So, the Synthesist variant of the Summoner lets you bond with your Eidolon rather than call it separately, however I've got a couple of questions that the SRD doesn't define:
1) When fused, do you still keep your gross physical characteristics? eg if I'm a human and I fuse with a Serpentine Eidolon, are my own arms & legs functional? And if yes, does that mean that I can use my base land speed rather than the Eidolon's?
2) If I "Gain the Eidolon's HP as temporary HP" am I able to use heal spells to 'heal' these if my temporary HP get damaged? Otherwise I have no idea how the Eidolon could be healed.
3) Do I get the Eidolon's saving throws? I'd assume no since it's not specified but otherwise I have no idea why they'd even be recorded.