Electron Microscope Observations on the Formation of Yolk Body in the Oocyte of Armadillidium vulgare

Electron microscope observations have been made on the formation of the yolk body in the oocyte of Armadillidium vulgare (terrestial isopoda). Organellae were abundant from the perinuclear region to the intermediate region of the ooplasm. Especially smooth surfaced endoplasmic reticulum (sER) of small vesicular type containing intracisternal granules were abundantly observed. The cisternae containing granules constitute the network branching and anastomosing in all directions throughout the ooplasm. With the morphological transformation of sER, the cisternae become to fill with granules, and granules aggregate to form granular masses, increasing in its number and electron density. During the growth of the oocyte, they may undergo physiochemical changes resulting in a homogeneous yolk body