George Lefevre and Caroline McGill AT? 
tween the halves of the dyads, which, however, are still lving side by side. 
In both drawings the heterotropic is recognized at a glance, as it is the 
only chromosome in the group without a mate. 
The divergence of the chromosomes occurs at unequal rates, those on 
the periphery lagging behind, those in the center taking the lead, while 
the heterotropic lags most of all and im late anaphases, when the others 
are grouped about the poles in a dome-shaped mass, the halves of the 
heterotropic may usually be seen some distance behind in the process 
(J and K of Fig. 3). 
As the chromosomes reach the poles, they become closely crowded to- 
gether and partially break up into a reticulum, although to a certain 
extent their identity is still retained in the nodes of the network. The 
centrosomes fade out and a new nuclear membrane forms but only to 
disappear shortly afterwards in preparation for the second division. In 
fact, there are indications that in some cases at all events this intervening 
resting stage between the two divisions is practically omitted. 
THe Second Maturation Diviston.—As soon as the nuclear mem- 
brane fades away the chromosomes reappear as dumb-bell shaped bodies, 
and as the new spindle forms they take up their position in the equatorial 
plate with the constriction at right angles to the long axis of the spindle. 
There are thirteen of these dyads, and the one single chromosome, the 
heterotropic. Even before the other chromosomes pass definitely into the 
equatorial plate, the heterotropic without undergoing division begins 
usually to move in advance toward one of the poles, as may be seen in 
Fig. 4, A and B, and it has nearly completed its journey before the diver- 
gence of the other chromosomes is commenced. There is, however, a good 
deal of irregularity in the movement apart of the chromosomes, especially 
during the early anaphase, the halves of each pair seeming to diverge at a 
more or less independent rate. This independence of movement, not only 
of the heterotropic, but of the other chromosomes as well, increases the 
difficulty of mechanical or electrical theories of the cause of divergence. 
Early stages in the progress of the undivided heterotropic chromosome 
toward one pole are shown in A and 6 of Fig. 4, while still later stages 
are represented in C and D. In the former drawings, both the m-chromo- 
some and the macro-chromosome are distinctly recognized in side view, 
while in D, although the heterotropic is still visible at one pole, the other 
chromosomes are closely massed together. As in Anasa tristis, polar 
views at the anaphase of this division clearly demonstrate the dimorphism 
of the daughter groups, since thirteen single chromosomes appear in one 
and fourteen in the other, the former being the one that lacks the hetero- 
