Page:Popular Science Monthly Volume 7.djvu/672

652 common number of young produced by bats, two and three may occur. More extended inquiry may show that these larger families are less rare than now appears, and even that as many as four young may be produced at a birth. For while bats are usually credited with only two nipples, an extra pair exists upon the Lasiurus noveboracensis.

The uniformity in number with each species is very striking. Twenty-two of one species had each two young, while forty of another had each one.

In the former case the young were placed one on the right and the other on the left of the body. But in the latter case the single young was invariably on the right side; while, in the single specimen of the undetermined Brazilian bat, the young was on the left side.

Equally striking with the above facts is the isolation of the females with young. Among forty-three Nyctinomus Brasiliensis was but a single male. No males were found near the twenty-two Vespertilio suhulatus. Osborn says that, of Molossus fumarius, all of one large lot were males; while at another time, in a large hollow tree, he found in one cavity about one hundred males, and in a second about the same number of females, with "apparently a few males here and there."

Evidently there is much to be learned respecting the domestic and social economy of these animals. Perhaps the males gather food for the females.

Perhaps the most important fact, from a practical point of view, is that of the power of the mother-bats to carry such a weight of young in addition to their own. Yet, so far as I know, all estimates of the extent of wing and size of muscle, which would be necessary to enable a man to fly, have been based upon the idea that the only flying mammal is a fair standard.

These estimates should be corrected so as to conform to the fact that a bat can fly with nearly double its ordinary weight. Even this may not encourage us to hope for a future race of flying-men. But it renders it worth considering whether a man, naturally slight of frame, with small head, could not so far reduce his weight by a flesh diet, and by the amputation of his legs, as to enable him, by special cultivation of his pectoral muscles, to work effectively a pair of wings less extensive than those now supposed to be required.