CHAPTER ONE 



ONTOGENY, AS A RECAPITULATION OF PHYLOGENY, SUG- 

 GESTS THE IDEA OF A CONTINUOUS ACTION EXERTED 

 BY THE GERM SUBSTANCE UPON THE SOMA THROUGH- 

 OUT THE WHOLE OF DEVELOPMENT. 



Everyone knows the fundamental biogenetic law of 

 Haeckel : ontogeny is a recapitulation of phylogeny, that 

 is, the development of the individual is a rapid resume of 

 the development of the species, a short reproduction of 

 the endless chain of its ancestors. 



The most important facts establishing this law, now 

 perhaps irrefutably, are so well known that we hardly 

 need to mention them here; for example: solipedation 

 develops gradually in the horse and only in the last stages 

 of its development ; many whales which later instead of 

 teeth have the so called whalebone have teeth in their jaws 

 while they are still in a fetal condition and cannot take 

 any nourishment ; the serpent while it is in the embryonic 

 state possesses its two pair of limbs, and so on. 



"The development of the organism," writes Roux, "is 

 not merely a production of the complex from the simple 

 by the most direct route. The ways are devious; and 

 many a forward step must be retraced. We mention only 

 the well known examples of the gill clefts and gill arteries 

 and their ultimate concrescence, the notochord also, and 

 the pituitary and pineal glands, structures quite super- 



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