412 THE PROCEEDINGS OF THE LINNEAN SOCIETY 



that theory in the apparent immutability of species, was quite 

 removed when its disciples could point to Dr. Bastian's experi- 

 ments as evidences of evolution and heterogenesis going on under 

 their very eyes. 



But Professor Tyndall, who, as we know, is capable of the 

 wildest nights of imagination when speculating upon what occurred 

 a few millions of years ago, was not disposed to believe that any 

 thing of the kind could occur in the present day. His thoroughly 

 scientific mind would not admit the possibility of living and 

 distinct organisms being generated from infusions of hay or beef 

 or mutton, or any thing else. He therefore instituted a series of 

 investigations and experiments, the results of which he commu- 

 nicated to the Royal Society in January last. He was led to 

 believe that the germs of many organisms, much too minute to be 

 visible under the most powerful microscope, were constantly float- 

 ing in the air. He also thought that these floating germs might 

 not be so destructible by heat as the organisms themselves, which 

 it is known are all killed by a heat of 300° of Fahrenheit. He 

 determined, therefore, to endeavour to supply the infusions with 

 an atmosphere deprived of all foreign atoms. 



The ingenious manner in which he effected this is given in the 

 paper before alluded to. 



The absolutely moteless condition of the atmosphei'e thus 

 obtained was shown by the fact that a concentrated beam of light 

 passed through the vessel containing the atmosphere was invisible, 

 though vivid before it entered and after it passed through. Hun- 

 dreds of these experiments were made with every imaginable infu- 

 sion ; and wherever the air was thus deprived of all floating germs, 

 and the infusion subjected to the usual heat, no bacteria or other 

 organisms ever made their appearance. 



This result, so beautifully worked out by Professor Tyndall, has 

 been sustained by the investigations of the Rev. AV. H. Dallinger 

 and Dr. Drysdale. 



