zyme systems. If what is accomplished in a cell and where it is accom- 

 plished are beginning to be understood, albeit vaguely, we are still almost 

 completely in the dark concerning both the evolutionary development 

 of the system and the mechanism of control. The cytologist tends to 

 look with some suspicion on the "ameba to man" notion of increasing 

 complexity, since the single-cell organism appears in most instances to 

 be at least as "sophisticated" in function and structure as any individual 

 cell in a multicellular organism. 



The Role of Cytology 



If the cell theory in modern dress has any validity, many problems 

 of biological operation may approach satisfactory solution only when 

 more is known of cellular function. Some of the areas in which cytology 

 plays an important and even dominant role are outlined below: 



Genetics 



Even a casual scrutiny of a textbook of genetics wiU disclose some- 

 thing of the debt which modern genetics owes to cytology. The theory, 

 supported by overwhelming evidence, that the chromosome is essentially 

 a linear organization of genetic material brought cytology and genetics 

 together to produce the highly fertile hybrid, cytogenetics. The bridge 

 between generations is a cell or pair of cells and this, in itself, makes 

 cytology of major concern to genetics. The formation of these important 

 cells (spores, gametes, zygotes) constitutes a series of cytological prob- 

 lems mostly, but not exclusively, associated with mitosis and meiosis. 

 The development of the asexual spore or fertilized egg into a mature 

 organism is also, in large measure, a problem at the cytological level in- 

 volving changes in cell structure and function. 



The major problem with which modern genetics is concerned is the 

 question of the mode of operation of genie material. Two aspects of 

 cytology must be considered in any attempt to answer this question: 

 namely, cellular organization at the level revealed by the electron micro- 

 scope, and the biochemical capacities of cells of various types. In studies 

 of these types, clonal lines of microorganisms and of plant and animal 

 cells in tissue culture appear to represent the most useful material. 



Medicine 



The role of cytology in medical practice and research is extensive. 

 Over a hundred years ago Rudolph Virchow contended that the cell 

 should be considered the unit of pathology as well as of structure and 

 function. Subsequent advances in both cytology and medicine have 



GENERAL REMARKS / 271 



