REPRODUCTION 



163 



and then each half divides again. Thus each micronucleiis gives rise to 

 four micronuclei (Fig. 132E'). Of these micronuclei, three undergo 

 degeneration, and the one remaining in each Paramecium divides again 

 into two parts, usually of unequal size (F). The smaller micronucleus 

 of each individual now passes over into the other individual {G), while 



FIRST MATURATION DIVISION OF MICRONUCLEUS 



SECOND AND THIRD 

 DIVISION OF MICRONUCLEUS 



THREE SOMATIC DIVISIONS OF rERTILlZE.D NUCLEUS 



FERTIUZATIOM 



TWO CONSECUTIVE DIVISIONS 

 GIVING FOUR NORMAL CELLS 



Fig. 132. — Diagram of the process of conjugation in Paramecium. The reference to 

 maturation in the figure will be clear only after a perusal of the section on oogenesis in 

 Chap. 16. {From Calkins, "Biology of the Protozoa.") 



the larger one is retained. The two pieces, one derived from each indi- 

 vidual, now fuse to make the fusion micronucleus {H). During these 

 stages of the process the macronucleus has been undergoing fragmentation 

 and sooner or later its parts degenerate completely. Soon after the 

 exchange of micronuclei the individuals separate and the process of 



