86 
R. Ruggles Gates. 
2*6 units, but since the chromosomes of the germ cells are shorter 
and stouter than in the somatic cells this difference cannot be 
directly compared with the length of the odd chromosome. Hance 
also concludes that there is no evidence of pairing of the somatic 
chromosomes. In this we cannot agree, as we believe that in 
other CEnothera forms the pairing, though weak, is sufficiently 
indicated in certain cases so that the extra or unpaired chromosome 
may sometimes be directly determined by this method (see Gates 
and Thomas 1914, pi. 35, Figs. 5, 6, 7, 10, 11, 15). Again, we have 
not found that accurate drawings of the chromosomes will show 
them to be of uniform width with even margin throughout, as 
Hance’s figures would indicate, although the departure from 
uniformity in width is not. as a rule, great. 
Coming now to the question of chromosome number in somatic 
tissues, it would seem at first impossible to reconcile the 
apparently contradictory results of Hance and Miss Lutz. A 
critical study has been made of the process of chromosome 
fragmentation in somatic tissues, although only incidental 
references to this work have been published. 1 We believe Hance 
has over estimated the significance of these somatic segmentations. 
We observed numerous “ clear areas ” and constricted portions of 
chromosomes, but the segments were almost invariably in 
alignment, showing clearly which belonged to the same 
chromosome. Moreover, delicate linin connections are usually 
visible connecting the two segments. Miss Lutz (1916) has made 
similar observations. Constrictions or incomplete segmentations 
have also been studied in Vicia Faba by Fraser and Snell (1911) and 
Sakamura (1915). In nearly all such cases it is clear which portions 
make up a given chromosome, and so it is much more sound to 
treat them as a whole chromosome than to attempt to rearrange 
these “ fragments ” on a hypothetical basis from measurements. 
Formerly we observed no segmentation of chromosomes in 
prophase nuclei, but more recently the writer has observed 
several cases of fragmentation in prophase. Nevertheless, we are 
inclined to look upon the phenomenon as a temporary one, related 
only to the mitotic cycle, and the segmentations in the prophase of 
one mitosis as probably bearing no relation to those of the next to 
follow. The name “ extra ” or “ supernumerary ” chromosomes 
applied by Hance to these segments is not a suitable one, for the 
actual number of whole chromosomes can be determined without 
difficulty by observation, as Hance himself has done in (E. scintillans 
1 Gates and Thomas 1914, 
