218 



SEX IN MICROORGANISMS 



Fig. AC. 



Variations in conjugation of Paraviechivi trichiuni, from Diller (1948), redrawn; 

 macronuclei omitted; degenerating micronuclei black: column a, the more common 

 scheme which is much like that of P. cctiidatimi, with occasional degeneration of one 

 nucleus after pregametic division, shown in 2 and 3, right; column b, similar to 

 a, but with autogamy instead of cross fertilization; column c, third pregametic 

 division omitted; column d, like c with autogamy; column e, like d for 1 and 2, 

 but with single nucleus in each conjugant after second division— these pass to mates 

 to develop parthenogenetically; column f, like e but with parthcnogenetic develop- 

 ment without passage to mate. 



