Changelings

As usual Nigel Posts interesting comments.....this time about changelings- a subject I know nothing about...
I found the information about Welsh changelings fascinating:-

"In Wales the changeling child (plentyn cael (sing.), plant cael (pl.)) initially resembles the human it substitutes, but gradually grows uglier in appearance and behaviour: ill-featured, malformed, ill-tempered, given to screaming and biting. It may be of less than usual intelligence, but again is identified by its more than childlike wisdom and cunning.
The common means employed to identify a changeling is to cook a family meal in an eggshell. The child will exclaim, "I have seen the acorn before the oak, but I never saw the likes of this," and vanish, only to be replaced by the original human child. Alternatively, or following this identification, it is supposedly necessary to mistreat the child by placing it in a hot oven, by holding it in a shovel over a hot fire, or by bathing it in a solution of foxglove."