•330 LORANDE LOSS WOODRUFF 



The recent work of Dawson^ in this laboratory, however, has 

 reopened one phase of the question. He found in an infusion 

 a race of Oxytricha hymenostonia without a micronucleus and 

 bred it successfully in pedigree cultures for several years. His 

 experiments showed that periodically the animals were in a 

 condition suggestive of conjugation, but merely abortive results 

 followed, such as 'cannibalism,' etc. In brief, Dawson's work 

 demonstrates that a morphologically differentiated micronucleus 

 is not a sine qua non for the life of the individual free-living cell 

 nor for the life of the race during reproduction by division. 

 And, further, it emphasizes the irreversibility of the transfor- 

 mation of micronucleus into macronucleus, since, in his long 

 series of experiments, during the stress, so to speak, of what must 

 be interpreted as abortive attempts to conjugate, micronuclei 

 were not forthcoming. 



More evidence indicating the sufficiency of the uninucleate 

 condition for the vegetative life of the cell has just been reported 

 by Landis and by Patten.- The former has under culture an 

 amicronucleate race of Paramecium caudatum. Furthermore, 

 he believes that this race can conjugate successfully, and if this 

 proves to be true it will raise a still more interesting question. 

 Miss Patten, of this laboratory, is studying a pedigree culture 

 of an amicronucleate race of Didinium nasutum which arose 

 from conjugating micronucleate individuals. 



The purpose of the present paper is to record the discovery 

 of other amicronucleate races, representing Oxytricha fall ax, 

 Urostyla grandis, and Paramecium caudatum. 



With regard to the technique employed, it will suffice to say 

 that it has involved the use of the several well-established 

 methods for the cytological study of the Infusoria, including 

 those used in our studies on endomixis.^ Certainly, the results 



' J. A. Dawson, An experimental stndy of an amicronucleate Oxytricha. 

 Jour. Exp. Zool., 1919, vol. 29, p. 473; 1920, vol. 30, p. 129. 



2 E. M. Landis, An amicronucleate race of Paramecium caudatum. Amer. 

 Naturalist, 1920, vol. 54, p. 453. M. W. Patten, The life-history of an amicro- 

 nucleate race of Didinium nasutum. Proc. Soc. Exp. Biol, and Med., 1921, 

 vol. 18, p. 188. 



3 L. L. Woodruff and R. Erdmann, A normal periodic reorganization process 

 without cell fusion in Paramecium. Jour. Exp. Zool., 1914, vol. 17, p. 425. 



