< Page:The Outline of History Vol 1.djvu
This page has been proofread, but needs to be validated.
53
THE AGE OF MAMMALS

egg. From the beginning it must breathe in air; it can never breathe under water as a tadpole can do. Now, a modern mammal is really a sort of reptile that has developed a peculiarly effective protective covering, hair; and that also retains its eggs in the body until they hatch so that it brings forth living young

This article is issued from Wikisource. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.