le structure
that they have descended from a possibly very much higher type of
organization than that which they now exhibit. Having for innumerable
generations ceased to require their legs, their eyes, and so forth, all
such organs of high elaboration have either disappeared or become
vestigial, leaving the parasite as a more or less effete representative
of its ancestry.

These facts of degeneration, as we have previously seen, are of very
general occurrence, and it is evident that their importance in the field
of organic evolution as a whole has been very great. Moreover, it ought
to be particularly observed that, as just indicated, the facts may be
due either to a passive _cessation_ of selection, or to an active
_reversal_ of it. Or, more correctly, these facts are probably _always_
due to the cessation of selection, although in most cases where species
in a state of nature are concerned, the process of degeneration has been
both hastened and intensified by the super-added influence of the
reversal of selection. In the next volume I shall have occasion to recur
to this distinction, when it will be seen that it is one of no small
importance to the general theory of descent.

* * * * *

We may now proceed to consider certain misconceptions of the Darwinian
theory which are largely, not to say generally, prevalent among
supporters of the theory. These misconceptions, therefore, differ from
those which fall to be considered in the next chapter, i. e.
misconceptions which constitute grounds of objection to the theory.

* * * * *

Of all the errors connected with the theory of natural selection,
perhaps the one most frequently met with--especially among supporters of
the theory--is that of employing the theory to explain all cases of
phyletic modification (or inherited change of type) indiscriminately,
without waiting to consider whether in particular cases its application
is so much as logically possible. The term "natural selection" thus
becomes a magic word, or Sesame, at the utterance of which every closed
door is supposed to be immediately opened. Be it observed, I am not here
alluding to that merely blind faith in natural selection, which of late
years has begun dogmatically to force this principle as the sole cause
of organic evolution in every case where it is _logically possible_ that
the principle can have come into play. Such a blind faith, ind