OENOTHERA MUTANTS WITH DIMINUTIVE CHROMOSOMES 517 
color is usually removed entirely from the linin; as a result, it is im- 
possible to detect the linin connections between the two heavily 
stained portions of the chromosome {i. e., the linin surrounding the 
unstained or clear area) and the observer is led to conclude that actual 
and complete transverse segmentation has occurred. However, if 
one examines these segments in somatic metaphase, it will be apparent, 
in the majority of cases at least, that these supposed segments lie in 
line with each other. (See figs. 7, 8, 9.) If the observer will connect 
the supposed segments with delicate side-lines and will then fill in the 
inclosed clear areas with soft crayon, he will usually find that he has 
a perfectly normal-appearing whole chromosome and that this is true 
whether the supposed segments are curved or straight. One occasion- 
ally finds these darkly stained portions entirely disconnected and out 
of line with each other (fig. 11), but there is generally plenty of evi- 
dence to show that they have been roughly torn apart by the knife 
in sectioning. Nuclear prophase chromosomes with clear areas are 
very frequently encountered (fig. 6). If such bodies are indeed whole 
chromosomes and not segments of chromosomes, then we should find 
corresponding halves of such chromosomes in anaphase, and these are 
shown in figs. 12 and 13. 
These clear areas may indicate points at which the chromatin 
matter has undergone some change whereby it becomes incapable of 
taking the stain, or of retaining it, when the section is extracted for 
chromosome study; it is also possible that these regions are empty 
spaces resulting from shrinkage of the chromatin matter following 
fixation. The fact that chromosomes are occasionally torn apart 
through this region in sectioning, is certainly indicative of weakness 
at this point. 
The above facts are related merely to show that owing to the com- 
plete extraction of stain from the linin surrounding clear areas in 
chromosomes, one may be led to conclude that a chromosome has 
actually divided transversely into two parts when it has not. How- 
ever, the writer has not attempted to prove that chromosomes never 
break apart through these regions, for it is possible that they do, in 
rare instances. 
In Oenothera, so far as I am aware, chromosomes with clear areas 
have been found in somatic tissues only. Geerts and Gates and Miss 
Thomas do not mention having observed this peculiarity in any of the 
chromosomes of the generative cells of 14 + -chromosome forms which 
