5i6 
ANNE M. LUTZ 
chromosome which had pulled apart in the middle. It is even con- 
ceivable that the slender body of 0. aberrans may have been merely a 
remnant of a trail of chromatin matter or a remnant of one of the very 
interesting "half-chromosomes" which they describe — the half of a 
chromosome which has separated from its mate on the heterotypic, 
instead of the homotypic, spindle, and which the authors believe 
degenerate later, in many cases. The small body in de Vries's rubri- 
nervis may have been merely a piece, which by some process had 
become detached from one of the long chromosomes. This raises 
the question. Have we any evidence to indicate that pieces sometimes 
become detached from chromosomes? 
Gates and Miss Thomas state (p. 537) that several cases were 
found in one of nine 15-chromosome plants having lata or semilata 
characters "in which the somatic chromosomes at metaphase were 
more or less completely divided transversely into two." They refer 
to Agar's studies of this phenomenon in Lepidosiren in which it was 
found that the chromatin matter only, and not the linin of the chro- 
mosomes, segmented. Their assertion that certain somatic chromo- 
somes of one of their 15-chromosome plants were "more or less com- 
pletely divided transversely into two," fails to give the reader a precise 
idea of the conditions which they observed. By "more or less com- 
pletely" do they mean that some were completely divided into separate 
parts and others only partially so? Their meaning is obscure. 
During the year spent in Professor Gregoire's laboratory especial 
attention was given to the study of these chromosomes and ample 
evidence was found to indicate that these supposed segments, at 
least in the majority of cases, were merely whole chromosomes with 
clear spaces, or unstained regions. As Gates and Miss Thomas state, 
these light areas were sometimes observed near the middle, and 
sometimes nearer one end (figs. 7, 8, 9, 10). Often, also, two such 
areas were found in one chromosome, giving the body the appearance 
of having divided transversely into three parts (fig. loc). Frequently, 
clear spaces were found in two or more chromosomes of a group (fig. 9), 
but I recall no instance in which all displayed this peculiarity. In 
heavily stained material it is often possible to detect the delicate side 
lines connecting these supposed segments of chromosomes, thus proving 
that in these particular cases at least, we are dealing with whole chro- 
mosomes (figs. loa, 12, 13). In extracting the stain (iron- 
haematoxylin) from material designed for chromosome studies the 
