334 



THE INTERNAL ENVIRONMENT OF THE BODY 



Part III 



777/5 animal 

 not followeci 

 further;samQ 

 as other 



1. Two paramecia come together 



2. Micronucleua divides. Macronucleus begins to dis- 

 integrate 



3. Micronuclei divide and three of foxir disappear 



-c 4. Remaining micronucleua divides unequally 



5. Smaller micronucleua crosses into other animal 



6. Each animal with its own larger micronucleua and 

 smaller one from other animal 



7. Two micronuclei fuse 



8. Two animals separate. Each ezconjugant with 

 fusion micronucleua 



9. Fusion micronucleua divides 



10. Two micronuclei divide 



11; Four micronuclei divide 



12. Four micronuclei become nxacronuclei, three dis- 



Micronucleua divides and animal divides 



14. In each of two micro- 

 nucleus divides and ani- 

 mals divide again 



Fig. 18.2. Mating of paramecia, a complicated process by which part of the 

 substance of heredity in the male micronuclei is exchanged between the mates and 

 later distributed to their descendants. The large nuclei or macronuclei, are repre- 

 sented by black spots. They are concerned with the bodily processes, and appear 

 to take no part in conjugation and gradually disappear during it. The micronuclei 

 that are exchanged between the mates are shown by small black dots; those that 

 disappear are shown by circles. (After Jennings. Courtesy, Wolcott: Animal Bi- 

 ology, ed. 3. New York, McGraw-Hill Book Co., 1946.) 



