ORGANIC EVOLUTION 23 



while not a demonstration, furnishes circumstantial 

 evidence too strong to be disregarded. 



The Evidence from Emhryology 



In passing from the egg to the adult the individ- 

 ual goes through a series of changes. In the course 

 of this development we see not only the beginnings 

 of the organs tliat gradually enlarge and change 

 into those of the adult animal, but also see some or- 

 gans appear and later disappear before the adult 

 stage is reached. We find, moreover, that the young 

 sometimes resemble in a most strikin"' wav the adult 

 stage of groups that we place lower in the scale of 

 evolution. 



Many years before Darwin advanced his theory 

 of evolution through natural selection, the resem- 

 blance of the young of higher animals to the adults 

 of lower animals had attracted the attention of zo- 

 ologists and various views, often very naive, had 

 been advanced to account for the resemblance. 

 Among these speculations there was one practically 

 identical with that adopted by Darwin and the jDost- 

 Darwinians, namely that the higher animals repeat 

 in their development the adult stages of lower ani- 

 mals. Later this view became one of the cornerstones 

 of the theory of organic evolution. It reached its cli- 

 max in the writings of Haeckel, and I think I may 

 add without exaggeration that for twenty-five years 

 it furnished the chief inspiration of the school of 



