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]
I have found the nebenkern in its perfect condition (fig. 7) only in material fixed in Flemming; although Zenker’s fixation showed some of the breaking-up stages. This may be due partly to poorer fixation in other mixtures and partly to chance, as not so many testes fixed in other agents were examined, and the appearance evidently represents a very brief stage. These fibers now begin to break up, and we get figures that remind one of Meves’s “mitochondrion körper”; that is, a darker staining center and radiating lines to the outer ring. (Fig. 11.) Sometimes stages a little later recall Paulmier’s “blackberry stage.” (Figs. 12 and 25.) Fig. 19_a_ is a surface view and fig. 19_b_ an optical section of a nebenkern that is in the process of breaking up. Figs. 20 and 21 have a part of one end cut off, while fig. 23 is a polar view. Fig. 22 is probably a forming blackberry stage.