1848.

We have seen a similar mental change occur contemporaneously in our
greatest naturalist, Carl Ernst von Baer. This gifted and profound
thinker and biologist, whose name marks a new epoch in the history of
evolution, had in his later years become wholly incompetent even to
understand those most important problems of his youthful labours
which opened up new paths of inquiry. While in his early years he laid
down principles of the greatest value to our modern doctrine of
evolution, and even went very near to adopting this hypothesis into
his system, at a later period he utterly denied it, and by his
writings on Darwinism proved that he was no longer generally capable
of mastering this difficult problem. As I am one of Von Baer's warmest
admirers, and in my "Evolution of Man," as well as in the "History of
Creation," and in other places, have most emphatically expressed that
sincere esteem, I thought I might venture to forbear from calling
attention to the discrepancy between the lucid, monistic principles of
Von Baer in his youth, and the confused dualistic views of his old
age. But as many opponents of Darwinism--and among them particularly
the Old Catholic philosopher of Munich, Huber, who has written a
series of articles in the "Augsburger Zeitung"--have made constant
capital out of the harmless talk of the feeble old Von Baer, I must in
this place explicitly declare that this dualistic prating of the old
man is quite incapable of shaking the monistic principles of the young
and enterprising pioneers of science, or of giving them the lie.

In his autobiography Von Baer gives us the explanation of this
striking contradiction. In 1834 he entirely and for ever abandoned
the province of the history of development, at which for twenty years
he had laboured incessantly, and where he had earned splendid laurels.
To escape from the haunting and importunate ideas of the science which
had so wholly absorbed him, he fled from Koenigsberg to Petersburg, and
subsequently busied himself in scientific inquiries of a quite
different character. Twenty-five long years passed by, and when
Darwin's work appeared in 1859, Von Baer had too long undergone a
metapsychosis to be able to understand it. In Von Baer, as in Virchow,
the course of this remarkable metapsychosis is highly instructive, and
will itself afford to the thoughtful psychologist an interesting
evidence of the doctrine of evolution.

However, the lack of comprehensi