264 GENEKATION. 



matter, ova, spores, or whatever it may be, no living organ- 

 isms make their appearance so long as these experimental 

 conditions are maintained. We also assume that simple boil- 

 ing, at 212 Fahr., does not necessarily destroy all germs, 

 which excludes experiments made in this way. This reduces 

 the question to a single, simple point : In infusions in which 

 the organic matter has not been destroyed by heat, do the 

 living organisms come from a spontaneous aggregation of or- 

 ganic molecules, or are they the result of the development 

 of ova ? 



In the case of the very lowest organisms making their ap- 

 pearance under these conditions, they are themselves so small, 

 that it would be reasonable to suppose that we might be 

 unable to see the ova, assuming that they exist. The organic 

 particles that are supposed to come together spontaneously are 

 also invisible, even under the highest magnifying powers at 

 our command. If we come to an exact definition of the term 

 spontaneous, we may say that it means an action " arising or 

 existing from natural inclination, disposition, or tendency, or 

 without external cause" (Worcester). With this definition, 

 the statement that a living organism is generated spontane- 

 ously can only mean that there is no cause that can be assigned 

 for its production. In point of fact, we simply acknowledge 

 that the mode and cause of generation of certain infusoria 

 are unknown, and the history of our knowledge of genera- 

 tion shows that the term spontaneous generation has always 

 been applied to the production of beings in a manner that is 

 incapable of satisfactory explanation. What we actually know 

 of the mode of generation of animal organisms teaches us 

 that all beings are produced and multiplied by ova, or by pro- 

 cesses of segmentation or budding of preexisting organisms ; 

 and our knowledge of these processes now extends to all ex- 

 cept the most minute infusoria, which have no apparent 

 structure. We know, also, that such organisms may develop 

 in pure water from particles floating in the atmosphere ; and 

 that particles in the air, singly invisible, may be developed 



