by the idea of evolution, and animals and plants have been studied broadly, — in the light of their ancestral history. Progress is dependent still upon advance in anatomy, physiology and embryology, but the point of view from which the facts are considered has been changed.
We have now traced the rise of zoölogy in its principal phases down to the beginning of its especially modern aspect. The study of animal life is so great a field that naturally it has a number of divisions; it remains, therefore, to mention in a summary way its chief departments. That part of the subject which embraces the study of animal structure is Morphology. This word is generally used in a broad sense to mean something more than Anatomy, which is one division of morphology. The study of microscopic anatomy is Histology. It is not a different kind of study, and is separated from anatomy merely as a matter of convenience. The investigation of stages in animal development is Embryology. These divisions make up Structural Zoölogy. The general description and classification of animals is Systematic Zoölogy. The modern name for classification is Taxonomy. The Geographical Distribution of animals has been widely studied and elevated to the rank of a special department. Another set of studies concerning the lineage of all animals (Evolution) has led to broad considerations of the relation of living animals to their surroundings, to the universe and to man, and has given rise to Philosophical Zoölogy. Standing co-ordinate with the great field of morphology is Physiology, which, broadly speaking, concerns itself with the vital processes of all living organisms. General Physiology clearly is a department of zoölogy. Many experiments are being made to determine the responses and adaptations of animals to stimulations and to changes in the medium in which they live. This has opened the field of Experimental Morphology. Studies of the mental powers and the mental phenomena in animals lead to Animal Psychology, which may fairly be considered a part of zoölogy. A division called Ætiology is often recognized, having as its object the investigation of the causes of zoölogical phenomena, but it need not be assigned an independent rank, as the study of all phenomena has the discovery of their causes as an ultimate object.
The animal world is too extensive to attempt to give an outline view of it here, and reference must be made to textbooks for further consideration. Fuller accounts of some of the subjects touched upon in this article will be found under Anatomy, Development of Animal Life, Evolution, Cell-Doctrine, Physiology, Protoplasm and Spontaneous Generation
See, also, articles on such zoölogists as Aristotle, Cuvier, Darwin, Mivart, Romanes, Wallace, Weismann and others.
Among the best books for the general reader and student of zoölogy are the following: Agassiz’s Methods of Study in Natural History; Huxley’s The Crayfish, An Introduction to the Study of Zoölogy; Hertwig’s General Principles of Zoölogy; Lankester’s Zoölogy in The Encyclopædia Britannica; Sedgwick and Wilson’s General Biology; Parker’s Elementary Biology; Thompson’s The Science of Life, The Study of Animal Life and Outlines of Zoölogy; Verworn’s General Physiology; Jordan and Kellogg’s Animal Life; Bell’s Comparative Anatomy and Physiology; Parker and Haswell’s Textbook of Zoölogy and Manual of Zoölogy; Boas’ Textbook of Zoölogy; Brook’s Handbook of Invertebrate Zoölogy; McMurrich’s Invertebrate Morphology; Shipley and McBride’s Textbook of Zoölogy; Weidersheim’s Comparative Anatomy of Vertebrates; Lang’s Comparative Anatomy; Romanes’ Darwin and after Darwin; Osborn’s From the Greeks to Darwin; Balfour’s Comparative Embryology; Marshall’s Vertebrate Embryology; Hertwig’s Textbook of Embryology; Korschelt and Heider’s Invertebrate Embryology; Wallace’s Geographical Distribution of Animals and Malay Archipelago; Bates’ Naturalist on the Amazons; Heilprin’s Geographical and Geological Distribution of Animals; and The Standard Natural History, edited by Kingsley. For books on birds, butterflies, insects etc. see those topics. Among the best smaller zoölogies for secondary schools are those of Colton, Davenport, Kellogg, Needham and Packard.
Zoöphyte (zō′ō-fīt), an old name for marine animals forming branching or tree-like colonies and, therefore, presenting a general resemblance to plants. The sponges, hydroids, branching corals and polyzoans were included under this very general title. The name signifies the plant-animal, and is more especially applicable to hydroids and branching corals. See Hydrozoa.
Zoöspore (zō′ō-spōr) (in plants), the swimming asexual spores of algæ, notably the green algæ. The name means animal-spores, referring to the fact that they move like aquatic animals. See Spore.
Zoroas′ter is the name of the founder of what is known as the Parsi religion of ancient Persia. He seems to have been born in Bactria, but most of the legends concerning his history are utterly unreliable. Even the time when he lived is uncertain, but it may be safely asserted to have been as early as 1000 B. C.; possibly he was a contemporary of Moses. The fundamental idea of Zoroaster's creed is its dualism. At the beginning there existed two spirits: Ormuzd, who represented the good, and Ahriman, the evil. Ormuzd is light and
