THE EVOLUTION OF SEX 



II 



ffl 



FIG. 3. The nu:-lei of two individuals of paramcecium 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. 



