Which was the worst of Thurber's dogs?

From the text:

But the Airedale, as I have said, was the worst of all my dogs. He really wasn't my dog, as a matter of fact: I came home from a vacation one summer to find that my brother Roy had bought him while I was away. A big, burly, choleric' dog, he always acted as if he thought I wasn't one of the family. There was a slight advantage in being one of the family, for he didn't bite the family as often as he bit strangers. Still, in the years that we had him he bit everybody but mother, and he made a pass at her once but missed.