REPRODUCTION 



163 



Diller (1936) observed in solitary Paramecium aurelia (Fig. 81), 

 certain micronuclear changes similar to those which occur in 

 conjugating individuals. The two micronuclei divide twice, form- 

 ing eight nuclei (a-d), some of which divide for the third time (e), 

 producing two functional and several degenerating nuclei (/). The 

 two functional nuclei then fuse in the "paroral cone" and form the 



Fig. 81. Diagram illustrating autogamy in Paramecium aurelia (Diller). 

 a, normal animal; b, first micronuclear division; c, second micronuclear 

 division; d, individual with 8 micronuclei and macronucleus preparing for 

 skein formation; e, two micronuclei dividing for the third time; f, two 

 gamete-nuclei formed by the third division in the paroral cone; g, fusion 

 of the nuclei, producing synkaryon; h, i, first and second division of 

 synkaryon; j, with 4 nuclei, 2 becoming macronuclei and the other 2 re- 

 maining as micronuclei; k, macronuclei developing, micronuclei dividing; 

 1, one of the daughter individuals produced by fission. 



synkaryon {g, h) which divides twice into four {i, j). The original 

 macronucleus undergoes fragmentation and becomes absorbed in the 

 cytoplasm. Of the four micronuclei, two transform into the new 

 macronuclei and two remain as micronuclei (k) each dividing into 

 two after the body divided into two (l). 



Another sexual process appears to have been observed by Diller 

 (1934) in conjugating Paramecium trichium in which there was 

 no nuclear exchange between the two conjugants. Wichterman 

 (1939, 1940) observed a similar process in P. caudatum and named it 

 cytogamy. Two small (about 200m long) individuals of P. caudatum 



