The great changes and improvements in physical and chemical scientific
education, which have taken place of late, have all resulted from the
combination of practical teaching with the reading of books and with
the hearing of lectures. The same thing is true in Biology. Nobody
will ever know anything about Biology except in a dilettante
"paper-philosopher" way, who contents himself with reading books on
botany, zoology, and the like; and the reason of this is simple and
easy to understand. It is that all language is merely symbolical of the
things of which it treats; the more complicated the things, the more
bare is the symbol, and the more its verbal definition requires to be
supplemented by the information derived directly from the handling, and
the seeing, and the touching of the thing symbolised:--that is really
what is at the bottom of the whole matter. It is plain common sense, as
all truth, in the long run, is only common sense clarified. If you want
a man to be a tea merchant, you don't tell him to read books about
China or about tea, but you put him into a tea-merchant's office where
he has the handling, the smelling, and the tasting of tea. Without the
sort of knowledge which can be gained only in this practical way, his
exploits as a tea merchant will soon come to a bankrupt termination.
The "paper-philosophers" are under the delusion that physical science
can be mastered as literary accomplishments are acquired, but
unfortunately it is not so. You may read any quantity of books, and you
may be almost as ignorant as you were at starting, if you don't have,
at the back of your minds, the change for words in definite images
which can only be acquired through the operation of your observing
faculties on the phenomena of nature.

It may be said:--"That is all very well, but you told us just now that
there are probably something like a quarter of a million different
kinds of living and extinct animals and plants, and a human life could