476 Chromosomes of Anasa Tristis and Anax Junius 
of the threads of the growth-period is made certain, and, furthermore, it 
is evident that the crosses are placed lengthwise upon the spindle. 
The number of chromosomes is now easily observed, fourteen in all, 
thirteen of which are in the form of crosses, while one, the heterotropic, 
is a simple, condensed, bipartite body. As the crosses condense, their 
centers, just before the disappearance of the nuclear membrane, become 
lighter and soon take the stain only faintly, while by the time the spindle 
is visible they have become completely hollowed out. The series of 
changes taking place in the formation of the crosses, and their conversion 
into the open tetrads may be followed through Fig. 2, J-L, and Fig. 3, 
A and B, successively. These figures also demonstrate the relation of the 
long axis of the cross to that of the spindle which are seen to be parallel. 
THe First Maturation Diviston.—After being taken up on the 
spindle the open tetrads rapidly undergo a condensation; all traces of 
the space between the arms disappear, and by the time the prophase is 
ended they have the form shown in side view in Fig. 3, C. Although the 
quadripartite character of the thirteen tetrads is still indicated by slight 
depressions or grooves on the surface, there is at this stage no separation 
of the four elements which have become fused with each other. In side 
views the broad face of the tetrads shows the demarcation of the four 
compound parts, while those tetrads which are seen on edge in these 
views appear as dumb-bell shaped bodies and therefore cannot be dis- 
tinguished, except in some cases by size, from the heterotropic chromo- 
some which has this appearance when seen in either vertical plane. In 
order to determine with certainty which chromosome is the heterotropic, 
one must examine the metaphase groups in polar view, in which all of 
the tetrads appear as dumb-bell shaped bodies, while the heterotropic is 
seen as a single chromosome, since its constriction lies in the horizontal 
plane. Fig. 3, D, shows these relations very plainly; there are thirteen 
double chromosomes which are the thirteen tetrads seen in polar view, 
while the heterotropic at h appears as a single oval body. The range in 
size from the smallest to the largest tetrad is also clearly indicated. FH 
is another polar view, but at a slightly later time when the separation of 
elements is just beginning in four of the tetrads. This breaking apart of 
the component parts of the tetrad proceeds rapidly with the beginning of 
the anaphase, until all four elements are entirely distinct from each other 
as the opposite pairs advance toward the poles of the spindle (/ and H 
of Fig. 3). G shows a daughter group in the early anaphase before the 
members of all of the pairs are entirely separated, while J is a similar 
view a little later. Im the latter, there is no longer any connection be- 
