510 
ANNE M. LUTZ 
has thrown a flood of light upon the origin of the small chromosome in 
14+^-chromosome offspring of 15-chromosome 0. lata X 14-chromo- 
some 0. Lamar ckiana. 
Chromosome degeneration was observed by Geerts in 21 -chromo- 
some offspring of 0. lata X 0. gigas, 0. Lamarckiana X 0. gigas and 
0. gigas X 0. Lamarckiana, all from de Vries's gardens. On the 
heterotypic spindles of the individuals which he studied he found 7 
pairs of whole chromosomes and 7 which were unpaired. With the 
first division the two members of each of the 7 pairs separated and 
passed to opposite poles, while 3 of the 7 unpaired members of the 
group usually moved towards one pole and 4 towards the other. As 
the 7 chromosomes approached the pole the longitudinal split, pre- 
paratory for the second division, became quite distinct, but was less 
clear and more irregular in the 3 or 4 remaining chromosomes. Some- 
times, also, the latter failed to reach the pole and were not included 
within the daughter nucleus. Later, 7 clearly split chromosomes and 
3 or 4 small ones showing the longitudinal spHt less clearly, were 
found at the equator of each of the two homotypic spindles. Thus, 
to each of the four poles were distributed 7 distinct chromosomes and 
often a number of irrgeular chromosomes or pieces of chromosomes. 
In regard to the fate of these fragments or irregular bodies, he says 
(italics not employed in the original) : ' ' Wenn die Tetradenkerne ent- 
stehen, wird hisweilen dieses Chromatin in den Kern aufgenommen, 
aber meistens liegen ausserhalb der Kernwand auch Chromatinteilchen. 
Diese Chromatinstiicke, welche ausserhalb der Kerne zuriickgelassen 
werden, entwickeln sich oft zu Zwergkernen, in den jungen Pollen- 
kornern sowie in dem jungen Embryosacke. Beim Auswachsen des 
Embryosackes verbleichen diese Zwergkerne und verschwinden all- 
mahlich." 
From Gates and Miss Thomas (pp. 538-539) we learn that . . 
in the heterotypic mitosis in the lata and semilata forms, the 15 chro- 
mosomes are usually distributed so that 7 go to one daughter-nucleus 
and 8 to the other. In rare cases the distribution is 9 and 6. . . . 
More frequently the extra chromosome is left behind, where it may 
be seen fragmenting and degenerating in the cytoplasm." 
A remarkable irregularity in 15-chromosome 0. lata ruhricalyx is 
described by Gates and Miss Thomas (pp. 541-542) and the statements 
which follow are of particular interest in view of the fact that the Cold 
Spring Harbor and Louvain studies have demonstrated the actual 
existence of 14+^-chromosome mutants: 
