and see what could be made of it. Either it would prove its capacity to
elucidate the facts of organic life, or it would break down under the
strain. This was surely the dictate of common sense; and, for once,
common sense carried the day.

[Even before the "Origin" actually came out, Huxley had begun to act as
what Darwin afterwards called his "general agent." He began to prepare
the way for the acceptance of the theory of evolution by discussing, for
instance, one of the most obvious difficulties, namely, How is it that
if evolution is ever progressive, progress is not universal? It was a
point with respect to which Darwin himself wrote soon after the
publication of the "Origin":--"Judging from letters...and from remarks,
the most serious omission in my book was not explaining how it is, as I
believe, that all forms do not necessarily advance, how there can now be
SIMPLE organisms existing." (May 22, 1860.)

Huxley's idea, then, was to call attention to the persistence of many
types without appreciable progression during geological time; to show
that this fact was not explicable on any other hypothesis than that put
forward by Darwin; and by paleontological arguments, to pave the way for
consideration of the imperfection of the geological record.

Such were the lines on which he delivered his Friday evening lecture on
"Persistent Types" at the Royal Institution on June 3,1859.

However, the chief part which he took at this time in extending the
doctrines of evolution was in applying them to his own subjects,
Development and Vertebrate Anatomy, and more particularly to the
question of the origin of mankind.