After Aristotle 77 



is efficient and stimulating but below the greatest, both are 

 enthusiastic and effective as investigators of fact, but timid and 

 ineffective in drawing conclusions. 



But Fabricius was more happy in his pupils than Theo- 

 phrastus, for we may watch the same Aristotelian ideas fer- 

 menting in the mind of Fabricius's successor, the greatest 

 biologist since Aristotle himself, William Harvey (i 578-1657). * 

 This writer's work On generation is a careful commentary on 

 Aristotle's work on the same topic, but it is a commentary not in 

 the old sense but in the spirit of Aristotle himself. Each state- 

 ment is weighed and tested in the light of experience, and the 

 younger naturalist, with all his reverence for Aristotle, does 

 not hesitate to criticize his conclusions. He exhibits an inde- 

 pendence of thought, an ingenuity in experiment, and a power 

 of deduction that places his treatise as the middle term of the 

 three great works on embryology of which the other members 

 are those of Aristotle and Karl Ernst von Baer (i 796-1 8j6). 2 



With the second half of the seventeenth century and during 

 a large part of the eighteenth the biological works of Aristotle 

 attracted less attention. The battle against the Aristotelian 

 physics had been fought and won, but with them the biological 

 works of Aristotle unjustly passed into the shadow that over- 

 hung all the idols of the Middle Ages. 



The rediscovery of the Aristotelian biology is a modern 

 thing. The collection of the vast wealth of living forms 

 absorbed the energies of the generations of naturalists from 

 Ray (1627-1705) and Willoughby (1635-72) to Reaumur (1683- 

 1757) and Linnaeus (1707-1778) and beyond to the nineteenth 

 century. The magnitude and fascination of the work seems 

 almost to have excluded general ideas. With the end of this 

 period and the advent of a more philosophical type of naturalist, 



1 William Harvey, Exercitation.es de generatione animalium^ London, 1651. 



2 Karl Ernst von Baer, Ueber die Entwickelungsgeschicbte der 

 Konigsbcrg, 1828-37. 



