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THE AMERICAN NATURALIST [Vol. LIV 



In addition to these characters there are also certain other 

 morphological characters which distinguish the race. The ami- 

 cronucleate race is larger than the wild ones so far observed. 

 The curve of the buccal groove is slightly greater than that of 

 the micronucleate animals. The posterior tip is slightly bent 

 toward the aboral side and the buccal groove itself is shal- 

 lower since the sides of the groove are bent outward. All evi- 

 dences so far indicate that the amicronucleate race has the poten- 

 tiality of forming from three to seven contractile vacuoles. 



Attempts have been made by the writer to induce conjugation. 

 A nourishing culture has been allowed to evaporate to half vol- 

 ume and small mass cultures have been submitted to various 

 experimental conditions but so far the writer has been unable 

 to induce conjugation in this race. Hance (2), however, in- 

 duced conjugation in the multivacuolate race by the method first 

 mentioned. Amicronucleate animals in conjugation are to be 

 found on the slides (made before Hance 's discovery of the extra 

 vacuoles) mentioned above. Hence the race has conjugated in 

 the past and attempts will be made to induce conjugation in the 



The main question in the future study of this race will be the 

 cytology of the conjugation process. This will require exper- 

 imental work on methods of inducing conjugation in the race 

 and the study of the conjugants so obtained. The effect, if any, 

 of the absence of the micronucleus on the division process will 

 also be observed. 



The maintenance of pure lines and the study of the nuclear 

 changes which proceed in ordinary vegetative existence will also 

 be an important part of the future work. If there is a process 

 of endomixis the same means will provide a basis for the study 

 of that phase. 



These two matters are the most interesting from the stand- 

 point of cytology, especially since the work of Calkins and Cull 

 (3) on conjugation, and Erdmann and Woodruff (4) on endo- 

 mixis, in Paramecium caudatum show that the active body is the 

 micronucleus and that the macronucleus breaks down and dis- 

 appears in both processes. 



Is the macronucleus affected by different cultural conditions 

 in any definite way and how does the behavior of the nuclei of 

 the micronucleate race compare with the behavior of the macro- 

 nucleus in the newly discovered race? The preliminary work 

 done so far indicates that there is a definite relation between 



