Studies in the Origin of Yolk: III. Oogenesis of the Firefly, Luciola gorhami

Abstract

ABSTRACT In the first two papers of this series1 one of us has shown, by studying both fixed and fresh preparations stained with vital dyes, that the Golgi elements in the youngest oocytes of the spider and Scolopendra consist of vacuoles which, after treatment with various fixatives, do not show any coagulum inside their interior, indicating that their contents are watery and non-fatty. When the oocyte begins to enlarge, the majority of these vacuoles, by a process of growth and deposition inside their interior of colloids in the form of free fat not miscible with the general cytoplasm, give rise to fatty yolk-vacuoles, which henceforward show a distinct black coagulum inside their interior after treatment with osmic acid. By this process the refractive index of the Golgi vacuoles is considerably raised, and it becomes increasingly easier to study them in fresh preparations. In the case of the firefly, Lucióla gorhami, however, which forms the subject of the present paper, we observed the remarkable thing that the Golgi vacuoles of the female primordial germ-cells contain free fat as proved by their blackening in 2 per cent, osmic acid in ten minutes. When the oocyte is differentiated and begins to enlarge many of these vacuoles grow in size and give rise to fatty yolk-vacuoles. Lucióla, therefore, is a very valuable material for the demonstration of the origin of the fatty yolk-vacuoles from the Golgi vacuoles, inasmuch as the latter are fatty from the very beginning.