What determines whether podcasts are played individually or sequentially on an iPod?

Basically, I have a lot of podcasts on my iPod.  

At one point, it would play just one podcast, and then stop. There was a period of a few weeks where I didn't listen to podcasts, and now when I go to listen to a podcast, when I finish one, the iPod begins playing the next. 

This is an issue for me because I generally listen to podcasts when going to sleep. As such, the iPod generally goes through maybe ~10 podcasts overnight, and I loose track of where I was.

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Basically, originally my iPod played podcasts one-by-one, I changed something, and now it does not. 

However, I've been through the menus on the iPod, and I cannot see anything that looks like it would be related to the podcast playback behaviour. Whatever was changed, It's not readily apparent the effects it has.