Removing a rear wheel of a town bike I'm a beginner in repairing bicycles. I have quite an old town bike. I'm trying to change the tires. I have trouble in taking out the back wheel. As you can see in the picture, there is a small piece of chain connected into the hub shell. 

I've checked for a small clasp or small screws to remove it but it doesn't seem to have any. Does anyone know how to remove this? Or am I doing something wrong? Any help is appreciated.
This picture shows a slightly better angle. You need to first loosen the lock nut slightly, then spin the adjuster barrel until it unscrews right off the threaded rod on the chain. When you re-assemble you reverse that, and have to re-adjust the tension so that it shifts properly.