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, zormally, there 
ts a steady alternation of growth and binary fisston, in the 
first stage of conjugation the nucleus ts reduced in size by at 
least two divisions, following rapidly, before intermediate growth 
can take place; in the second stage, the zormal bulk of the 
nucleus ts restored by the addition of nuclear substance from 
another individual. 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). 
Series of cell-divisions. Alternation of 
growth and binary fission producing many 
unicellular individuals. 
