162 THE SCIENCE OF BIOLOGY 



tionary concept is as fundamental in biology as the helio- 

 centric theory in astronomy or the theory of the earth's 

 sphericity in geography. This great biological generaliza- 

 tion was not established before the close of the Renaissance, 

 mainly because it was unthinkable from the standpoint of 

 traditional cosmogony and because its demonstration de- 

 pended upon so wide a range of facts. The older idea of the 

 structure of the heavens had passed away by the end of the 

 seventeenth century. But there did not seem to be adequate 

 reason for doubting the scriptural account of the origin of 

 the universe. The Mosaic account was still accepted despite 

 the difficulties which now began to be recognized. The case 

 is not dissimilar from what occurred in the nineteenth cen- 

 tury when attempts were made, to exclude man from his 

 place in the animal world, by the anti-evolutionists. 



THE TBANSMUTATIONISTS OF THE EIGHTEENTH CENTURY 



The first scientific formulation of organic evolution oc- 

 curred toward the middle of the eighteenth century. The 

 biological contribution of the Renaissance had consisted of 

 the progressive increase of knowledge in natural history. 

 During the fifteenth, sixteenth, and seventeenth centuries, 

 knowledge concerning the number and kinds of animals and 

 plants and their distribution was acquired. By the opening 

 of the eighteenth century the question of their origin had 

 begun to demand something more than formal explanation. 

 The very number of different kinds of animals made it 

 difficult to understand how all could have been named by 

 Adam or how the progenitors of so many kinds could have 

 been contained within the ark of Noah. Moreover, the 

 problems of geographical distribution were being acknowl- 

 edged. The animals found upon oceanic islands presented 

 puzzling questions, which were at first explained on the 

 theory that the ancestors of these animals had been trans- 

 ported thither by man. But men came to doubt the possi- 



