TEACHING AND LEARNING. 



given (Fig. i ) the curve obtained by averaging 1 the results of 

 nine students for the relations of protoplasmic movement to 

 temperature in a tip cell of Nitella, and with it is given an indi- 

 vidual record taken at random. 



-*v 



E 



\ 



/ 



if 



Se 



\ 



\\ 



x - 



X 







10' 15" 20" 25 J 



30' 



35 



40- 



45- 



55 



FIG. i. CURVE (POLYGON) OF PROTOPLASMIC MOVEMENT IN NITELLA UNDER 



VARYING TEMPERATURES. 



The continuous line is an average of the results of nine students; the broken line is 



the result of one student. 



Of very great value, too, are the generalized diagrams often 

 called for in this course. Nothing can surpass them for secur- 

 ing clearness of vizualization. 



In a course such as this, which brings the student so often 

 to the borders of philosophy, some attention must be given to 

 theories and theorizing, and even to speculation. There are 

 many, however, who will not agree with the w r isdom of laying 

 so much stress upon these as is done in the following pages. 

 Certainly their profitable educational use depends upon the 

 temperament of the teacher. Any teacher who does not 

 naturally take a deep interest in such matters, or who does not 

 feel confidence in his ability to use this method without losing 

 control of it, had better not attempt to use it extensively, if at 

 all. Theorizing has this justification, that the current theories 



