Under a magnification of 125X, this photomicrograph reveals both fertilized (A), and unfertilized (B) Ascaris sp. eggs, and a Trichuris sp. egg (C). Using an unstained mount of formalin in preserved feces, note that fertilized Ascaris spp. eggs are rounded, and exhibit a thick mammillated shell, while unfertilized eggs are elongated and larger, thinner shelled, and covered by a more visible mammillated layer than the fertilized eggs.