Memoirs: On the Relation of the Mitochondria and Golgi Apparatus to Yolk-Formation in the Egg-Cells of the Common Earthworm, Lumbricus Terrestris

1. The yolk-nucleus is merely a mass of mitochondria. 2. The mitochondria arise as a cap of threads over the nucleus, and this cap grows in size and density, migrates away from the nuclear membrane and breaks up into its component mitochondrial threads. These threads become evenly spread throughout the cytoplasm of the cell. 3. The mitochondria are not clearly defined in the very young oogonia. 4. The Golgi apparatus consists of numbers of Golgi elements lying separate in the cytoplasm. There is never any attempt at concentration of these elements round one central mass. 5. The Golgi elements are probably little platelets or spheroids somewhat resembling blood corpuscles in shape. They are not rods. As fixed by Da Fano technique, each element is a little plate with a very lightly impregnating centre and a very heavily impregnating rim. 6. The Golgi elements may probably arise from the cytoplasm. 7. The nucleus contains two nucleoli; an early arising karyosome, homogeneous and solid in structure, and a plasmo some arising later This plasmosome is liquid in consistency and contains an argentophil core. The karyosome disappears before the oocyte is half grown, but the plasmosome remains in the nucleus while the egg remains in the ovary. 8. No visible nucleolar extrusions into the cytoplasm were observed. 9. Yolk probably arises from the cytoplasm; no direct metamorphosis of either mitochondria, Golgi apparatus, or nucleolus into yolk was observed.