The Girls Own Paper, Vol. VIII, No. 355, October 16, 1886 | Page 5

and unless the edges of their feeding troughs be protected by metal,
will nibble them to pieces in a few days. Indeed, so strong is this
instinct, that the health of the animals is greatly improved by putting
pieces of wood into their cages, merely for the purpose of allowing
them to exercise their chisel-edged teeth. Even when they have nothing
to gnaw, the animals will move their jaws incessantly, just as if they
were eating, a movement which gave rise to the idea that they chewed
the cud.
It is worthy of remark that other animals, which, though not rodents,
need to possess chisel-edged incisor teeth, have a similar habit. Such is
the hippopotamus, and such is the hyrax, the remarkable rock-haunting
animal, which in the authorised translation of the Scriptures is called
the "coney," and which in the Revised Version is allowed in the margin
to retain its Hebrew name, "shaphan."
The enamel 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
sustenance even to a rat. In the summer time it often abandons for a
time the house, the farm, the barn, and seeks for a change of diet by the
brook. These water-haunting creatures are naturally mistaken for the
vegetable-feeding water-vole, and so the latter has to bear the blame of
their misdoings.
There are lesser inhabitants of the brook which are injurious both to the
eggs and young of fish. Among them are several of the larger
water-beetles, some of which are so large and powerful that, when
placed in an aquarium with golden carp, they have made havoc among
the fish, always attacking them from below. Although they cannot kill
and devour the fish at once, they inflict such serious injuries that the
creature is sure to die shortly.
I do not mean to assert that the water-vole is never injurious to man.
Civilisation disturbs for a time the balance of Nature, and when man
ploughs or digs the ground which had previously been untouched by
plough or spade, and sows the seeds of herbs and cereals in land which
has previously produced nothing but wild plants, he must expect that
the animals to whom the soil had been hitherto left will fail to
understand that they can no more consider themselves as