Two stages in the division of the egg 111

45. A group of cells resulting from division, the first step
in machine building 135

46. A later step in machine building, the gastrula 135

47. The arm of a monkey 144

48. The arm of a bird 144

49. The arm of an ancient half-bird, half-reptile animal 144

50. Diagram to illustrate the principle of heredity 156

THE STORY OF THE LIVING MACHINE.

INTRODUCTION.

==Biology a New Science==.--In recent years biology has been spoken of as
a new science. Thirty years ago departments of biology were practically
unknown in educational institutions. To-day none of our higher
institutions of learning considers itself equipped without such a
department. This seems to be somewhat strange. Biology is simply the
study of living things; and living nature has been studied as long as
mankind has studied anything. Even Aristotle, four hundred years before
Christ, classified living things. From this foundation down through the
centuries living phenomena have received constant attention. Recent
centuries have paid more attention to living things than to any other
objects in nature. Linnaeus erected his systems of classification before
modern chemistry came into existence; the systematic study of zoology
antedated that of physics; and long before geology had been conceived in
its modern form, the animal and vegetable kingdoms had been comprehended
in a scientific system. How, then, can biology be called a new science
When it is older than all the others?

There must be some reason why this, the oldest of all, has been recently
called a _new_ science, and some explanation of the fact that it has
only recently advanced to form a distinct department in our educational
system. The reason is not difficult to find. Biology is a new science,
not because the objects it studies are new, but because it has adopted a
new relation to those objects and is studying them from a new
standpoint. Animals and plants have been studied long enough, but not as
we now study them. Perhaps the new attitude adopted toward living nature
may be tersely expressed by saying that in the past it has been studied
as _at rest_, while to-day it is studied as _in motion_. The older
zoologists and botanists confined themselves largely to the study of
animal