Principles of animal biology

Zoölogy is the science of animals. This was the definition centuries ago, when zoölogy was almost exclusively the classification and naming of animals. Since that time there has arisen a vast body of doctrine concerning modes of life, life processes, inter-relations of animals, development, distribution, and descent, most of which has little bearing on classification, which is now founded upon principles as basic as those underlying other branches of science. For the purposes of this volume, anything that has to do with animals is part of zoölogy. This book is, in practice, one long definition of zoölogy. It includes morphology, physiology, ecology, zoögeography, paleontology, taxonomy, and evolution as part of the zoölogical sciences. This book, being a general discussion, will contain elementary facts and principles from each of these branches of science. Students should find it a useful exercise to stop and reflect which of the divisions of zoölogy are, at any given moment, actually being studied.