The Nature and Origin of Yolk

Abstract

ABSTRACT The advance of modern cytology has necessitated the division of the cytoplasmic inclusions into two groups, the protoplasmic inclusions or living organellæ capable of spontaneous growth, division and movement within the cell, and the deutoplasmic inclusions or non-living reserve materials of the cell built up by the activity of the living protoplasm, representing a stage in the anabolic processes of the cell. The Golgi apparatus and the mitochondria both belong to the former group and appear, in the present state of our knowledge, to be specially associated with cell anabolism and often, if not always, in oögenesis with the special case of yolk formation. Sometimes the yolk is produced indirectly by the action of these organellæ, at other times either the Golgi elements or the mitochondria swell up and themselves transform into yolk spheres. In the latter case it is difficult to decide whether an element at any given stage of the transformation process should be considered a deutoplasmic or a protoplasmic body.