§2] 



EFFECT ON GENERAL FUNCTIONS 



229 



sive movement becomes slower, and finally ceases, while the 

 rotation continues, but in ever diminisliing rapidity. A new 

 axis of rotation is assumed, running lengthwise and obliquely, 

 or running transversely, in the short axis of the body. Finally, 

 somewhere between 38° and 40°, motion ceases. Thus, the 

 optimum temperature for the activities of the protoplasm lies 

 at about 30° C, and the maximum temperature is perhaps 10° 

 higher. 



The experiments upon plant protoplasm, amreboid organisms, 

 and ciliated cells thus agree in demotistratiug a close relation be- 



so 



70 



60 



60 



40 



30 



20 



10 





70 



00 



50 



30 



20 



10 



0' 



10 



30 



40 



50 



Fig. 70. — A set ol curves having the same meaning as those of Fig. 69. In this case, 

 however, the temperature first falls and then rises, instead of rising first and then 

 falling. (From Engelmann, '77.) 



tween temperature and protoplasmic movement. This relation 

 is such that, as the temperature is elevated above the freezing 

 point of water, the movements regularly increase, and reach 

 their greatest activity at about the temperature of slow-running 

 waters in the midst of summer, namely, about 25° to 30° C* 



* The maximum temperature attained by bodies of ordinary water inhabited 

 by organisms seems to be close to the position of the optimum temperature of 

 organisms. Yet, temperature data concerning the waters from which the organ- 



