practice in observation failed to make my sight so quick and so accurate
as it ought to have been for my purpose. At that time I failed to
apprehend the fact of my deficient quickness of sight; it ought to have
taught me much, but I was not prepared to learn the lesson.

Chemistry fascinated me. The excellent teacher (Göttling) always
demonstrated the true connection of the phenomena under consideration;
and the theory of chemical affinity took strong hold upon me.

Note-taking at these lectures was a thing I never thought of doing; for
that which I understood forthwith became a part of me, and that which I
failed to understand seemed to me not worth writing down. I have often
felt sorry for it since. But as regards this point, I have always had
through my whole life the perfectly clear conviction that when I had
mastered a whole subject in its intimate relations I could go back upon,
and then understand, details which at the time of hearing had been
unintelligible to me.

In botany I had a clear-sighted, kind-hearted teacher (Batsch). His
natural system of botany[20] gave me great satisfaction, although I had
always a painful perception of how much still remained for him to
classify. However, my view of Nature as one whole became by his means
substantially clearer, and my love for the observation of Nature in
detail became more animated. I shall always think of him with gratitude.
He was also my teacher in natural history. Two principles that he
enunciated seized upon me with special force, and seemed to me valid.
The first was the conception of the mutual relationship of all animals,
extending like a network in all directions; and the second was that the
skeleton or bony framework of fishes, birds, and men was one and the
same in plan, and that the skeleton of man should be considered as the