Helminth Ova: Typical fertilized egg with thick outer mammillated coat (60 x 45Ám)

Unfertilized eggs are elongated and larger in size (85 x 45Ám). Note the thin shell, an irregular, mammillated outer layer and granular contents.

Ascaris Lumbricoides eggs.

Fertile eggs may lack the mammillated layer and are called "decorticated" eggs.

Photomicrographs from the Atlas of Medical Parisitology: