LIFE COMES ONLY FROM LIFE 



the life of the class rises higher and higher in func- 

 tion and capacities. The mechanisms thus required 

 are and can only be derived from an organism already 

 existing. For it is proved as clearly as it is possible 

 to prove a negative that spontaneous generation does 

 not exist. 



It is not probable, but it may be, that the future 

 will reveal to us conditions that determine the forma- 

 tion of an organic living cell, or its plasmodium, from 

 its inorganic constituents otherwise than from a pre- 

 existing parent organism. As yet life has never been 

 brought by man directly into being from the inorganic 

 world, though every conceivable means has been tried. 

 Many persons have thought that they had shown the 

 formation of life in solutions protected from the in- 

 troduction of existing life ; but careful examination 

 has always shown that in someway access to the outer 

 world had been permitted, or the pre-existing life 

 therein had not been destroyed. With greater care 

 the maxim, " Omne vivum e vivo," has invariably 

 proved to be true. 



The phenomena that constitute Life, in its origin 

 and relation to those of Inorganic nature, are best 

 studied in its lowest and simplest forms, especially 

 in those of Plant life. Haeckel and many other 

 writers, in treating of the early forms of life, higher 

 in type than the so-called Monera, have dwelt almost 



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