62 AMONG THE GREEKS. 



he does not carry his conception of Nature as 

 Aristotle does into the law of gradual development 

 of organic life, but like Parmenides, Democritus, 

 and Anaxagoras, he conceives of animals as arising 

 directly from the earth: " Plants and trees," he says 

 (Book V. 780), " arise directly out of the earth in 

 the same manner that feathers and hair grow from 

 the bodies of animals. Living beings certainly have 

 not fallen down from heaven, nor, as Anaxagoras 

 supposed, have land animals arisen from the sea. 

 But as even now many animals under the influence 

 of rain, and the heat of the sun, arise from the 

 earth, so under the fresh, youthful, productive 

 forces of the younger earth, they were spontane- 

 ously produced in larger numbers. In this manner 

 were first produced birds, from the warmth of 

 spring ; then other animals sprang from the womb 

 of the earth, since first mounds grew up from 

 which people sprang forth, for they had been 

 nourished within. In an analogous manner these 

 young earth-children were nourished by springs 

 of milk." 



Only as an after-thought, not as a part of Nature's 

 method, Lucretius borrows from Epicurus, and thus 

 probably indirectly from Empedocles, the Survival 

 of the Fittest idea that some of these earth-born 

 beings were unable to live, and were replaced by 

 others. As a rationalist, he naturally suppressed 

 the mythological Centaur and Chimaera from his 

 direct history of Creation. In the following pas- 



