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 résumé 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- 
II 
