CHAPTER VII. 

 VITALITY. 



A normal active protozoon is a bit of protoplasm in which the 

 vital activities are perfectly balanced, correlated and coordinated 

 in response to internal and external stimuli. If the physiological 

 balance is disturbed by abnormal activity or inactivity in one or 

 other function the result is evident in the general vitality of the 

 organism. The organization, however, is not rigidly fixed and 

 undergoes adaptive changes in response to the new T conditions until 

 activities are again coordinated. The Protozoa thus agree with all 

 protoplasm in having the power of adaptation or ability of the pro- 

 toplasmic substances to react within limits to unusual stimuli in 

 such a way as to maintain perfect correlation and coordination under 

 the new conditions. 



An interesting case of orderly response to unusual conditions 

 was the fusion of two conjugating individuals of Uroleptus mobilis 

 (Calkins, 1924). Instead of separating at the end of twenty-four 

 to twenty-six hours as in ordinary conjugation, these two individu- 

 als remained attached for six days during which time the usual 

 reorganization processes occurred in each. On the seventh day they 

 fused along the entire ventral side, forming a bilaterally symmetrical 

 individual with two oppositely placed mouths and peristomes, two 

 contractile vacuoles and two independent sets of macro- and micro- 

 nuclei (Fig. 127). On the eighth day this remarkable creature 

 divided three times, giving eight double individuals all similar to 

 the original bilaterally symmetrical one from which they came. 

 They continued to divide at the rate of approximately one division 

 per day on the average for a period of four hundred and five days 

 and through three hundred and sixty-seven divisions. The interest- 

 ing fact here is the correlation of two distinct sets of structures and 

 functions so as to act harmoniously and synchronously as one indi- 

 vidual, and the setting up of an entirely new organization. Had 

 the two individuals separated as in normal conjugation their meta- 

 bolic processes would not have been synchronous, the periods of 

 division would have been more or less similar but not identical. In 

 the double individuals the two sets of eight macronuclei behaved 

 differently in different individuals. In one case each set would fuse 

 prior to division to form a single ellipsoidal macronucleus (Fig. 128), 

 behaving thus like tw 7 o normal individuals when ready to divide 



