July, 1922] 
CLELAND OENOTHERA FRANCISCANA 
399 
been too long and complexly woven, and in the second contraction the 
massing of the material in the center has rendered conditions too obscure, 
to permit a study of the individual chromosomes to be made. From 
now on, however, it becomes increasingly possible to make such a study, 
and to determine what relation the individual chromosomes bear to each 
other and whether or not this relation is uniform. The conditions that 
we find are very interesting. 
When the second contraction knot begins finally to loosen, it does 
so in a definite way. It lengthens out, and from a more or less rounded, 
spherical mass assumes a roughly cylindrical form (figs. 22, 23). As it 
grows longer, the individual bivalent chromosomes which compose it begin 
to show more clearly (fig. 23), and, despite the fact that the figure is still 
obscurely massed in the center, their appearance suggests a definite ar- 
rangement. From one end of the figure it is common to find a single 
loop or ring protruding, and from the other end, two loops. Various 
others may be seen emerging from the sides of the central cylindrical 
portion. At this time the exact arrangement of the chromosomes is not 
clear, but the general cylindrical shape of the whole, and the uniform 
placing of such loops as can be seen clearly, indicate that they do have 
a definite positional relationship to each other. 
As the figure opens out more and more and the nucleus passes into 
diakinesis, it becomes possible to make out the arrangement with greater 
clearness. The central part of the figure resolves itself into a closed circle, 
composed of four univalent chromosomes attached end to end (fig. 24). 
Linked to this circle at different places are rings, each of which is com- 
posed of two univalent chromosomes which are attached to each other 
at both ends. To certain of these rings there is linked in turn another 
ring made up in the same way. It is possible to count these rings in most 
cases, and we find that there are five of them present, which, together 
with the circle of four chromosomes, make a total of fourteen chromosomes, 
a circle of four and five pairs. 
The chromosome pairs begin to separate from each other almost as 
soon as the second contraction knot begins to loosen, so that it has been 
impossible to find a case in which all the chromosomes were still occupying 
their original position with reference to one another, after the knot had 
completely loosened. Fortunately, however, the rings do not seem to 
separate in the same order at all times, so that it has been possible by 
studying many cases of linking to get quite a definite idea of the original 
arrangement; and in spite of the fact that I have found no case in which 
they have all remained together long enough to be clearly observed, I have 
become quite convinced that there is a definite arrangement of the chromo- 
somes which is rarely if ever disturbed. In the first place, it is certain 
that the closed circle of four chromosomes is practically always present. 
I have found no case in which it was certainly lacking, but every good 
