GENERAL EMBRYOLOGY. 



changed. It has been found, indeed, that spores, particu- 

 larly of bacteria, develop an extreme power of resistance, 

 and in many cases must be boiled more than ten minutes 

 before they are destroyed. As the final result of all the 

 recent experiments and observations it can only be said 

 that the present existence of spontaneous generation is not 

 proved. Now the question is, With what right can it be 

 claimed that spontaneous generation is now going on or 

 has ever taken place ? 



First Origin of Life. Whoever, in agreement with 

 the teachings of astronomy, adopts the view that our earth 

 was at one time in a fluid condition and has gradually 

 cooled, must assume that life on the earth has not .existed 

 from eternity, but at some time has had its beginning. 

 If he wishes to base his explanation, not upon a super- 

 natural act of creation, nor upon arbitrary hypotheses, 

 like that of the transferrence of living germs from other 

 worlds through the agency of meteors, there is left to him 

 only the hypothesis that, according to the generally pre- 

 vailing and still to be observed laws of affinity, or chemical 

 relationship, compounds of carbon, oxygen, hydrogen, 

 nitrogen, and sulphur have been brought together to 

 produce living substance. This process is called spon- 

 taneous generation. If the carbon, oxygen, nitrogen, etc., 

 which are now combined in a stable manner in organisms 



o 



were formerly unstable, the conditions for the origin of 

 organic compounds, through whose wider combination life 

 would be possible, may have been more favorable. TJius 

 the hypothesis of the first origin of life through spontaneous 

 generation is carried to a logical postulate. 



But the theory cannot be extended to mean that spon- 

 taneous generation must even now exist. For that there 

 can be no basis; indeed, many facts point in the contrary 

 direction. As Darwin, in his doctrine of the struggle 

 for existence, has shown in a masterly way, the potentialities 

 of existence upon the surface of our earth are exhausted. 

 New living creatures are only possible when others perish. 

 Why, then, should spontaneous generation engage further 



