372 THE BIOLOGY OF STENTOR 



as in free-living protozoa, and a total dependence which might 

 best be exemplified by the anucleate mammalian red blood cell — 

 whose fellow traveler in the blood stream, the leucocyte, is 

 relatively autonomous and practically indistinguishable from para- 

 sitic amoebas. In the cellular slime molds free-living amcebas 

 cooperate in forming multicellular fruiting bodies. What remains 

 constant throughout is self-dependence of the cell as a packaged 

 nuclear-cytoplasmic duality capable of some degree of independent 

 life. 



The further similarity between unicellular organisms and tissue 

 cells is found in the fact that the genome of protozoa is evidently 

 just as complex as that of metazoa and their tissue and germ cells. 

 Higher organisms do not have larger or longer or more numerous 

 chromosomes and hence, evidently, have not a correspondingly 

 greater number of genes, nor is the behavior of their nuclei more 

 complex. In present-day terms, this implies that the protozoan 

 nucleus contains as much "information" as the egg or tissue cell 

 (Elsasser, 1958). This uniformity suggests that the nucleus is 

 concerned first of all with the life of the individual cell, and that 

 in multicellular forms there is developed among the cells another 

 system of intercellular reactions, about which we still know 

 practically nothing, which provide the information for multi- 

 cellular differentiation. Evolution, with its teaching of the con- 

 tinuity of life, leads us to regard free-living and tissue cells as 

 basically the same, multicellular organisms arising either by the 

 adherence of products of cell division, as in the algae, or by a 

 partitioning of a multinucleated cell into a multicellular body as 

 seen in the Accela or in insects. A transcending unity of all cells, 

 not as parts but as expressing what Woodger (1929) called the cell 

 type of organization, certainly provides the most hopeful heuristic 

 principle. This does not exclude the possibility that protozoa have 

 taken this type of organization to extremes of multiple specializa- 

 tion of the cytoplasmic phase, or that we can learn as much from 

 them by contrast as by comparison with other cells. 



4. Stentor and metazoa 



Stentors elaborate themselves in only one direction, to form 

 another stentor. In this regard they are like eggs but lack the 

 multiple potentialities of embryonic cells. Repeated cleavage 



