SEX IN PROTOZOA 227 



Nuclear Reorganizaiion in Other Ciliates 



It would be reasonable to suppose that nuclear reorganization 

 comparable to that in species of Faraiiieciu'in would also be found in 

 other ciliates, and it is. Woodruff (1941) gave a review of these proc- 

 esses under the head "Endoniixis." 



One approach to this question has been to separate animals after 

 they had become associated for conjugation. Calkins (1921) acci- 

 dentally separated a pair of conjugants of U role puis mobilis soon 

 after they had come together. The individuals were isolated and 

 found to undergo nuclear reorganization. Calkins cut off the anterior 

 ends of fused pairs of this species, yet the separated animals regen- 

 erated and underwent nuclear reorganization. When the cutting was 

 done in an earlier stage, Calkins assumed that autogamy took place, 

 but when he cut off the anterior ends while the migratory nuclei were 

 passing through that region, some other explanation was presumed 

 to apply. Cutting off the anterior ends of exconjugants just after 

 separation did not interfere with completion of nuclear reorganiza- 

 tion. Ilowaisky (1926) also stated that individuals of Stylonychia 

 my tills underwent complete nuclear reorganization when forcefully 

 separated after becoming associated for conjugation. The initial con- 

 tacts between conjugants were presumed to stimulate the nuclear 

 changes. On the other hand, Moore (1924) found no nuclear reor- 

 ganization in individuals of Spathidhim spatlmla when separated soon 

 after becoming associated for conjugation. 



Nuclear reorganization in single animals in the active state has 

 been reported for a number of different ciliates. Heidenreich (1935) 

 described various patterns of reorganization in several kinds of endo- 

 zoic astomatous holotrichs during which the old macronucleus was 

 replaced by a new one from micronuclear sources. He referred to the 

 process as parthenogenesis. DaCunha and Muniz (1930) described 

 endomixis in Balantidhnn siviile, and I have seen a reorganization of 

 that type in a similar form of Balantidhivi. 



For the Hypotricha, Klee (1926) reported nuclear reorganiza- 

 tion in Eiiplotes longipes; Ivanic (1929) described nuclear changes in 

 Euplotes char 071 and E. patella, and Kay (1946) for Oxytricha bifaria. 

 Horvath (1947, 1948a,b) produced amicronucleate races of Kahlia 

 simplex either by treatment \\\x\\ ultraviolet light or by excess prod- 

 ucts of bacterial metabolism. By the first method, micronuclei were 



