ar; but are
of no use in the classification of the higher groups. How it comes, that
certain parts of the structure, by which the habits and functions of the
species are settled, are of no use in classification, whilst other
parts, formed at the same time, are of the greatest, it would be
difficult to say, on the theory of separate creations.

{430} _Origin_, Ed. i. p. 414, vi. p. 570.

{431} _Origin_, Ed. i. p. 414, vi. p. 570.

Some authors as Lamarck, Whewell &c., believe that the degree of
affinity on the natural system depends on the degrees of resemblance in
organs more or less physiologically important for the preservation of
life. This scale of importance in the organs is admitted to be of
difficult discovery. But quite independent of this, the proposition, as
a general rule, must be rejected as false; though it may be partially
true. For it is universally admitted that the same part or organ, which
is of the highest service in classification in one group, is of very
little use in another group, though in both groups, as far as we can
see, the part or organ is of equal physiological importance: moreover,
characters quite unimportant physiologically, such as whether the
covering of the body consists of hair or feathers, whether the nostrils
communicated with the mouth{432} &c., &c., are of the highest generality
in classification; even colour, which is so inconstant in many species,
will sometimes well characterise even a whole group of species. Lastly,
the fact, that no one character is of so much importance in determining
to what great group an organism belongs, as the forms through which the
embryo{433} passes from the germ upwards to maturity, cannot be
reconciled with the idea that natural classification follows according
to the degrees of resemblance in the parts of most physiological
importance. The affinity of the common rock-barnacle with the
Crustaceans can hardly be perceived in more than a single character in
its mature state, but whilst young, locomotive, and furnished with eyes,
its affinity cannot be mistaken{434}. The cause of the greater value of
characters, drawn from the early stages of life, can, as we shall in a
succeeding chapter see, be in a considerable degree explained, on the
theory of descent, although inexplicable on the views of the
creationist.

{432} These instances occur with others in the _Origin_, Ed. i. p.
416, vi. p. 572.

{433} _Origin_, Ed. i. p