REPRODUCTION AND LIFE CYCLES 407 



boiling water for three quarters of an hour. The contents of the 

 flasks remained unchanged. Spallanzani then op(!ned the flasks and 

 after a short period they were found to be full of living organisms. 

 Needham objected to the experiments on the ground that the boiling 

 had killed the "vegetative force" of the infusion. However, the 

 idea of spontaneous generation was not finally disproved until the 

 time of Pasteur and T3mdall, who proved that living germs may 

 be carried about by dust in the air and that only when air con- 

 taining dust particles can be excluded from substances it is certain 

 that bacteria will not grow in them. 



Other Theories of the Origin of Life 



The theory of the simultaneous creation of life and this planet does 

 not agree with such theories as the scientists offer to account for the 

 origin of the eartli. Whether we accept the nebular hypothesis of 

 LaPlace, the later planetesimal hypothesis of Chamberlin, or the still 

 later theories of Green or Shapley, we are confronted in all of them by 

 the formation of our jjlanet from material far too hot to sustain life. 

 As Jeans says, ''The physical condition under which Hfe is feasible is 

 only a tiny fraction of tlie range of physical conditions which pre\^ail 

 in the universe as a whole." The theory sometimes advanced that 

 life may have been transferred from another planet does not help us 

 much, for we still have to account for life's origin. As has been so 

 well said of life on Mars, which of any of our planetary neighbors 

 has concUtions the most possible for supporting life, "Man recon- 

 structed to walk on Mars would be crushed to death by his own 

 weight on the eartli." Special creation as advocated by the early 

 Church does not help the scientist very much, for it still leaves life 

 to be accounted for. It allows of no scientific investigation and so 

 it cannot be used by the biologist. 



Probably the theory which has the most hope of ultimate solution 

 is the belief that at some time life arose by a chance combination of 

 chemical elements of which the earth is made. Evidence found in 

 the rocks indicates that the earth is much older than its inhabitants. 

 Professor Henry F. Osborn pointed out the striking similarity of the 

 salts found in the blood and those found in sea water. He made the 

 suggestion that life might have originated in some pool in which the 

 saUne contents contained the life elements found in protoplasm. 

 Would it be too much to speculate on the origin of some simple form 

 of life by allowing a flash of lightning to release the pure nitrogen 

 H. w. H. — 27 



