EVOLUTION 
505 
reproduction of organisms already existing, has always 
been the method "Omne vivum ex ovo" (all life from an 
e gg)> "omne vivum e vivo" (all life from preexisting life). 
438. Method of Evolution. To recognize that evolution 
is the method of creation still leaves unanswered the im- 
portant question as to the method of evolution. By what 
process was the gradual development of the living world 
accomplished? Various hypotheses have been elaborated 
in answer to this question. We can here only briefly 
outline three of the most important ones. 
FIG. 388. Louis Agassiz. (From Ballard's "Three Kingdoms.") 
i. Agassiz' s Hypothesis. The great teacher and student 
of nature, Louis Agassiz, believed that the vast array of 
plant and animal species, past and present, had no material 
