hat Bodo saw eating grass._
_Make a picture of what Bodo saw when he was in the tree._

XVI.

THINGS TO THINK ABOUT

Can you think why our horses are larger than the wild horses?
How many toes does a horse have on each foot? On what part of the foot
does he walk? Where is the horse's heel? Do you think the horse's
foot has always been the same shape that it is to-day?
On what part of the foot does the cow walk? How many toes does she
have?
On what part of the foot does the cat walk? How many toes does she
have?

_Ancestors of Our Mammals_

The wild horses that Bodo saw were about the size of ponies.
Long before the Tree-dwellers lived there were horse-like creatures
the size of a fox.
Long before that there was a time when there were no horses at all.
Great reptiles moved about on the land, they swam in the seas, or they
flew through the air.
All other creatures feared them.
The tiny mammals that lived then were about the size of rats and mice,
but these mammals were not like rats and mice.
The little mammals ran, but they did not run fast, for their feet were
not well fitted for running.
They climbed rocks and trunks of trees, and hid in holes in the
ground.
They ate the eggs of the large reptiles, and became their enemies.

[Illustration: _A reptile_]

Millions of years passed; great changes took place.
Parts of the land slowly sank beneath the seas, and out of the seas
rose dry land.
Most of the larger reptiles died, but the mammals multiplied.
They grew to be as large as the fox or the sheep.
At first they were all very much alike and they lived in about the
same way.
But as they became more and more unlike they had very different ways.
Some became like cats, and some like dogs.

[Illustration: _An ancestor of our mammals_]

Some became like rhinoceroses and some like hogs.
Others became like monkeys, and still others became like horses.

THINGS TO DO

_Look at the picture above and tell how this animal must have changed
to become more like a dog, a cat, a pig, a cow, or a horse._

XVII.

THINGS TO THINK ABOUT

What part of the wild horse's foot touched the ground when he ran?
What happens to muscles that are not used? What happens to muscles
that are used most?

_The Story of the Wild Horse_

Perhaps you have seen the zebra.
If you have, you must have noticed