logical time. The more that
we think about this antithesis between the naturalistic and the
non-naturalistic interpretations, the greater must we feel the contrast
in respect of rationality to become; and, therefore, I need not spend
time by saying anything further upon the antecedent standing of the two
theories in this respect. The evidence, then, which I am about to adduce
from the study of development in the life-histories of individual
organisms, will be regarded by me as so much unquestionable evidence in
favour of similar processes of development in the life-histories of
their respective species--in so far, I mean, as the two sets of changes
admit of being proved parallel.

[Illustration: FIG. 26.--Antlers of Stag, showing successive
addition of branches in successive years. Drawn from nature (_Brit.
Mus._).]

In the only illustration hitherto adduced--viz. that of deers'
horns--the series of changes from a one-pronged horn to a fully
developed arborescent antler, is a series which takes place during the
adult life of the animal; for it is only when the breeding age has been
attained that horns are required to appear. But seeing that every animal
passes through most of the phases of its development, not only before
the breeding age has been attained, but even before the time of its own
birth, clearly the largest field for the study of individual development
is furnished by embryology. For instance, there is a salamander which
differs from most other salamanders in being exclusively terrestrial in
its habits. Now, the young of this salamander before their birth are
found to be furnished with gills, which, however, they are never
destined to use. Yet these gills are so perfectly formed, that if the
young salamanders be removed from the body of their mother shortly
before birth, and be then immediately placed in water, the little
animals show themselves quite capable of aquatic respiration, and will
merrily swim about in a medium which would quickly drown their own
parent. Here, then, we have both morphological and physiological
evidence pointing to the possession of gills by the ancestors of the
land salamander.

It would be easy to devote the whole of the present chapter to an
enumeration of special instances of the kinds thus chosen for purposes
of illustration; but as it is desirable to take a deeper, and therefore
a more general view of the whole subject, I will begin at the
foundation, and grad