Fig. Z. Diagrammatic outline of conjugation in Paraiuechan caudatwn, 



original. 



1, pair of conjugants become attached along oral region; 2, first pregametic micro- 

 nuclear division; 3, second pregametic division; 4, degeneration of three products of 

 second division, fourth product dividing to form pronuclei, migratory pronuclei in 

 paroral cone; 5, passage of migratory pronuclei to other conjugant; 6, fusion of 

 pronuclei to form svncarya; 7, separation of conjugants, division of syncarya, begin- 

 ning of resolution of macronuclei; 8 second postzygotic nuclear division, early 

 skein stage of macronuclei; 9, third postzygotic nuclear division, late skein stage 

 of macronuclei; 10, in each exconjugant four products of syncaryon become macro- 

 nuclear anlagen, degeneration of three products, persistence of eighth product as 

 functional micronucleus; 11, first postconjugation cell division, two anlagen going 

 to each daughter; 12, second postconjugation division, each cell has a new macronu- 

 clcus and a new micronucleus derived from the syncaryon. 



211 



