My current single acting Wheatstone bass has a large number of holes with valves in the bellows. I call them gills.
A previous one (by Lachenal) had a few holes with valves in the ends, I think in the action boards. It was a long time ago: I don’t think it had conventional reed pans which pulled out, as in smaller instruments.
The Wheatstone with the gills is a vastly superior instrument to the Lachenal.