949 STUDY OF NATURAL HISTORY. 
every natural group. Now, as there must, in the 
natural system, be a harmony of design, that har- 
mony, if it is not universal, and extending to the 
most minute particulars, cannot be worthy of those 
attributes belonging to the God of Nature. We 
must not, therefore, content ourselves with noting 
the variations we are speaking of, and viewing them 
as simply confined to the group in which they oceur; 
for this would be taking a narrow and confined view 
of things. Our business is to trace them in all 
other groups— not only such as are adjoining, but in 
those belonging to the same great division of animals: 
we must, as it were, ascertain how far they are ampli- 
fied and expanded ; and trace their prevalence in as 
wide a circle, and through as great a number of other 
assemblages, as possible. We should ever bear in 
mind, that nature every where presents those two 
kinds of relations already explained, namely, affinity 
and analogy; and that both these universally be- 
long to all groups. Hence we may conclude that ¢ 
there must be a certain order in which analogies 
occur, and that the series in one group will occur 
in precisely the same order in another. Were it 
otherwise, there would be a want of harmony, utterly 
inconsistent with that ideal perfection which we 
attach to the system of nature. Accordingly it 
has been found, that in a number of ornithological 
groups, these analogies do actually occur in precisely 
the same order, and with the same regularity, as the 
seasons of one year follow and correspond to the 
seasons of another. It is, then, to these modifi- 
cations of form which every circular genus presents, 
that we give the name of sub-genera (144.). Now, 
