conditions are evidently the same as in the other
species described--an unsymmetrical heterochromosome bivalent in the
first spermatocyte, giving rise by the second maturation division to
equal numbers of dimorphic spermatozoa, one class receiving the large
heterochromosome, the other class the small one.

Doryphora decemlineata (Family Chrysomelidae).

_Doryphora decemlineata_ has been the most difficult one of the
collection to work out satisfactorily. The chromosomes in the
spermatogonial plates were in most cases much tangled, and the behavior
of the heterochromosome pair was such as to suggest an "accessory
chromosome" rather than an unequal pair. Abundant material for the study
of somatic cells was at hand, but nothing favorable could be found in
the sections.

Two spermatogonial plates, containing 36 chromosomes, are shown in
figures 151 and 152 (plate XII). The small heterochromosome (_s_) is
slightly elongated. The synizesis and synapsis stages are especially
clear. The chromosomes, after the last spermatogonial mitosis go over
immediately into a synizesis stage consisting of a polarized group of
short loops, which later straighten and unite in pairs (figs. 153 and
154). From these loops are formed the spireme (figs. 155-158), which
splits and segments, producing various cross, dumb-bell, and ring forms
(figs. 159-163). As in most of the other species of Coleoptera, the
unequal pair is not distinguishable until the spireme stage. Figure 162
is an unusual prophase in which all of the equal pairs show a
longitudinal split as well as a transverse constriction, and the larger
heterochromosome (_l_) is also split. Figure 163 shows a somewhat later
and more common prophase in which the unequal pair, one ring, crosses,
and dumb-bells may be seen. This figure, as well as figures 164-168,
show the unequal pair in various relations to the other chromosomes.
This pair in _Doryphora_ consists of a large V-shaped chromosome with a
small spherical one attached to it in different positions. When the
small one is behind the V, the group has the appearance of an
orthopteran "accessory."

Figures 169-171 show the separation of the two elements outside of the
equatorial plate, while in figure 168 the unequal pair is in line with
the other chromosomes. In figure 172, an anaphase, the unequal elements
are barely separated, while the metakinesis of the other pairs is much
further advanced.

Figures 173 and 174 are equatoria