38 PERIOD II. 



modern treatise on animal structure. 1 Poupart followed 

 the later stages of the development of a feather. Mery 

 gave a minute yet animated description of the wood- 

 pecker's tongue, explaining how it is rendered effective 

 for the picking up of insects, how it is protruded and 

 retracted, how it is stowed away when not in use. 

 Tournefort figured the oblique fibres of a leguminous 

 pod, which he called muscles, and showed how they 

 twist the valves and squeeze out the seeds. 



Natural theology was much in the thoughts of the 

 naturalists who studied and wrote between 1660 and 

 1740. Ray discoursed upon the Wisdom of God as 

 manifested in the Creation. Swammerdam regularly 

 closed the divisions of his Biblia Natures with expres- 

 sions of pious admiration. A long list of books 

 expressly devoted to the same theme might be given. 2 

 One weakness of the natural theologians was their habit 

 of looking upon the universe as existing for the con- 

 venience of man. Still more fatal was the partiality 

 with which they stated the facts. While they dwell 

 upon the adaptations which secure the welfare of 

 particular animals or plants, they are silent about the 

 sufferings caused by natural processes. 



Spontaneous Generation. 



During many ages every naturalist thought that he 

 had ample proof of the generation without parents of 

 animals and plants. He knew that live worms appear 

 in tightly-closed flasks of vinegar ; that grubs may be 

 found feeding in the cores of apples which show no 

 external marks of injury ; and that weeds spring up in 



1 The second of the two has actually been so treated, but with- 

 out mention of Perrault's name. 



2 See Krause's Life of Erasmus Darwin. 



