Are CV joints directional?

[76m2002]

I just pulled off the inside CV joint of our '91 318is, and noticed that one side has a single groove going around the perimeter of the cylindrical housing, and the other side has two grooves. Also, it seems that I can push the assembly outwards on one side, but not the other.  

Which side of the CV joint should face the diff?

Thanks for any suggestions,
Ian