ADVANCE OF ZOOLOGY. 23 



the eighteenth century, but were not built into 

 their scientific inductive form until the nineteenth 

 century. 



Yet the Greek traditions in natural history per- 

 sisted as the environment of the Evolution idea as 

 late as the end of the eighteenth century, and, as 

 we shall see, the idea itself was framed solely upon 

 Greek speculation. Most prominent among these 

 Greek guesses at the truth was the doctrine of 

 Abiogenesis, or generatio czquivoca the spontane- 

 ous origin of life from lifeless matter. This fallacy 

 exerted a most potent influence in shaping the 

 crude theories of Evolution which were advanced 

 during the seventeenth and eighteenth centuries; 

 the absurdity of these theories reacting unfavourably 

 upon the true Evolution idea by throwing it into 

 discredit. 



The accumulation of the natural evidences of 

 Evolution was the work of centuries. Besides the 

 advances in Astronomy, Geology, and Physical 

 Geography, there was the slow upbuilding of the 

 great branches of Biology. First, correct ideas of 

 structure or Comparative Morphology of animals 

 and plants, and connected with this the structure 

 of extinct forms preserved as fossils ; with this 

 knowledge came the appreciation of the meaning 

 of variations and of gradual development in struct- 

 ure, and the meaning of vestigial or degenerate 

 structures. Then came the knowledge of function 

 and the physiology, first of man, then of the lower 



