REGENERATION 187 



of an " equipotential ontogenetic system " : 

 the blastula is such a system. Further, " in 

 the blastula each element is equally able to play 

 any single part in the formation of one totality. 

 Any particular cell would have played another 

 single part, had you cut the blastula in some 

 other direction; it can play any single part 

 required. And what it actually does in the 

 special case normal or experimental is al- 

 ways in harmony with that which is done by 

 its fellow-cells, which possess the same great 

 potentiality as itself. Let us then call our^ 

 blastula an^harmonious-equipotential system." 

 The existence of such systems is Driesch's 

 first and most important proof of vitalism, and 

 a little consideration will show that in previous 

 pages we have been studying various things 

 which come under this category, such as 

 Tubularia, earthworms, and the branchial ap- 

 paratus of Clavellina which, as Driesch says, 

 " is the very type of a harmonious equipoten- 

 tial system; each element of it is able to per- 

 form any single morphogenetic action that is 

 required and all the elements work together 

 in harmony in each single case. For the cut 

 can be made quite at random." Let us com- 

 plete the matter in Driesch's own words they 

 cannot be improved upon " If normal undis- 

 turbed embryogenesis alone would result in the 



