Friday evening
debramcp and I decided to introduce Roughy and Finnegan to each other. It consisted mostly of hissing, growling, hiding under the coffee table, and ugly-looking (though apparently not damaging) fights. After some hours of this, we separated them again for the night. We were worried that this was not going to go well...
Saturday we let them out together for short periods and got more of the same, though the fights were looking less ugly. By the evening, they had progressed to sitting in the same room glaring at each other between tussles, so we decided to leave them together overnight.
Then, on Sunday:
Of course, they're still spending a lot of time chasing each other around and wrestling, but now it looks like two kittens playing.