90 



INDI\aDUALITY IN ORGANISMS 



when a certain size or length is 

 attained, or the appearance of 

 buds at a certain distance from 

 the chief growing tip in plants, are 

 cases in point. In many cases ex- 

 perimental control and alteration 

 of these relations throw a flood of 

 light upon the problem of their 

 nature. It is with material and 

 experiments of this sort that the 

 present chapter is largely 

 concerned. 



I have shown elsewhere that 

 the process of progressive develop- 

 ment and differentiation in the 

 individual is accompanied by a 

 decrease in the metabolic rate 

 determined by the accumulation 

 of relatively inactive constituents 

 in the protoplasm. These changes, 



which constitute 



JL 



Figs, 42, 43. — Tuhiilaria: Fig. 42, a single 

 individual; Fig. 43, asexual reproduction 

 from tip of stolon. 



senescence, may 

 end in death if 

 they go far enough. 

 On the other hand, 

 any change which 

 brings about the 

 removal of such 

 previously accu- 

 mulated material 

 makes possible an 



acceleration in metabolic rate, and such changes con- 



