Page:First course in biology (IA firstcourseinbio00bailrich).pdf/441

 the fold of the skin extend to the hind legs? The tail? Are the finger bones or the palm bones more prolonged to form the wing skeleton?

(Phyllostoma spectrum) of South America. × 1/6.

The skin of the wing is rich in blood vessels and nerves, and serves, by its sensitiveness to the slightest current of air, to guide the bat in the thickest darkness. Would you judge that the bat has sharp sight? Acute hearing?

The moles do not hibernate; the bats do. Give the reason for the difference. If bats are aroused out of a trance-like condition in winter, they may die of starvation. Why? The mother bat carries the young about with her, since, unlike birds, she has no nest. How are the young nourished? Order. Why?. (Key, p. 193.)

The Gnawing Mammals.—These animals form the most numerous order of mammals. They lack canine teeth. Inference? The incisors are four in number in all species