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, but which on the whole have develoi^ed independently, 

 nay, more often in pronounced opposition to each other; these are 

 on the one side the systematic, 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 oppo- 

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

 many instances disajipeared. 



Aristotle, the great Greek philosopher, has been distinguished 

 as the Father of Natural History, which means that his ]3redeces- 

 sors' fragmentary knowledge of zoology could not be compared 

 with the well-arranged order in which Aristotle had broiTght 

 together his own and the previously existing knowledge of the 

 nature of animals. In Aristotle favorable external conditions were 

 united with more 'favorable mental ability. Equipped with the 

 literary aid of an extensive library, and the pecuiiiary means then 

 more indispensable than now for natural-history investigation, he 

 pursued the inductive method, the only one which is capable of 

 furnishing secure foundations in the realm of natural science. It 

 is a matter for great regret that there have been preserved only 

 parts of his three most important zoological works, " Ilistoria 

 auimalinm," " De partibus," and " De generatione," works in 

 whicli zoology is founded as a universal science, since anatomy and 

 embryology, physiology and classification find equal consideration. 

 How far Aristotle, notwithstanding many errors, attained to 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 it was known to Aristotle, though 

 only lately rediscovered by Johannes Miiller, that many sharks are 

 not only viviparous, but that also in their case the embryo becomes 

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



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