Sorry to go off topic, but can I just ask where you learned so much about these little critters, RAZD? That was a fascinating post. I had no idea that the Portuguese man o' war was actually a colony. (It features prominently in a Sherlock Holmes story.) I didn't actually know, either, that single-celled organisms tend to co-operate to this extent. But it does lend support to the idea which intrigues me, that multicellular organisms can be seen as collections of symbiotic colonies of cells as well, which joined together in ages past because it was beneficial for them to specialise and therefore expend less energy on survival.

I've learned a lot from your posts here, and from the links you've provided. Thanks.