either the synapsis stage
nor the prophase forms are so clear on this point as in some of the
other species studied. Figures 17 and 18 show metaphases of the two
classes of second spermatocytes, the chromosomes varying somewhat in
form in different preparations and even in different cysts of the same
preparation. An early anaphase of this mitosis is shown in figure 19;
here the small chromosome is already divided. It was impossible to find
good polar views of the daughter plates in the two classes of second
spermatocytes, but it is evident from figure 19 and other similar views
of the second spermatocyte spindle that, as in _Tenebrio_, one-half of
the spermatids will contain one of the derivatives of the small
chromosome, the other half one of the products of its larger homologue.

Sections of male pupae were examined for equatorial plates of somatic
mitoses. Figure 1 is a specimen of such plates. As might be expected,
this figure resembles quite closely the spermatogonial equatorial plate
(fig. 3) in number, form, and size of chromosomes, the small one being
present in both. Figure 2 is from the follicle of a young egg; here we
find 28 chromosomes, but no small one. The chromosome corresponding to
the larger member of the unequal pair in the male evidently has a
homologue of equal size in the female. The chromosome relations in the
male and female somatic cells are therefore the same as in _Tenebrio
molitor_, and must have been brought about by the development of a male
from an egg fertilized by a spermatozoon containing the small
chromosome, and a female from an egg fertilized by a spermatozoon
containing the larger heterochromosome.

Trirhabda canadense.

In _Trirhabda canadense_ the spermatogonial chromosomes are invariably
smaller than in _T. virgata_, but similar size relations prevail. The
spermatogonial plate (fig. 21) contains 30 chromosomes, 29 large and 1
extremely small. In the growth stages the association of the two
unequally paired chromosomes with a rather large plasmosome is more
evident than in _T. virgata_ (figs. 22-23). In this species the unequal
pair is more often found at a different level from the other chromosomes
in the early metaphase of the first maturation mitosis (fig. 24), but it
later comes into the plate with the other chromosomes (figs. 25-27), and
divides earlier than most of the other bivalents (fig. 27). In a polar
view of this metaphase the largest chromosome often appears doubl