much regretted that I did not make
this part of the subject clearer. I left out this and many other
subjects, which I now see ought to have been introduced. I have inserted
a discussion on this subject in the foreign editions. (110/7. In the
third Edition a discussion on this point is added in Chapter IV.) In
no case will any organic being tend to retrograde, unless such
retrogradation be an advantage to its varying offspring; and it is
difficult to see how going back to the structure of the unknown supposed
original protozoon could ever be an advantage.

Page 13 of your letter: I have been more glad to read your discussion
on "dominant" forms than any part of your letter. (110/8. Harvey
writes: "Viewing organic nature in its widest aspect, I think it is
unquestionable that the truly dominant races are not those of high, but
those of low organisation"; and goes on to quote the potato disease,
etc. In the third edition of the "Origin," page 56, a discussion is
introduced defining the author's use of the term "dominant.") I can now
see that I have not been cautious enough in confining my definition
and meaning. I cannot say that you have altered my views. If Botrytis
[Phytophthora] had exterminated the wild potato, a low form would have
conquered a high; but I cannot remember that I have ever said (I am
sure I never thought) that a low form would never conquer a high. I have
expressly alluded to parasites half exterminating game-animals, and
to the struggle for life being sometimes between forms as different as
possible: for instance, between grasshoppers and herbivorous quadrupeds.
Under the many conditions of life which this world affords, any group
which is numerous in individuals and species and is widely distributed,
may properly be called dominant. I never dreamed of considering that
any one group, under all conditions and throughout the world, would be
predominant. How could vertebrata be predominant under the conditions
of life in which parasitic worms live? What good would their perfected
senses and their intellect serve under such conditions? When I have
spoken of dominant forms, it has been in relation to the multiplication
of new specific forms, and the dominance of any one species has been
relative generally to other members of the same group, or at least to
beings exposed to similar conditions and coming into competition. But I
daresay that I have not in the "Origin" made myself clear, and space has
rendere