For you inter-species households out there, how do you successfully integrate cats and dogs?

Boo and Wylie are doing well on their own for now, but when can I start leaving them alone together? I think Wylie is jealous of Boo, but he doesn't seem to do anything other than seek our attention. Wylie is a gentle dog and Boo is pretty tolerant of Wylie. Sometimes, though, he gets scared when Wylie gets too close. But his reactions have definitely calmed down.

Wylie is ten years old and Boo is just over a year.

Any suggestions?

Oh, here's the two of them:





P.S. That's a penny on the ground, not a stray poo.