There is one other matter of some interest and moment on which I would
say a few words. To thoroughly instructed biologists, such words will
be quite needless; but, in a society of this kind, the possibilities
that lie in the use of the instrument are associated with the
contingency of large error, especially in the biology of the minuter
forms of life, unless a well grounded biological knowledge form the
basis of all specific inference, to say nothing of deduction.

I am the more encouraged to speak of the difficulty to which I refer,
because I have reason to know that it presents itself again and again
in the provincial societies of the country, and is often adhered to
with a tenacity worthy of a better cause. I refer to the danger that
always exists, that young or occasional observers are exposed to, amid
the complexities of minute animal and vegetable life, of concluding
that they have come upon absolute evidences of the transformation of
one minute form into another; that in fact they have demonstrated
cases of heterogenesis.

This difficulty is not diminished by the fact that on the shelves of
most microscopical societies there is to be found some sort of
literature written in support of this strange doctrine.

You will pardon me for allusion again to the field of inquiry in which
I have spent so many happy hours. It is, as you know, a region of life
in which we touch, as it were, the very margin of living things. If
nature were capricious anywhere, we might expect to find her so here.
If her methods were in a slovenly or only half determined condition,
we might expect to find it here. But it is not so. Know accurately
what you are doing, use the precautions absolutely essential, and
through years of the closest observation it will be seen that the