REPRODUCTION 



155 



the Microsporidia, autogamy initiates the spore-formation at the 

 end of schizogonie activity of individuals as in Thelohania legeri 

 (Fig. 68). 



Recently Diller (1936) observed in solitary Paramecium aurelia 

 (Fig. 77), certain micronuclear changes similar to those which 

 occur in conjugating individuals. The two micronuclei divide 

 twice, forming eight nuclei, some of which divide for the third 

 time, producing two functional and several degenerating nuclei. 

 The two functional nuclei then fuse in the "preoral cone" and 



Fig. 77. Diagram illustrating autogamy in Paramecium aurelia 

 (Diller). a, normal animal; b, first micronuclear division; c, second 

 micronuclear division; d, individual with 8 micronuclei and a macro- 

 nucleus preparing for skein formation; e, some micronuclei dividing 

 for the third time, with two functional nuclei near 'preoral cone'; f, 

 two gamete-nuclei formed by the third division in the 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 

 remaining as micronuclei; k, macronuclei developing, micronuclei 

 dividing; 1, one of the daughter individuals produced by fission. 



form the synkaryon which divides twice into four. 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, each dividing 

 into two after the body divides into two. Diller is "inclined 



