So I've been reading about corals, SPS in particular. For instance, I found out tonight about the three types of reef - fringing, barrier and atoll. How SPS corals reproduce and form is very interesting. I get that a stony coral is actually a colony of polyps sitting in coralites. However, the polyps are connected by living tissue so how distinct are they? I'm curious about what is shared by that living tissue and the interaction between polyps. It also makes me curious about how we rationalize why SPS might encrust before branching. Perhaps genetic coding?