By the hedgerow in the garden my terrier, Freckle, has just come across two pugnacious shrews, engaged in one of their sanguinary battles. The high belligerent parties are not exactly formidable to outsiders, it is true, being not quite three inches long apiece from snout to haunches, not counting an inch and a half of tail, oddly square in outline, to finish off their appearance. Yet they are savage fighters, for all that, in their intertribal quarrels. When shrew meets shrew, then comes the tug of war. It very seldom happens that they do not join battle, and the victor in the fray usually kills and eats his discomfited rival. So fierce a heart in so small a body is rare, but the shrew knows not what fear means. This particular pair of combatants were so automatically intent on the fortunes of war that Freckle was upon them and investigating their nature with her inquisitive nose before they even woke up to the fact of her presence.

Most people seem to confuse shrews with mice; but, indeed, our small combatants are widely different creatures from those timid little beasts; they belong to a wholly different group of mammals. Mice are rodents, descendants of the same common ancestor with the rats and dormice, and not remotely related to the squirrels and the rabbits. Shrews, on the other hand, are insectivores, first cousins of the moles, the hedgehogs, and the desmans. Externally, it is true, they resemble considerably the mice and voles; but those who have followed the course of recent natural history must be aware by this time that “appearances are deceitful.” If an animal looks very much like something else, the chances are that it is altogether different. This is particularly the case with the insectivores and the marsupials, each of which great groups has independently developed a series of forms absurdly like the mice, the squirrels, the porcupines, and the jerboas, because each fills approximately the same place in nature. For example, small mammals which creep about among grass and matted herbage are likely to assume a mouse-like shape. This has happened among rodents in the case of the mice and field-voles, among insectivores in the case of the shrews, and among Australian marsupials in the case of the pouched kangaroo-mice. Our English shrew is a pretty little creature of this common type, with thick soft fur like a mouse’s, only a trifle redder, and so mousey in shape that it is seldom discriminated from the true mice, save by naturalists and gamekeepers. Even externally, however, it differs much from mice in its long pointed snout—a marked insectivorous feature—as well as in its square and abruptly cut-off tail, where the mouse’s is rounded, tapering, and slender. When you come to the teeth and internal anatomy, however, the creature is an insectivore, displaying at once quite a separate character.

Mice, as everybody knows, feed mainly on se............