150 INDIVIDUALITY IN ORGANISMS 



at this stage of development is only three or four milli- 

 meters. 1 In the adult animal, however, the range of 

 dominance as indicated by the length of the first zooid 

 may be ten or twelve millimeters or even more under 

 certain conditions. Evidently with advancing differen- 

 tiation of the nervous system the conductivity has 

 increased, and so the transmission-decrement has be- 

 come less and the range of transmission greater. 



In Stenostomum also the more advanced the devel- 

 opment of a zooid, the greater the distance from its 

 head-region at which the head-region of a new zooid 

 is determined, as will appear by reference to Fig. 29 

 (p. 81). Other animal forms which undergo agamic 

 reproduction show similar relations, and it is also 

 probable that the increasing capacity for co-ordination 

 and control of parts with advancing development, so 

 far as it depends on the nervous system, results to 

 some extent from the increase in efficiency of trans- 

 mission, though various other factors may also be 

 concerned. 



In plants also similar relations appear. In the dif- 

 ferentiated part of the plant stem the range of domi- 

 nance of a bud or a growing tip over others is very much 

 greater than in the embryonic region of the growing tip, 

 but their later development is inhibited by the growing 

 tip as a whole, even though further growth has greatly 

 increased the distance between them. The dominance 

 of the growing tip as a whole has a much greater range 

 in the differentiated parts of the plant than the domi- 

 nance of its apical region over much nearer parts in the 



1 Child, "Studies on the Dynamics of Morphogenesis. Ill," 

 Jour, of Exp. ZooL, XI, 1911. 



