THE BEGINNINGS OF LIFE. 259 



as many living things, both animal and vegetable, which 

 are produced by the fortuitous aggregation of "mole- 

 cules organiques," as there are others which reproduce 

 themselves by a constant succession of generations/ 

 But it was the experiments of Needham, more espe- 

 cially, that aroused one who was for a long time the 

 most celebrated opponent of these doctrines. The re- 

 nowned Abbe Spallanzani soon took up the question, 

 and entered into a controversy with Needham on the 

 subject. He maintained that the air of our atmosphere 

 bears with it everywhere the germs of infusorial ani- 

 malcules and of other organic forms, and that Needham 

 had not taken sufficient account of this fact in his 

 experiments. In this view he was supported by the 

 fantastic assumptions of Bonnet, and their doctrine 

 since known by the name of ' Panspermtsm ' has re- 

 ceived the most powerful support from Pasteur and 

 others in our own times. The questions in dispute 

 could not be settled by these two champions, and suc- 

 cessive advocates were continually springing up in 

 favour of one or other of the adverse doctrines till 

 the commencement of our own century. Two of the 

 most famous of them, Gleichen and Otho F. Muller, 

 were dissentients from the doctrines of Bonnet and 

 Spallanzani. A little later Treviranus made known an 

 important fact in favour of the doctrine of heterogeny, 

 to the effect that the species of animalcules found in 

 the infusions varied with, and seemed to depend upon, 

 minute differences in the nature of the infusions them- 



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