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PROTOZOOLOGY 



or four individuals are occasionally involved. For example, conjuga- 

 tion of three animals was observed in P. caudatum by Stein (1867), 

 Jickeli (1884), Maupas (1889) and in Blepharisma vndulans by 

 Giese (1938) and Weisz (1950). Chen (1940b, 1948) made a careful 

 study of such a conjugaion which he found in Paramecium bur- 



Fig. 88. Conjugation of three individuals in Paramecium bursaria, 

 X365 (Chen), a, late prophase of the first nuclear division (the individual 

 on right is a member of a race with "several hundred chromosomes," 

 while the other two belong to another race with "about 80 chromosomes") ; 

 b, anaphase of the third division (each individual contains 2 degenerating 

 nuclei); c, beginning of pronuclear exchange between two anterior ani- 

 mals; d, e, synkaryon formation; f, after the first division of synkaryon, 

 one daughter nucleus undergoing degeneration in all animals. 



