Spathidium spathula. 



341 



162 (1909) 



Endomixis and encystment in Spathidium spathula. 



By E. LUCILE MOORE (by invitation). 



[From the 0 shorn Zoological Laboratory, Yale University, New 



Haven, Conn.] 



In a pedigree culture of Spathidium spathula there has been 

 no indication of endomixis at any time during active vegetative 

 life, and experiments were undertaken to determine the possi- 

 bility of inducing an independent reorganization process in con- 

 jugating individuals by preventing nuclear interchange. Since 

 conjugation in this race produces a significant increase in the divi- 

 sion rate of the majority of exconjugant lines, 1 it was expected 

 that a similar physiological effect would follow endomixis. Pairs 

 in an early stage of fusion were separated by spurting from a 

 pipette, and the division rates of lines derived from such split- 

 conjugants were compared with those of normal exconjugant and 

 non-con jugant lines. 



Of seventeen exconjugant lines, thirteen produced an average 

 -of 7-3 generations more than the parent lines during the first fifteen 

 days. Of thirty-nine split-conjugant lines, however, all but four 

 produced essentially the same number of generations as the parent 

 lines, indicating, apparently, that endomixis had not occurred. 

 Additional evidence further supported this view. 



Endomixis, however, has been observed in this race during 

 encystment. Cytological study of encysted individuals at various 

 stages in the process has revealed the fragmentation and resorp- 

 tion of macronuclear material, the persistence of micronuclei, 

 and the formation of macronuclear anlagen. The physiological 

 significance of endomixis during encystment has not been deter- 

 mined. 



The complete paper will appear in the Journal of Experimen- 

 tal Zoology. 



1 L. L. Woodruff and Hope Spencer, Proc. Soc Exp. Biol, and Med., 192 1, 

 xviii, 240. 



