Gl4 Child, Di'iescli's harmonic equipotential systems in form-regulation. 



discovered an apparent ineqiiipotentiality in jthe polar direction, 

 „eine gewisse Differenz des Eiplasniabaues in „animal-vegetativer" 

 Richtung — , welche zwar nicht ausreicht, dem Keim den Charakter 

 eines harmonisch-äqiiipotentiellen Systems zu nehmen, aber doch 

 der Sonderentwickelung einzelner Elemente desselben Widerstände 

 verschiedener Intensität entgegensetzt" (Driesch, 1900, p. 407). 

 He suggests by way of interpretation that „ein allmähliches Starrer- 

 werden des Plasmas" takes place. In later papers he has referred 

 to this case as showing an „Einschränkung", „Verundeutlichung", 

 or „Maskierung" of the harmonic equipotentiality. The question 

 at once arises as to the differences in actual experiment between 

 an inequipotential system and an equipotential system with „masked" 

 equipotentiality. How is the one to be distinguished from the 

 other? So far as I am aware Driesch has not given us a basis 

 for such distinction. 



It seems to me important to distinguish between fact and 

 assumption in this case. The fact is that the sea-urchin egg is not 

 equipotential in certain respects. Driesch assumes that the equi- 

 potentiality is „masked" or made indistinct by certain physical 

 characteristics of the cytoplasm. What reasons are there for such 

 an assumption? The only one which I am able to find is that 

 Driesch must interpret visible inequipotentiality in this manner, 

 i. e., as a „masking" of the real equipotentiality, or else must admit 

 that the sea-urchin egg is not an equipotential system in the „animal- 

 vegetative" direction. In other words this interpretation is merely 

 an attempt to save the general hypothesis as applied to this parti- 

 cular case; the sea-urchin egg is assumed to be equipotential, and 

 visible inequipotentialities must then be assumed to be something 

 non-essential. 



If Driesch admits that my observations on Tubularia show 

 anything that cannot be regarded as approximate proportionality, 

 he may readily interpret them as a „masking" of the equipotentia- 

 lity, if proportionality has any connection with it. If, however, as 

 Driesch seems at present to believe, proportionality is involved 

 in only the most vague indefinite sense, then I see no possibility 

 of distinguishing between equipotentiality and inequipotentiality. 



Drie sell's conception of the „normal" or typical form as a 

 „Zweck" toward which the course of morphogenesis is directed involves 

 a sharp distinction between „normal" and „abnormal" or „atypical". 

 The entelechy determines the normal form and individual departures 

 from the norm or failures to attain it are due to incidental physical 

 or chemical conditions, or are „errors" etc. It is not difficult to 



the results of Coaklin and Driesch concern different genera. The error on ray 

 part was due, however, to inadvertence, not to ignorance of the literature as Driesch 

 so kindly suggests. 



