230 



At its inception, cytology was a dis- 

 tinct science which showed relatively 

 little relationship to other sciences. Cy- 

 tologists did not need to master the 

 techniques of other sciences, nor were 

 these sciences in turn concerned with 

 the findings of cytology. In only one 

 direction was cytology a science which 

 involved more than one discipline. It 

 was equally a botanical and a zoological 

 field. Plant and animal cytologists had 

 much more in common than either of 

 them had with other branches of 

 botany or zoolog}'. Except for this one 

 relationship, however, cytology re- 

 mained a science apart for some 

 decades. 



The position of cytology changed, 

 however, as it began to feel the need 

 for techniques from the other sciences 

 to supplement its own, and as other 

 sciences began to discover that the 

 solution of their own problems required 

 going back to protoplasm itself, where 

 alone the answers to the really funda- 

 mental questions are to be found. On 

 the one hand, cytologists began to uti- 

 lize for their own purposes the tech- 

 niques of genetics, biochemistry, and 

 histochemistr)'. On the other hand, 

 they found themselves helping to fur- 

 nish the answers to the questions the 

 geneticists, the biochemists, the taxono- 

 mists, and the evolutionists were rais- 

 ing. Cytology rather suddenly became, 

 therefore, an experimental, as well as 

 an observational science, and it became 

 a fundamental contributor to, if not an 

 integral part of, other important 

 branches of biology. 



This transformation of the science 

 of cytology began at the turn of the 

 century with the rediscovery of Men- 

 del's work. This discovery marked the 

 birth of the science of genetics and im- 

 mediately this new science found a 

 use for cytology. When Mendel's work 

 was finally brought to light in 1900, 

 cytological analyses had reached a 

 point where the parallelism between 



CYTOLOGY ; 



<i 

 chromosome behavior and gene be- ' 

 havior could be appreciated. It was 

 Sutton who was the first to make this 

 parallelism clear and to show convinc- 

 ingly that hereditary determiners are 

 distributed among the chromosomes 

 and carried bv them. From this time 

 on, cytology became a handmaiden of 

 genetics, and its importance to genet- I 

 ics soon became so apparent that the 

 two sciences became to a considerable j 

 extent fused into the new synthetic " 

 science of cytogenetics. 



As a result of these developments, 

 cytologists can no longer confine their 

 interests and competencies to the kill- 

 ing, sectioning, staining and observing 

 of cell structures. And he must in ad- 

 dition become almost inevitablv a 

 biochemist and preferably a biphysi- 

 cist as well, for many of the most in- 

 triguing problems of cytology now have 

 to do with the identification and analy- 

 sis of key chemical compounds in the 

 cell and the roles which these specific 

 compounds or classes of compounds 

 play in heredity and other cellular ac- 

 tivities. 



Again, cytology has proved in re- 

 cent years to be of marked use in the 

 solution of the problems of taxonomy 

 and evolution. Much can be learned 

 regarding the relations between species 

 or races by a comparative study of 

 chromosomes, with respect either to 

 their numbers or their structures. It has 

 been discovered that evolutionary de- 

 velopment often involves alterations 

 in chromosome number or structure, 

 so that analysis of these cvtological 

 characteristics ma\- shed important 

 light on evolutionary history and on 

 species relationships. 



In still another direction, c\tology 

 has proved to be of fundamental im- 

 portance, namclv in the solution of 

 physiological problems. Physiology has 

 become increasingly concerned with 

 something more than the functions of 

 tissues and organs, the behavior of or- 



