l evolution of new
environments to which the organism's innate capacity of change has
enabled it to adapt itself. We have warrant for this possibility in the
case of the Axolotl and in other similar cases of neoteny. And these
cases further bring home to us the fact, to which I have already
referred, that the full development of the functional reproductive
organs is nearly always associated with the final stages of the
life-history.

On this view of the succession of characters in the life-history of
organisms, how shall we explain the undoubted fact that the development
of buds hardly ever presents any phenomena corresponding to the
embryonic and larval changes? The reason is clearly this, that budding
usually occurs after the embryonic stage is past; when the characters of
embryonic life have been worked out by the machine. When it takes place
at an early stage in embryonic life, as it does in cases of so-called
embryonic fission, the product shows, either partly or entirely,
phenomena similar to those of embryonic development. The only case known
to me in which budding by the adult is accompanied by morphological
features similar to those displayed by embryos is furnished by the
budding of the medusiform spore-sacs of hydrozoon polyps. But this case
is exceptional, for here we have to do with an attempt, which fails, to
form a free-swimming organism, the medusa; and the vestiges which appear
in the buds are the umbrella-cavity, marginal tentacles, circular canal,
etc., of the medusa arrested in development.

But the question still remains, are there no cases in which, as implied
by the recapitulation theory, variations in any organ are confined to
the period in which the organ is functional and do not affect it in the
embryonic stages? The teeth of the whalebone whales may be cited as
a case in which this is said to occur; but here the teeth are only
imperfectly developed in the embryo and are soon absorbed. They have
been affected by the change which has produced their disappearance in
the adult, but not to complete extinction. Nor are they now likely to be
extinguished, for having become exclusively embryonic they are largely
protected from the action of natural selection. This consideration
brings up a most important aspect of the question, so far as
disappearing organs are concerned. Every organ is laid down at a certain
period in the embryo and undergoes a certain course of growth until
it obtains full functio