36 PERIOD II. 



important truth that almost every fossil marks with 

 considerable precision a particular stage in the earth's 

 history. 



Comparative Anatomy : the Study of Biological Types. 



Between 1660 and 1740 the scope of natural history 

 became sensibly enlarged. System had been hitherto 

 predominant, but the systems had been partial, 

 treating the vertebrate animals and the flowering 

 plants with as much detail as the state of knowledge 

 allowed, but almost ignoring the invertebrates and the 

 cryptogams. System was now studied more eagerly 

 than ever by such naturalists as Ray and Linnaeus, 

 but new aspects of natural history were considered, 

 new methods practised, new groups of organisms in- 

 cluded. Many remarkable vertebrates were anatomically 

 examined for the first time. Claude Perrault and his 

 colleagues of the Academic des Sciences dissected 

 animals which had died in the royal menagerie, and 

 compared the parts and organs of one animal with those 

 of another ; Duverney compared the paw of the lion 

 with the human hand ; in England Tyson studied the 

 anatomy of the chimpanzee, porpoise, opossum, and 

 rattlesnake, searching everywhere for the transitions 

 which he believed to connect all organisms, and to 

 form " Nature's Clew in this wonderful labyrinth of the 

 Creation." The new microscopes helped to bring the 

 lower and smaller animals into notice. From 1669, 

 when Malpighi described the anatomy and life-history 

 of the silkworm, a succession of what we now call 

 biological types were studied ; among these were many 

 invertebrates. Edmund King and John Master con- 

 tributed to Willis's treatise De Anima Brutorum (1672) 

 the anatomies of the oyster, crayfish, and earthworm, 



