The “häkenformige Gebilde” moves away from the periphery, its sides elongate, break, and unite at the nuclear end, thus form the polygonal nebenkern. “Derselbe geht also in diesem Falle direckt aus den Spindelfasern hervor.” When the protoplasm does divide a similar process takes place. The spindle remains divide at an equatorial line and each half forms a nebenkern, and, as he says: “Also auch hier geht der Nebenkern direckt aus den Spindelfasern hervor. Vielleicht geht in den Spermatiden der Nebenkern überhaupt immer aus den Spindelfasern hervor, in dem die langfädige Verbindüngsbrücke, die ihn oft mit dem Kern verbindet, sich wohl als ein noch einige zeit persisttirender Rest der esteren deuten lässt.”
In his paper on _Limax_ (’89, 1) he followed the nebenkern through all the divisions and thinks it a constant organ of the cell. In the second part of the paper on _Helix_ and _Paludina_ the nebenkern was considered as formed from the remains of the spindlepole and the centrosome. Later Platner (’89, 2) found the nebenkern in the pancreas cells. In reports upon _Pygæra_ and _Sphinx_ he changed the name nebenkern to mitosome. The centrosome lies in front of the nucleus and forms the point of the head. This he calls the nebenkern. From the spindle remains arise two bodies. A large, fibrous one from the equatorial end has a clear space around it and the axial filament passes through it. It soon elongates and forms the tail. This is the large mitosome. The other is much smaller and arises from the polar end of the spindle fibers. It takes its place in the angle between the large mitosome and the nucleus. Here it persists till the nucleus begins to elongate, when it lengthens and surrounds the basal end of the spermatozoon tail. This is the small mitosome.
Platner (’85) saw a true nebenkern. I have already criticized the use of the word “nebenkern,” as the name for the spindle remains in the spermatocytes. Platner himself later denied the nuclear origin of the nebenkern. His results (’86, 2) agree with mine concerning the uniting, converging, staining and bending of the spindle-fiber remains and their passing to the tail. Again, Platner (’89, 1) probably followed the centrosome and attraction sphere, as well as the nebenkern, in the second part of the paper on _Helix_ and _Paludina_. In the pancreas the body is a result of secretion, and is not a nebenkern. In _Pygæra_ Platner’s large mitosome is the real nebenkern, as shown by its fibrous structure, its surrounding clear space and destiny. His small mitosome is what I have described as the acrosome, and he is mistaken as to its final use. The body he called centrosome in the nucleus is the persisting accessory chromosome. Such would be my interpretation of his figures.