Method of pure cultures, Theory of specific organ- 

 isms, Pasteur {i86i). 



Spontaneous generation again, Bastian {1872). 



Biogenesis firmly established, Cheyne, Cohn, Rob- 

 erts, Tyndall, etc. 



2. Evolution vs. Epigenesis. 



(See article Embryology, Encyclopaedia Britannica, 9th Ed.; 

 Hertwig, Text-book of Embryology, pp. 23-27.) 



Aristotle, observations on the chick (History of 

 Animals, p. J 42). 



Harvey (165 i). (See his works pp. 228, 336, 457.) 



" Omne vivum ex ovo." 



" Epigenesis." 

 Malpighi (1672) (Appendix to Anatome Plantarum). 



" Praedelineation." 



Bonnet and Haller (1742-1768), "Evolution." 

 (See Whitman, Woods HoU Lectures, 1S94, p. 225.) 



Discovery of spermatozoa, Hamm and Leeuwenhoek 



(1677). 



Ovists (Schwammerdam, Malpighi, Haller, Bon- 

 net, Spallanzani) vs. Animalculists (Leeuwen- 

 hoek, Hartsoker, Dalenpatius). 



Casper Friedrich Wolff (1759), Epigenesis re- 

 vived. 



Christian Pander (18 17), The three germ-layers. 



Carl Ernst von Baer (18 19-]-). 



The mammalian ovum discovered. 

 Epigenesis established. 

 Modern embryology founded. 



