CHAPTER TWO 



PHENOMENA WHICH INDICATE A CONTINUOUS FORMA- 

 TIVE ACTION WHICH IS EXERTED BY PARTS OF THE 

 SOMA UPON THE OTHER PARTS THROUGHOUT THE 



WHOLE OF DEVELOPMENT HYPOTHESIS OF THE 



NATURE OF THE FORMATIVE ACTION. 



i. Phenomena Which Indicate a Continued Formative 



Action 



Among the phenomena which seem to indicate indis- 

 putably a continuous formative action exercised by a 

 more or less great part of the soma upon the other parts 

 throughout the whole of development, those of the re- 

 generation of amputated organs take a first place. 



It is known that when the antennae of a snail, the 

 chelae of a crab, the feet of a salamander or the head of 

 a worm are amputated, these organs are reproduced even 

 when the amputation is performed during adult life. 



Spallanzani has cut the feet and tail off the same sala- 

 mander six successive times, and Bonnett seven times, 

 and each time feet were reproduced of exactly the same 

 size as the former ones without any increase or decrease 

 in any part. These facts show that the formative agent 

 whatever it may be is always external to the part formed, 

 and that it exercises upon the whole development of that 

 part and throughout its entire duration a continuous ac- 

 tion, and further that it remains itself unaltered even 



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