perhaps, of more value than mere
difference of food, or tubercles upon the teeth; especially, as it can
be proved, that the sort of food an animal eats, is often dependent on
the circumstances in which it may be placed.

Of the _Rats_, properly so called, there are numerous species, as well
as varieties. Their size is, in general, about the same as the Black
and Norway rats--both of which belong to England, and have been
introduced, by means of ships, into every country upon the habitable
globe. They are said to have come originally from Asia. There is one
species of rat, however, that is much larger than either of these--the
Gigantic rat, found in Indian countries, and which in size quite equals
a rabbit!

The habits of the rats are too well-known to require description.
Some--as the Wood Rat and Florida Rat of America--dwell apart from the
habitations of man, in the woods; where, instead of living in burrows,
they construct large nests, by collecting together heaps of sticks,
leaves, and grass.

_Mice_ may be regarded as only a smaller kind of rats; and of these
there are many distinct species--both in the Old and New Worlds.

The _Marmots_ are, perhaps, the most interesting of the small rodents.
They stand in a sort of connection with the squirrels, more especially
the ground squirrels: on the other hand, they resemble rabbits; and they
have still many points of identity with rats. They belong to the
northern zones of Europe, Asia, and America. There are three or four
species belonging to the Old World; and a great many to North America.
Moreover there is a considerable difference in the habits of these
species, which has led zoologists to separate them into several genera.
One genus, called the Seed-eaters, is a very curious kind. The marmots
of this genus have a pair of pockets or pouches--one on the outside of
each cheek--in which they actually carry seeds and other articles of
food to their burrows. These pouches, when filled, impart to the little
creatures a most ludicrous appearance.

The marmots usually live in large communities--in burrows, as rabbits
do. These burrows are sometimes very extensive--especially so, in the
case of the prairie marmot of America--better known as the Prairie Dog--
whose _villages_ sometimes cover an extent of many square miles; and
whose odd social habits have been repeatedly and accurately described by
late travellers who have crossed the American continent.

The _