References 175 



time the behavior of the infusorian is a link in the 

 chain of causes by which the final form is brought 

 about, but it is concerned more in determining the 

 general shape of the body than the finer details of 

 its internal structure. 



What is true in this case has, I believe, a rather 

 general application. The gross general behavior 

 of an animal plays, I believe, a subordinate though 

 at times an important role in the determination of 

 organic form. But when we turn our attention to 

 the internal processes which are responsible for the 

 finer details of organization may we not again en- 

 counter problems of behavior? May not the dif- 

 ferentiation of these parts be, to a considerable de- 

 gree at least, the result of the behavior of their com- 

 ponent elements? The study of differentiation in 

 higher organisms where it is possible to follow the 

 activities of the various cells which make up the 

 body makes it evident that such is the case. The 

 role of this factor will be considered in the chapter 

 on The Behavior of Cells. 



REFERENCES 



CHILD, C. M. (i) Studies on regulation. IV. 

 Some experimental modifications of form regula- 

 tion in Leptoplana. Jour. Exp. Zool. i, 95, 1904. 

 (2) The regulatory change of shape in Planaria 

 dorotocephala. Biol. Bull. 16, 277, 1909. (3) 



