H. G. Wells's Text-Book of Biology is a practical guide for students of natural science, especially those working through vertebrate anatomy, development, and examination preparation without constant access to a teacher. Born from the author's experience teaching by correspondence, it argues that real understanding comes not from memorization, but from disciplined observation, careful sketching, and the patient discovery of general principles through concrete facts. The book defends the "type system" of study, using representative organisms to build a comparative grasp of life. At its center is the rabbit, introduced as a familiar vertebrate whose body reveals the relation between structure and function: backbone, limbs, skull, tail, hair, and diaphragm all point to a life of speed, burrowing, and mammalian adaptation. The text defines essential anatomical terms, explains metabolism as the breakdown of food for energy, and traces digestion from mouth to intestine, including the distinctive cecum and appendix of the herbivore. It then broadens to the frog, whose simpler organs and skull illuminate vertebrate evolution, from reproductive and nervous systems to the cartilaginous foundations of the skull and jaw. This edition has been fully restored with modern typesetting, custom cover design.