Zoology
2 of the 7 encyclopedias on this shelf carry an entry for Zoology. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
zo-ol'o-ji, the science of animal life. The zoologist is interested in knowing how the parts of an animal's body are made up, what they are used for, how animals manage to live, under what conditions they thrive, how they are distributed, how they produce their kind, and what changes take place with change of circumstances. He is also interested in classifying animals,--setting them off in groups and naming them. There are several subordinate subjects, as ornithology, or the study of birds, entomology, or the study of insects, conchology, or the study of shells, paleontology, or the study of fossils, etc. The first great name among zoologists is Aristotle, the Greek. He described many animals, dividing them into those with blood and those that are bloodless. In the latter class he placed snails, clams, insects, etc. The next great name is that of the Swedish Linnaeus. He introduced a system of arrangement by class, order, genus, species, and variety, a plan still followed. He recognized six classes, mammals, birds, amphibia, fishes, insects, and worms. A Frenchman, Lamarck, distributed the primary classification into vertebrates and invertebrates. Cuvier, also a Frenchman, grouped his classes under four absolute, distinct types,--vertebrates, mollusks, radiates, and articulates. The English Darwin contributed the idea of the origin of species by the influence of changed conditions acting through long periods of time. See also articles on various scientists as HUXLEY; PLINY; LINNAEUS; CUVIER; DARWIN; OWEN; LAMARCK; WALLACE; HAECKEL, and AGASSIZ; and on the principal animals, as the ELEPHANT; SEAL; SHARK; EAGLE; FROG; OYSTER; STARFISH; EARTHWORM; AMOEBA, etc.
Collier's New Encyclopedia (1921)
that portion of natural history which treats of the classification, structure, habits and habitations of animals. Closely related to zoology is the study of embryology, while comparative anatomy and physiology are the branches which dominate the study of the physical structure of man.