36 THE LIVING WORLD. 



nearest to the condition of simple protoplasm. The 

 disproof of the claims of the earliest biologists who 

 believed in the abiogenetic origin of the higher 

 animals, is therefore no proof or even indication 

 that this does not occur in the lowest organisms. 

 The question, therefore, finally settled around the 

 origin of the lowest and smallest forms of life. 

 From this point the matter has been chiefly one of 

 care in experimenting. It was found by some that 

 low organisms, bacteria, infusoria, etc., would arise 

 in closed flasks filled with various material for food, 

 even after all apparent precautions had been taken 

 to exclude everything alive. But other experiment- 

 ers employing greater precautions for the exclusion 

 of living matter obtained opposite results. The ver- 

 dict vibrated from one side to the other, as different 

 experiments were made known, until at length Pas- 

 teur and Tyndall showed that the negative conclu- 

 sion was the only tenable one. Tyndall, more espe- 

 cially, by a series of careful experiments conducted 

 in a manner beyond reach of criticism, so conclu- 

 sively proved that with the proper precautions no 

 living organisms could arise in any solution without 

 the access of previously living organisms, that no 

 one has seriously questioned the matter since. This 

 result, indeed, is only a negative one. It simply 

 shows that no living organisms did arise under the 

 conditions of the experiment. But it is so conclu- 

 sive that scientists have, with practical unanimity, 

 given up all claim that there is the slightest evidence 

 for the possibility of spontaneous generation. And 

 this is admitted by the very men who still insist that 



