THE GENESIS OF LIFE. 175 



further inquiry, that the organisms which appear in infusions 

 belong to the lowest grades of animal and plant life, and 

 possess a vitality of very low and elastic kind. Even 

 animals of tolerably high organisation, such as the " wheel 

 animalcules" of our ponds and ditches, which possess a 

 nervous system and complex structure, may be dried arti- 

 ficially, kept for months in a mummified and parched con- 

 dition, and yet be revived on the application of moisture. 

 If, therefore, animalcules of a very high grade may be 

 desiccated and revived many times in succession without 

 injury, it is only reasonable to believe that the lower forms 

 occurring in infusions forms which appear to hover, as it 

 were, on the verge of vitality may successfully withstand 

 the rigorous conditions of the experimentalist And if this 

 be true of the adult forms of these lowly animalcules, the 

 assertion must apply with still greater force to their mere 

 germs, which must be regarded as possessing vitality of yet 

 lower kind than the adult beings. It may therefore be 

 reasonably urged that unless clear evidence be afforded 

 that boiling, even of prolonged extent, absolutely kills 

 bacteria, animalcules, and their germs, which may exist in 

 fluids, the results obtained in such experiments do not 

 weaken the theory of biogenesis. According to this theory 

 negative results are explained by assuming that the con- 

 ditions of the infusion have favoured the death by boiling 

 of the contained life ; whilst the affirmative results probably 

 depend on the fact that the germs or organisms were 

 favoured in some fashion in their struggle for existence, and 

 survived their literal trial by fire. Dr. Bastian himself has 

 duly recorded the significant fact remarked by the Abbe 

 Spallanzani that the date of the appearance of life in 

 infusions bears a distinct relation to the time the liquids 

 have been boiled, and to the degree of heat to which they 

 have been subjected. Long continuance of the ebullition 

 usually delays, or may altogether prevent, the appearance 

 of living organisms ; and vice versa, some infusions, owing 

 to special peculiarities or conditions, present exceptions to 



