nd to make a mystery out of a
mechanism.

THE CHARACTERS OF WILD ANIMALS AND PLANTS FOLLOW THE SAME LAWS OF
INHERITANCE AS DO THE CHARACTERS OF DOMESTICATED ANIMALS AND PLANTS.

Darwin based many of his conclusions concerning variation and heredity on
the evidence derived from the garden and from the stock farm. Here he was
handicapped to some extent, for he had at times to rely on information much
of which was uncritical, and some of which was worthless.

Today we are at least better informed on _two_ important points; one
concerning the _kinds_ of variations that furnish to the cultivator the
materials for his selection; the other concerning the modes of inheritance
of these variations. We know now that new characters are continually
appearing in domesticated as well as in wild animals and plants, that these
characters are often sharply marked off from the original characters, and
whether the differences are great or whether they are small they are
transmitted alike according to Mendel's law.

Many of the characteristics of our domesticated animals and cultivated
plants originated long ago, and only here and there have the records of
their first appearance been preserved. In only a few instances are these
records clear and definite, while the complete history of any large group
of our domesticated products is unknown to us.

Within the last five or six years, however, from a common wild species of
fly, the fruit fly, Drosophila ampelophila, which we have brought into the
laboratory, have arisen over a hundred and twenty-five new types whose
origin is completely known. Let me call attention to a few of the more
interesting of these types and their modes of inheritance, comparing them
with wild types in order to show that the kinds of inheritance found in
domesticated races occur also in wild types. The results will show beyond
dispute that the characters of wild types are inherited in precisely the
same way as are the characters of the mutant types--a fact that is not
generally appreciated except by students of genetics, although it is of the
most far-reaching significance for the theory of evolution.

A mutant appeared in which the eye color of the female was different from
that of the male. The eye color of the mutant female is a dark eosin color,
that of the male yellowish eosin. From the beginning this difference was as
marked as it is to-day. Breeding experiments show that eosin eye color
differs from the red