SEX IN PROTOZOA 223 



authors ciupliusi/cd the absence of any process of syngainy in "endo- 

 niixis." In rlie same \ ear llerrwig (1914) described a process of 

 nuclear reorLiani/.arit)n in this species w hicli he called parthenogenesis. 



"Endoniixis" has also been described for VavLrincciu'in Ctrudatuvi, 

 first very incompletely by Erdmann and Woodrutf (1916) and more 

 fully by Che j fee (1930) (Fig. AE, 13 to 22). According to Che j fee 

 the macronucleus begins to fragment while two micronuclear divi- 

 sions produce four small nuclei (13 to 16). Three of these degen- 

 erate while the fourth undergoes division (17, 18). After a second 

 micronuclear division (19) two nuclei become anlagen and the other 

 two remain as micronuclei (20). One cell division distributes one of 

 each type of nucleus to each of the two daughters (21, 22). The 

 similarity of the micronuclear behavior in the earlier stages to that in 

 conjugation is striking, and if a process of nuclear fusion should have 

 been overlooked this might prove to be autogamy. 



Erdmann's (1925) account of "endomixis" in P. Inirsaria is very 

 incomplete, and apparently such a process is very rare in that species. 

 Stranghoner (1932) described "endomixis" in P. miiltmiicromiclea- 

 tinn involving eight to ten generations. Again the nuclear history is 

 similar to that of conjugation, especially in the earlier stages. "Endo- 

 mixis" has been reported to occur in Faramecium polycaryum by 

 \\'oodruff and Spencer (1923) and in F. nephridiatimt by Gelei 

 (1938), but without details. 



Autogamy 



Diller announced the discovery of autogamy in Paramecium 

 awelia in 1934 and gave a full account of it in 1936 (Fig. AE, 1 to 

 12). This process occurs in single individuals and parallels the events 

 described as "endomixis" by Woodruff and Erdmann (1914), except 

 that a crescent stage develops in preparation for the first pregametic 

 micronuclear division (2), and fusion of gamete nuclei takes place. 

 After the second micronuclear division (3), most of the micronuclei 

 degenerate, while a third division (5) produces two pronuclei (6) 

 which unite (7) in self-fertilization or autogamy. Meanwhile the 

 macronucleus passes through a series of skein stages (4 to 8) before 

 fragmenting into small pieces (8 to 10). Pronuclear fusion takes place 

 in the paroral cone which forms at the place where exchange of 

 pronuclei occurs in conjugation. From the syncaryon (8), four nu- 

 clei are produced by two divisions (9, 10). Two of the four grow 

 into anlagen (11), and a single cell division (12), accompanied by 



