THE WONDERS OF LIFE 



but, at the same time, given us the key to open the 

 closed doors of embryology, and to learn the causes of the 

 ontogenetic processes as well. I formulated this view in 

 the twentieth chapter of the General Morphology, in 

 forty-four theses, of which I will quote only the follow- 

 ing three: i. The development of organisms is a physio- 

 logical process, depending on mechanical causes, or 

 physico-chemical movements. 40. Ontogenesis, or the 

 development of the organic individual, is directly de- 

 termined by phylogenesis, or the evolution of the organic 

 stem (phylon) to which it belongs. 41. Ontogenesis is 

 a brief and rapid recapitulation of phylogenesis, deter- 

 mined by the physiological functions of heredity and 

 adaptation. The pith of my biogenetic principle is ex- 

 pressed in these and the remaining theses on the causal 

 nexus of biontic and phyletic development. At the 

 same time I make it quite clear that I reduce the physical 

 process of ontogenesis, and also phylogenesis, to a pure 

 mechanics of the plasm (in the sense of the critical 

 philosophy) . 



The comprehensive fundamental law of organic 

 development was briefly formulated by me in the fifth 

 book of the General Morphology and in the tenth chapter 

 of the History of Creation (developed more fully in the 

 fourteenth chapter of the tenth edition, 1902). I after- 

 wards sought to establish it securely in two different 

 ways. In the first place, I proved in my Studies of the 

 G astral a Theory (1872-1877) thatin all the tissue-animals, 

 from the lowest sponges and polyps to the highest 

 articulata and vertebrates, the multicellular organism 

 develops from the same primitive embryonic form (the 

 gastrula), and that this is the ontogenetic repetition, in 

 virtue of heredity, of a corresponding stem-form (the 

 gastrcea) . In the second place, I made the first attempt 

 in my Anihropogeny (1874) to illustrate this recapitula- 

 tion theory from the instance of our own human organ- 



380 



