xv.] SPONTANEOUS GENERATION. 355 



Led by various theoretical considerations which I 

 cannot now discuss, but which looked promising enough 

 in the lights of that day, Buffon and Needham doubted 

 the applicability of Redi's hypothesis to the infusorial 

 animalcules, and Needham very projierly endeavoured 

 to put the question to an experimental test. He said 

 to himself, if these infusorial animalcules come from 

 germs, their germs must exist either in the substance 

 infused, or in the water with which the infusion is 

 made, or in the superjacent air. Now, the vitality of 

 all germs is destroyed by heat. Therefore, if I boil 

 the infusion, cork it up carefully, cementing the cork 

 over with mastic, and then heat the whole vessel by 

 heaping hot ashes over it, I must needs kill whatever 

 germs are present. Consequently, if Kedi's hypothesis 

 hold good, when the infusion is taken away and allowed 

 to cool, no animalcules ought to be developed in it; 

 whereas, if the animalcules are not dependent on pre- 

 existing germs, but are generated from the infused 

 substance, they ought, by-and-by, to make their aj:>pear- 

 ance. JSTeedhain found that, under the circumstances 

 in which he made his exj)eriments, animalcules always 

 did arise in the infusions, when a sufficient time had 

 elapsed to allow for their development. 



In much of his work Needham was associated with 

 Buffon, and the results of their experiments fitted in 

 admirably with the great French naturalist's hypothesis 

 of " organic molecules," according to which, life is the 

 indefeasible property of certain indestructible mole- 

 cules of matter, which exist in all living things, and 

 have inherent activities by which they are distinguished 

 from not living matter. Each individual living organ- 

 ism is formed by their temporary combination. They 

 stand to it in the relation of the particles of water to 

 a cascade, or a whirlpool ; or to a mould, into which 



