Name some characteristics of Hippomanes

1. oval to disc-shaped structures 2. variable in colour 3. ranging in size from 5 to 15 cm 4. loat freely or may be attached to the allantochorion by means of a stalk 5. transverse section, they often reveal a layered appearance 6. central nucleus of cellular debris is surrounded by concentric layers of mucoprotein, calcium and phosphates.