cytology was well equipped with regard to these requirements. The basic 

 concept, of course, was the notion that the cell represented the unit of 

 structure, function, and reproduction. 



In 1865, Gregor Mendel published a paper in which he described the 

 results of certain crosses involving garden peas. He found that the con- 

 trasting characters with which he was concerned were distributed among 

 the offspring according to a rather simple and precise mathematical for- 

 mulation. For some thirty-five years few people were aware of this work, 

 but in 1901 several outstanding biologists including Correns, deVries, 

 and von Tschermak discovered and publicized Mendel's work. Thus the 

 modern science of genetics became established with the basic concept 

 that hereditary characters (more precisely potentialities) were deter- 

 mined by specific factors, later called genes, which were transmitted 

 from parent to offspring through the gametes. The parallels between the 

 deduced behavior of the genes and the observed behavior of the chromo- 

 somes made it inevitable that the geneticist would, in due course, accept 

 the chromosome as the carrier of the genes — or, in other words, accept 

 some version of Weismann's chromosome theory of heredity. The first 

 half of the twentieth century has found the majority of trained cytologists 

 concerned with the relationship between chromosome behavior and 

 genetic effect. This has been to the distinct advantage of genetics, but 

 probably at the cost of advance in fundamental knowledge of the cell. 

 This overshadowing of cytology by genetics presumably accounts for our 

 very considerable ignorance of many of the fundamental structures and 

 functions of the cell. 



Prior to the middle forties, the approach to cytology tended to be 

 largely descriptive and qualitative and the term "cytologist" was generally 

 restricted to those workers primarily concerned with the nucleus and 

 even more specifically to those interested in questions of general struc- 

 ture and behavior of chromosomes. In recent years, however, the ap- 

 proach to cytological problems has been not only far more dynamic and 

 quantitative but also more in terms of the whole cell. Such changes in 

 attitude and outlook are evolutionary rather than revolutionary. The 

 history of cytology begins with the cell as a unit; continues with a study 

 of its parts; and ultimately returns to the cell as reflecting the integration 

 of its parts. The considerable progress of the past few years in cytology 

 seems to have resulted partly from refusion of the several branches of 

 cellular biology and partly from the development of new techniques for 

 examination of cellular structure and processes. In a later chapter several 

 of the techniques and types of equipment, widely used in modern studies 



THE CELL CONCEPT / 5 



