THEORIES OF INDIVIDUALITY 45 



is effective only within a certain limit of distance which 

 we may call its range, and since physiological dominance 

 depends upon the transmitted change it is similarly 

 limited in range. If physiological individuation depends 

 upon dominance of this sort associated with the meta- 

 bolic gradient determined by transmitted changes, the 

 range of dominance must determine a physiological 

 limit of size, which the individual cannot exceed without 

 the physiological isolation of some part from the domi- 

 nance which previously determined the individuality. 

 As already pointed out, the range of the transmitted 

 change and so the range of dominance varies with the rate 

 of reaction in the dominant region and with the conduc- 

 tivity of the protoplasm; therefore the physiological size 

 limit of the individual must vary with the same factors. 

 Reproduction in its simplest asexual forms results 

 from the physiological isolation^ of parts of the indi- 

 vidual body in consequence of their coming to lie beyond 

 the physiological limit of size. Such physiological 

 isolation may result from: first, increase in size of the 

 body of the individual by continued growth until some 

 part of it is brought beyond the range of dominance; 

 secondly, decrease in the range of dominance and limit 

 of size by decrease in the rate of reaction in the dominant 

 region ; thirdly, decrease in the conductivity of the proto- 

 plasm for the transmitted changes; fourthly, the direct 

 local action of some external factor on a subordinate 

 part, increasing its rate of reaction to a sufficient de- 

 gree to make it more or less independent of or insus- 

 ceptible to the effects transmitted from the dominant 



^ Child, "Die physiologische Isolation von Teilen des Organismus," 

 Vortrage und Aufsdtze iiher Entwickelungsmechanik, H, XI, 191 1. 



