HISTORY OF ZOOLOGY. 



Methods of Zoological Study. — In the history of zoology we can 

 distinguish two great currents, which have been united in a few men, Ijut 

 which on the wliole have developed independently, nay, more often in 

 pronounced opposition to each other; these are on the one side the system- 

 atic, on the other the morphologico-physiological mode of studying animals. 

 In this brief historical summary they will be kept distinct from one another, 

 although in the commencement of zoological investigation there was no 

 opposition between the two points of view, and even later this has in many 

 instances disappeared. 



Aristotle, the great Greek philosopher, has been called the Father of 

 Natural History. Equipped with the literary aid of an extensive library and 

 pecuniary means, he pursued the inductive method, the only one capable of 

 furnishing secure foundations in the realm of natural science. There 

 have been preserved only parts of his three most important zoological 

 works, "Historia animalium," "De partibus," and "De generatione," 

 works in which zoology is founded as a universal science, since anatomy 

 and embryology, physiology and classification find equal consideration. 

 How far Aristotle, notwithstanding many errors, had a correct knowledge 

 of the structure and embryology of animals, is shown by the fact that many 

 of his discoveries have been confirmed only within a century. Thus 

 Aristotle knew, though only lately rediscovered by Johannes Miiller, that 

 many sharks are not only viviparous, but that also the embryo becomes 

 fixed to the maternal uterus and there is formed a contrivance for its 

 nutrition resembling the mammalian placenta; he knew the difference 

 between male and female cephalopods, and that the young cuttlefish has 

 a preoral yolk-sac. 



The position which Aristotle took in reference to the classification of 

 animals is of great interest; he mentions in his writings about five 

 hundred species. Since he does not mention very well-known forms, 

 like the badger, dragon-fly, etc., we can assume that he knew many more, 

 but did not regard it necessary to give a catalogue of all the forms known 

 to him, and that he mentioned them only if it was necessary to refer to 

 certain physiological or morphological conditions found in them. 



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