LECTURE XVI. 

 ONTOGENY AND PHYLOGENY. 



Correspondence between geological and embryologi- 

 cal succession. Agassiz. 



" Life history of the individual an epitome of the 

 life history of the race.', Hwckel. " Unter jedem 

 Grab liegt eine Weltgeschichte." Why is this so ? 

 Repetition of organs by law of heredity. Modification 

 by natural selection. 



Significance of gills in man ; of pineal eye ; of 

 valves in blood vessels ; of rudimentary organs ; of 

 inguinal hernia. Segmentation of mammalian egg. 

 Simian characters seen in childhood. Human body 

 full of degenerate organs. " Pensioners retained for 

 the good they have done." Advancement in one 

 organ necessitates degeneration in others. Change 

 in human body perpetual. Advancement of brain, 

 hand, pelvis, great toe, etc. ; degeneration of wisdom 

 teeth, ear muscles, lower jaw, little toe, etc. Embry- 

 ology reveals history of race. Embryo of animal tells 

 its ancestry ; outside, its environment. 



