Embryology 337 



heredity of the fowl. The egg, when hatched, will develop 

 just as did all ancestors until those of a few generations 

 back; but then at the end of the series of changes there 

 appears a chick or perhaps, in later mature plumage, a hen, 

 with black feathers, no red, no speckled, but all pure black. 

 That plumage-color tendency has been added to the germ 

 heredity of the egg, during those last few generations, and 

 imposed upon the life history of the previous ancestry. 

 Still the germ was not changed in any preceding develop- 

 ments. In all other matters it unfolds over again just what 

 the ancestors underwent. The recentness of the character 

 is revealed in its liability to easy abandonment. Being a 

 newly acquired heredity it is not hard to eradicate. What 

 was done by ten generations can be undone by ten others. 

 But if it continues advantageous it will not be undone ; but 

 will become more and more confirmed. And in that way, at 

 times long past, all the characteristics of the fowl were 

 experimentally added and then built up and confirmed. 

 The character of the feathers themselves, of the wings and 

 legs ages back ; of the general form long ages back ; and still 

 farther back, in a remote past when neither legs nor wings 

 had begun, the circulatory system, the nerves, the stomach 

 and digestive organs, succeeded, as evolutionary improve- 

 ments upon the organization of the bunch of associated cells, 

 which clung together in mutual support as a primitive 

 growth, a bell-shaped metazoa drifting in a primeval lagoon. 

 Thus we see that the primitive creatures grow, in their 

 few hours of full development, in exactly the same way as 

 the higher creature grows in the first few hours of its longer 

 career. And of course we may see other creatures which 



