I saw this post today discussing how symmetry was maintained in a fetus while it was growing. In particular, a rat fetus was injected in the leg so that the leg would stop growing. The leg was then able to communicate with the placenta and the rest of its body to stop growing until the leg began to grow again.
I thought it was an interesting read connecting some of the topics that I have already mentioned in my symmetry series. I also know the above chipmunk is not a rat, but chipmunks are cute and rats are not.