wxWidgets on Solaris8

hello,
i am trying to compile wxWidgets on a Solaris8 box, but get this message:

checking for XML_ParserCreate in -lexpat... yes
checking for mspack.h... no
checking for X... no
configure: error: X11 not found, please use --x-includes and/or --x-libraries options (see config.log for details)

any advice much appreciated