PREFACE 



About a generation ago, biologists devoted considerable time to 

 a discussion of the vitalistic and mechanistic conception of Hfe 

 processes. The impulse for this discussion was given at that time 

 by the experiments of Roux and of Driesch upon the development 

 of eggs, parts of which had been destroyed or removed in the 

 first stages of segmentation. It was generally or frequently 

 observed that the development of the mutilated egg resulted in 

 the formation of a normal organism. Driesch maintained that 

 this phenomenon could not be adequately explained on a purely 

 physico-chemical basis, but that in addition a metaphysical 

 guiding principle inherent in the organism as a whole was to be 

 postulated. The opposite view was held by Roux. The 

 controversy was never settled, for the simple reason that on 

 account of the microscopic size of the egg cells the experiments of 

 both authors had to be purely qualitative. An adequate explana- 

 tion of natural phenomena is possible only on the basis of quanti- 

 tative experiments and such an explanation consists in the 

 derivation of the results from a rationahstic mathematical 

 formula (a so-called '4aw") without the introduction of arbitrary 

 constants. 



Phenomena of regeneration occur not only in eggs but in adult 

 animals and plants as well. The problem is, first, why does 

 mutilation of an organism give rise to phenomena of growth 

 which do not occur without mutilation, and second, why does 

 the new growth frequently (though not always) result in some 

 kind of restoration of the old form of the mutilated organism. 

 The same mysterious "guiding principle," which had been 

 suggested by the vitalists for the egg, was suggested also for the 

 explanation of the seemingly purposeful character of regeneration 

 in adult animals and plants, since regeneration leads frequently 

 to the restoration of that form which is characteristic of the 

 organism as a whole. 



An enormous hterature exists on the regeneration in both 

 animals and plants, but the experiments reported were gener- 

 ally merely qualitative in character, and where an attempt at 



