496 C. M. Child 



functional capacity. In all cases where a difference in localiza- 

 tion exists, structure is more narrowly localized than functional 

 capacity. On this fact, which I believe to be of fundamental 

 importance for the problem of form, depends the abihty of a part 

 to become a whole when isolated. 



In order to bring out clearly the difference between Holmes* 

 hypothesis and my own, we may make use of Holmes' diagram 

 (Fig. i). According to my hypothesis, the various parts. A, By 

 C, D, etc., though perhaps visibly different as regards structure, 

 each possess the physiological properties of the others or of some 

 of the others in some degree. B, G and F, for example, the parts 

 contiguous to A, are capable in some degree of activities similar 

 to those characteristic of y^, but as long as A, a region of greater 

 energy or frequency or rapidity as regards these particular activi- 

 ties is present the correlations arising from it obscure, inhibit or 

 modify the activities of B, G, F, so that they appear structurally 

 and functionally to be different from A. But when A is removed, 

 the parts B, G, F become at once the dominating parts as regards 

 the y^-activities and the correlations between them and other 

 parts become similar in kind, to those which previously existed 

 between yf and the other parts, though probably different in degree. 

 In short B, G, F, or certain portions of them are substituted func- 

 tionally for A simply because in the absence of A their activities 

 must, by virtue of their constitution, be somewhat similar to those 

 of A. No entelechy or other pecuhar principle is needed to guide 

 or determine this substitution. It occurs with the same certainty 

 as any other physical phenomenon in all cases where these parts 

 possess the functional capacities to which attention has been 

 called above. According to this hypothesis, the undifferentiated 

 cells postulated by Holmes are not only unnecessary, but could 

 not substitute for A if present, because the parts B, G, F are more 

 Hke A than are the undifferentiated cells and would therefore 

 dominate in the process of substitution. 



The y^-processes are undoubtedly in most cases, if not in all, 

 at first less energetic or less rapid or both, than they originally were 

 in A, and in consequence of this difference the system may regain 

 its original condition of equilibrium in either one of two ways. If 



