This animal sometimes called the mulot, is less than the rat, but larger than the common mouse. It is not to be found in houses, but lives in woods and fields. It is remarkable for its large and prominent eyes; and it differs also from the rat and mouse in the contour of its hair, which is tolerably white under the belly, and a reddish brown on the back; they are very generally and abundantly diffused, especially in hilly countries. They appear to be a long time in attaining their full growth, as they vary considerably in size. The largest are better than four inches in length, and the smaller, which appears to be aged, are an inch shorter; and as they are found of all the intermediate sizes there can be no room to doubt their being the same species. It was probably from ignorance of this fact that some naturalists have distinguished them into two species, calling the one the Great Field Rat, and the other the Field Mouse. Ray, who first fell into this error, seems to acknowledge himself unacquainted with any more than one species; and though the short description he gives of two species appear to differ, yet we ought not to conclude that both exist, first, because he himself knew but one; secondly, because we know only one, and notwithstanding all my researches, I have been enabled to discover but one kind; thirdly, because Gesner, and other naturalists, speak only of one, under the name of _mus agrestis major_, which they affirm to be common; and because Ray says the other kind, which he calls _mus domesticus medius_, is also very common; it is therefore impossible but that one or other of these authors must have seen both since they declare they are both common; fourthly, because as in this same species large and small individuals are found, that circumstance might lead them to consider the former as one, and the latter as another; and, lastly, because the descriptions of these two pretended species are in no respect complete; and we ought not to trust such vague characteristics to establish a specific difference. The ancients, indeed, mention two species, the one under the denomination of _mus agrestis major_, the other under that of _mus agrestis minor_. These two species are very common, and we are as well acquainted with them as the ancients were; the first is our long-tailed field-mouse; and the other, known by the name of the short-tailed field-mouse, but as it materially differs both from the rat and long-tailed field-mouse, I have not followed the generic appellation, but adopted that of the Italian, and call it _campagnol_.