SOME PROBLEMS OF REGENERATION. 207 



that what we call a formative force or a vital force is the prop- 

 erty of living things to assume a given form under certain con- 

 ditions. If so, is there here legitimate ground for investigation, 

 or rather let me ask, can we hope to extend our investigations 

 beyond the knowledge of the internal and external conditions 

 within which new forms arise. It is this uncertainty in regard 

 to the problem of vitality that we need first to clear up, and it 

 seems to me that this is the cardinal point for us to examine at 

 present. It is possible, I think, by means of experiment alone, 

 to determine how far and in what sense we can pursue the 

 investigation of the causes of form. In this regard experi- 

 mental studies on the regeneration of animals and plants offer 

 a most admirable field for future work. 



