CHAPTER XII. 



SPONTANEOUS GENERATION. 



" Spontaneous Generation," or " Abiogenesis," is the 

 term applied to the alleged production of living beings 

 without the pre-existence of germs of Siny kind, and there- 

 fore without the pre-existence of parent organisms. - The 

 question as to the possibility of spontaneous generation is 

 one which has been long and closely disputed, and which 

 cannot be said to be yet definitely settled. It will be suffi- 

 cient, therefore, to indicate some of the facts upon which 

 the belief in Abiogenesis is founded, and to point out some 

 general considerations upon the same. 



If an animal or vegetable substance be soaked in hot or 

 cold water, we obtain what is called an " organic infusion " 

 — that is to say, a fluid holding organic matter in solution. 

 If such an infusion be boiled, any adult living beings which 

 might be present in it are destroyed, and the fluid certainly 

 becomes temporarily deprived of all active life. If, how- 

 ever, such an infusion be exposed for a certain length of 

 time to the air, a series of changes is inaugurated which end 

 in its becoming tenanted by numerous living organisms. 



The first phenomenon observable is usually the forma- 

 tion upon the surface of the infusion of a delicate film or 

 scum. If a fragment of this film or pellicle be examined 

 microscopically, it is found to consist of numberless moving 



