Then this afternoon, I was in the yard trying to get him some exercise, and he chased sticks nicely but when I turned my back he went after my pants legs, then coat, then mittens. I don't know whether to call it aggression or overexcited playing, but it is hard to stop him once he starts. In all these cases I was eventually able to get the leash or the mitten away from him, then hold his collar and stroke him as I asked for a sit and treated him, and he did calm down.
Eegad. I have my work cut out for me!