Fluctuations always oscillate around an average, and if removed
from this for some time, they show a tendency to return to it. This
tendency, called retrogression, has never been observed to fail, as it
should, in order to free the new strain from the links with the average,
while new species and new varieties are seen to be quite free from their
ancestors and not linked to them by intermediates.
The last few lectures will be devoted to questions concerning the great
problem of the analogy between natural and artificial selection. As
already stated, Darwin made this analogy the foundation stone of his
theory of descent, and he met with the severest objections and
criticisms precisely on this point. But I hope to [19] show that he was
quite right, and that the cause of the divergence of opinions is due
simply to the very incomplete state of knowledge concerning both
processes. If both are critically analyzed they may be seen to comprise
the same factors, and further discussion may be limited to the
appreciation of the part which each of them has played in nature and
among cultivated plants.
Both natural and artificial selection are partly specific, and partly
intra-specific or individual. Nature of course, and intelligent men
first chose the best elementary species from among the swarms.
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