658 



ENDOMIXIS 



did not occur in their material. None have been observed by other in- 

 vestigators studying what they interpret as endomixis in various species. 

 As already stated, none were found by Diller in endomixis in Trichodina. 

 Certainly none occur in Paraclevelandia simplex, according to the clear- 



Figure 163. 1, Autogamy, Woodruff race (gamete nuclei in contact in the paroral 

 cone at the right; five or six degenerating nuclei are visible; macronucleus in skein); 

 2, autogamy, Woodruff race (synkaryon formation; gamete nuclei enclosed within a 

 common membrane; paroral cone; no degenerating micronuclei visible; macronucleus in 

 skein) ; 3, autogamy, isolation, Philadelphia race (synkaryon, in paroral cone, in meta- 

 phase of first division; no degenerating micronuclei seen; macronuclear skein frag- 

 menting; a number of macronuclear bodies of various stages of degeneration present in 

 the cell). Animals 1 and 2 are from mass cultures. (From Diller, 1936.) 



cut description of Kidder (1938). So from the latter account alone it is 

 evident that endomictic phenomena actually do occur. Synkaryon forma- 

 tion is not a necessary antecedent to the formation of a macronuclear 

 primordium (Figs. 162, 163). 



But confining attention to Paramecium aurelia, the fact must be 

 emphasized that almost the entire picture, and not merely the crucial 

 detail of the presence or absence of a synkaryon, differs in the endomixis 

 of Woodruff and Erdmann and the autogamy of Diller. In endomixis, 



