ts the most remarkable growth is among the
ants, the bees, and their kindred. These creatures have very wonderful
habits; they combine together for the making of what we may call
states, they care for their young, they wage great battles, they keep
slaves, they domesticate other insects, and in many ways their acts
resemble the doings of man. Coming at about the same time as man,
these intellectual insects help to mark this later stage of the earth
as the intellectual period in its history. Now for the first time
creatures are on the earth which can form societies and help each
other in the difficult work of living.

Among the mollusks, the most important change is in the creation of
the great, strong swimming squids, the most remarkable creatures of
the sea. Some of these have arms that can stretch for fifty feet from
tip to tip.

Among the plants, the most important change has been in the growth of
flowering plants, which have been constantly becoming more plenty, and
the plants which bear fruits have also become more numerous. The
broad-leaved trees seem to be constantly gaining on the forests of
narrow-leaved cone-bearers, which had in an earlier day replaced the
forests of ferns.

In these Tertiary ages, as in the preceding times of the earth, the
lands and seas were much changed in their shape. It seems that in the
earlier ages the land had been mostly in the shape of large islands
grouped close together where the continents now are. In this time,
these islands grew together to form the united lands of Europe, Asia,
Africa, Australia, and the twin American continents; so that, as life
rose higher, the earth was better fitted for it. Still there were
great troubles that it had to undergo. There were at least two
different times during the Tertiary age termed glacial periods, times
when the ice covered a large part of the northern continents,
compelling life of all sorts to abandon great regions, and to find new
places in more southern lands. Many kinds of animals and plants seem
to have been destroyed in these journeys; but these times of trial, by
removing the weaker and less competent creatures, made room for new
forms to rise in their places. All advance in nature makes death
necessary, and this must come to races as well as to individuals if
the life of the world is to go onward and upward.

Looking back into the darkened past, of which we yet know but little
compared with what we would like to know, we ca