Nikonos III 15mm lens (seeking forgotten knowledge )

Forgive me if this is a dumb question, but how does it all seal up?

Is there glass in the nauticam adaptor (I can't tell from the pictures 😁)? So the camera is in the housing as usual, but with no lens attached, then the adaptor is fitted as a normal port would be and the lens just connects on the wet side by bayonet?

Or is there no glass in the adaptor, but a seal between lens and adaptor?

(Not planning on getting anything like this but just curious)

Thanks!