Potatoes and Villagers

Today I found my first potatoes ever on Minecraft. They were in a village. At first I thought it was the village I had found before. But then I saw villagers, and the last village had no villagers, because they'd all turned to zombies and wandered away.

So I found the farm, and instead of wheat and carrots, it had potatoes and carrots.

I still haven't found anymore dogs. Where do they all go to?  The game is so much more fun with dogs. And they do the hunting for you, so you don't die so much.