ARISTOTLE 



erroneous. As examples of this we may quote his 

 discussions and conclusions upon preformation and 

 epigenesis and upon the time of sex-determination 

 in the embryo." 

 Aristotle's The main contributions of Aristotle to embryology, 

 '^'ttoiis to ^^ judged from the viewpoint of a modern embryo- 

 embryo- logist,^ may be stated as follows : 



logy. '^ ^ ■' 



1 . Following the lead of men like the author of the 

 Hippocratic treatise tt. yoi'rjs, Aristotle greatly 

 extended the field of careful and accurate obser- 

 vation, and was thereby enabled to introduce 

 for the first time the comparative method into 

 embryology, and so to arrange the available 

 data in an orderly way This is expressed, e.g., 

 by his classification of animals according to their 

 methods of embryonic development. 



2. He stated in the clearest terms the two rival 

 theories of preformation and epigenesis, and 

 decided in favour of the latter. He also laid 

 down that the sex of the embryo was deter- 

 mined at the very beginning of its development. 



3. He clearly stated that generic characteristics 

 precede specific characteristics in embryonic 

 development, and, by his theory that the various 

 faculties of Soul developed successively in the 

 embryo, foreshadowed the modern theory of 

 " recapitulation." By his observation that the 

 " upper " parts of the embryo develop more 

 rapidly than the " lower " parts he foreshadowed 



" For a useful general estimate of Aristotle's work, see 

 E. S. Russell, The Interpretation of Development and Heredity 

 (1930), pp. 11-24. 



*" See, e.g., J. Needham, A History of Embryology (1934), 

 pp. 36 ff. 



