in Zoology and Botany. 187 
groups of organized beings, appear to indicate the direct con- 
trary; for the analogies of external nature all indicate the 
utmost variety and irregularity. Beautiful as are the exam- 
ples of creative design exhibited in the universe, and admi- 
rable as are the adaptations of one part of nature to another, 
there is no department of the creation which is tied down to 
mathematical laws and numerical properties further than is 
sufficient for the due performance of its destined functions. 
There are indeed certain mathematical laws which regulate 
the motions of bodies and their chemical combinations, but 
these do not give to the face of nature that symmetrical and 
artificial appearance which is aimed at by the zoological sy- 
stems above-mentioned. For example, the relative distances 
of the planets, their magnitudes, and the number of their 
satellites conform to no known numerical law. The fixed 
stars exhibit no regular arrangement, either in their magni- 
tudes, distances, or positions, but appear scattered at random 
across the sky. ‘To descend to our own earth, no symmetry 
is traceable in the forms of islands or continents, the courses 
of rivers, or the directions of mountain-chains. Organic life 
exhibits the same irregularity,—no two plants, and no two 
leaves of the same plant were ever perfectly identical in size, 
shape, colour, and position. In the “human face divine,” 
portrait-painters affirm that the two sides never correspond ; 
and even when the external form of an animal exhibits an ap- 
pearance of bilateral or radiate symmetry, nature departs from 
it im her arrangement of the internal structure. In short, 
variety is a great and a most beautiful law of Nature; it is 
that which distinguishes her productions from those of art, 
and it is that which man often-exerts his highest efforts in 
vain to imitate. When, therefore, we find a system of classi- 
fication proposed as the natural one which departs from this 
universal law of variety, and fetters the organic creation down 
to one unalterable geometrical figure or arithmetical number, 
there is, I think, a strong @ priori presumption that such a 
system is the work not of nature but of art. 
2. It follows from the irregularity of external nature, as 
seen on the surface of the earth, that the groups of organized 
beings must be irregular also, both in their magnitudes and 
in their affinities. In proof of this it must be granted that 
the final cause of the creation of every animal and plant is 
the discharge of a certain definite function in nature, and not 
the mere occupation of a certain post in the classification : 
in short, that the design of creation was to form not a cabinet 
of curiosities, but a living world. Few, I trust, would hesi- 
tate to admit this proposition. If, then, the different modifi- 
