mel also has an important part to play in the structure of the
molar teeth. Each tooth is surrounded with the enamel plate, which is so
intricately folded that the tooth looks as if it were made of a series
of enamel triangles, each enclosing the tooth matter.

This structure is common to all the members of the group to which the
water-rat belongs. It is the more remarkable because we find a somewhat
similar structure in the molar teeth of the elephants, which, like the
rodents, have the incisor teeth largely developed and widely separated
from the molars.

There is nothing in the appearance of the water-rat which gives any
indication of its aquatic habits.

For example, we naturally expect to find that the feet of swimming
animals are webbed. The water-loving capybara of South America, the
largest existing rodent, has its hoof-like toes partially united by
webs, so that its aquatic habits might easily be inferred even by those
who were unacquainted with the animal. Even the otter, which propels
itself through the water mostly by means of its long and powerful tail,
has the feet furnished with webs. So has the aquatic Yapock opossum of
Australia, while the feet of the duck-bill are even more boldly webbed
than those of the bird from which it takes its popular name. The
water-shrews (whom we shall presently meet) are furnished with a fringe
of stiff hair round the toes which answers the same purpose as the web.

But the structure of the water-rat gives no indication of its habits, so
that no one who was unacquainted with the animal would even suspect its
swimming and diving powers. Watch it as long as you like, and I do not
believe that you will see it eating anything of an animal nature.

I mention this fact because it is often held up to blame as a
mischievous animal, especially deserving the wrath of anglers by
devouring the eggs and young of fish.

As is often the case in the life-history of animals as well as of men,
the blame is laid on the wrong shoulders. If the destruction of fish be
a crime, there are many criminals, the worst and most persistent of
which are the fish themselves, which not only eat the eggs and young of
other fish, but, Saturn-like, have not the least scruple in devouring
their own offspring.

Scarcely less destructive in its own insidious way is the common
house-rat, which eats everything which according to our ideas is edible,
and a good many which we might think incapable of affording