If, then, the degeneration to a simple brood-sac takes place only by very
slow transitions, each stage of which may last for centuries, how could the
much more complex ASCENDING evolution possibly have taken place by sudden
leaps? I regard this argument as capable of further extension, for
wherever in nature we come upon degeneration, it is taking place by minute
steps and with a slowness that makes it not directly perceptible, and I
believe that this in itself justifies us in concluding that THE SAME MUST
BE TRUE OF ASCENDING evolution. But in the latter case the goal can seldom
be distinctly recognised while in cases of degeneration the starting-point
of the process can often be inferred, because several nearly related
species may represent different stages.

In recent years Bateson in particular has championed the idea of saltatory,
or so-called discontinuous evolution, and has collected a number of cases
in which more or less marked variations have suddenly appeared. These are
taken for the most part from among domesticated animals which have been
bred and crossed for a long time, and it is hardly to be wondered at that
their much mixed and much influenced germ-plasm should, under certain
conditions, give rise to remarkable phenomena, often indeed producing forms
which are strongly suggestive of monstrosities, and which would undoubtedly
not survive in free nature, unprotected by man. I should regard such cases
as due to an intensified germinal selection--though this is to anticipate a
little--and from this point of view it cannot be denied that they have a
special interest. But they seem to me to have no significance as far as
the transformation of species is concerned, if only because of the extreme
rarity of their occurrence.

There are, however, many variations which have appeared in a sudden and
saltatory manner, and some of these Darwin pointed out and discussed in
detail: the copper beech, the weeping trees, the oak with "fern-like