34 ROBERT T. HANCE. 



matic cells of the evening primrose, CEnothera scintillans, de 

 Vries, and of the pig, Sus scrofa, in which the diploid chromosome 

 number of the soma was found to be variable. The bearing of 

 these facts upon the individuality theory is indicated. 



THE CYTOLOGICAL CONDITIONS IN CEnothera scintillans. 



The somatic, or diploid, number of chromosomes in CEnothera 

 scintillans is fifteen. In material collected from three generations 

 of these plants variations of this number have been found to 

 range from fifteen to twenty-one. This diversity in number is 

 not due to additions to the chromosome complex but to the frag- 

 mentation of certain individuals. From a preliminary study of 

 the root tips of a fourth generation of O. scintillans I am inclined 

 to believe that here the increase in chromosome number is not 

 as great as just indicated. Breaks or clear areas occur in certain 

 chromosomes which make what may be a single chromosome, 

 appear as two. In my earlier material the possible relationship 

 of chromosome portions on either side of the clear space was not 

 so obvious as in the latest specimens. The last root tips col- 

 lected present these portions in such perfect alignment as to 

 suggest that they are a part of a common body. The clear areas 

 are variable in extent and in certain cases one portion of the 

 chromosome may be turned at right angles to the other. In a 

 few instances the separation seems to be complete. The blank 

 spaces in these "hyphenated" chromosomes may well be weak 

 spots where under certain conditions breaks occur. As I have 

 not yet determined the nature of these clear intervals in the chro- 

 mosomes, for the sake of analysis, in this paper, all the separate 

 chromatic bodies are considered as individual chromosomes. 



Since the chromosomes are small and have no marked charac- 

 teristics by which they may be recognized, measurements have 

 to be resorted to. Some interesting results have been the out- 

 come. 



1 . The total of the chromosome lengths of any complex whether 

 it has the normal or higher number of chromosomes is the same. 

 This indicated that no chromosomes have been added. 



2. When the fifteen chromosomes of the normal complex are 

 arranged according to decreasing length it is found that they 



