OOGENESIS OF LITHOBIUS FORFICATUS

Abstract

Summary.1. The nucleolus of the oocyte nucleus is at first basiphil, then amphophil and finally completely acidophil showing prominent vacuoles. It discharges into the nucleus deeply basiphil circular and irregular masses of a chromatin‐like substance. The former remain in the nucleus and form secondary nucleoli which, becoming acidophil, ultimately disappear. The irregular masses, the nucleolar extrusions, are first plastered round the nuclear membrane where they bud off small pieces in the cytoplasm. Later they are detached from the nuclear membrane and lie in the cytoplasm where they become amphophil and then acidophil. As a rule they disappear before the vitelline yolk puts in its appearance.2. Strong evidence has been adduced by a comparative study of the various genera of scorpions with and without yolk in the oocytes in favour of the view that nucleolar extrusions are probably concerned in yolk formation.3. The Golgi apparatus in young oocytes consists of small rods collected in a patch on one side of the nucleus. Evidence, both direct and indirect, has been adduced in favour of the view that Golgi rods are transformed into fatty yolk. The Golgi rods, therefore, have a nutritive function in the oocyte of Lithobius.4. The fatty yolk is blackened even by chrome‐osmium, indicating the presence of free unsaturated fat in its constitution. The true vitelline yolk appears a considerable time after the fatty yolk and goes yellowish brown in osmic acid.5. In a centrifuged egg fixed by prolonged osmic acid method the fatty yolk forms a black band at one pole, whereas the vitelline yolk is thrown down at the other pole. The middle area of the egg consists of the mitochondria, the nucleus and the unchanged Golgi rods whose amount is, roughly speaking, inversely proportional to that of the fatty yolk.