558 THE EVOLUTION OF LIFE. 



it would have a warrant higher than that of many beliefs 

 which are regarded as established. But the evidence is far 

 from exhausted. 



At the outset it was remarked that the phenomena pre- 

 sented by the organic world as a whole, cannot be properly 

 dealt with apart from the phenomena presented by each 

 organism, in the course of its growth, development, and 

 decay. The interpretation of either implies interpretation of 

 the other; since the two are in reality parts of one process. 

 Hence, the validity of any hypothesis respecting the one 

 class of phenomena, may be tested by its congruity with 

 phenomena of the other class. We are now about to pass 

 to the more special phenomena of development, as displayed 

 in the structures and functions of individual organisms. If 

 the hypothesis that plants and animals have been progres- 

 sively evolved be true, it must furnish us with keys to these 

 phenomena. We shall find that it does this; and by doing 

 it gives numberless additional vouchers for its truth. 



