THE EVOLUTION OF SEX 



I 



in 



E 



Fig. 3. — The nu lei of two individuals of paramoecium in I (homozygous 

 in certain factors, and heterozygous in other factors), are represented as divid- 

 ing twice (in II and III); the first division, II, is represented as reducing, 

 i.e. segregation occurs ; the second division, III, is represented as equational, 

 i.e. no reduction but division of factors, as in the next or conjugation division, 

 IV, also. 



