In this revised edition of Outlines of Biology a general account of life and of living things; the properties and structural details of matter in general and of living matter in particular, and the basic agreements and differences between the various living systems including a broad hint as to their mode of origin, is given in the introductory section. The main subject matter is then treated in two parts- Botany and Zoology. In the concluding chapters on evolution and heredity, the fundamental principles uniting the living things have been firmly established.