THE EVOLUTION IDEA 131 



During a long i:)eriod all naturalists were 

 simi)ly compilers. Among these compilers were 

 Clusius, Rondelet, Belon; finally we find Con- 

 rad Gesner (1516-1565) writing a complete 

 bibliography of zoologj^ and leading the natural- 

 ists of the sixteenth century. About this time 

 Cesalpin (1519-1603) wrote of vegetable anat- 

 omy, and there sprang up in Padua the School 

 of Anatomy of Vesalius (1514-1564) , Fallopius, 

 and his pupil Fabricius, who in turn taught the 

 immortal Harvey. In 1619 Harvey discovered 

 the circulation of the blood and founded embry- 

 ology. The systematic classification of animals 

 and plants then arose as a distinct branch in the 

 writings of Ray (1628-1704), Tournefort, and 

 Magnol. Ray was the precursor of Linnseus. In 

 the second half of the seventeenth century and 

 beginning of the eighteenth, the study of the 

 smaller organisms began with Leeuwenhoek, 

 Malpighi, and Swammerdam. "We owe to this 

 period," says St. Hilaire, "the foundation of 

 Microscopy; Anatomy enriched and joined to 

 Physiology ; Comparative Anatomy studied with 

 care ; Classification placed on a rational and sys- 

 tematic basis." It was these sciences, especially 

 the rise of clearer ideas on the nature of species, 

 which first gave speculation upon Evolution its 

 modern trend, bringing up the origin and the 

 mutability of species as two great central ques- 

 tions. 



