472 THE AMERICAN NATURALIST [Vol. LII 



going a cycle of changes— both in structure and function 

 —and is being stimulated, responding, behaving, and 

 even migrating into new environments, in response to 

 internal and external stimulation. This is indicative of 

 the dawn of a new era in the study of ontology (cf. 

 Thompson, '17). As Bancroft (Ml, p. 178) suggested, 

 Sedgwick (MO, p. 177) saw clearly for the moment, as it 

 were, but not in practice and concretely, the dynamic 

 conception of individual development, although it is very 

 evident that he saw the unity or continuity of the on- 

 togenetic cycle. However, it has remained for Child ( M5, 

 M5a, '15/;) who, apparently adapting largely the dy- 

 namic conceptions of the plant and animal ecologists, and 

 to a lesser degree those of the physiologists, has now 

 given expression, in a clear and concrete manner, to the 

 dynamic ideas in individual developmental responses, and 

 special attention is called to his important work. 



That the life cycle varies in its degree of susceptibility 

 to environmental influence has been pointed out by Ver- 

 non ( '99, p. 199), DeVries (1900), Bancroft ( Ml, p. 175), 

 and others (Woods, MO; Pike and Scott, M5; Pike, M7). 

 Vernon's law is expressed ('03, p. 199) as follows: ''In 

 fact, it would seem to be a law of general application that 



