e accessory chromosome," it
appears to me that in a case like the aphid, where the paired elements
of the five bivalent chromosomes are separated in the first maturation
mitosis, there may be as many as seventeen kinds of spermatozoa instead
of two. If, however, we suppose that the sex characters are segregated
in the first maturation mitosis, there would, of course, be two equal
classes of spermatozoa with reference to that character.

In _Stenopelmatus_ the element _x_ in certain stages closely resembles
the "accessory chromosome" of McClung, and especially that described by
Baumgartner for _Gryllus domesticus_, but its origin and fate are
different. It first appears attached to an end of the spireme in the
growth stage of the young spermatocytes, where it is much smaller than
in later growth stages. It gradually increases in size, is a conspicuous
element in the first maturation spindle, goes into one of each pair of
spermatocytes of the second order, and there degenerates during the rest
stage between the two maturation mitoses. The whole history of this
element suggests that it may be rejected chromatin analogous to that
observed in the ovogenesis of many forms. In _Sagitta_, for example, a
considerable quantity of chromatin granules is given off by the
chromosomes and cast out into the cytoplasm near the close of ovogenesis
(Stevens, '03). Rueckert ('92) has described a similar casting out of
chromatin material by the chromosomes of the oocytes of _Pristiurus_.

The spermatogenesis of _Stenopelmatus_, therefore, differs from that of
the other Orthoptera which have been described in having (1) a larger
number of chromosomes (46), (2) an even number in the spermatogonia, (3)
an accessory chromatin structure in the spermatocytes of the first
order, which disappears before the second maturation division.

In _Blattella_ we have a typical "accessory chromosome," according to
McClung. It appears (1) in all resting spermatogonia closely associated
with a nucleolus, (2) in the spermatogonial mitoses as an odd chromatin
element, making 23 in all, (3) in the growth stage of the spermatocytes
connected with an end of the spireme and also with the nucleolus. It
becomes separated from the other chromatin in the tetrad-stage, remains
nucleolus-like in form, and later appears in the first maturation
division either among the chromosomes or in a more or less aberrant
position. It passes into one of each pair of spermatocytes of