2 THE BIOLOGY OF STENTOR 



several species, including the commonest, the cortical pattern is 

 conveniently outlined by a series of pigmented stripes so that the 

 organization of individualities and the identification of local areas 

 and grafted patches is quite evident in the living material. This 

 offers many advantages. With cells and patches self-marked, 

 operations can be guided and specified, and the whole range of 

 classical grafting experiments and transplantations can be ex- 

 tended to the cell level of organization. Fixing and staining are not 

 required to follow the performance of grafts so that experiments 

 proceed rapidly and can be done in sufficient number for valid 

 conclusions. Complex, specific, asymmetric elaborations of form 

 increase the number of responses to alteration of the system which 

 we can observe and measure, and render Stentor highly relevant 

 to the great unsolved problem of organic form. A cytoarchitecture 

 which has repeatedly been postulated as necessary to explain the 

 orderly development of eggs is visibly displayed in stentors and 

 does in fact play a cardinal role in their morphogenesis. 



Different species of Stentor can be grafted together almost as 

 readily as cells and cell parts of one species. The cytoplasms and 

 nuclei of two or even more species can be combined in any desired 

 proportions, and this is a new method of ''transduction" by 

 which not only different genetic material may be added to a cell 

 but also alien cytoplasm. These chimeras persist and do not fall 

 apart, cytoplasms mingle and nuclei are maintained at least for a 

 considerable time in foreign cytoplasm on which they often exert 

 a visible influence. 



The macronucleus, which alone is significant in the vegetative 

 life of stentors, is clearly visible in the living animal. Enucleations 

 are not difficult. Stentors therefore provide additional examples 

 in which the contribution of the nucleus may be assessed by 

 determining the consequences of its absence. The more types of 

 cell in which this operation is possible the more likely we are to 

 come to general conclusions. Moreover, the extended form of the 

 nucleus in Stentor allows us to remove all or only a desired portion 

 of it. Such quantitative operations, when combined with additions 

 of enucleated or highly nucleated cytoplasmic masses vary the 

 ratio of nucleus to cytoplasm in extremes not heretofore possible. 

 Interesting consequences of this imbalance are evident in stentors. 



The same properties which permit grafting also make possible 



