the fusion of two nuclei, one of which was derived from the male and the 

 other from the female parent. This finding was confirmed and extended 

 in application to both plants and animals by a number of workers, in- 

 cluding the great German botanist, Strasburger. This finding, more than 

 anything else, pointed to the importance of the nucleus in heredity. The 

 second development, generally credited to Edouard van Beneden, was 

 the demonstration that gametic nuclei contained half the number of 

 chromosomes of the zygote, from which it could be concluded that 

 gametogenesis involved some type of reduction division in which mater- 

 nal and paternal chromosomes segregated. The significance of these 

 findings were realized by Weismann and led directly to development of 

 the Chromosome Theory of Heredity which was further established by 

 many workers including especially Boveri and Sutton. Elucidation of 

 the process of meiosis, which was a necessary prelude to cytogenetics, 

 proved a somewhat more difficult problem but by 1903 the main features 

 had been described by Flemming, van Beneden, Boveri, Montgomery, 

 and Sutton. 



The extranuclear aspects of cytology lagged far behind nuclear studies 

 and, indeed, have only recently received major attention. A number of 

 workers in the late 1800's including Heitzmann, Klein, Flemming, and 

 Biitschli described a vacuolar or reticular texture which may be con- 

 sidered as representing the modern submicroscopic reticulum even 

 though the originally described network was probably a fixation artefact. 

 Various inclusions such as plastids, mitochondria, and the Golgi complex 

 were recognized and studied in some detail by a number of workers 

 before 1900. Meyer, de Vries, and Meves discussed questions of origin 

 and function of plastids; Benda used methods of differential staining to 

 reveal mitochondria; Kingsbury (1912) was the first to suggest that the 

 mitochondria function in cellular respiration though this activity was not 

 clearly proven until 1934 when Bensley and Hoerr separated them from 

 live tissue; the Golgi complex discovered by C. Golgi in 1898 in nerve 

 cells was later found to be present in many kinds of animal cells but its 

 significance is still somewhat obscure. Finer inclusions named "micro- 

 somes" by Hanstein in 1882 were studied in detail by Altmann over a 

 period of years but there is considerable doubt that even the finer of 

 Altmann's granules represent the microsomal portion of the modern 

 biochemical cytologist. 



Before a science is properly established as such, it must have ( 1 ) one 

 or more basic concepts, (2) a body of observational and experimental 

 data, and (3) a series of working hypotheses. By the turn of the century, 



4 / CHAPTER 1 



