332 THE BIOLOGY OF STENTOR 



can and may solely support the phenotypic expressions in the 

 form and functions of the cell. Hence the old macronucleus has 

 to be destroyed though it seems to be carried along for support of 

 the cell until the new nucleus is ready to take over. We know 

 practically nothing of how the intricate machinations of the micro- 

 nuclei are guided such that some degenerate and others do not, 

 that one should form a stationary and the other a migratory 

 pronucleus, and that of the products of their union some should 

 produce the macronucleus and others remain as micronuclei. Yet 

 it can be assumed that grafting, like cutting experiments, are as 

 possible in conjugating stentors as in vegetatives ; and this presages 

 a new field of experimentation in which the manipulation of 

 conjugating animals in a variety of ways, or the grafting of con- 

 jugants to non-conjugants or to other conjugants of a different 

 stage, or the fusion of different species of stentors during conjuga- 

 tion, may provide clues toward an analysis and understanding of 

 the forces at work during the amazing performance of fertilization 

 and nuclear renewal. 



