PARAMECIUM OF CLASS INFUSORIA 



99 



disintegrates, and the micronuclei undergo two divisions which pro- 

 duce a total of eight. Six of these disappear, and then the cell 

 divides; one of the remaining micronuclei goes to each. This 

 nucleus then undergoes two divisions. Two of these four become 

 macronuclei, and two remain as micronuclei. The micronuclei then 

 divide again as the entire cell divides to form daughters, each with 

 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. 



I » . . • 



B. 



* ^^^■^^- — 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. (Prom Jennings. Be- 

 havior of the Lower Ojffanisms, published by The Columbia University Press.) 



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 rencAv the vitality 

 of the individuals. In recent years, not only sexual reproduction but 

 also district sexes have been described for Paramecium.* 



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



