192 INDIVIDUALITY IN ORGANISMS 



stream which I have used elsewhere/ the plant is some- 

 what like a stream flowing in an alluvial channel, capable 

 of shifting and removing previous structural deposits, 

 and, when its rate is highest, of holding all its sediment 

 in suspension. The animal, on the other hand, repre- 

 sents a condition like that in the stream when deposition 

 of sediment is going on and giving rise to stable structure, 

 even where the rate of flow is highest. In such a stream 

 the most stable structure develops where the rate of 

 flow is highest, while the structure developed with a 

 low rate of flow is readily altered or eliminated by an 

 increase in rate. 



The fundamental differences in behavior between 

 plant and animal are of course associated with this 

 difference. Since the plant is to a large extent incapable 

 of developing morphological colloid structures, such as 

 nerve and muscle, its reactions to external factors are 

 limited very largely to growth reactions, instead of being 

 motor reactions like those in most animals. The low 

 degree of individuation and physiological efficiency in 

 the plant as compared with the animal must also depend 

 on this low degree of physiological stabihty in the pro- 

 toplasmic substratum. 



AGAMIC REPRODUCTION IN RELATION TO PHYSIOLOGICAL 



ISOLATION 



The occurrence of reproduction in consequence of 

 physiological isolation of parts under experimental con- 

 ditions makes it highly probable that at least many of 

 the processes of agamic reproduction in nature are like- 



^ Child, "The Regulatory Processes in Organisms," Jour, of 

 Morphol.,XXll, 191 1. 



