70 



ELEMENTS OF BIOLOGY 



MACRONUCLEUS 

 MICRONUCLEUS 





ID. 



DIVISION OF EACH 

 MICRONUCLEUS 



INTERCHANGE OF 

 MICRONUCLEI 



FUSION OF MICRO- 

 NUCLEI 



SEPARATION OF 

 CONJUGANTS 



a I RISEOFNEW 

 ^ MACRO NUCLEI 



mal into daughters, each with a 

 portion of both macro- and micro- 

 nucleus. The oral groove now re- 

 appears in each of the daughter 

 paramoecia, which are now in form 

 identical with the original parent. 

 The protoplasm of the animal, 

 which before the division may be 

 regarded as old, has by reason of 

 the changes that occur during divi- 

 sion become the protoplasm of 

 young animals. The restoration of 

 the properties of young protoplasm 

 to protoplasm which has become 

 aged is called rejuvenescence. 



Conjugation. The paramoecium 

 is apparently capable of continuing 

 to divide in this fashion indefinitely 

 so long as the conditions in which 

 it lives are suitable. However, more 

 often the rate of division slows 

 down after a time and is restored 

 after an interchange of nuclear ma- 

 terial between two individuals takes 

 place, a process that is essentially 

 sexual and undoubtedly is compa- 

 rable to the fertilization process in 

 higher animals. This process is 

 called AMPHIMIXIS. It is effected as 



Fig. 21. — Scheme representing the con- 

 jugation of two paramoecia. Note the dis- 

 appearance of the macronuclei, the repeated 

 divisions of the micronuclei, and the inter- 

 change of micronuclei. 



