Pare attributed the cause of anomalies of excess to an excessive quantity of semen, and anomalies of default to deficiency of the same fluid.

He has collected many instances of double terata from reliable sources, but has interspersed his collection with accounts of some hideous and impossible creatures, such as are illustrated in the accompanying figure, which shows a creature that was born shortly after a battle of Louis XII, in 1512; it had the wings, crest, and lower extremity of a bird and a human head and trunk; besides, it was an hermaphrodite, and had an extra eye in the knee.

Another illustration represents a monstrous head found in an egg, said to have been sent for examination to King Charles at Metz in 1569.

It represented the face and visage of a man, with small living serpents taking the place of beard and hair.

So credulous were people at this time that even a man so well informed as Pare believed in the possibility of these last two, or at least represented them as facts.
At this time were also reported double hermaphroditic terata, seemingly without latter-day analogues.