Page:Popular Science Monthly Volume 7.djvu/666

646, quite good eating themselves. So there should be made a distinction between them as between the venomous and the harmless serpents and the more and the less poisonous spiders.

Perhaps one element of distrust of the bat family arises from their apparent non-conformity to either of the common animal types. The bat seems to be either a bird with hair and teeth, bringing forth its young alive, or a mammal with wings, and the general aspect and habit of a bird. Add to these exceptional features that their attitude, when at rest, is always head downward, and that their legs are so turned outward as to bring the knees behind instead of in front, and we may almost pardon the common dislike of the whole family of bats.



We may as well state at once that a bat is really a mammal; that is, it agrees with moles, rats, sheep, horses, cats, monkeys, and men, in bringing forth its young alive, and nursing them by milk; in having red blood-corpuscles, which contain no nucleus; in being clothed with hair; and in possessing a corpus callosum, that is, a band of fibres connecting the two cerebral hemispheres.

There are other anatomical features which link the bats closely with the moles and shrews and hedge-hogs. Indeed, the bat might be described as a flying mole, or the mole as a burrowing bat.

Twenty years ago one of these phrases might have been as acceptable as the other; for they would have implied only an ideal connection between the forms. But now, when the idea of an actual evolution or derivation of widely different forms from me another, or from common stocks, is rapidly becoming the fundamental postulate of all biological research, we are bound to inquire whether one mode of expression is not much more likely to be true than the other.