THANX, Eddie. Actually, I did *not* know this - it's apparently true for Russia, but not so for at least some of the other countries, even the ones that were part of the Russian Empire. I know families in places like Lithuania, Poland, and Ukraine (maybe a few others, too) did have last names. The problems there were that during different periods (on again/off again between roughly 1850 and 1940) Jewish BMD were not permitted to be legally registered, so the only records during those times were secretly kept by churches - that's why you'll sometimes see records called baptisms for Jews, who - of course - were not baptized in any church!
Germany was a different situation entirely. I don't remember the date - it's been a few years since I worked on German Jewish profiles, but I think it was mid-1800s when German law required last names. Prior to that, they had been recorded with patronymics - didn't include ben/bat (meaning son/daughter of) but just used father's first name as their last name - what a colossal mess - every generation had a different last name and you could only build a tree by looking at father's first name going all the way back.