468 GARY N. CALKINS 



cence of the ex-con jugant nor 5\dth vitality of the series derived 

 from it. This was the case of the XZ2 series. The same is true 

 of an individual from which the anterior end is cut off during a 

 stage in conjugation when both pronuclei are present in the cut 

 individual. This was demonstrated in the case of the XV3 

 series. Here the protoplasmic connection between the con- 

 jugating individuals was perfect, but removing the other indi- 

 vidual by cutting did not prevent the normal reorganization of the 

 macronucleus and restoration of vitality, nor, probably, did 

 it prevent the union of the pronuclei which were present when 

 the cell was cut. In these two cases therefore so far as amphi- 

 mixis is concerned, the nuclear relations were the same as in 

 any normal ex-conjugant. 



Exactly the same phenomena of nuclear reorganization, re- 

 juvenescence, and cyclical changes occurred, however, in a con- 

 jugating individual which was cut while the two migrating pro- 

 nuclei were passing each other at the anterior fused ends; these 

 were removed by the operation as described above for the 

 X75 series. Here there could be no amphimixis nor, indeed, any 

 diploid number of chromosomes unless the stationary pro- 

 nucleus fused with a product of the third division of one of the 

 other micronuclei. This is a possibility, but I have no evidence 

 for or against it. Nevertheless, the regular routine of reorgani- 

 zation and rejuvenescence went on as though connection with 

 the other individual had been maintained to the end. An 

 identical history was shown by an individual from which the 

 anterior ends were cut while in the stages of the first and second 

 maturation divisions and in individuals cut while in the prophase 

 stage of the first maturation division. Removal of the proto- 

 plasm of the other individual thus has no apparent effect upon 

 the continuation of the processes of maturation once these are 

 started. 



The problem narrows down to the questions. When do these 

 processes start? and What starts them? The latter can be 

 answered only by hypothesis, but the former may be further 

 analyzed. It is conceivable that the protoplasm of an individual 

 ready to conjugate is all set, so to speak, for the succession of 



