
teristics of the land are more varied than those of the 
water, so it is that land birds vary more in form and 
species than aquatic birds: these last, again, are more 
numerous as individuals of a single species than the 
former; for it rarely happens that any land species is to be 
