Continuous Formative Influence 23 



by differentiated cells upon other less differentiated cells 

 which are immediately adjacent to them." 



"In the latter process very different degrees of action 

 are possible. There can, for example, emanate from the 

 differentiated cells an influence which simply sets free 

 the process of differentiation allowing the entire series 

 of necessary changes after this preliminary impulse to 

 proceed of itself. Or, each of these changes may not 

 merely receive from the differentiated cell a simple 

 initial impulse, but may on the contrary be determined 

 ,by that throughout. Between these two extremes one 

 can imagine a \vhole series of intermediate stages. On 

 account of the at first atypical disposition of the material 

 which at last becomes typically differentiated I am 

 inclined to think that the action of the differentiated cells 

 upon the nondifferentiated cells is not a mere liberating 

 one or a mere stimulating one." 



These facts of postgeneration indicate then above all 

 that the action of the half embryo already formed upon 

 the other half in process of formation is exercised in a 

 continuous manner throughout the whole development 

 of this latter. 



One would be led also to this conclusion, that there 

 is a continuous action exercised throughout the whole of 

 development, by the fact that the postgeneration of the 

 undeveloped half goes on with greater rapidity, so that 

 it soon overtakes the other half and proceeds with it to 

 the same stage of development. 



"Wilhelm Roux : Uber die kiinstliche Hervorbringung ,,halber" 

 Embryonen durch Zerstorung einer der beiden ersten Furchungszellen, 

 sowie uber die Nachentwicklung, Postgeneration der fehlenden 

 Korperhalfte. Virchows Archiv, Bd. 114. October 1888, P. 279 282. 

 Gesamm. Abhandl., Zw. Band. P. 507 509. 



