EUGLENA, AMOEBA, AND PARAMECIUM 



299 



two micronuclei and one macronucleus, the typical condition for 

 this species. Endomixis may occur in P. caudatum also. Endo- 

 mixis seems to have about the same effect as conjugation. 



There is still difference of opinion as to the exact function of con- 

 jugation and endomixis, but the chief result of the processes seems 

 to be the reorganization of the nuclear substance. This may allow 

 for variations in the fundamental constitution of the race. Accord- 

 ing to some authors these processes rejuvenate or renew the vitality 

 of the individuals. Very recently, not only sexual reproduction but 

 also distinct sexes have been described for Paramecium.* These 

 results are all possibilities. 



Behavior 



This animal is an active swimmer and necessarily shows ready 

 response to environmental factors. Its behavior consists of its 

 spiral course in locomotion, avoiding reactions, responses to food 





' ' . ' • ■.♦*•. 



. . .. '• 



A. 



* : ' ' ^ . : 





-• L. 



B. 



Fig. 101.— Reaction of paramecia to a drop of 0.5 per cent NaCl. A, Introduction 

 of the drop beneath the cover glass; B, four minutes later. (From Jennings, be- 

 havior of the Lower Organisms, The Columbia University Press.) 



material, contact and other minor reactions. Its reactions to stimuli 

 are somewhat similar to those described for Amoeba; however, it 



♦Sonneborn, Science News Letter, Aug. 21, 1937. 



