subjects which have no connection with each other, except that they
relate chiefly to the parental instincts of some animals I have
observed, and to the instincts of the young at a very early period of
life.

While taking bats one day in December, I captured a female of our common
Buenos Ayrean species (Molossus bonariensis), with her two young
attached to her, so large that it seemed incredible she should be able
to fly and take insects with such a weight to drag her down. The young
were about a third less in size than the mother, so that she had to
carry a weight greatly exceeding that of her own body. They were
fastened to her breast and belly, one on each side, as when first born;
and, possibly, the young bat does not change its position, or move, like
the young developed opossum, to other parts of the body, until mature
enough to begin an independent life. On forcibly separating them from
their parent, I found that they were not yet able to fly, but when set
free fluttered feebly to the ground. This bat certainly appeared more
burdened with its young than any animal I had ever observed. I have seen
an old female opossum (Didelphys azarae) with eleven young, large as old
rats--the mother being less than a cat in size--all clinging to various
parts of her body; yet able to climb swiftly and with the greatest
agility in the higher branches of a tree. The actual weight was in this
case relatively much greater than in that of the female bat: but then
the opossum never quitted its hold on the tree, and it also supplemented
its hand-like feet, furnished with crooked claws, with its teeth and
long prehensile tail. The poor bat had to seek its living in the empty
air, pursuing its prey with the swiftness of a swallow, and it seemed
wonderful to me that she should have been able to carry about that great
burden with her one pair of wings, and withal to be active enough to
supply herself and her young with food.