EVIDENCES OF EVOLUTION 57 



clues. Again, we consider the circuitous- 

 ness of the frog's life-history and find in it an 

 evidence of the reality of recapitulation. We 

 say that in the development of many of its 

 organs the frog repeats steps which were 

 taken by the fish stock from which the race 

 of Amphibians sprang. We then use this as 

 one of "the evidences of evolution" — which 

 we have already assumed. But the fallacy 

 here is simply that we cannot directly demon- 

 strate the truth of the doctrine of descent; 

 we can only bring forward facts which sug- 

 gest it, and which it serves to interpret. 



When all is said, then, there remains good 

 reason for keeping firm hold of this idea, 

 which was first clearly stated in its full evo- 

 lutionary importance by Haeckel, first in 

 his notable "Generelle Morphologic," and 

 later in his more popular treatises. This he 

 termed the "fundamental biogenetic law" 

 that "Ontogeny, or the development of the 

 individual, is a shortened recapitulation of 

 phylogeny, or the evolution of the race." 



Even apart from recapitulation, we must 

 admit the suggestive general fact that the 

 developing organism passes through a series 

 of stages, which often differ from one another 

 in the same sort of way as related species 

 differ from one another. 



Experimental Evolution. — In his "Nova 



