It looks like Nerite eggs.
I've found they disappear on their own over time.They are really hard to get off. It take a lot of elbow grease to get them off the glass. Might take using a razor blade.
lol I hate my nerites. I don't see how some people can keep so many nerites and still keep their tank clean. Now if they'd eat their own eggs, that would be Awesome!Nerite eggs for sure. I've switched to stocking only one per tank as they lay eggs everywhere, even on my MTS!