without that chimes in with and stimulates it, may be the beginning
of that unsettlement of equilibrium which results in the crash of
action, unless it is timely counteracted.

If another objector maintains that the vibrations within the germ as
above supposed must be continually crossing and interfering with one
another in such a manner as to destroy the continuity of any one
series, it may be replied that the vibrations of the light proceeding
from the objects that surround us traverse one another by the
millions of millions every second yet in no way interfere with one
another. Nevertheless, it must be admitted that the difficulties of
the theory towards which I suppose Professor Hering to incline are
like those of all other theories on the same subject--almost
inconceivably great.

In "Life and Habit" I did not touch upon these vibrations, knowing
nothing about them. Here, then, is one important point of
difference, not between the conclusions arrived at, but between the
aim and scope of the work that Professor Hering and I severally
attempted. Another difference consists in the points at which we
have left off. Professor Hering, having established his main thesis,
is content. I, on the other hand, went on to maintain that if vigour
was due to memory, want of vigour was due to want of memory. Thus I
was led to connect memory with the phenomena of hybridism and of old
age; to show that the sterility of certain animals under
domestication is only a phase of, and of a piece with, the very
common sterility of hybrids--phenomena which at first sight have no
connection either with each other or with memory, but the connection
between which will never be lost sight of by those who have once laid
hold of it. I also pointed out how exactly the phenomena of