CHROMOSOMAL VESICLES AND THE STRUCTURE OF 

 THE RESTING NUCLEUS IN PHASEOLUS. 



J. McA. KATER, 

 ST. Louis UNIVERSITY SCHOOL OF MEDICINE. 



In 1885 Rabl formulated a theory which is essentially our 

 modern theory of continuity of chromosomes. Since that time 

 cytologists and geneticists have very thoroughly discussed this 

 problem, with its bearing on our conception of the structure of 

 the nucleus and the related problems of genetics. Unfortunately, 

 even at the present time, a large part of the evidence for the 

 individuality of chromosomes is purely inferential; consequently 

 the subject still rests on a rather hypothetical basis. Only in 

 one case have the chromosomal vesicles with clear outlines been 

 traced through the resting nucleus and in this instance the condi- 

 tions were such that the observations cannot be applied to 

 other forms with any degree of safety (Richards, 1917). Other 

 workers have identified chromophilic bands in the resting nucleus 

 as chromosomes, but the outlines of the vesicles were not visible 

 (Sharp, 1914; Wenrich, 1916). In addition to the above isolated 

 cases a great deal of strong inferential evidence for the indi- 

 viduality of chromosomes has been accumulated (Boveri, Conklin, 



etc.). 



While engaged in studying the cytological changes accompany- 

 ing the ripening and germination of the seeds of the common 

 bean, Phaseolus vulgaris, a number of observations were made 

 which indicated that Phaseolus affords favorable material for 

 studying the reconstruction of daughter nuclei and interpreting 

 their resting structure. This material was even more promising 

 because of the fact that the resting nucleus of Phaseolus is quite 

 similar to that of some other plants. 



I wish to express my gratitude to Mr. G. T. Kline, artist, St. 

 Louis University School of Medicine, for his skillful preparation 

 of the plates, and to Professor Albert Kuntz for kindly reading 

 the manuscript. 



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