40 



CONJUGATION. 



separate and growth, followed by binary fission, proceeds. 

 The whole process can be illustrated thus : — 



Fig. 14.— Diagram to Illustrate Typical Conjugation. 



Each nucleus grows to 

 double its bulk. 



Each divides into two. 

 And into foar. 



Transfer of one from 

 each. 



^Cell-divisions. 



The process is not really quite so simple as here shown, for the 

 nucleus often grows to 4N and divides into eight, or it may be still 

 larger and divide still more, or only one half of the first division may 

 continue the divisions. 



The essential part to notice is that whereas, normally, there 

 is a steady alternatw?i of growth and binary fission, in the 

 first stage of conjugation the micleiis is reduced in size by at 

 least two divisions, following rapidly, before into'^nediate growth 

 can take place ; in the second stage, the normal bulk of the 

 nucleics is restored by the addition of nuclear substance from 

 another individttal. The fresh individuals produced by sub- 

 sequent binary fissions all have their nuclear material derived 

 from the two conjugating individuals. The cycle of pro- 

 tozoan individuals may be indicated thus : — 



^ Conjugation (mixture of nuclear material). 



V Series of cell-divisions. Alternation of 



growth and binary fission producing many 



unicellular individuals. 



