Where does this go?

Call me stupid if you like, but I'm extremely tired and after a weekend flat out working on the mark 1 I'm looking at this pipe (fitting new engine) on my 1.3 driver and thinking where the bloody hell does this go..



The big fat black one I'm looking at - this is the old engine but same pipe.

Its just ya crankcase breather mate plugs onto bottom of airfilter when ya put it on