i So LEISURE-TIME STUDIES. 



dry hay which had been allowed to lie on the floor ; such 

 dust being not only a fertile source of infection, but present- 

 ing matter which, as already remarked, resisted sterilisation 

 by boiling in a very marked manner. But perhaps the 

 most important hint thrown out by Tyndall in his remarks 

 bears upon the relative vitality of germs \ this being a point 

 to which, as we have seen, Dr. Bastian has specially directed 

 attention. The passage of a germ from a hard, dried, and 

 indurated state, to a soft and plastic condition in which it 

 is likely to become developed into an active living organism, 

 is, as Tyndall remarks, probably performed " by different 

 germs in different times. Some are more indurated than 

 others, and require a longer immersion to soften and ger- 

 minate." Hence we may explain in a clear manner the 

 startling results obtained by Bastian and other experimenters, 

 by assuming that cases of speedy sterilisation of infusions 

 by heat depend for their success on the softened nature of 

 their contained germs ; whilst instances of delayed sterili- 

 sation, and of the appearance of life after prolonged boiling, 

 may be reasonably explained on the supposition that the 

 continued heat has gradually softened and awakened the 

 vitality of " hard and resistant " germs. ' 



Space would fail us were we to attempt to give further 

 quotations from these interesting remarks, but sufficient has 

 been said to show that the opponents of spontaneous gene- 

 ration are not behindhand in mustering their forces for the 

 renewed discussion of this great question, and in detailing 

 the results of investigations which would seem to carry with 

 them the explanation of the knotty points offered for solution 

 by the other side. 



In a closing sentence it may not be out of place to 

 note the plain refutation which careful microscopic work 

 has given to certain statements made by the advocates 

 of spontaneous generation regarding the alleged spon- 

 taneous development of lower organisms in protected 

 infusions, and also respecting the transformation of lower 

 into higher forms. Not content with assuming that lower 



