The Fine Structure of the Growth Region of Ovary in Ascaris lumbricoides var. suum with Special Reference to the Rachis

Abstract

The growth region of the ovary was reinvestigated with the electron microscope in the hope of obtaining further information pertaining to the origin and significance of the rachis and the fine structure of the ovary in this region. The rachis was observed as a branched body in the upper region of the growth zone and as a circular body in the middle and lower regions of the growth zone. Germ cells were observed to be in protoplasmic continuity with the rachis in each region examined. The quantity of organelles and inclusions in the rachis was observed to increase in the middle and lower regions. Evidence was obtained to eliminate the possibility of the rachis being a continuation of the terminal cell. Observations also suggest that the rachis does not arise from an incomplete division of cellular bodies. Hence, the rachis is thought to have its origin from germ cells forming a syncytium after being initially separated from one another. The rachis is considered to be reservoir whose function is to facilitate the intake of nutritive materials by the primary oocytes. The epithelial cells in the upper region of the growth zone were observed to contain secretory vesicles.