The Kansas University Science Bulletin, Vol. I, No. 2, February, 1902Various
Science
The Kansas University Science Bulletin, Vol. I, No. 2, February, 1902
Various
Science -- Periodicals
There are, in _Gryllus_ spermatids, two quite permanent and prominent
extra-nuclear bodies. The larger of these I shall call _nebenkern_,
because I believe it originates from the spindle remains, and goes to
form the tail covering. Its behavior is as follows: At the beginning
of the telophase the fibers which had connected the centrosomes with
the chromosomes bulge out like barrel staves, as Henking (’91) has
described. These break loose from the chromosomes and centrosomes
as the clear space begins to form around the chromatin mass (fig.
2); but they are not separated into two rings, as in _Anasa_
and _Pyrrhocoris_. As the dividing cell membrane is formed, the
middle portions of the fibers are drawn together and the so-called
“mid-body” is formed. Some of the fibers unite, producing thicker
ones, as seen in figs. 1, 2, and 3. In the last-named figure some
of the central fibers seem to be still united with those of the
companion spermatids.
As the daughter-cell shortens and the nucleus takes a more central
position these fibers unite still more, shorten, bend together (figs.
4, 5, and 6), and finally assume the shape shown in fig. 7. I shall
call it for the present the “striated condition,” or simply “striated
nebenkern.” The shape resembles that of an egg with rather sharply
drawn-out ends. The surface is occupied at intervals with deeply
staining lines which look much like hoops. In most cases the long
axis of the nebenkern is at right angles to the axis of the spindle
from which it was formed, while the striæ, or dark lines, are in
planes parallel to it, as is seen in figs. 7 and 8_a_. In a few cases
the lines are parallel to the long axis of the nebenkern, as shown in
fig. 8_b_. Fig. 9 exhibits a partial end view of the nebenkern, while
fig. 26 represents a polar view in all planes.
The fibers in figs. 4 and 5 are not all in the same plane, giving
frequently, with changing focus, the impression that the lines are
the edges of plates. Even in figs. 7 and 8, the appearances shown
made me hesitate for some time before I dared say that the lines
represent striæ on the surface and not plates extending through the
body. But the end views (figs. 9 and 26) and the two drawings in fig.
19 show clearly that we are dealing with encircling hoops and not
dividing plates. Just how or why the fibers bend and assume the shape
of figs. 7 and 8 I am not able to say, but I am sure it is not an
artefact, as might be supposed, because I have found them occupying
whole cysts of several testes, and nearly all of them were as regular
and definite as fig. 7.[A]
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