Human eggs (secondary oocytes) and C-Fern spores are similar in size and shape (ca. 120 microns diameter). A vial containing 300,000 C-Fern spores (ca. 240 mg) is a graphic demonstration of the number of eggs (primary oocytes) in the ovaries of a 7-year-old girl. Only 400 - 500 of these will be released as secondary oocytes during her reproductive years.