There are certainly more than 100,000 species of insects, and yet
anybody who knows one insect--if a properly chosen one--will be able to
have a very fair conception of the structure of the whole. I do not mean
to say he will know that structure thoroughly, or as well as it is
desirable he should know it; but he will have enough real knowledge to
enable him to understand what he reads, to have genuine images in his
mind of those structures which become so variously modified in all the
forms of insects he has not seen. In fact, there are such things as
types of form among animals and vegetables, and for the purpose of
getting a definite knowledge of what constitutes the leading
modifications of animal and plant life, it is not needful to examine
more than a comparatively small number of animals and plants.
Let me tell you what we do in the biological laboratory which is lodged
in a building adjacent to this. There I lecture to a class of students
daily for about four-and-a-half months, and my class have, of course,
their text-books; but the essential part of the whole teaching, and that
which I regard as really the most important part of it, is a laboratory
for practical work, which is simply a room with all the appliances
needed for ordinary dissection.
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