A HISTORY OF SCIENCE 



of species, genera, orders, and classes of beings through 

 endless transmutations is in a sense explained; but 

 what of the first term of this long series? Whence 

 came that primordial organism whose transmuted de- 

 scendants make up the existing faunas and floras of 

 the globe? 



There was a time, soon after the doctrine of evolu- 

 tion gained a hearing, when the answer to that ques- 

 tion seemed to some scientists of authority to have been 

 given by experiment. Recurring to a former belief, 

 and repeating some earlier experiments, the director of 

 the Museum of Natural History at Rouen, M. F. A. 

 Pouchet, reached the conclusion that organic beings 

 are spontaneously generated about us constantly, in 

 the familiar processes of putrefaction, which were 

 known to be due to the agency of microscopic bacteria. 

 But in 1862 Louis Pasteur proved that this seeming 

 spontaneous generation is in reality due to the exist- 

 ence of germs in the air. Notwithstanding the con- 

 clusiveness of these experiments, the claims of 

 Pouchet were revived in England ten years later by 

 Professor Bastian; but then the experiments of John 

 Tyndall, fully corroborating the results of Pasteur, 

 gave a final quietus to the claim of " spontaneous gen- 

 eration" as hitherto formulated. 



There for the moment the matter rests. But the end 

 is not yet. Fauna and flora are here, and, thanks to 

 Lamarck and Wallace and Darwin, their develop- 

 ment, through the operation of those "secondary 

 causes" which we call laws of nature, has been proxi- 

 mally explained. The lowest forms of life have been 

 linked with the highest in unbroken chains of descent. 



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