thout natural enemies where everything was favorable. They
promptly multiplied so rapidly that within a few years their descendants
were numerous enough to eat up practically every green thing they could
reach. Two decades ago, the single province of Queensland was forced to
expend $85,000,000 in a vain effort to put down the rabbit plague. The
remarkable statement has been made that in some places nature has taken a
hand in causing a new type of rabbit to evolve. Finding the situation
desperate, some of the animals have begun to develop into tree-climbing
creatures. The animals exist in such numbers that the available food upon
the ground is insufficient for all, and so some elimination results. But
the young rabbits with longer claws, varying in this way on account of
congenital factors, have an advantage over their fellows because they can
climb some of the trees and so obtain food inaccessible to the others. If
the facts are correctly reported, and if the process of selection on the
basis of longer claws and the climbing habit is continued, the original
type of animal is splitting up into a form that will remain the same and
live upon the ground, and another that will be to all intents and purposes
a counterpart of our familiar squirrel. All the evidence goes to show that
squirrels have evolved from terrestrial rodents; if the data relating to
Australian rabbits are correct, nature is again producing a squirrel-like
animal by evolution in a region where the former natural situation has
been interfered with by man.

The laws of biological inheritance have received close and deep study by
numerous investigators of Darwinian and post-Darwinian times, because from
the first it was clearly recognized that a complete description of
nature's method of accomplishing evolution must show how species maintain
the same general characteristics from generation to generation, and also
how new qualities may be fixed in heredity as species transform in the
course of time. Before our modern era in biology, the fact of inheritance
was accepted as self-sufficient; now much is known that supplements and
extends the incomplete account given by natural selection of the way
evolution takes place.

It is not possible in the present brief outline to describe all the
results of recent investigations, but some of them are too important to be
passed over. Perhaps the most interesting one is that the laws of heredity
seem to be the same for man