Signed key contains signer's user ID?

[takethebus at gmx.de]

Hi everybody,

does a signed key contain the signer's user ID or only his key ID? Do
you need to posses the signer's public key to see where he is the
signer of a signed key? My gpg works that way, but I wonder whether it
simply suppresses the display of the signer's user ID, if I don't
posses his public key.

I'm grateful for answers.
Sansibar