Alfaholic is right, the canister is designed to be used with a sealed fuel system and instead of venting vapours to air it feeds them into this canister where I suspect the vapour can re-condense and flow back into the tank. Any excess vapour is fed into the inlet manifold. The canister is mounted vertically and each of the small pipes goes inside to different heights, like a fractation tower in miniture.
I've only come across this stuff in US market cars, but the idea is that the fuel filler cap is sealed at ambient pressure, but can vent to air if pressure in the tank is too high (like in hot weather, and can allow air in to displace the vacuum formed as fuel is used.
The little pipes go back to the fuel tank, and one goes to the inlet manifold somewhere.
I reconnected all this gubbins in my Barracuda, mainly to stop the tank venting to air in the garage and stinking the house out
If you want to get rid of it, plug the inlet manifold pipe and the fuel return pipes at the tank, ditch the canister and run a vented filler cap, or keep the sealed filler cap and put a small vent valve on one of the pipes. I got one of these on the Green Machine and it will only allow vapour to vent out if it reaches a certain pressure first, and it still allows air in
to counter fuel starvation as the tank runs down. No raw fuel smells in my house!