Phylum Ciliophora [ 227 



Diller (1936) observed in P. Aurelia a different manner of replacement of nuclei, 

 by autogamy. In this process, the nuclei of a solitary cell go through the preliminaries 

 of conjugation; two haploid nuclei, sister products of one act of mitosis, unite to form 

 a zygote nucleus; and this divides in the usual manner to produce micronuclei and 

 macronuclei. Wichtermann (1939, 1940) observed that two cells, joined as in conju- 

 gation, may simultaneously undergo autogamy instead of exchanging nuclei. 



In the normal conjugation of ciliates, the gamete nuclei produced in each cell, 

 being sister products of mitosis, are genetically identical; and the zygote nuclei pro- 

 duced after interchange are also genetically identical with each other. Autogamy is 

 believed to produce diploid nuclei which are completely homozygous. Thus the sexual 

 processes of the ciliates tend strongly to limit the variability of the progeny. This is a 

 peculiar and surprising feature of the group. 



The ciliates have attracted experimental study, beyond what has already been 

 implied, of various functions, including nutrition, inheritance of acquired characters, 

 and regeneration after injury. 



Hall and his associates (1940-1945) have shown that Colpidiinn campylum and 

 Tetraphymena Geleii (the latter is in their earlier papers called Glaucoma piriformis) 

 require thiamin and probably riboflavin. Nutritional requirements, rather than such 

 an entity as vitality, are presumably responsible for the limited life of early attempted 

 pure cultures. As to minerals, the same scholars demonstrated the necessity of Ca and 

 Fe: others have demonstrated the necessity of K, Mg, and P. 



It has been observed of certain cultures in which the rate of division has been in- 

 creased by exposure to high temperature that they would continue to divide abnor- 

 mally rapidly when returned to normal temperatures. The peculiarity disappeared in 

 individuals which conjugated. By refrigeration or by application of chemicals, there 

 have been produced "monsters," individuals of abnormal structure, which have repro- 

 duced themselves through many generations, and have proved capable eventually of 

 giving rise to normal individuals. Jollos (1913) designated as Dauermodifikationen, 

 that is, enduring changes, modifications of the type described. They are actually 

 acquired characters which can be inherited within limits. It is evident that they are 

 determined by macronuclei or by cytoplasm, and that they are not in conflict with 

 the principle that the truly enduring heredity of nucleate organisms Hes in nuclei 

 which divide mitotically. 



Balamuth (1940) reviewed the literature of experimental mutilation of Protozoa 

 and gave a bibliography of 173 titles. Most of the experiments have been performed 

 on ciliates. The conclusions from them include these, that regeneration of parts arti- 

 ficially cut away takes place with different degrees of facility in different groups, 

 and that it is effected, if at all, by the same mechanism by which the parts are pro- 

 duced after division or excystment. The less elaborate ciliates, as Opalina and 

 Paramaecimn, are usually killed by mutilation, since this allows the fluid inner 

 cytoplasm to escape. In Stentor, injury to the crown of membranelles results in the 

 appearance of a new crown of membranelles on the side of the body, followed by its 

 migration to the injured area. In Stylonychia and Euplotes, destruction of one cirrus 

 is followed by the appearance, in a certain area of the surface, of the primordia of a 

 complete set of cirri; the original cirri are absorbed, and the new ones migrate along 

 the surface to their proper stations. The regulation of regeneration is explained, as 

 are various other phenomena, in a review by Weisz (1954). 



Micronuclei are necessary for unlimited hfe and for sexual reproduction, but not 

 for regeneration and a long period of Hfe. Schwartz kept a culture of Stentor alive 



