164 LEISURE-TIME STUDIES. 



Abbe, Needham's experimentation was of faulty kind ; since, 

 by the exercise of care in sealing the flasks, and by prolonged 

 exposure to heat, we see that life within the flasks is exter- 

 minated, and outward vitality hindered from gaining admit- 

 tance to a field wherein its fertility might be exemplified. 

 Once again, therefore, and in Italy, the balance of scientific 

 opinion, backed by demonstrative proof, goes down heavily 

 weighted against the doctrine of " spontaneous generation." 

 But Spallanzani did not rest content with a simple 

 refutation of the results of Needham's experiments. He 

 perceived the necessity which had arisen for a positive 

 deliverance on the subject of experimentation, and for an 

 explanation of what in Needham's case had produced the 

 development of life, and of what in his own case had been 

 excluded. Out of Spallanzani's necessity grew the hypothesis 

 which in modern days is widely known as the "germ theory." 

 According to this idea Spallanzani held that the atmosphere 

 and fluids of all kinds were charged with the germs or eggs 

 of the lower forms of animal and plant life. Under certain 

 conditions such as that of extreme dryness these germs 

 remained sterile and unproductive. Once introduced, how- 

 ever, into a medium adapted for their development such a 

 medium being exemplified by an infusion of organic matter 

 the germs, like seeds placed in a suitable soil, developed into 

 the adult forms of animalcules. The germs in the fluids, 

 according to Spallanzani, were destroyed by heat; those 

 contained in the atmosphere were prevented from gaining 

 access to his infusions, and hence the fluids remained per- 

 manently barren. The day of the actual demonstration of 

 the existence of germs was not yet ; but the germ theory of 

 Spallanzani at once sprang into favour as a reasonable 

 hypothesis, taking the latter appellation to indicate a theory 

 which explains all the facts of a case, and is, at the same 

 time, contradictory to none, of the origin of lower life 

 in closed vessels. The supporters of this theory were 

 formerly known as " Panspermatists," and the theory itself 

 as that of "Panspermy." The old term "spontaneous," 



